A novel four component modified Biginelli reaction for the synthesis of C-2 functionalized dihydropyrimidines has been established. The approach uses assembly of less explored acetyl acetone with aromatic aldehyde, thiourea, and dimethyl sulphate to construct a novel 5-acetyl 2-methylthio dihydropyrimidine system, which works as an efficient well-designed intermediate for generating C-2 modified Biginelli libraries with nitrogen nucleophiles. Phenyl hydrazine, semicarbazide, and aryl semicarbazides are successfully used as N-nucleophiles to generate C-2 functionalized dihydropyrimidine derivatives, which fulfil the demands of active pharmacophore. Time economy, step economy, and a single pot reaction with moderate to excellent yield are the major advantages of this novel method.
Turkish Journal of Chemistry Turk J Chem (2021) 45: 1980-1987 © TÜBİTAK doi:10.3906/kim-2105-59 http://journals.tubitak.gov.tr/chem/ Research Article A four-component modified Biginelli reaction: A novel approach for C-2 functionalized dihydropyrimidines Harsha NARKHEDE*, Avinash DHAKE, Vaidhyanathan BALASUBRAMANIYAN Department of Pharmaceutical Chemistry, S.M.B.T College of Pharmacy, Dist-Nashik, India Received: 01.06.2021 Accepted/Published Online: 21.09.2021 Final Version: 20.12.2021 Abstract: A novel four component modified Biginelli reaction for the synthesis of C-2 functionalized dihydropyrimidines has been established The approach uses assembly of less explored acetyl acetone with aromatic aldehyde, thiourea, and dimethyl sulphate to construct a novel 5-acetyl 2-methylthio dihydropyrimidine system, which works as an efficient well-designed intermediate for generating C-2 modified Biginelli libraries with nitrogen nucleophiles Phenyl hydrazine, semicarbazide, and aryl semicarbazides are successfully used as N-nucleophiles to generate C-2 functionalized dihydropyrimidine derivatives, which fulfil the demands of active pharmacophore Time economy, step economy, and a single pot reaction with moderate to excellent yield are the major advantages of this novel method Key words: Biginelli reaction, green synthesis, 4-MCR, 2-Methylthio-1,4-DHPMs, N- nucleophiles Introduction The synthesis of structurally diverse compounds has gained prime importance to generate molecular libraries in the drug discovery process The focused issues for the novel developed reaction are the generation of these molecular libraries with excluding the drawbacks of classical reactions such as step-by-step process, tedious workup, use of toxic/expensive reagents/solvents/catalysts, long cyclisation period, and poor yield Multicomponent reactions (MCR) are the hottest area in organic synthesis to generate scaffolds of drug like candidates [1,2] Many pharmacophores have been generated from MCRs in medicinal chemistry, including praziquantel, nifedipine, and clopidogrel, to name a few [3,4] Biginelli reaction, as a 3-CR was conceptualized in 1893 [5], and it gives simplicity of the reaction to generate dihydropyrimidines (DHPMs) with varied pharmacophores From common organic reagents as well as the structural complexity with all six positions of pyrimidine nucleus, (Figure 1a) amenable to multiple chemical decorations, yielding a large library of compounds The current surge of interest in this area in the last two decades is largely due to the diligent work of Kappe and his group [6,7] Dihydropyrimidines (DHPMs) are the N-based heterocycle obtained from Biginelli MCR and have shown remarkable pharmacological activities [8–10] The discovery of monastrol (Figure 1b) with its pharmacological activities in 1999 was a watershed moment [11,12] Another fillip to Biginelli reaction (and other MCRs) was provided by the advent of green chemistry as a defining protocol for organic synthesis The major attribute of MCR include, atom economy, step economy as well as saving energy and time resulting from simple work-up procedures [13–15] A survey of recent literature revealed that modifications at the N1, C2, and N3 are particularly productive in offering drug-like candidates Looking towards the libraries generated by the classical Biginelli reaction and the number of C2 modified DHPM derivatives showed tremendous scope for medicinal chemistry in the last decade [16] In our earlier work on DHPMs [17,18], we noticed that working on DHPM areas deserve more effort As revealed in the 2004 review of Kappe and several subsequent reviews, there have been abundant activities in DHPM-2-oxo/2-thio/2-amino with C5ester Unarguably, the activity spectrum of these 5-ester substituted DHPM – Monastrol led to the flood of publications on them, both DHPM-2-one and 2-thione We also noticed that a handful of papers have been reported on 5-acetyl DHPMs It appears to enrich the 5-acetyl DHPM chemistry, since they too display useful activities such as, anticancer, calcium channel blocker, antiviral, antiinflammatory, antitubercular, antioxidant, and antibacterial activities [9,10,19–21] We also noticed that 5-acetyl DHPMs are conspicuously absent in many review articles and are less explored * Correspondence: narkhede.harsha@gmail.com 1980 This work is licensed under a Creative Commons Attribution 4.0 International License NARKHEDE et al / Turk J Chem OH R4 R3 R N1 R1 1a O R2 N X H3 C NH O H3 C N H S 1b Figure a- General structure of Biginelli adduct, b: Monastrol structure The 2-methylthio function has potential for a variety of nucleophilic displacements leading to biologically useful drug candidates In this regard, current report highlights utility of this substrate by using few selected N-nucleophiles, viz hydrazine hydrate, phenyl hydrazine, aryl semicarbazides, which will function as a lead for designing of new drug targets [16,22,23] Materials and methods 2.1 General All chemicals and reagents (AR) were procured from commercial sources Melting points were determined by calibrated digital melting point apparatus (Make- Labline) TLC analysis was carried out on precoated Silica gel 60 F254 aluminum plates procured from Merck, Germany, and spots were visualized by UV light and/or by iodine vapors Fourier-transform infrared (FT-IR) spectra for all the synthesized intermediates and final compounds were recorded on a JASCO 4100 FTIR spectrophotometer in the range of 4000–500cm–1 Proton nuclear magnetic resonance (1H NMR) spectra and carbon nuclear magnetic resonance (13C NMR) spectra were scanned using Bruker Avance Neo 500MHz spectrometer using DMSO-d6/CDCl3 as solvent Chemical shift (δ) values are reported in ppm with TMS as an internal standard Mass spectra were recorded on a Synapt-XS using the TOF MS ES+ method. 2.2 Synthesis General procedure for synthesis of 1-(6-Methyl-2-methylsulfanyl-4-phenyl-1,4-dihydro-pyrimidin-5-yl)-ethanone: 5a The mixture of benzaldehyde (1a, 1.01 mL, 0.01 mol), acetyl acetone (2, 1.03 mL, 0.01 mol) and thiourea (3, 0.91 g, 0.012 mol) was transferred to a reaction flask, and the flask was cooled to 0–5 °C in an ice bath Dimethyl sulphate (4, 1.5 mL, 0.012 mol) was added drop wise over 10 The temperature rose to 60-65°C as a result of the ferocious reaction Once the vigorous reaction ceased, 10 mL of ethanol was added and the reaction mixture was refluxed for 3-4 hours, along with stirring The progress of reaction was monitored by TLC The reaction mixture was cooled to 0°C and triturated with crushed ice and cold water The solid separated was filtered off and washed with cold ethanol followed by ether The crude product obtained was crystallized from hot ethanol to obtain compound 5a Similarly, compounds 5b-e were obtained by using aryl aldehydes viz 3-hydroxy-4-methoxybenzaldehyde, 4-nitrobenzaldehyde, 4-chlorobenzaldehyde, and 2-hydroxy benzaldehyde respectively with acetyl acetone, thiourea and dimethyl sulphate by following similar reaction protocols 1-(6-Methyl-2-methylsulfanyl-4-phenyl-1,4-dihydro-pyrimidin-5-yl)-ethanone, (5a) Yield: 78%, Ochre yellow solid; mp- 128–129 ℃; Rf- 0.52 (Benzene: Ethyl acetate, 7:3) FTIR (KBr, Ʋmax/cm–1): 3278 (sec NH), 3194 (Ar CH), 3027 (Ali CH), 1699 (C=O), 1616 (C=N), 1455 (Ar C=C), 1327 (C-N) 1H-NMR: (500MHz, DMSO): δ 2.15 (s, 3H, C6-CH3), δ 2.24 (s, 3H-SCH3), δ 2.35 (s, 3H, CO-CH3) δ5.29-5.30 (s, 1H, C4-H), δ 7.09-7.46 (m, Ar.-CH, 5H), δ10.28 (s, 1H, -NH) 13 C-NMR: (500 MHz, DMSO): δ 194.67 (C=O), 173 (C=N), 126-139 (Ar C=C), 110.36 (C=C), 53.68 (C4), 52.77 (S-CH3), 30.31 (CO-CH3), 18.15 (C6-CH3) ESI-MS: m/z calcd for C14H16N2OS 260.4 found 264.4 [M+4]+ 1-[4-(4-hydroxy-3-methoxyphenyl)-6-methyl-2-(methylsulfanyl)-1,4-dihydropyrimidin-5-yl]ethenone, (5b) Yield: 70%, Brown solid, mp- 171–172 ℃; Rf- 0.24 (Benzene: Ethyl acetate, 7:3) FTIR (KBr, Ʋmax/cm-1): 3436 (-OH) 3290 (sec NH), 3189, (Ar CH), 3035 (Ali -CH) 1711 (C=O), 1631 (C=N), 1512, 1454 (Ar C=C), 1326 (C-N), 1384 (C-O); H-NMR : (500MHz, DMSO): δ 2.11 (s, 3H, C6-CH3), δ 2.28 (s, 3H-SCH3), δ 2.32 (s, 3H, CO-CH3), δ 5.20-5.21 (s, 1H, C4H), δ 6.57-6.85 (m, Ar-CH, 3H), δ 9.03 (s, OH), 9.65 (s, 1H, -NH), δ10.20 (s, 1H, -NH) 13C-NMR : (500 MHz, DMSO): δ 194.98 (C=O), 173.59 (C=N), 115-147 (Ar C=C), 110.02, 111.18 (C=C), 55.48 (C4), 53.62 (S-CH3), 30.03 (CO-CH3), 18.00 (C6-CH3) 1981 NARKHEDE et al / Turk J Chem 1-[6-methyl-2-(methylsulfanyl)-4-(4-nitrophenyl)-1,4-dihydropyrimidin-5-yl]ethenone, (5c) Yield: 87%, Yellow grey solid, mp- 192–193 ℃; Rf- 0.50 (Benzene: Ethyl acetate, 7:3); FTIR (KBr, Ʋmax/cm–1): 3270 (sec NH), 3184 (Ar -CH), 3078 (Ali CH), 1699 (C=O), 1636 (C=N), 1464, 1418 (Ar C=C), 1347 (C-N), 1521 (C-NO2) 1-[4-(4-Chloro-phenyl)-6-methyl-2-methylsulfanyl-1,4-dihydro-pyrimidin-5-yl]-ethanone, (5d) Yield: 82%, buff solid; mp-177–178 ℃; Rf- 0.45 (Benzene: Ethyl acetate, 7:3) FTIR (KBr, Ʋmax/cm–1): 3279 (sec NH), 3176 (Ar CH), 3024 (Ali CH), 1709 (C=O), 1619 (C=N),1490, 1455 (Ar C=C), 1327 (C-N), 762 (C-Cl) 1-[4-(3-hydroxyphenyl)-6-methyl-2-(methylsulfanyl)-1,4-dihydropyrimidin-5-yl]-ethenone, (5e) Yield: 78%, Occur yellow solid, mp- 176–177 ℃; (Benzene: Ethyl acetate, 7:3) Rf-0.28 IR (KBr, Ʋmax/cm–1): 3450 (OH), 3296 (sec NH), 3183, (Ar CH), 3068 (Ali -CH), 1719 (C=O), 1631 (C=N), 1509, 1445 (Ar C=C), 1325 (C-N), 1380 (C-O) General procedure for synthesis of 1-(2-hydrazinyl-6-methyl-4-phenyl-1,4-dihydropyrimidin-5-yl) ethanone, (6a) To 10ml ethanolic solution of 5a (260mg,1mmol), hydrazine hydrate (75mg, 1.5mmol) in 10ml ethanol was added drop wise and mixture was stirred under reflux conditions The completion of reaction was monitored by TLC (2-4hrs) After the completion of reaction, crude mass obtained was cooled to room temperature and poured on to crushed ice Obtained product was filtered off, washed with ether, dried, and recrystallized using ethanol to give product 6a Similarly, compounds 6b-e were obtained by using phenyl hydrazine/semicarbazide/aryl thiosemicarbazides 1-(2-hydrazinyl-6-methyl-4-phenyl-1,4-dihydropyrimidin-5-yl) ethenone, (6a) Yield: 81%, Buff solid, mp- 152–153 ℃; Rf = 0.56 (Benzene: Ethyl acetate, 7:3); FTIR (KBr, Ʋmax/cm–1): 3432 (pri NH2), 3283 (sec NH), 3192 (Ar CH), 3025 (Ali CH), 1701 (C=O), 1607 (C=N), 1454 (Ar C=C), 1330 (C-N), 1184, 1115 (N-N) 1H-NMR: (500MHz, DMSO-d6): δ 2.15 (s, 3H, C6-CH3), δ 2.34 (s, 3H, CO-CH3) δ5.31 (s, 1H, C4-H), δ 7.23-7.36 (m, Ar-CH, 5H), δ 9.78 (s, 1H, -NH), δ10.29 (s, 1H, -NH), δ 12.11 (s, 2H, -NH) 13C-NMR: (500MHz, DMSO-d6): δ 194.66 (C=O), 173.98 (C=N), 126-144 (Ar C=C), 110.36 (C=C), 53.68 (C4), 30.31 (CO-CH3), 18.15 (C6-CH3) ESI-MS: m/z calcd for C13H16N4O; 244.29 found 246 [M+2]+ 1-[6-methyl-4-phenyl-2-(2-phenylhydrazinyl)-1,4-dihydropyrimidin-5-yl]ethenone (6b) Yield: 51%, Buff solid; mp- 117–118 ℃; Rf = 0.6 (Benzene: Ethyl acetate, 7:3); FTIR (KBr, Ʋmax/cm–1): 3356 (sec NH), 3196, 3100 (Ar CH), 3026 (Ali CH)1712 (C=O), 1634 (C=N), 1600, 1558, 1495, 1455 (Ar C=C), 1339 (C-N), 1190, 1143, 1110 (N-N) 1H-NMR: (500 MHz, DMSO-d6): δ 1.97 (s, 3H, C6-CH3), δ 2.07 (s, 3H, CO-CH3), δ5.30 (s, 1H, C4-H), δ 6.65-7.51 (m, Ar-CH, 10H), δ 8.93 (s, 1H, -NH), δ9.18 (s, 1H, -NH), δ 9.77 (s, 1H, -NH) 13C-NMR: (500 MHz, DMSO-d6): δ 194.23 (C=O), 173.11 (C=N), 124-142 (Ar C=C), 112.40, 111.15(C=C), 55.87 (C4), 16.97 (CO-CH3), 16.27 (C6-CH3) ESI-MS: m/z calcd for C19H20N4O; 320 found 324 [M+4]+ 2-(5-acetyl-6-methyl-4-phenyl-1,4-dihydropyrimidin-2-yl)hydrazinecarboxamide (6c) Yield: 88%, Light brown solid; mp- 190–192 ℃; Rf- 0.33 (Benzene: Ethyl acetate, 7:3); FTIR (KBr, Ʋmax/cm–1): 3400 (pri NH2), 3217 (sec NH), 3083 (Ar CH), 1715 (keto C=O), 1681 (Amide C=O), 1632 (C=N), 1602, 1575, 1492 (Ar C=C), 1383 (C-N), 1182, 1113 (N-N) 1H-NMR: (500 MHz, DMSO-d6): δ 2.11 (s, 3H, C6-CH3), δ 2.31 (s, 3H, CO-CH3) δ5.28-5.29 (s, 1H, C4-H), δ 6.78-7.72 (m, Ar-CH, 9H), δ 9.21 (s,1H,-NH), δ10.02 (s,1H,-NH), δ 9.81(s,1H, -NH), δ7.97(s,1H, -NH).13C-NMR: (500 MHz, DMSO-d6): δ 194.20 (C=O), δ 167.46 (C=N), δ 126.48-144.21 (Ar C=C), δ 109.71 (C=C), δ 55.87 (C4), δ 31.48 (CO-CH3), δ 18.97 (C6-CH3) ESI-MS: m/z calcd for C14H17N5O2 287.31 found 287 [M+] 1-[6-Methyl-4-(4-nitro-phenyl)-2-(N’-phenyl-hydrazino)-1,4-dihydro-pyrimidin-5-yl]-ethanone (6d) Yield: 92%, Red brown solid; mp- 121–122 ℃; Rf= 0.56 (Benzene: Ethyl acetate; 7:3); FTIR (KBr, Ʋmax/cm–1): 3397 (sec NH), 3108 (Ar CH), 3077 (Ali CH), 1708 (C=O), 1632 (C=N), 1599, 1559, 1455 (Ar C=C), 1345 (C-N), 1186, 1108 (N-N), 1520 (CNO2) 1H-NMR: (500 MHz, DMSO-d6): δ 1.98 (s, 3H, C6-CH3), δ 2.07 (s, 3H, CO-CH3), δ5.45 (s, 1H, C4-H), δ 6.67-7.96 (m, Ar-CH, 9H), δ 9.03 (s, 1H, -NH), δ9.39 (s, 1H, -NH), δ 9.81 (s, 1H, -NH), δ 9.91 (s, 1H, -NH) 13C-NMR: (500 MHz, DMSO-d6): δ 194.23 (C=O), 173.34 (C=N), 123.11-146.75 (Ar C=C), 112.50, 110.51(C=C), 55.34 (C4), 17.14 (CO-CH3), 11.83 (C6-CH3) ESI-MS: m/z calcd for C19H19N5O3; 365.5 found 363.15 [M-2]+ 2-[5-acetyl-4-(4-chlorophenyl)-6-methyl-1,4-dihydropyrimidin-2-yl]-N-(4-chlorophenyl)-hydrazinecarboxamide (6e) Yield: 89%, Yellow buff solid; mp- 156-157℃; Rf= 0.5 (Benzene: Ethyl acetate; 7:3); FTIR (KBr, Ʋmax/ cm-1): 3425, 3313 (pri NH2), 3215 (sec NH), 3000 (Ar CH), 1689 (keto C=O), 1653 (Amide C=O), 1611 (C=N), 1587, 1550, 1491 1455 (Ar C=C), 1357 (C-N), 1182, 1117 (N-N).1H-NMR: (500 MHz, DMSO-d6): δ 2.13 (s, 3H, C6-CH3), δ 2.19 (s, 3H, CO-CH3) δ 5.31 (s, 1H, C4-H), δ5.93 (s,1H -NH) δ 7.24-7.46 (m, Ar-CH, 9H), δ 8.69 (s,1H,-NH), δ 9.80 (s,1H,-NH), δ 10.36 (s,1H, -NH) 13C-NMR: (500 MHz, DMSO-d6): δ 194.57 (C=O), δ 174.15 (C=N), 155.78 (CO-NH) δ 124.44-144.82 (Ar C=C), δ 110.26 (C=C), δ 52.99 (C4), δ 30.41 (CO-CH3), δ 18.23 (C6-CH3) ESI-MS: m/z calcd for C20H19Cl2N5O2; 432.30 found 437.21 [M+4]+ 1982 NARKHEDE et al / Turk J Chem Results and Discussion In hitherto reported literature, these 5-acetyl 2-methylthio DHPM derivatives have been obtained by initial synthesis of the corresponding thione by classical Biginelli reaction, followed by its conversion to the S-methyl derivatives by using methyl iodide or dimethyl sulphate [3,16,22,24] (Scheme a) The Atwal approach uses 3-CR to generate S-methyl function at C2 position using S-methyl iso-thiourea with poor yield Also, this S-methyl iso-thiourea needs to be synthesized from thiourea and dimethyl sulphate, which increases one step for synthesis [25] (Scheme b) Another route involves use of the classical Biginelli reaction followed by addtion of POCl3 to generate 2-chloro group in DHPMs [26] which subsequently reacted with N/O/C- nucleophiles to generate scaffolds of DHPM compounds While various routes were studied, we envisioned that greening the process may be attempted in more than one aspect and, thus, scripted to run the reaction using a novel 4-component approach We first carried out the reaction with aryl aldehyde, acetyl acetone and thiourea to get the 5-acetyl DHPM-2-thione and treated it with Me2SO4 rather than methyl iodide (as a greener choice), followed by the classical approach, i.e Scheme a It worked well Further, the modification has been done by the Atwal approach using aryl aldehyde, acetyl acetone, and S-methyl iso-thiourea, i.e cheme b as a 3-component reaction to obtain 5-acetyl-2-methylthio DHPMs, but this showed poor yield as compared to Scheme a To continue work on DHPMs, a simpler and more elegant a novel 4-MCR method was developed for synthesizing 5-acetyl-2-methyl thio DHPMs in a single pot, single step synthesis using aryl aldehyde, acetyl acetone, thiourea, and Me2SO4 in good to excellent yield. It too worked well with comparable yields We then reasoned that designing a 4-component reaction could offer a much better protocol The reaction of aryl aldehydes 1a-e, acetylacetone (1,3-dicarbonyl compound) 2, thiourea and dimethyl sulphate was attempted in a one pot reaction to get 5a-e in a single step (Table 1, Novel 4-MCR approach) After adding dimethyl sulphate, vigorous reaction was noted, and the temperature of reaction increased up to 60–65 ℃ Once the vigorous reaction had ceased, ethanol was added to the reaction mixture, which was then stirred with reflux to complete the reaction To our delight, the paradigms gave an acceptable yield for 4-CR The structure was fully confirmed with analysis/ spectral data Repeating the protocol with other aldehydes confirmed the reliability of the reactions The general applicability of this 4-component reaction created our new series of 5-acetyl-2-methylthio DHPMs and further processed to replace S-methylthio group with N-nucleophiles viz hydrazine hydrate, phenyl hydrazine, semicarbazide and aryl semicarbazide offers C-2 functionalized novel DHPM-nucleophile molecular hybrids. Among the synthesized series of 5-acetyl-2-methythio DHPMs, selected compounds 5a, 5c, and 5d produced a series of newly designed target compounds 6a-e after treatment with various nucleophiles (Table 2) We have successfully synthesized hybrids of C2 functionalized O R1 CHO O + H3 C R1 O S CH3 + H2 N NH2 HCl, EtOH Re flux NH H3 C H3 C N H S R1 O DMS EtOH, Re flux H3 C H3 C N N H S Me Scheme 1a : Synthe s is of 5-a ce tyl-2-me thylthio DHPMs via Cla s s ica l Bigine lli reaction R1 NH R OOC H Me O + H2 N S CH3 R1 O EtOH, Re flux H3 C Scheme 1b: Synthe s is of 5-a ce tyl-2-me thylthio DHPMs via Atwa l approach H3 C N N H S Me Scheme Synthesis of 5-acetyl-2-methylthio DHPMs via earlier approaches 1983 NARKHEDE et al / Turk J Chem Table Synthesis of 5-acetyl-2-methylthio DHPMs via novel 4-MCR approach O R1 CHO O + H3C S 1a-e R1 O EtOH, NH2 + (CH3)2SO4 Reflux CH3 + H N H3C H3C N Entry Code R1 Time (h) Rf a % Yield SMe N H 5a-e mp ℃ 5a H 0.52 78 128–129 5b 2-OH, 3-OCH3 4.5 0.24 70 171–172 5c 4-NO2 0.50 87 192–193 5d 4-Cl 5.5 0.45 82 177–178 5e 3-OH 0.28 78 176–177 R1= -H, 2-OCH3 4-OH, 4-NO2, 4-Cl, 3-OH Solvent system: Benzene: Ethyl acetate (7:3); Visualizing agent: I2 vapors: yellow spots, / short UV 254 nm: purple spots a Table Synthesis of C2 functionalised DHPMs with N-nucleophiles R1 O -Nu- H3C H3C N N H (ii) R1 O H3C N H3C SMe 5a/ c/ d N H Nu a-e Entry Code R1 Nu- Time(h) Rf a %Yield mp ℃ 6a -H -NHNH2 2.5 0.56 81 152–153 6b -H -NHNHPh 0.6 51 117–118 6c -H -NHNH C(O)NH2 0.33 88 191–192 6d 4-NO2 -NHNHPh 4.5 0.56 92 121–122 10 6e 4-Cl NHNHC(O)NH (4-Cl)Ph 0.50 89 156–157 Solvent system: Benzene: Ethyl acetate (7:3); Visualizing agent: I2 vapors: Yellow spots, / Short UV 254 nm: purple spots, Nu-= -NHNH2; -NHNHPh; -NHNHC(O)NH2 -NHNHC(O)NH-(4-Cl) Ph a DHPMs with N-nucleophiles using the S-methylthio system as an intermediate compound These compounds were also fully characterized. By using this approach, assorted C2 functionalized DHPM libraries can be generated using N/O nucleophiles as well These experiments illustrate a greener approach to obtain C2 substituted-DHPM derivatives of versatile bioactivity Work on these lines is in progress in our labs. To propose an idea about the mechanism, several observations have been made which provide a clue to the probable pathway The reaction involves post modification of the Biginelli DHPMs using acetyl acetone, thiourea, aromatic aldehyde and dimethyl sulphate as a one-pot 4CR There are two plausible reaction mechanisms, the first one is, the initial formation 1984 NARKHEDE et al / Turk J Chem R S CH3 -H+ R H+ S CH3 -Nu- R Nu + H3 C SH Figure Proposed reaction mechanism of Biginelli thione, which subsequently reacts with dimethyl sulphate to offer 2-methylthio DHPMs The second possibility includes initial reaction of S-methylation of thiourea to give S-methyl iso-thiourea which itself participates in the Biginelli reaction By considering various observations, the reaction pathway can be proposed as followsWhen the Acetyl acetone, S-methyl iso-thiourea and aryl aldehyde are mixed, no exothermic reactions are observed When aromatic aldehyde, ethyl acetoacetate and thiourea were mixed with ethanol, reaction did not proceed When all four reactants, are mixed together, the exothermic reaction was noted, due to formation of S-methyl iso-thiourea, S-MITU (Confirmed with TLC) Due to rise in temperature, reaction gets initiated Exothermic reaction (60-65℃) was due to formation of S-MITU from thiourea and dimethyl sulphate The reaction is quite exothermic and needs to be controlled [27] Thus, an assumption can be obtained from the above observations, that the reaction follows the second route for the synthesis of 2-methylthio DHPMs i.e the S-MITU formation is the first step followed by the Biginelli with the established protocol [28] The next step is the step of the nucleophilic substitution reaction After addition of N-nucleophiles, to 5-acetyl 2-methylthio DHPM derivatives, a peculiar odour of methyl mercaptan, CH3SH (odour of rotten cabbage) was reported [29] This confirms the elimination of CH3SH This signifies the probable mechanism, i.e replacement of S-methyl function with nucleophile, Figure Improvements in % yield, time economy, step economy and mild reaction conditions, are the key features of the novel MCR The reported classical approaches to generate C2 functionalised DHPMs involve 3-4 step synthesis to reach final products along with use of toxic reagents like POCl3 and methyl iodide This novel 4-CR method is advantageous over the earlier reported methods in relation to number of steps, time, and avoiding use of nongreener agents such as POCl3 The method also uses dimethyl sulphate as a methylating agent, instead of the expensive, unstable compound methyl iodide, which most researchers used earlier [3,16,22,24,30] Thus, newly designed MCR also avoids the use of these toxic/ expensive reagents, which are some added benefits of this novel approach The 2-methylthio system in DHPMs has proven its scope as a versatile intermediate for generation of drug like molecules by reaction with N/O-nucleophiles [9,16] In this regard, we have reported use of 2-methylthio DHPMs reaction with N-nucleophiles which will be screened as an active pharmacological motif A preliminary investigation is under way at NCI, USA for anticancer screening In comparison, we used a greener and more economical reaction protocol for synthesis of C-2 functionalised DHPM libraries. All the compounds were screened for FT-IR analysis, and the presence of functional groups was confirmed Prototype structures of compounds from 2-methylthio DHPMs series, viz compounds 5a, 5b and C-2 functionalised DHPMs 6a-e were confirmed through 1H NMR, 13C NMR, and mass spectroscopy. The analysis of spectroscopic data confirms the structures of newly syntheiszed molecules [Refer Supplementary information Figure: 1S-21S] The synthesized substrate (C-2 functionalized DHPM i.e 2-methylthio dihydropyrimidine) has diverse scope for generation of libraries The synthesis of novel 5-acetyl 2-methylthio DHPM derivatives were reported for the first time via a novel four component modified Biginelli reaction Modified novel reaction was also compared with earlier reported classical Biginelli and Atwal modified reaction In comparison to earlier reported reaction protocols, novel method allows one pot, single step for generation of intermediate, i.e 5-acetyl 2-methylthio dihydropyrimidine Thus, novel method demonstrates more benefits over earlier reported reaction protocols Discussion In continuation of our interest in DHPM derivatives, herein we report an efficient and novel method for the synthesis of 5-acetyl 2-methylthio DHPMs The method allows more efficient, time-saving, one pot and single step reaction with moderate to excellent yield The importance of 2-methylthio function in DHPMs was emphasized because it serves as a good leaving group and can react with N/O-nucleophiles This led to the synthesis of C2-functionalsed DHPMs with use of selected N-nucleophiles, and the conjugates formed may fulfil the demand of active pharmacophores Use of one pot 4-MCR increases efficiency of synthesis, and incorporation of N-nucleophiles introduces diverse complexity in the DHPM nucleus, which will be the potential future targets (drug discovery pipeline) for development of APIs Acknowledgement We acknowledge SAIF, Punjab, Chandigarh, India for spectral determinations 1985 NARKHEDE et al / Turk J Chem References Zarganes-Tzitzikas T, Dömling A Modern multicomponent reactions for better drug syntheses Organic Chemistry Frontiers 2014; 1: 834–837 doi: 10.1039/c4qo00088a Herrera RP, Marqués-López E Multicomponent Reactions: Concepts and Applications for Design and 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Nevagi R, Narkhede H Novel dihydropyrimidine derivatives as antibacterial agents Der Pharma Chemica 2014; 6: 135–139 19 Mostafa A, Selim K Synthesis and anticancer activity of new dihydropyrimidinone derivatives European Journal of Medicinal Chemistry 2018; 156: 304–315 doi: 10.1016/j.ejmech.2018.07.004 20 Li Y, Tan T, Zhao Y, Wei Y, Wang D et al Anticancer polymers via the Biginelli reaction ACS Macro Letters 2020; : 1249–1254 doi: 10.1021/acsmacrolett.0c00496 21 Huseynzada A, Jelch C, Akhundzada H, Soudani S, Ben C et al Synthesis, crystal structure and antibacterial studies of dihydropyrimidines and their regioselectively oxidized products RSC Advances 2021; 11: 6312–6329 doi: 10.1039/D0RA10255E 22 Sawant R, Sarode V Synthesis, spectral characterization and analgesic activity of 2-methylthio-1,4-dihydropyrimidines Iranian Journal of Pharmaceutical Research 2011; 10: 733–739 doi: 10.22037/ijpr.2011.1022 23 Singh B, Mishra M, Saxena N, Yadav G, Maulik P Synthesis of 2-sulfanyl-6-methyl-1 , 4-dihydropyrimidines as a new class of antifilarial agents European Journal of Medicinal Chemistry 2008; 43: 2717–2723 doi: 10.1016/j.ejmech.2008.01.038 24 Kaur H, Machado M, Kock C, Smith P, Chibale K Primaquine-pyrimidine hybrids: Synthesis and dual-stage antiplasmodial activity European Journal of Medicinal Chemistry 2015; 101: 266–273 doi: 10.1016/j.ejmech.2015.06.045 1986 NARKHEDE et al / Turk J Chem 25 Atwal K, Rovnyak G, Schwartz J, Moreland S, Hedberg A et al Dihydropyrimidine calcium channel blockers: 2-Heterosubstituted 4-Aryl1,4-dihydro-6-methyl-5-pyrimidinecarboxylic acid esters as potent mimics of dihydropyridines Journal of Medicinal Chemistry 1990; 33: 1510–1515 26 Singh K, Singh K, Wan B, Franzblau S, Chibale K Facile transformation of Biginelli pyrimidin-2(1H)-ones to pyrimidines In vitro evaluation as inhibitors of Mycobacterium tuberculosis and modulators of cytostatic activity European Journal of Medicinal Chemistry 2011; 46: 2290–2294 doi: 10.1016/j.ejmech.2011.03.010 27 Shildneck W Organic Synthesis, Collective Volume -II, John Wiley & Sons, 1943 28 Li JJ Biginelli reaction In: Name Reactions Springer International Publishing, Cham, 2021 doi: 10.1007/978-3-030-50865-4 29 Merck Index, An Encyclopedia of Chemicals, drugs and biologicals (2006) 5956 30 Dallinger D, Kappe C Creating chemical diversity space by scaffold decoration of dihydropyrimidines Pure and Applied Chemistry 2005; 77: 155–161 doi: 10.1351/pac200577010155 1987 Supplementary Information: Article Category: Research paper Title: A four-component modified Biginelli reaction: A novel approach for C-2 functionalized dihydropyrimidines Author(s): Harsha I Narkhede*, Avinash S Dhake, Balasubramaniyan V Department of Pharmaceutical chemistry, S.M.B.T College of Pharmacy, Dhamangaon, Nashik, M.S India422403 Prototype intermediate compounds and all final compounds are characterized by FT-IR, 1HNMR, 13C NMR and mass spectrometry Presence of absorption band in the range at 16961720 cm-1 reveals the presence of keto carbonyl in the structure Ureide N-H band was located at 3290-3278 cm-1 and C=N is confirmed by presence of absorption band at 1607-1636 cm-1 in all 5a-e and 6a-e Presence of N-N bond in 6a-e is confirmed by presence of strong absorption band at 1105-1120 cm-1 whereas absorption band at 3400-3500 cm-1 confirms the presence of primary amine in compound 6a and 6e Absorption band at 1653-1681 cm-1 shows presence of amide carbonyl in compounds 6c and 6e In 1H NMR spectra, two singlet δ 1.97-2.15ppm, δ 2.20-2.35ppm designates the methyl proton at C-6 and acetyl proton at C-5 position respectively Similarly, a singlet at δ 5.5.20-5.31 ppm is attributed to the C-4 proton of DHPM ring Appearance of singlet due to S-Methyl at δ 2.25 ppm in all series compounds, disappearance of S-methyl and appearance of extra -NH singlet in compounds 6a-e represents displacement of S-methyl by N-nucleophiles Presence of three -NH peaks at δ 9.78, 10.29, 12.11 ppm in 6a represents two -NH proton and -NH2 proton peaks respectively Also, singlet at δ 8.93, 9.18 and 9.77 ppm represent three -NH peaks in 6b and 6d For compounds substituted with thiosemicarbazide as a nucleophile 6c showed three -NH peaks at δ 7.97, 9.21, 9.81 ppm and -NH2 peak at δ10.02 ppm In all compounds, a multiplet at δ 6.57-7.72 ppm reveals identity of aromatic protons In 13C NMR, δ 18.5, 30.31, 55-58, 110, 125-150, 173 and 194 ppm show presence of C6-CH3, keto-CH3, C4-carbon, C=C, Ar C=C, C=N and C=O respectively Presence of S-methyl is confirmed by presence of δ 52-53 ppm in compound 5a and 5b Absence S-methyl group in series of compounds 6a-e confirms the displacement of Smethyl with N-nucleophiles Molecular ion peaks, base peaks and further fragments of Mass analysis shows structural resemblance with molecular weight of compounds Figure 1S: 1-(6-Methyl-2-methylsulfanyl-4-phenyl-1,4-dihydro-pyrimidin-5-yl)-ethanone, (5a) H-NMR: (novel MCR approach) -0.0001 3.4009 2.5725 2.5095 2.5061 2.5026 2.4437 2.3914 2.3427 2.2576 2.2521 2.1611 5.3146 5.3069 7.6997 7.4620 7.4026 7.3945 7.3886 7.3632 7.3602 7.3487 7.3335 7.3134 7.2869 7.2846 7.2723 7.2682 7.2527 7.2501 7.2360 9.7743 9.7704 10.2975 15A1 1H_8scan DMSO {D:\Spectra} nmr BRUKER AVANCE NEO 500 MHz NMR SPECTROMETER SAIF, P.U CHANDIGARH Current Data Parameters NAME Jun29-2020 EXPNO 90 PROCNO F2 - Acquisition Parameters Date_ 20200629 Time 13.18 h INSTRUM Avance Neo 500 PROBHD Z119470_0333 ( PULPROG zg30 TD 65536 SOLVENT DMSO NS 16 DS SWH 14705.883 Hz FIDRES 0.448788 Hz AQ 2.2282240 sec RG 44.0334 DW 34.000 usec DE 6.79 usec TE 296.2 K D1 1.00000000 sec TD0 SFO1 500.1730885 MHz NUC1 1H P0 3.33 usec P1 10.00 usec PLW1 22.02300072 W 11 10 0.99 3.16 1.44 3.13 1.00 1.22 2.46 1.84 2.59 0.94 0.89 F2 - Processing parameters SI 65536 SF 500.1700011 MHz WDW EM SSB LB 0.30 Hz GB PC 1.00 ppm Figure 2S: 13C-NMR:1-(6-Methyl-2-methylsulfanyl-4-phenyl-1,4-dihydro-pyrimidin-5-yl)-ethanone (5a) BRUKER AVANCE NEO 500 MHz NMR SPECTROMETER SAIF, PANJAB UNIVERSITY, CHANDIGARH 53.68 52.77 39.89 39.72 39.55 39.39 39.22 39.05 38.89 31.32 30.35 30.31 26.19 18.15 173.98 167.21 144.46 142.80 142.31 139.71 132.86 132.75 130.63 130.44 129.55 129.15 129.00 128.93 128.85 128.77 128.66 128.52 128.45 128.25 127.98 127.59 126.77 126.71 126.45 110.36 197.56 194.67 205.22 15A1 C13CPD DMSO {D:\Spectra} nmr Current Data Parameters NAME Jun29-2020 EXPNO 91 PROCNO F2 - Acquisition Parameters Date_ 20200629 Time 14.09 h INSTRUM Avance Neo 500 PROBHD Z119470_0333 ( PULPROG zgpg30 TD 65536 SOLVENT DMSO NS 1024 DS SWH 37037.035 Hz FIDRES 1.130281 Hz AQ 0.8847360 sec RG 101 DW 13.500 usec DE 6.50 usec TE 297.0 K D1 2.00000000 sec D11 0.03000000 sec TD0 SFO1 125.7804233 MHz NUC1 13C P0 3.33 usec P1 10.00 usec PLW1 79.56099701 W SFO2 500.1720007 MHz NUC2 1H CPDPRG[2 waltz65 PCPD2 80.00 usec PLW2 22.02300072 W PLW12 0.34411001 W PLW13 0.17308000 W F2 - Processing parameters SI 32768 SF 125.7679200 MHz WDW EM SSB LB 1.00 Hz GB PC 1.40 220 200 180 160 140 120 100 80 60 40 20 ppm Figure 3S: ESI-MS: 1-(6-Methyl-2-methylsulfanyl-4-phenyl-1,4-dihydro-pyrimidin-5-yl)-ethanone (5a) WATERS,Q-TOF MICROMASS (ESI-MS) SAIF/CIL,PANJAB UNIVERSITY,CHANDIGARH HARSHA 15A (0.160) Cm (2:15-26:78) TOF MS ES+ 2.61e3 201.5355 2614 100 264.7302 2227 264.8729 1935 201.5977 1959 279.7525 1875 279.9073 1670 446.9582 1600 % 202.6159 1485 202.6783 1239 374.1213 1172 374.3663 1105 183.3069 1034 359.2700 876 448.0300 670 203.2752 453 138.3097 222 82.5332 176 60 80 100 120 254.1372 245.5970 247 241 172.6421 169 113.7051 102 140 160 180 393.5529 532 280.8129 314.2366 339.8882 449 450 441 200 220 240 260 394.5296 199 280 300 320 340 360 380 400 442.7452 266 420 462.2481 373 481.5189 306 482.5993 110 440 460 480 500 m/z Figure 4S: ESI-MS: 1-(6-Methyl-2-methylsulfanyl-4-phenyl-1,4-dihydro-pyrimidin-5-yl)-ethanone (5a) WATERS,Q-TOF MICROMASS (ESI-MS) HARSHA 15A (0.160) Cm (2:15-26:78) 100 SAIF/CIL,PANJAB UNIVERSITY,CHANDIGARH TOF MS ES+ 2.61e3 201.5355 2614 264.7302 2227 201.5977 1959 264.8729 1935 201.6116 1883 202.6159 1485 % 202.6783 1239 183.3069 1034 183.3596 954 183.4454 834 183.9407 302 180 185 265.9126 419 203.7270 238 184.4432;166 203.2752 453 191.8810 392 190 192.4957 115 195 200 205 210 215 220 254.1372 247 245.5970 241 219.8975 136 267.0419 99 247.7088 163 225 230 235 240 245 250 255 260 265 270 m/z Figure 5S: 1H-NMR:1-[4-(4-hydroxy-3-methoxyphenyl)-6-methyl-2-(methylsulfanyl)-1,4-dihydropyrimidin -5yl]ethenone, (5b) -0.0001 2.5089 2.5054 2.5018 2.3200 2.1123 3.3970 3.7421 5.2111 5.2036 6.8552 6.8511 6.8401 6.7323 6.7161 6.5942 6.5902 6.5779 6.5739 9.0312 8.7870 9.7750 9.6593 9.6558 10.2018 15D 1H_8scan DMSO {D:\Spectra} nmr 10 BRUKER AVANCE NEO 500 MHz NMR SPECTROMETER SAIF, P.U CHANDIGARH Current Data Parameters NAME Jun29-2020 EXPNO 100 PROCNO F2 - Acquisition Parameters Date_ 20200629 Time 14.13 h INSTRUM Avance Neo 500 PROBHD Z119470_0333 ( PULPROG zg30 TD 65536 SOLVENT DMSO NS 16 DS SWH 14705.883 Hz FIDRES 0.448788 Hz AQ 2.2282240 sec RG 72.6482 DW 34.000 usec DE 6.79 usec TE 296.2 K D1 1.00000000 sec TD0 SFO1 500.1730885 MHz NUC1 1H P0 3.33 usec P1 10.00 usec PLW1 22.02300072 W 11 10 3.06 3.11 3.11 1.00 1.20 1.08 1.22 0.78 0.45 1.10 1.04 1.02 F2 - Processing parameters SI 65536 SF 500.1700014 MHz WDW EM SSB LB 0.30 Hz GB PC 1.00 ppm Figure 6S: 13C-NMR : (5b) BRUKER AVANCE NEO 500 MHz NMR SPECTROMETER SAIF, PANJAB UNIVERSITY, CHANDIGARH 18.00 55.48 53.62 39.89 39.72 39.55 39.39 39.22 39.05 38.89 30.03 118.64 115.28 111.18 110.02 133.72 147.40 146.14 144.00 173.59 194.98 15D C13CPD DMSO {D:\Spectra} nmr 10 Current Data Parameters NAME Jun29-2020 EXPNO 101 PROCNO F2 - Acquisition Parameters Date_ 20200630 Time 10.16 h INSTRUM Avance Neo 500 PROBHD Z119470_0333 ( PULPROG zgpg30 TD 65536 SOLVENT DMSO NS 433 DS SWH 37037.035 Hz FIDRES 1.130281 Hz AQ 0.8847360 sec RG 101 DW 13.500 usec DE 6.50 usec TE 297.9 K D1 2.00000000 sec D11 0.03000000 sec TD0 SFO1 125.7804233 MHz NUC1 13C P0 3.33 usec P1 10.00 usec PLW1 79.56099701 W SFO2 500.1720007 MHz NUC2 1H CPDPRG[2 waltz65 PCPD2 80.00 usec PLW2 22.02300072 W PLW12 0.34411001 W PLW13 0.17308000 W F2 - Processing parameters SI 32768 SF 125.7679190 MHz WDW EM SSB LB 1.00 Hz GB PC 1.40 220 200 180 160 140 120 100 80 60 40 20 ppm Figure 7S: H-NMR:1-(2-hydrazinyl-6-methyl-4-phenyl-1,4-dihydropyrimidin-5-yl) ethenone, (6a) BRUKER AVANCE NEO 500 MHz NMR SPECTROMETER SAIF, P.U CHANDIGARH -0.0000 2.5004 2.3439 2.1593 3.3957 5.3168 7.3611 7.3465 7.3315 7.3050 7.2845 7.2700 7.2549 7.2399 9.7865 10.2987 12.1184 17A 1H_8scan DMSO {D:\Spectra} nmr 11 Current Data Parameters NAME Jun29-2020 EXPNO 110 PROCNO F2 - Acquisition Parameters Date_ 20200629 Time 14.16 h INSTRUM Avance Neo 500 PROBHD Z119470_0333 ( PULPROG zg30 TD 65536 SOLVENT DMSO NS 16 DS SWH 14705.883 Hz FIDRES 0.448788 Hz AQ 2.2282240 sec RG 33.0999 DW 34.000 usec DE 6.79 usec TE 296.2 K D1 1.00000000 sec TD0 SFO1 500.1730885 MHz NUC1 1H P0 3.33 usec P1 10.00 usec PLW1 22.02300072 W 13 12 11 10 3.21 3.30 1.00 2.47 1.25 2.66 1.01 0.71 0.78 F2 - Processing parameters SI 65536 SF 500.1700040 MHz WDW EM SSB LB 0.30 Hz GB PC 1.00 ppm Figure 8S: 13C-NMR: 1-(2-hydrazinyl-6-methyl-4-phenyl-1,4-dihydropyrimidin-5-yl) ethenone, (6a) BRUKER AVANCE NEO 500 MHz NMR SPECTROMETER SAIF, PANJAB UNIVERSITY, CHANDIGARH 18.15 39.71 39.54 39.38 39.21 39.04 30.31 53.68 110.36 128.52 128.16 127.58 126.45 144.45 142.80 173.98 194.66 17A C13CPD DMSO {D:\Spectra} nmr 11 Current Data Parameters NAME Jun29-2020 EXPNO 111 PROCNO F2 - Acquisition Parameters Date_ 20200629 Time 14.42 h INSTRUM Avance Neo 500 PROBHD Z119470_0333 ( PULPROG zgpg30 TD 65536 SOLVENT DMSO NS 527 DS SWH 37037.035 Hz FIDRES 1.130281 Hz AQ 0.8847360 sec RG 101 DW 13.500 usec DE 6.50 usec TE 297.5 K D1 2.00000000 sec D11 0.03000000 sec TD0 SFO1 125.7804233 MHz NUC1 13C P0 3.33 usec P1 10.00 usec PLW1 79.56099701 W SFO2 500.1720007 MHz NUC2 1H CPDPRG[2 waltz65 PCPD2 80.00 usec PLW2 22.02300072 W PLW12 0.34411001 W PLW13 0.17308000 W F2 - Processing parameters SI 32768 SF 125.7679215 MHz WDW EM SSB LB 1.00 Hz GB PC 1.40 220 200 180 160 140 120 100 80 60 40 20 ppm Figure 9S: ESI-MS: 1-(2-hydrazinyl-6-methyl-4-phenyl-1,4-dihydropyrimidin-5-yl) ethenone, (6a) WATERS,Q-TOF MICROMASS (ESI-MS) SAIF/CIL,PANJAB UNIVERSITY,CHANDIGARH HARSHA 17A (0.159) Cm (2:15-23:82) TOF MS ES+ 1.22e3 264.7461 1221 100 264.7778 1148 201.5632 1033 201.5770 1003 264.9680 907 201.6323 902 % 198.3253 812 159.6697 445 159.7867 401 202.2000 344 183.4190 297 374.0648 306.8193 267 202.6159 236 265.4679 197 314.2280 191 362.6855 168 196 249.9605 292.8671 137 126 347.4203 246.6518;94 99 160.2612 165 82.5243 83 60 80 154.4614 64 100 120 140 160 374.1402 305 202.2347 313 180 200 220 240 260 280 300 320 340 360 442.8170 268 443.1144 201 395.7983 209 443.9968 134 397.7878 129 492.3229 504.9095 112 90 425.5803;93 380 400 420 440 460 480 500 m/z Figure 10S: H-NMR: 1-[6-methyl-4-phenyl-2-(2-phenylhydrazinyl)-1,4-dihydropyrimidin-5-yl]ethenone (6b) 9.7755 9.1878 8.9393 7.5156 7.4994 7.4850 7.4786 7.4607 7.4459 7.4122 7.3989 7.3892 7.3803 7.3644 7.3488 7.3408 7.3255 7.3109 7.2969 7.2832 7.2692 7.2479 7.2337 7.2196 7.2058 7.1837 7.1723 7.1571 7.1410 7.1257 7.1096 7.0943 7.0837 7.0665 6.9493 6.9339 6.6851 6.6706 6.6560 5.3082 5.3014 3.3466 2.5043 2.5011 2.4979 2.0789 1.9781 -0.0001 17B 1H_8scan DMSO {D:\Spectra} nmr 12 BRUKER AVANCE NEO 500 MHz NMR SPECTROMETER SAIF, P.U CHANDIGARH Current Data Parameters NAME Jun29-2020 EXPNO 120 PROCNO F2 - Acquisition Parameters Date_ 20200629 Time 15.46 h INSTRUM Avance Neo 500 PROBHD Z119470_0333 ( PULPROG zg30 TD 65536 SOLVENT DMSO NS 16 DS SWH 14705.883 Hz FIDRES 0.448788 Hz AQ 2.2282240 sec RG 95.7854 DW 34.000 usec DE 6.79 usec TE 297.6 K D1 1.00000000 sec TD0 SFO1 500.1730885 MHz NUC1 1H P0 3.33 usec P1 10.00 usec PLW1 22.02300072 W 13 12 11 10 3.14 3.02 1.10 1.38 2.33 2.87 2.35 2.08 2.32 2.56 1.21 1.00 1.01 1.04 F2 - Processing parameters SI 65536 SF 500.1700035 MHz WDW EM SSB LB 0.30 Hz GB PC 1.00 ppm Figure 11S: 13C-NMR: 1-[6-methyl-4-phenyl-2-(2-phenylhydrazinyl)-1,4-dihydropyrimidin-5-yl]ethenone (6b) BRUKER AVANCE NEO 500 MHz NMR SPECTROMETER SAIF, PANJAB UNIVERSITY, CHANDIGARH 16.97 16.60 39.91 39.74 39.58 39.41 39.24 39.08 55.87 145.88 143.40 140.13 130.67 128.97 128.63 128.53 128.25 127.16 126.61 126.45 126.11 125.50 124.37 118.42 112.40 111.15 173.11 17B C13CPD DMSO {D:\Spectra} nmr 12 Current Data Parameters NAME Jun29-2020 EXPNO 121 PROCNO F2 - Acquisition Parameters Date_ 20200629 Time 15.35 h INSTRUM Avance Neo 500 PROBHD Z119470_0333 ( PULPROG zgpg30 TD 65536 SOLVENT DMSO NS 1024 DS SWH 37037.035 Hz FIDRES 1.130281 Hz AQ 0.8847360 sec RG 101 DW 13.500 usec DE 6.50 usec TE 297.9 K D1 2.00000000 sec D11 0.03000000 sec TD0 SFO1 125.7804233 MHz NUC1 13C P0 3.33 usec P1 10.00 usec PLW1 79.56099701 W SFO2 500.1720007 MHz NUC2 1H CPDPRG[2 waltz65 PCPD2 80.00 usec PLW2 22.02300072 W PLW12 0.34411001 W PLW13 0.17308000 W F2 - Processing parameters SI 32768 SF 125.7679203 MHz WDW EM SSB LB 1.00 Hz GB PC 1.40 220 200 180 160 140 120 100 80 60 40 20 ppm Figure 12S: ESI-MS: 1-[6-methyl-4-phenyl-2-(2-phenylhydrazinyl)-1,4-dihydropyrimidin-5-yl]ethenone (6b) WATERS,Q-TOF MICROMASS (ESI-MS) SAIF/CIL,PANJAB UNIVERSITY,CHANDIGARH HARSHA 17B (0.132) Cm (3:12-16:29) TOF MS ES+ 3.68e3 279.7851 3683 100 279.9563 2618 361.2396 2625 % 361.3507 2340 280.8374 1209 362.3145 1145 281.0251 1064 324.8347 730 185.5764 383 159.7435 214 60 80 100 120 140 160 200 220 240 363.4467 352 264.9046 121 260 280 442.9400 600 393.6495 532 314.2366 339 202.6298 228.3504 195 161 180 344.3126 791 423.7531 262 443.9147 255 444.8389;132 300 320 340 360 380 400 420 440 460 480 500 m/z Figure 13S : 2-(5-acetyl-6-methyl-4-phenyl-1,4-dihydropyrimidin-2-yl)hydrazinecarboxamide (6c) H-NMR: BRUKER AVANCE NEO 500 MHz NMR SPECTROMETER SAIF, P.U CHANDIGARH -0.0001 2.5251 2.5216 2.5182 2.3114 2.1199 10.0246 9.2153 7.9758 7.9617 7.9590 7.9335 7.9196 7.9169 7.8858 7.8626 7.7222 7.7075 7.7021 7.6744 7.6420 7.6274 7.6141 7.5991 7.5862 7.5711 7.5262 7.5105 7.4953 7.4656 7.3959 7.3523 7.3489 7.3371 7.3224 7.2975 7.2783 7.2730 7.2636 7.2567 7.2423 7.1415 7.0829 6.8324 6.7997 6.7811 5.2943 5.2874 3.7212 HIN-6 1H_8scan DMSO {D:\Spectra} nmr 52 Current Data Parameters NAME Jan26-2021 EXPNO 520 PROCNO F2 - Acquisition Parameters Date_ 20210127 Time 9.43 h INSTRUM Avance Neo 500 PROBHD Z119470_0333 ( PULPROG zg30 TD 65536 SOLVENT DMSO NS DS SWH 14705.883 Hz FIDRES 0.448788 Hz AQ 2.2282240 sec RG 23.9816 DW 34.000 usec DE 6.79 usec TE 295.5 K D1 1.00000000 sec TD0 SFO1 500.1730885 MHz NUC1 1H P0 3.33 usec P1 10.00 usec PLW1 20.93000031 W 11 10 4.14 3.26 1.00 1.13 0.81 2.40 2.74 6.83 9.41 F2 - Processing parameters SI 65536 SF 500.1699934 MHz WDW EM SSB LB 0.30 Hz GB PC 1.00 ppm Figure 14S: 13 C-NMR: 2-(5-acetyl-6-methyl-4-phenyl-1,4-dihydropyrimidin-2-yl)hydrazinecarboxamide (6c) BRUKER AVANCE NEO 500 MHz NMR SPECTROMETER SAIF, PANJAB UNIVERSITY, CHANDIGARH 18.97 39.59 39.42 39.26 31.48 30.35 53.87 152.23 148.25 144.21 132.95 130.78 129.55 129.32 129.22 128.64 128.60 127.45 126.61 126.48 109.71 167.46 HIN-6 C13CPD DMSO {D:\Spectra} nmr 52 Current Data Parameters NAME Jan26-2021 EXPNO 521 PROCNO F2 - Acquisition Parameters Date_ 20210127 Time 10.43 h INSTRUM Avance Neo 500 PROBHD Z119470_0333 ( PULPROG zgpg30 TD 65536 SOLVENT DMSO NS 512 DS SWH 37037.035 Hz FIDRES 1.130281 Hz AQ 0.8847360 sec RG 101 DW 13.500 usec DE 6.50 usec TE 300.2 K D1 2.00000000 sec D11 0.03000000 sec TD0 SFO1 125.7804233 MHz NUC1 13C P0 3.33 usec P1 10.00 usec PLW1 83.14099884 W SFO2 500.1720007 MHz NUC2 1H CPDPRG[2 waltz65 PCPD2 80.00 usec PLW2 20.93000031 W PLW12 0.32703000 W PLW13 0.16449000 W F2 - Processing parameters SI 32768 SF 125.7678973 MHz WDW EM SSB LB 1.00 Hz GB PC 1.40 200 180 160 140 120 100 80 60 40 20 ppm Figure 15S: ESI-MS: 2-(5-acetyl-6-methyl-4-phenyl-1,4-dihydropyrimidin-2-yl)hydrazinecarboxamide (6c) SAIF,PANJAB UNIVERSITY ,CHANDIGARH SYNAPT-XS#DBA064 04-Feb-2021 16:01:19 HARSHA HIN-6 (0.138) Cm (5:7-(10:16+3)) 1: TOF MS ES+ 1.81e5 188.1174 181424 100 % 185.1194 131431 231.1263 50086 215.1355 38101 188.6585 28320 207.1048 21016 171.0903 18786 106.0720 3390 100 105 110 115 144.0493 2190 131.0074 1790 117.0325 1064 120 125 130 135 140 145 153.0637 4692 150 155.5573 7165 155 163.5435 3884 160 165 189.1183 12662 177.6123 9437 175 180 185 190 195 217.1154 15996 221.6331 4968 211.0854 893 200 205 210 215 220 299.0941 21359 299.1596 18338 287.1124 17472 229.1087 8223 207.6099 7146 189.1603 6321 177.0278 1026 170 199.1454 14255 225 230 232.1287 4746 235 243.1084 3506 240 245 252.1308 256.1219 4118 4707 250 255 268.1202 6070 276.1545 6504 281.0672 6596 289.1240 4741 299.6612 8713 259.1138 3027 260 265 270 275 280 285 290 295 300 305 m/z Figure 16S: H-NMR: 1-[6-Methyl-4-(4-nitro-phenyl)-2-(N'-phenyl-hydrazino)-1,4-dihydro-pyrimidin-5-yl]-ethanone (6d) 9.8134 9.0384 8.2693 8.2523 8.2352 8.2215 7.9602 7.8941 7.8765 7.8267 7.8088 7.6935 7.6781 7.6001 7.5848 7.5712 7.5538 7.5331 7.5177 7.5045 7.4952 7.4863 7.4779 7.4697 7.4674 7.4545 7.4416 7.4261 7.4118 7.3910 7.3673 7.3015 7.2940 7.2862 7.2795 7.2701 7.2630 7.1822 7.1667 7.1185 7.1027 7.0871 6.8987 6.8831 6.6743 5.4644 5.4572 3.4208 2.9903 2.5566 2.5207 2.5177 2.2788 2.2341 2.1831 2.1419 2.1269 2.0703 2.0563 2.0483 2.0154 1.9846 1.9825 1.8782 -0.0001 HIN-5 1H_8scan DMSO {D:\Spectra} nmr 51 BRUKER AVANCE NEO 500 MHz NMR SPECTROMETER SAIF, P.U CHANDIGARH Current Data Parameters NAME Jan26-2021 EXPNO 510 PROCNO F2 - Acquisition Parameters Date_ 20210127 Time 9.41 h INSTRUM Avance Neo 500 PROBHD Z119470_0333 ( PULPROG zg30 TD 65536 SOLVENT DMSO NS DS SWH 14705.883 Hz FIDRES 0.448788 Hz AQ 2.2282240 sec RG 32.4379 DW 34.000 usec DE 6.79 usec TE 295.4 K D1 1.00000000 sec TD0 SFO1 500.1730885 MHz NUC1 1H P0 3.33 usec P1 10.00 usec PLW1 20.93000031 W 11 10 2.88 1.41 1.41 0.84 1.10 0.25 1.58 0.62 0.80 0.91 1.32 2.46 1.11 0.91 1.00 1.04 0.24 0.23 0.19 0.13 F2 - Processing parameters SI 65536 SF 500.1699952 MHz WDW EM SSB LB 0.30 Hz GB PC 1.00 ppm Figure 17S: 13 C-NMR: (6d) HIN-5 C13CPD DMSO {D:\Spectra} nmr 51 173.34 150.61 146.75 146.63 146.05 146.00 145.93 145.78 144.83 144.64 144.37 142.55 139.99 139.31 139.01 133.55 133.43 131.78 129.16 129.13 129.04 128.93 128.67 128.23 127.92 127.44 127.32 126.85 126.00 125.93 124.62 124.52 124.46 124.36 124.21 123.98 123.86 123.67 123.43 123.29 123.11 120.28 119.86 118.57 113.62 112.78 112.50 112.43 110.51 110.32 55.70 55.34 40.36 39.95 39.78 39.70 39.61 39.54 39.45 39.28 39.11 38.95 17.14 16.71 12.57 11.83 BRUKER AVANCE NEO 500 MHz NMR SPECTROMETER SAIF, PANJAB UNIVERSITY, CHANDIGARH Current Data Parameters NAME Jan26-2021 EXPNO 511 PROCNO F2 - Acquisition Parameters Date_ 20210127 Time 10.16 h INSTRUM Avance Neo 500 PROBHD Z119470_0333 ( PULPROG zgpg30 TD 65536 SOLVENT DMSO NS 512 DS SWH 37037.035 Hz FIDRES 1.130281 Hz AQ 0.8847360 sec RG 101 DW 13.500 usec DE 6.50 usec TE 300.2 K D1 2.00000000 sec D11 0.03000000 sec TD0 SFO1 125.7804233 MHz NUC1 13C P0 3.33 usec P1 10.00 usec PLW1 83.14099884 W SFO2 500.1720007 MHz NUC2 1H CPDPRG[2 waltz65 PCPD2 80.00 usec PLW2 20.93000031 W PLW12 0.32703000 W PLW13 0.16449000 W F2 - Processing parameters SI 32768 SF 125.7679148 MHz WDW EM SSB LB 1.00 Hz GB PC 1.40 200 180 160 140 120 100 80 60 40 20 ppm Figure 18S: ESI-MS: (6d) SAIF,PANJAB UNIVERSITY ,CHANDIGARH SYNAPT-XS#DBA064 04-Feb-2021 15:58:34 HARSHA HIN-5 (0.138) Cm (5:6-11:14) 1: TOF MS ES+ 4.53e6 301.1567 4532181 % 100 412.1978 1163780 302.1600 922501 306.1396 824732 382.1529 568504 149.0318 354398 100 121.0343 4394 110 120 136.0393 4973 130 140 150.0359 15179 150 160 173.1169 129909 179.5804 7022 170 180 190 229.1535 242.1054 205.0972 105268 217.1168 75744 58208 22583 200 210 220 230 240 250 261.0575 52268 260 280 338.3591 182659 324.1512 172545 281.0660 20177 270 290 300 310 320 456.2375 417287 413.2010 284611 307.1449 254505 330 340 383.1554 87398 363.1302 355.0885 47741 48088 350 360 370 380 390 411.1158 14041 400 410 426.2148 55274 420 437.2162 154325 445.1438 5952 430 440 450 457.2410 79590 460 470 485.1365 42218 480 490 503.1330 13514 500 510 519.1662 24529 m/z 10 Figure 19S: H-NMR: 2-[5-acetyl-4-(4-chlorophenyl)-6-methyl-1,4-dihydropyrimidin-2-yl]-N-(4-chlorophenyl)-hydrazine- carboxamide (6e) BRUKER AVANCE NEO 500 MHz NMR SPECTROMETER SAIF, P.U CHANDIGARH -0.0001 3.4471 3.4093 2.5560 2.5206 2.5171 2.5136 2.4490 2.3773 2.3559 2.3086 2.2998 2.2642 2.2104 2.1906 2.1564 2.1394 1.1355 5.3178 5.3100 8.6904 7.4604 7.4542 7.4502 7.4405 7.4364 7.4330 7.4194 7.4157 7.4108 7.2740 7.2679 7.2539 7.2501 7.2441 5.9343 9.8063 9.8022 10.3650 HIN-7 1H_8scan DMSO {D:\Spectra} nmr 53 Current Data Parameters NAME Jan26-2021 EXPNO 530 PROCNO F2 - Acquisition Parameters Date_ 20210127 Time 9.45 h INSTRUM Avance Neo 500 PROBHD Z119470_0333 ( PULPROG zg30 TD 65536 SOLVENT DMSO NS DS SWH 14705.883 Hz FIDRES 0.448788 Hz AQ 2.2282240 sec RG 40.8881 DW 34.000 usec DE 6.79 usec TE 295.5 K D1 1.00000000 sec TD0 SFO1 500.1730885 MHz NUC1 1H P0 3.33 usec P1 10.00 usec PLW1 20.93000031 W 12 11 10 0.32 0.82 0.77 0.22 1.41 2.11 2.00 0.70 0.20 0.20 F2 - Processing parameters SI 65536 SF 500.1699955 MHz WDW EM SSB LB 0.30 Hz GB PC 1.00 ppm Figure 20S:13C-NMR: (6e) BRUKER AVANCE NEO 500 MHz NMR SPECTROMETER SAIF, PANJAB UNIVERSITY, CHANDIGARH 18.23 52.99 40.34 39.93 39.78 39.60 39.43 39.26 39.11 38.93 30.41 110.26 144.82 141.73 139.47 132.20 128.53 128.34 128.30 124.44 119.12 155.78 174.15 194.57 HIN-7 C13CPD DMSO {D:\Spectra} nmr 53 Current Data Parameters NAME Jan26-2021 EXPNO 531 PROCNO F2 - Acquisition Parameters Date_ 20210127 Time 11.10 h INSTRUM Avance Neo 500 PROBHD Z119470_0333 ( PULPROG zgpg30 TD 65536 SOLVENT DMSO NS 512 DS SWH 37037.035 Hz FIDRES 1.130281 Hz AQ 0.8847360 sec RG 101 DW 13.500 usec DE 6.50 usec TE 300.2 K D1 2.00000000 sec D11 0.03000000 sec TD0 SFO1 125.7804233 MHz NUC1 13C P0 3.33 usec P1 10.00 usec PLW1 83.14099884 W SFO2 500.1720007 MHz NUC2 1H CPDPRG[2 waltz65 PCPD2 80.00 usec PLW2 20.93000031 W PLW12 0.32703000 W PLW13 0.16449000 W F2 - Processing parameters SI 32768 SF 125.7679165 MHz WDW EM SSB LB 1.00 Hz GB PC 1.40 200 180 160 140 120 100 80 60 40 20 ppm 11 Figure 21S: ESI-MS: (6e) SAIF,PANJAB UNIVERSITY ,CHANDIGARH SYNAPT-XS#DBA064 04-Feb-2021 16:04:01 HARSHA HIN-7 (0.138) 1: TOF MS ES+ 1.79e6 301.1569 1791720 100 171.0413 1719502 281.0661 1236435 % 295.0822 912599 173.0384 569533 283.0632 489291 222.0798 446991 302.1602 334418 128.0333 232435 123.0110 21911 100 110 120 224.0771 131559 149.0318 141.9668 100381 52534 154.0143 19661 130 140 150 160 190.0162 52853 170 180 190 205.0527 19085 200 210 254.9982 116503 229.1541 21194 220 230 240 249.0928 27678 250 260 359.2591 147209 338.3594 134076 270.9713 70065 270 303.1634 28051 280 290 300 310 376.0169 42992 339.3633 331.2417 19810 12741 320 330 340 350 360 370 380 392.5340 10183 437.2166 413.2877 36539 425.0329 43588 8690 453.1914 465.0983 10579 10128 390 410 450 400 420 430 440 460 470 485.1376 16209 480 490 503.1278 11550 500 m/z 12 ... 10.1351/pac200577010155 1987 Supplementary Information: Article Category: Research paper Title: A four-component modified Biginelli reaction: A novel approach for C-2 functionalized dihydropyrimidines. .. dihydropyrimidines Author(s): Harsha I Narkhede*, Avinash S Dhake, Balasubramaniyan V Department of Pharmaceutical chemistry, S.M.B.T College of Pharmacy, Dhamangaon, Nashik, M.S India422403 Prototype... derivatives were reported for the first time via a novel four component modified Biginelli reaction Modified novel reaction was also compared with earlier reported classical Biginelli and Atwal modified