Luận án tiến sĩ Công nghệ hóa hữu cơ: Application of mil-68 (In), Fe3O (BPDC)3, MOF-235 as catalysts for C-N and C-O bond forming reactions

iii THESIS SUMMARY This thesis describes the synthesis, characterization and catalytic applications of based metal-organicframework In-MOF and iron-based metal-organic frameworks Fe-MOF

VIETNAM NATIONAL UNIVERSITY ± HO CHI MINH CITY

HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY

HA THANH MY PHUONG

AS CATALYST FOR Cí1$1'&í2 BOND

FORMING REACTIONS

PhD THESIS

HO CHI MINH CITY 2020

VIETNAM NATIONAL UNIVERSITY ± HO CHI MINH CITY

HO CHI MINH CITY UNIVERSITY OF TECHNOLOGY

HA THANH MY PHUONG

CATALYST FOR CíN AND CíO BOND FORMING

REACTIONS

Major: Organic Chemical Technology

Major code: 62520301

Independent examiner 1: Assoc Prof Dr Nguyen Phuong Tung

Independent examiner 2: Assoc Prof Dr Hoang Thi Kim Dung

Examiner 1: Assoc Prof Dr Tran Ngoc Quyen

Examiner 2: Assoc Prof Dr Nguyen Thi Le Thu

Examiner 3: Assoc Prof Dr Ton That Quang

ADVISORS:

1 Prof Dr Phan Thanh Son Nam

2 Dr Le Thanh Dung

i

DECLARATION OF ORIGINALITY

I hereby declare that this is my own research study The research results and conclusions

in this thesis are true, and are not copied from any other resources The literature references have been quoted with clear citation as requested

Thesis Author

Signature

Ha Thanh My Phuong

ii

7Ï07Ҳ7/8Ұ1È1

/XұQiQQj\WUuQKEj\ SKѭѫQJSKiSWәQJKӧSÿһFWUѭQJKyDOêYjKRҥWWtQK[~FWiFFӫDYұWOLӋXNKXQJFѫNLPORҥL,QGLXP,Q-MOF) là MIL-68 (In) YjYұWOLӋXNKXQJ FѫNLPVҳW)H-02) EDRJӗP)H3O(BPDC)3 và MOF-&iFYұWOLӋX02)Qj\ÿѭӧFVӱGөQJOjPFKҩW[~FWiFGӏWKӇFKRFiFSKҧQӭQJKuQKWKjQKOLrQNӃW&í1Yj&í2ÿӇWәQJKӧSFiFKӧSFKҩW-nitro-3-arylimidazo[1,2-a]pyridine, 2,4-diarylpyridine và các Į-acyloxy ether

&KѭѫQJÿҫXWLrQFӫDOXұQiQQj\WUuQKEj\WәQJTXDQWjLOLӋXYӅFiFYұWOLӋX,Q-MOF và Fe-02)FөWKӇOjYұWOLӋX MIL-68(In), Fe3O(BPDC)3 và MOF-7әQJTXDQYӅFҩXWU~FWtQKFKҩWSKѭѫQJSKiSWәQJKӧSÿһFWtQKYjӭQJGөQJ[~FWiFFӫDFK~QJ1JRjLUDFKѭѫQJQj\FNJQJWәQJTXDQYӅFiFSKҧQӭQJKuQKOLrQNӃW&í1Yj&í2ÿӇWәQJKӧScác KӧS FKҩW 2-nitro-3-arylimidazo[1,2-a]pyridine, 2,4-diarylpyridine và Į-acyloxy ether

&KѭѫQJWKӭKDLFӫDOXұQiQQj\WUuQKEj\TXiWUuQKWKӵF 68(In), Fe3O(BPDC)3 và MOF-235 và NKҧRViWFiFÿLӅXNLӋQWәQJKӧS FiFKӧSFKҩW-nitro-3-arylimidazo[1,2-a]pyridine, 2,4-diarylpyridine và Į-acyloxyether YӟLFiF[~FWiFMIL-68(In), Fe3O(BPDC)3 và MOF-WѭѫQJӭQJ

QJKLӋPWәQJKӧSYұWOLӋXMIL-&KѭѫQJWKӭEDFӫDOXұQiQQj\WUuQKEj\NӃWTXҧYjWKҧROXұQYӅYұWOLӋX0,/-68(In),

Fe3O(BPDC)3 và MOF-ÿmWәQJKӧSYjNKҧQăQJӭQJ GөQJFiFYұWOLӋX02)Qj\tUrQFiFSKҧQӭQJhình thành OLrQNӃW&íN và Cí2&iF02)Qj\ÿѭӧFWәQJKӧS EҵQJFiFSKѭѫQJSKiSQKLӋW dung môi và [iFÿӏQKFiFÿһFWUѭQJKRiOê EҵQJSKѭѫQJSKiS ÿRPXRD, SEM, TEM, TGA, FT-IRSKkQEӕNtFKWKѭӟFOӛ[ӕSYjÿRKҩSSKө YұWOêQLWѫ.ӃWTXҧWKX ÿѭӧFFKRWKҩ\Fác In-MOF và Fe-MOF Qj\FyKRҥWWtQK[~FWiFFDRFKRFiFSKҧQӭQJKuQKWKjQKOLrQNӃW&í1 và CíO và QKӳQJ [~FWiFQj\ÿѭӧF WKXKӗLYjWiLVӱGөQJQKLӅXOҫQPjNK{QJEӏJLҧPÿiQJNӇKRҥWWtQK[~FWiF 7KHRKLӇXELӃWWӕWQKҩWFӫDchúng tôi, nKӳQJFKX\ӇQKRi này VӱGөQJFKҩW[~FWiF0,/-68(In), Fe3O(BPDC)3 and MOF-FKѭDÿѭӧFÿӅFұSWUѭӟFÿk\WURQJWjLOLӋX

iii

THESIS SUMMARY

This thesis describes the synthesis, characterization and catalytic applications of based metal-organicframework (In-MOF) and iron-based metal-organic frameworks (Fe-MOFs) including MIL-68(In), Fe3O(BPDC)3 and MOF-235 These MOFs were used as heterogeneous catalysts for &í1and CíObond forming reactions to synthesize

indium-2-nitro-3-aryl imidazo[1,2-a]pyridines, 2,4-diarylpyridines and Į-acyloxy ethers

The first chapter of this thesis provides a literature review of In-MOF and Fe-MOFs including MIL-68(In), Fe3O(BPDC)3 and MOF-235 An overview of their structures, properties, synthesis and characterization methods and catalytic applications are described In addition, the chapter also reviews &í1and &í2 bond forming reactions

for the synthesis of 2-nitro-3-aryl imidazo[1,2-a]pyridines, 2,4-diarylpyridines and

Į-acyloxy ethers

The second chapter of this thesis presents the experimental process of synthesizing 68(In), Fe3O(BPDC)3 and MOF-235 and test catalytic activity of these MOFs on &í1DQG&í2 bonds forming reactions

MIL-The third chapter of this thesis presents the results and discussion about the synthesized MOFs and the ability to apply these MOFs on &í1DQG&í2 bonds forming reactions These MOFs were prepared by solvothermal methods and characterized by PXRD, SEM, TEM, TGA, FT-IR, pore size distribution and nitrogen physisorption measurements These MOFs were found to be highly catalytically active for CíN and

&í2 bonds forming reactions The In-MOF and Fe-MOFs catalysts could be recovered and reused several times without a significant degradation in catalytic activity To the best of our knowledge, these transformations using MIL-68(In), Fe3O(BPDC)3 and MOF-235 catalysts were not previously mentioned in the literature

iv

ABSTRACT

Three highly porous indium-based organic frameworks (In-MOF) like MIL-68(In), based organic frameworks (Fe-MOFs) such as Fe3O(BPDC)3 and MOF-235 were synthesized and characterized by PXRD, SEM, TEM, TGA, FT-IR, pore size distribution and nitrogen physisorption measurements In-MOF were used as heterogeneous catalysts for &í1 DQG &í2 forming reactions to synthesize 2-nitro-3-

iron-aryl imidazo[1,2-a]pyridines Fe3O(BPDC)3 was employed as heterogeneous catalyst for CíN bond forming reactions to synthesize 2,4-diaryl pyridines MOF-235 was utilized as heterogeneous catalyst for &í2 bond forming reactions to synthesize Į-acyloxy ethers These catalytic systems offered practical approaches with high yields and selectivity Additionally, broad functionality was shown to be compatible The In-MOF and Fe-MOFs catalysts could be recovered and reused several times without significant degradation in catalytic activity To the best of our knowledge, these transformations using MIL-68(In), Fe3O(BPDC)3 and MOF-235 catalysts were previously achieved under heterogeneous catalysis conditions in the literature

v

ACKNOWLEDGMENT

I reserve special thanks to my research advisors, Prof Dr Phan Thanh Son Nam and Dr

Le Thanh Dung, who have supported me over the course of my research work Their motivation, patience, enthusiasm and immense knowledge have kept me going during the past four years I was so lucky to have such a precious opportunity to work under their guidance I really would like to learn more from such renowned and respected chemists

I would aslo like to thank Assoc Prof Dr Pham Thanh Quan and Dr Phan Thi Hoang Anh for their insight and questions that have undoubtedly helped me progress to this point I would like to thank Assoc Prof Dr Le Thi Hong Nhan, Dr Truong Vu Thanh and Dr Nguyen Thanh Tung for guiding me how to recognize and find the best ways to solve the scientific problems

I would be remiss if I did not acknowledge all members of my group (Lieu Ngoc Thien, Doan Hoai Son) for the stimulating discussions in Organic Chemistry Division Additionally, I wish to acknowledge three undergraduate students (Phan Thi Bao Trang,

Le Thi Thanh Binh, To Chi Trung) and and graduated student (Le Duc Thuan) for their helps during the time they studied in laboratory

I also thank to my colleagues in Chemical Engineering Department at TayDo University for their encouragement My deepest gratitude to my family The support and love from

my family is of inestimable value

vi

TABLE OF CONTENTS

TABLE OF CONTENTS vi

LIST OF FIGURES viii

LIST OF SCHEMES xii

LIST OF TABLES xiv

LIST OF ABBREVIATION xv

INTRODUCTION 1

CHAPTER 1 LITERATURE REVIEW OF MIL-68(In), Fe3O(BPDC)3, MOF-235 $1'&í1&í2%21')250,1*5($&7,216 3

1 1 Metal-organic frameworks 3

1 2 Synthesis and structure of MIL-68(In), MOF-235 and Fe3O(BPDC)3 11

1.2 1 Synthesis and structure of MIL-68(In) 13

1.2 2 Synthesis and structure of MOF-235 15

1.2 3 Synthesis and structure of Fe3O(BPDC)3 17

1 3 Application of MIL-68 (In), MOF-235 and Fe3O(PBDC)3 in catalysis 18

1 4 &í1DQG&í2ERQGIRUPing reactions 24

1.4.1 &í1ERQGIRUPDWLRQLQV\QWKHVLVRI-nitro-3-arylimidazo[1,2-a]pyridine derivatives 25

1.4.2 &í1ERQGIRUPDWLRQIRUV\QWKHVLVRIaryl substituted pyridines 28

1.4.3 &í2ERQGIRUPDWLRQIRUV\QWKHVLVRIĮ-acyloxy ethers 34

EXPERIMENTAL 40

2.1 Introduction 40

2.2 Synthesis of MIL-68(In), Fe3O(BPDC)3 and MOF-235 41

2.2.1 Materials and instrumentation 41

2.2.2 Catalyst synthesis 41

2.3 Catalyitic studies of MIL-68(In), Fe3O(BPDC)3 DQG02)RQ&í1 DQG&í2ERQGIRUPLQJUHDFWLRQV 44

2.3 1 Materials and instrumentation 44

2.3 2 Catalytic studies of MIL-,Q RQ&í1ERQGIRUPDWLRQUHDFWLRQ between 2-aminopyridines and nitroalkenes 45

2.3 3 Catalytic studies of Fe3O(BPDC)3 RQ&í1ERQGIRUPDWLRQUHDFWLRQ between N,N-dialkylanilines with ketoxime carboxylates 46

vii

2.3 4 Catalytic studies of MOF-235 RQ&í2ERQGIRUPDWLRQUHDFWLRQfor the direct esterification of carboxylic acids with C(sp3)íH bonds to form Į-acyloxy

ethers 46

RESULT AND DISCUSSION 48

3 1 Characterization of MIL-68(In), MOF-235 and Fe3O(BPDC)3 48

3.1.1 Characterization of MIL-68(In) 48

3.1.2 Characterization of MOF-235 53

3.1.3 Characterization of Fe3O(BPDC)3 58

3 2 Catalyitic studies of MIL-68(In), Fe3O(BPDC)3 DQG02)RQ&í1 DQG&í2ERQGIRUPLQJUHDFWLRQV 63

3.2.1 Catalytic studies of MIL-68(In) on CN bond formation reactions (1) 63

3.2.2 Catalytic studies of Fe3O(BPDC)3 on CN bond formation reactions (2)

83

3.2.3 Catalytic studies of MOF-235 on CO bond forming reaction (3) 103

CONCLUSION AND RECOMMENDATIONS 124

4 1 Summary of current work 124

4 2 Contributions of this thesis 124

4 3 Recommendations 125

LIST OF PUBLICATIONS 127

LIST OF OTHER PUBLICATIONS 128

REFERENCES 129

APPENDICES 139

viii

LIST OF FIGURES

Figure 1.1 Example Metal-Organic Framework (MOF) The yellow sphere represents

the pore space within the crystal structure [5] 3

Figure 1.2 Year wise publication status from 2000 to 2015 of various aspects of MOFs (a) MOFs, (b) MOFs as luminescent materials, (c) MOFs for gas storage, (d) MOFs as magnets, (e) MOFs for drug delivery and (f) MOFs as catalyst (data source: Sci-finder, retrieved on October, 12 2015) [6] 4

Figure 1.3 Potential polytopic organic acids as linkers in MOFs [6] 6

Figure 1.4 Coordination geometries of transition metal ions [6] 7

Figure 1.5 Examples of SBUs from carboxylate MOFs O, red; N, green; C, black [27] 7

Figure 1.6 The values in parentheses represent the pore volume (cm3.g-1) of these materials [29] 8

Figure 1.7 Aspects of crystallization in synthesis of solid compounds [32] 9

Figure 1.8 (a) Synthesis conditions commonly used for MOF preparation; (b) indicative summary of the percentage of MOFs synthesized using the various preparation routes [33] 11

Figure 1.9 MIL-68(In) SBU (gray: carbon; red: oxygen; teal: indium) [42] 14

Figure 1.10 View of the structure of MIL-68(In) along the c axis [42] 14

Figure 1.11 View of a chain of InO4(OH)2 octahedra in MIL-68(In) [42] 15

Figure 1.12 The structures of MOF-235 (Fe, blue; O, red; Cl, teal; C, gray) [53] 16

Figure 1.13 Inorganic and organic building units used to assemble MOF-235: (a) oxygen-centered iron-carboxylate trimer (Fe, blue;O, red; C, gray) shown in ball-and-stick and polyhedral representations of trigonal prismatic geometry (blue) and (b) ditopic links, 1,4-benzenedicarboxylate (BDC) [53] 16

Figure 1.14 The basic unit of MOF-235 in solvent (a) and activated (b) [53] 17

Figure 1.15 Organization of the two orthogonally interpenetrated trigonal bipyramidalbuilding units of of Fe3O(BPDC)3 [45] 18

Figure 1.16 Proposed mechanisms for the Strecker reaction catalyzed by In-MOF [65] 20

Figure 1.17 Some biologically active heterocycles containing 3-aryl substituted imidazopyridines [86-88] 25

Figure 1.18 Selected bioactive agents containing the poly-arylated pyridine structure [95, 96] 29

Figure 1.19 Selected examples of Į-acyloxy ethers [103] 35

Figure 3.1 X-ray powder diffractograms of the MIL-68(In) 49

Figure 3.2 SEM and TEM micrograph of the MIL-68(In) 49

ix

Figure 3.3 TGA analysis of the MIL-68(In) 50

Figure 3.4 Pore size distribution of the MIL-68(In) 51

Figure 3.5 FT-IR spectrum of terephthalic acid (a), and the MIL-68(In) (b) 52

Figure 3.6 Nitrogen adsorption/desorption isotherm of the MIL-68(In) Adsorption data are shown as closed circles and desorption data as open circles 53

Figure 3.7 X-ray powder diffractograms of the MOF-235 54

Figure 3.8 SEM and TEM micrograph of the MOF-235, respectively 54

Figure 3.9 TGA analysis of the MOF-235 55

Figure 3.10 Pore size distribution of the MOF-235 56

Figure 3.11 FT-IR spectrum of 1,4-benzenedicarboxylic acid (a), and MOF-235 (b) 57 Figure 3.12 Nitrogen adsorption/desorption isotherm of the MOF-235 Adsorption data are shown as closed circles and desorption data as open circles 58

Figure 3.13 Powder X-ray diffractograms of the Fe3O(BPDC)3 59

Figure 3.14 SEM and TEM micrograph of the Fe3O(BPDC)3 59

Figure 3.15 TGA analysis of the Fe3O(BPDC)3 60

Figure 3.16 FT-IR spectrum of ¶-biphenyldicarboxylic acid (a), and the Fe3O(BPDC)3(b) 61

Figure 3.17 Pore size distribution of the Fe3O(BPDC)3 62

Figure 3.18 Nitrogen adsorption/desorption isotherm of the Fe3O(BPDC)3 Adsorption data are shown as closed triangles and desorption data as open triangles 62

Figure 3.19 Yields of 2-nitro-3-phenylimidazo[1,2-a]pyridine at varied temperatures 64 Figure 3.20 Yields of 2-nitro-3-phenylimidazo[1,2-a]pyridine at various catalyst amounts 65

Figure 3.21 Yields of 2-nitro-3-phenylimidazo[1,2-a]pyridine with diverse reactant mole proportions 66

Figure 3.22 Yields of 2-nitro-3-phenylimidazo[1,2-a]pyridine in miscellaneous solvents 67

Figure 3.23 Yields of 2-nitro-3-phenylimidazo[1,2-a]pyridine with different co-catalysts 68

Figure 3.24 Yields of 2-nitro-3-phenylimidazo[1,2-a]pyridine at varied co-catalyst quantities 68

Figure 3.25 Yields of nitro-3-phenylimidazo[1,a]pyridine at diverse 2-aminopyridine concentrations 69

Figure 3.26 Leaching assessment showed that 2-nitro-3-phenylimidazo[1,2-a]pyridine was not generated in the absence of the solid catalyst 70

Figure 3.27 Yields of 2-nitro-3-phenylimidazo[1,2-a]pyridine with miscellaneous homogeneous catalysts 71

Figure 3.28 Yields of 2-nitro-3-phenylimidazo[1,2-a]pyridine with miscellaneous MOF-based catalysts 72 Figure 3.29 TEMPO test showing that the reaction could not proceed in the presence

x

of radical trapping reagent 73

Figure 3.30 Argon test indicating that the reaction could proceed in dichloroethane under argon 74

Figure 3.31 Argon test indicating that yield was adjusted by the amount of dichloroethane 75

Figure 3.32 Catalyst reusability 77

Figure 3.33 X-ray powder diffractograms of the new (a) and recovered (b) catalyst 77

Figure 3.34 FT-IR spectrum of the new (a) and recovered (b) catalyst 78

Figure 3.35 Yield of 2,4-diphenylpyridine vs temperature 84

Figure 3.36 Yield of 2,4-diphenylpyridine vs reactant molar ratio 85

Figure 3.37 Yield of 2,4-diphenylpyridine vs solvent 86

Figure 3.38 Yield of 2,4-diphenylpyridine vs oxidant 87

Figure 3.39 Yield of 2,4-diphenylpyridine vs oxidant amount 88

Figure 3.40 Yield of 2,4-diphenylpyridine vs catalyst quantity 89

Figure 3.41 Leaching test verified that 2,4-diphenylpyridine was not generated in the absence of the iron-organic framework catalyst 90

Figure 3.42 Yield of 2,4-diphenylpyridine vs heterogeneous catalysts 91

Figure 3.43 Yield of 2,4-diphenylpyridine vs homogeneous catalysts 91

Figure 3.44 Yield of 2,4-diphenylpyridine in the presence of radical scavengers 93

Figure 3.45 Catalyst recycling studies 94

Figure 3.46 FT-IR spectrum of the fresh (a) and recovered (b) catalyst 94

Figure 3.47 X-ray powder diffractograms of the fresh (a) and recovered (b) catalyst 95 Figure 3.48 Conversion and selectivity vs reaction time 96

Figure 3.49 Yields of 1,4-dioxan-2-yl 4-methoxybenzoate vs temperature 104

Figure 3.50 Yields of 1,4-dioxan-2-yl 4-methoxybenzoate vs catalyst concentration 105 Figure 3.51Yields of 1,4-dioxan-2-yl 4-methoxybenzoate vs 4-methoxybenzoic acid:1,4-dioxane molar ratio 106

Figure 3.52 Yields of 1,4-dioxan-2-yl 4-methoxybenzoate vs oxidant 107

Figure 3.53 Yields of 1,4-dioxan-2-yl 4-methoxybenzoate vs oxidant quantity 107

Figure 3.54 Yields of 1,4-dioxan-2-yl 4-methoxybenzoate vs homogeneous catalysts 108

Figure 3.55 Yields of 1,4-dioxan-2-yl 4-methoxybenzoate vs heterogeneous catalysts 109

Figure 3.56 Leaching experiment revealed that 1,4-dioxan-2-yl 4-methoxybenzoate was not generated in the absence of the solid catalyst 110

Figure 3.57 Yield of 1,4-dioxan-2-yl 4-methoxybenzoate in the presence of pyridine 111

Figure 3.58 Yield of 1,4-dioxan-2-yl 4-methoxybenzoate under air and under argon112 Figure 3.59 Catalyst recycling investigation for the direct esterification of 4-methoxybenzoic acid with 1,4-dioxane 113

xi Figure 3.60 XRD results of the new (a) and reutilized (b) catalysts 114Figure 3.61 FT-IR results of the new (a) and reutilized (b) catalysts 114

xii

LIST OF SCHEMES

Scheme 1.1 The synthesis of 4-(1,3-diphenylprop-2-ynyl)morpholine via C±H bond

activation using the MIL-68(In) catalyst [68] 21

Scheme 1.2 The cyclocondensation of 1,2-phenylenediamine with acetone to form 2,3-dihydro-2,2,4-trimethyl-1H-1,5-benzodiazepine using MOF-235 as catalyst [74] 21

Scheme 1.3 7KHGLUHFW&í&FRXSOLQJRI-methylindole with N,N-dimethylacetamide via R[LGDWLYH&í+IXQFWLRQDOL]DWLRQXVLQJMOF-235 catalyst [75] 22

Scheme 1.4 The arylation between benzothiazole and benzaldehyde utilizing MOF-235 catalyst [61] 22

Scheme 1.5 The reaction between 2-aminobenzamide and benzyl alcohol using Fe3O(BPDC)3 catalyst [46] 23

Scheme 1.6 The synthesis of 3-acetylcoumarin from salicylaldehyde and methyl acetoacetate using Fe3O(BPDC)3 catalyst [76] 23

Scheme 1.7 The direct alkenylation of 2-methylquinoline with benzaldehyde via &í+ bond activation using Fe3O(BPDC)3 catalyst [77] 23

Scheme 1.8 Synthesis of 2-nitro-3-aryl imidazo[1,2-a]pyridines [89] 25

Scheme 1.9 Additional information for mechanism with no catalyst [89] 26

Scheme 1.10 Additional information for plausible mechanism with catalyst [89] 26

Scheme 1.11 Visible light synthesis of 2-nitro-3-arylimidazopyridine [90] 27

Scheme 1.12 Plausible photocatalytic pathway for synthesis of 2-nitro-3-aryl substituted imidazopyridine [90] 28

Scheme 1.13 Copper-catalyzed reaction of 2-arylpyridine N-oxides [97] 29

Scheme 1.14 Ru-catalyzed cyclization of acetophenones with NH4OAc and DMF [98] 30

Scheme 1.15 Plausible mechanism for synthesis 2,4-diaryl pyridines [98] 30

Scheme 1.16 Cycloaddition of oximes and diynes [99] 30

Scheme 1.17 Fe-catalyzed cyclization of ketoxime acetates and N,N-dimethylaniline [59] 31

Scheme 1.18 Plausible reaction mechanism of synthesis 2,4-diaryl-disubstituted pyridines by using N,N-dialkylanilines [59] 31

Scheme 1.19 Synthesis of 2-aryl pyridines [100] 32

Scheme 1.20 Proposed mechanism of synthesis of 2-aryl pyridines [100] 32

Scheme 1.21 Fe-catalyzed cyclization of ketoxime acetates and N,N-dimethylaniline for the synthesis of pyridines [101] 33

Scheme 1.22 Proposed reaction mechanism [101] 33

Scheme 1.23 Fe-catalyzed green synthesis of pyridines from ketoxime acetates [102] 34

Scheme 1.24 Plausibled mechanism [102] 34

Scheme 1.25 Reaction of benzoic acid with ethers [82] 36

xiii

Scheme 1.26 A plausible reaction mechanism [82] 36

Scheme 1.27 Coupling of 1,4-dioxane to heteroaryl carboxylic acids and fused aryl carboxylic acids [60] 36

Scheme 1.28 The possible mechanism of coupling reaction [60] 37

Scheme 1.29 Direct esterfication of 1,4-dioxane with various heteroaryl carboxylic acids derivatives [104] 37

Scheme 1.30 The possible reaction pathways esterification of alkylbenzenes with cyclic ethers [104, 105] 38

Scheme 1.31 Direct esterfication of 1,4-dioxane with various propiolic acid derivatives [105] 38

Scheme 1.32 The possible reaction pathways [105] 39

Scheme 1.33 Cu(acac)2 catalyzed cross-dehydrogenative coupling reaction for the synthesis of Į-acyloxy ethers [106] 39

Scheme 1.34 The proposed scheme of the reaction [106] 39

Scheme 2.1 Synthesis procedure of MIL-68(In) 42

Scheme 2.2 Synthesis procedure of MOF-235 43

Scheme 2.3 Synthesis procedure of Fe3O(BPDC)3 44

Scheme 3.1 The synthesis of 2-nitro-3-phenylimidazo[1,2-a]pyridine utilizing MIL-68(In) catalyst 63

Scheme 3.2 Plausible reaction mechanism 76

Scheme 3.3 The cyclization reaction between (E)-acetophenone O-acetyl oxime acetate and N,N-dimethylaniline utilizing iron-organic framework catalyst 83

Scheme 3.4 Plausible reaction mechanism 98

Scheme 3.5 The direct esterification of 4-methoxybenzoic acid with 1,4-dioxane utilizing MOF-235 catalyst 103

Scheme 3.6 Proposed reaction mechanism 112

xiv

LIST OF TABLES

Table 1.1 Crystallographic parameters of MIL-68(In) [42], MOF-235 [43, 44] and

Fe3O(BPDC)3 [45] 12Table 3.1 The comparison table of thermal properties for MIL-68(In), MOF-235 and

Fe3O(BPDC)3 63

Table 3.2 Optimized synthetic conditions of reaction (1) 78

Table 3.3 Synthesis of 2-nitro-3-aryl imidazo[1,2-a]pyridines utilizing MIL-68(In)

catalyst 79Table 3.4 The comparison table of isolated yield of 2-nitro-3-aryl imidazo[1,2-

a]pyridines with previous studies [83] 82

Table 3.5 Optimized synthetic conditions of reaction (2) 99

Table 3.6 The cyclization reaction of N,N-dimethylaniline with various ketoxime

carboxylates utilizing Fe3O(BPDC)3 catalyst 99Table 3.7 The comparison table of isolated yield of 2,4-diphenylpyridines with

previous studies [83] 102

Table 3.8 Optimized synthetic conditions of reaction (3) 115

Table 3.9 Synthesis of Į-Acyloxy ethers using MOF-235 catalyst 118Table 3.10 The comparison table of isolated yield of 2-nitro-3-aryl imidazo[1,2-

a]pyridines with previous studies [83] 121

xv

LIST OF ABBREVIATION

4 Å MS 4 Angstrom Molecular Sieve

AAS Atomic Absorption Spectrophotometry

CDC Cross Dehydrogen Coupling

DABCO 1,4-diazabicyclo [2.2.2] octane

FID Flame Ionization Detector

FT-IR Fourier Transform Infrared Spectroscopy

GCMS Gas chromatography±mass spectrometry

GC-MS Gas chromatography±mass spectrometry

H2BDC 1,4-benzenedicarboxylic acid

H2BPDC ¶-biphenyldicarboxylic acid

HCMC Ho Chi Minh City

HCMUT Ho Chi Minh City University of Technology

HKUST Hong Kong University of Science and Technology

IRMOF Isorecticular Metal-Organic Framework

INOMAR The Center for Innovative Materials and Architectures MCRs Multi-component Coupling Reactions

MIL 0DWHULDX[VGHO¶,QVWLWXW/DYRLVLHU

xvi

MOF Metal-Organic Framework

NCS N-Chlorosuccinimide

NMR Nuclear Magnetic Resonance

NIST The National Institute of Standards and Technology

OBA ¶- oxybisbenzoate

PCPs Porous Coordination Polymers

PXRD Powder X-Ray Diffraction

SBUs Secondary Building Units

SC- XRD Single-Crystal X-ray Diffraction

SEM Scanning Electron Microscopy

SET Single Electron Transfer

TsOH p-Toluenesulfonic acid

VAST Vietnam Academy of Science and Technology

VNU Vietnam National University

1

INTRODUCTION

In the chemical industry and industrial research, catalysis plays a vital role Homogeneous catalysis using transition metal complexes is an area of research that has grown enormously in recent years But one decisive disadvantage of homogeneous transition metal catalysis is the loss of the transition metal during the work-up of the product mixture [1] Today chemists are faced with new challenges as concerns for the environment and scarcity of resources calling for greener processes Moreover, a catalyst capable of dissolving in solution will need to be separated later if it is to be recycled for re-usage (as per the principles of green chemistry) The concentration limits for metal content are becoming increasingly more challenging The removal of metal residues from post reaction mixtures has therefore become a major issue for the pharmaceutical industry Conventional methods used to remove metals include chromatography, activated carbon, extraction, distillation and recrystallization but these offer poor selectivity and can lead to active pharmaceutical ingredient (API) loss And

it is difficult to remove homogeneous catalyst impurities in the final products, especially

in pharmaceutical industry because the synthesis of drug substances involves the use of transition-metal catalysts and the residual elemental impurities would consequently reside in the drug substances [2] Meanwhile, heterogeneous catalysis performs an indispensable task in chemical and pharmaceutical industries, generally offering the minimization of toxic and hazardous waste MOFs have emerged as environmentally benign alternatives for catalysis and they have recently attracted significant attention with advantages in replacing homogeneous catalysts in chemical process

Imidazo[1,2-a]pyridines are a prominent collection of biologically active

nitrogen-containing heterocycles that exhibit universal applications in medicinal chemistry, agrochemistry, and materials science Pyridine derivatives constitute a significant class

of nitrogen-containing heterocycles that offers a wide range of applications in pharmaceutical, agrochemical, and fine chemical industries Į-Acyloxy ethers have gained substantial consideration as omnipresent structural constituents in abundant bioactive natural products, medicinal chemicals, and agrochemicals Many transition-metal catalytic systems, both in homogeneous and heterogeneous catalysis, were

The first purpose of this thesis is to prepare In-MOF and Fe-MOFs including 68(In), Fe3O(BPDC)3 and MOF-235 The second objective is to study their use as heterogeneous catalysts for the direct C±N and C±O bond forming reactions to

MIL-synthesize 2-nitro-3-aryl imidazo[1,2-a]pyridines, 2,4-diarylpyridines and Į-acyloxy

ethers To the best of our knowledge, the C±N and C±O bond forming reactions for the

synthesis of 2-nitro-3-aryl imidazo[1,2-a]pyridines, 2,4-diaryl pyridines and Į-acyloxy

ethers using these In-MOF and Fe-MOFs were not previously mentioned in the literature

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Fe3O(BPDC)3, MOF-235 AND &í1, &í2 BOND FORMING

REACTIONS

1 1 Metal-organic frameworks

Metal-organic frameworks, or MOFs (Figure 1.1), have emerged as an extensive class

of crystalline materials with ultrahigh porosity and enormous internal surface areas (up

to 90% free volume), extending beyond 6000 m2.g-1 [3] They are also known for their extraordinarily high surface areas, tunable pore size, and adjustable internal surface properties [4]

These properties, together with the extraordinary degree of variability for both the organic and inorganic components of their structures, make MOFs of interest in potential applications During the last one decade, immense research has been conducted on MOFs and the number of publications in the field (Figure 1.2) are escalating year by year due to the varied assortments of structural topologies and due to diverse applications impending in almost all essential fields [6] like clean energy [7], most significantly as storage media for gases such as hydrogen and methane [8] and as high-capacity adsorbents to meet various separation needs [9-12] Additional applications in membranes [13, 14], thin film devices [15, 16], biomedical imaging [17, 18] and catalysis [19] are increasingly gaining importance

Figure 1.1 Example Metal-Organic Framework (MOF) The yellow sphere represents

the pore space within the crystal structure [5]

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Metal-organic frameworks (MOFs, also known as porous coordination polymers or PCPs) are an emerging class of porous materials constructed from metal containing nodes (also known as secondary building units, or SBUs) and organic linkers [20] Compared to conventionally used microporous inorganic materials such as zeolites, these organic structures have the potential for more flexible rational design, through

Figure 1.2 Year wise publication status from 2000 to 2015 of various aspects of MOFs (a) MOFs, (b) MOFs as luminescent materials, (c) MOFs for gas storage, (d) MOFs as magnets, (e) MOFs for drug delivery and (f) MOFs as catalyst (data source: Sci-finder,

retrieved on October, 12 2015) [6]

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control of the architecture and functionalization of the pores [21] The term MOF was popularized by Yaghi and coworkers around 1995 for a layered cotrimesate that showed reversible sorption properties [22, 23] The concept of isoreticular chemistry [24] was made popular in 2002 for a series of Zn dicarboxylates but has also been extended to other materials The first structural model for the mixed-linker compounds was reported

in 2001 [25]

MOFs are composed of two major components: a metal ion or cluster of metal ions and

an organic molecule called a linker For this reason, the materials are often referred to

as hybrid organic±inorganic materials The combination of the two components of a MOF, the metal ion or cluster and the organic linker, provides endless possibilities The sum of the physical properties of the inorganic and organic components and the possible synergistic play between the two provide intriguing properties for a MOF Organic linker with different functionality, i.e bidentate to polydentate aromatic carboxylates (Figure 1.3) have been used to develop the variety of MOFs Similarly, as shown in

Figure 1.4, the metal coordination and geometry are paramount in guiding their structural framework [6]

As described above, SBUs are simple geometric figures representing the inorganic clusters or coordination spheres that are linked together by the organic components to form the product framework [26] Examples of some SBUs that are commonly encountered in metal carboxylate MOFs are illustratedin Figure 1.5 The choice of metal ions and the linkers used ultimately determines the type of network obtained [27]

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Figure 1.3 Potential polytopic organic acids as linkers in MOFs [6]

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The high porosity and the absence of hidden volumes in MOFs in principal render them quite useful for volume specific applications like adsorption, separations, purification purposes, and catalysis [28] The proof of permanent porosity requires measurement of reversible gas sorption isotherms at low pressures and temperatures To prepare MOFs with even higher surface area (ultrahigh porosity) requires an increase in storage space per weight of the material It is important to keep the pore diameter in the micropore range (below 2 nm) by judicious selection of organic linkers in order to maximize the BET surface area of the framework because it is known that BET surface areas obtained from isotherms are similar to the geometric surface areas derived from the crystal structure The BET surface areas of MOFs and typical conventional materials were estimated from gas adsorption measurements (Figure 1.6) [29]

The synthesis of metal-organic frameworks (MOFs) has attracted immense attention during the last two decades The main goal in MOF synthesis is to establish the synthesis conditions which facilitate the formation of well-defined inorganic building blocks without decomposition of the organic linker In MOF synthesis, the kinetics of

Figure 1.6 The values in parentheses represent the pore volume (cm3.g-1) of these

materials [29]

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crystallization must be appropriate to allow nucleation and growth of the desired phase

to take place [30] The formation of the highly ordered MOFs occurs first via an

assembly of the primary building blocks to defined secondary building blocks (SBUs), and then to the MOF crystallizes [31] A two-step process of the formation of a crystal include as follows: nucleation is followed by crystal growth Nucleation is the assembly

of ions or molecules to form a cluster Below a certain size the cluster is not stable and re-dissolves Once the cluster attains a minimum size (critical size rc about nm range), it

is thermodynamically stable and is called a nucleus The Gibbs free energy of crystallization is composed of two terms, the surface term (Defected Ground Structures-DGS) and the volume term, which scale with r2 and r3 respectively, (Figure 1.7, centre) [32]

There are two approaches for MOF syntheses: liquid-phase syntheses and solid-phase syntheses Most syntheses of MOF are liquid-phase syntheses in which metal salt and ligand solutions are mixed together and solvent is added to a mixture of solid salt and ligand in a reaction vial In this method, selected solvent can be based on different

Figure 1.7 Aspects of crystallization in synthesis of solid compounds [32]

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aspects such as reactivity, solubility, redox potential, stability constant, etc Solvent also plays an important role in determining the thermodynamics and activation energy for a particular reaction Compare to liquid-phase syntheses, solid-phase syntheses of MOFs

is quicker and easier, but it always faces difficulties obtaining single crystals, and thereby determining product structure, which is otherwise quite easy in solution phase reactions [33] Although routine synthesis of MOFs involves hydro/solvothermal methods [34], other methods such as microwave-assisted synthesis [35], electrochemical synthesis [36, 37], mechanochemical synthesis [38], and sonochemical synthesis [39-41] have been applied as alternatives for MOF synthesis A summary of the various approaches for MOF preparation and indicative summary of the percentage of MOFs synthesized using the various preparation routes is illustrated in Figure 1.8 [33]

However, heterogeneous catalysis was one of the earliest proposed applications for crystalline metal-organic frameworks (MOF) materials Although crystalline MOFs have many catalytically relevant features like zeolites (large internal surface areas and uniform pore and cavity sizes), they also differ in important ways such as they can be synthesized in much greater chemical variety than zeolites and their catalytic niche may

be high-value-added reactions (production of fine chemicals, delicate molecules, individual enantiomer, etc) that can be accomplished under milder conditions [19] Moreover, MOFs could become preferred over zeolites and other catalysts for the synthesis of (chiral) drugs and other high added value fine chemicals The syntheses of these complex substances will usually demand highly efficient and (enantio)selective catalysts, especially when polyfunctional substrates or chiral centers are involved Meanwhile, the use of MOFs in onepot multi-component coupling reactions (MCRs) and sequential (tandem) reactions allows process simplification, avoiding costly time and energy consuming isolation and purification of intermediate products The high added value of fine chemical products on the one hand and the design of new more economic processes on the other hand could largely compensate for the possible higher costs of MOFs as compared to other alternative catalysts The wonderful application of MOFs in catalysis should go in one of these directions: (i) asymmetric catalysis; (ii) one-pot multi-component coupling reactions; (iii) multifunctional MOFs for one-pot tandem reactions; or (iv) a combination of them [32]

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1 2 Synthesis and structure of MIL-68(In), MOF-235 and Fe 3 O(BPDC) 3

Among numerous synthetic methods and techniques used for the preparation of solid materials, solvothermal methods have been confirmed to be among the most effective and convenient routes under relatively mild conditions Solvothermal reactions involve the use of an organic or inorganic solvent at elevated temperature and autogeneous pressure in a sealed system (usually Teflon-lined autoclaves or glass vials) [34] If water

is used as the solvHQWWKHPHWKRGLVFDOOHG³K\GURWKHUPDOV\QWKHVLV´Crystallographic parameters of MIL-68(In) [42], MOF-235 [43, 44] and Fe3O(BPDC)3 [45] (Table 1.1)

Figure 1.8 (a) Synthesis conditions commonly used for MOF preparation; (b) indicative summary of the percentage of MOFs synthesized using the

various preparation routes [33]

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Table 1.1 Crystallographic parameters of MIL-68(In) [42], MOF-235 [43, 44] and

Fe3O(BPDC)3 [45]

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Formula weight (g.mol-1)

5 Crystal system Orthorhombic Hexagonal Tetragonal

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Unit cel dimensions (Å)

Langmuir_1139(5)

BET_974 Langmuir_774 BET_1750(50)

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The successful synthesis of a targeted metal-organic frameworks will depend largely on the experimental conditions such as many reaction parameters including composition of the reactants, temperature and pressure, concentration, reaction time, pH value and solubility and solvent [26] The most commonly used organic solvents are dimethyl formamide, diethyl formamide, acetonitrile, acetone, ethanol, methanol, etc Mixtures

of solvents have also been used to avoid problems of differing solubility for the different starting materials [33]

1.2 1 Synthesis and structure of MIL-68(In)

Up to now, a series of articles have described the syntheses of indium based organic frameworks Among of them, the syntheses of indium carboxylates have been extensively investigated In 2008, one of the first syntheses based on indium metal sites MIL-68(In) was introduced by Volkringer et.al [42] This MOF was prepared from a mixture of indium nitrate, terephthalic acid, and DMF placed in a Teflon-lined Parr

metal-autoclave and heated for 48 h at 100 °C in an oven [42] In 2014, Choi et al have also

discovered the preparation of MIL-68(In) based hexagonal wires as early-stage kinetic products and the generation of QMOF-2-based pointed hexagonal rods as final-stage thermodynamic products from a one-step solvothermal reaction of In(NO3)3 with an excess amount of H2BDC [47] In 2015, Jin et al synthesized uniform MIL-68(In) nano/micro-rods via a facile solvothermal synthesis using NaOAc as modulator agent

[48]

The indium-based terephthalate analogs of MIL-68(In) have been obtained with indium (network composition: M(OH)(O2C-C6H4-CO2), M = In) by using a solvothermal synthesis technique (Figure 1.9) using N,N-dimethylformamide as a solvent (48 h, at

100 °C) Its three-dimensional network is an illustration of a Kagome´-like lattice [49, 50] with infinite chains of octahedral units linked through the terephthalate ligand, delimiting triangular and hexagonal channels (window diameter 16 Å) [42] The MIL-68(In) is composed of infinite 1D chains of In atoms linked with BDC, and has open 1D channels [51]

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The arrangement of the hexagonal and triangular channels with the Kagome´lattice type

(3.6.3.6) and N,N-dimethylformamide moieties are located in the triangular tunnels

(Figure 1.10) The structure model was then considered in the parent orthorhombic symmetry with a double cell volume: a) 21.7739(6), b) 37.677(1), and c) 7.2330(1) Å and V) 5933.8(2) Å3 The octahedral units are trans-connected through the hydroxyl groups to form infinite files running along the c axis Adjacent octahedra are linked to each other via the terephthalate ligands (Figure 1.11) [42]

Figure 1.9 MIL-68(In) SBU (gray: carbon; red: oxygen; teal: indium) [42]

Figure 1.10 View of the structure of MIL-68(In) along the c axis [42]

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1.2 2 Synthesis and structure of MOF-235

The iron-based metal-organic framework MOF-235 was synthesized according to a slightly modified literature procedure [44, 52, 53] In 2005, Yaghi and coworkers introduced this MOF pure phase materials by heating equimolar amounts of dicarboxylic acid (H2BDC) and iron salt FeCl3.6H2O (85 oC, 24 h) in ethanol solvent [53] In 2011,

Sung et al have used solvothermal synthesized MOF-235 for the removal of harmful

dyes (anionic dye methyl orange and cationic dye methylene blue) from contaminated

water via adsorption [52] In 2012, Anbia et al have been hydrothermally synthesized

MOF-235 which used for gas adsorption In this procedure the reaction solution transferred into a Teflon-lined autoclave and heated at 85 oC for 24 h [44] In 2016, the

MOF-235 crystals were prepared via a rapid microwave-assisted method and the

photocatalytic performance of the as-synthesized sample on the degradation of organic

dye was investigated in detail by Li et al

The structure of MOFs constructed from oxo-centered trinuclear iron clusters and benzenedicarboxylate links The MOF-235 or Fe3O(BDC)3(DMF)3][FeCl4](DMF)3] is orange octahedral single crystals in which each iron atom is trivalent, yielding an overall cationic framework, and it was first synthesized by Yaghi and coworkers in 2005 using

a solvothermal method [43] The crystal structures of MOF-235 is built-up from sharing octahedral iron trimers that are connected through linear (BDC) links as shown

corner-in Figure 1.12 [53]

Figure 1.11 View of a chain of InO4(OH)2 octahedra in MIL-68(In) [42]

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These structures have the net for the assembly of trigonal prismatic building blocks The carboxylate carbon atoms in the Fe3O(CO2)6-type cluster serve as the points-of-extension that define the vertexes of a trigonal prismatic secondary building unit (SBU)

(Figure 1.13)

In this structure, such an SBU has been linked by two ditopic links: benzenedicarboxylate (BDC) to give MOF-235 [53] The Fe3O plane of each trimer has Fe-(µ3-O)-Fe angles (120°) and Fe Fe separations of 3.33 Å The diameter of the

1,4-Figure 1.12 The structures of MOF-235 (Fe, blue; O, red; Cl, teal; C, gray) [53]

Figure 1.13 Inorganic and organic building units used to assemble MOF-235: (a) oxygen-centered iron-carboxylate trimer (Fe, blue; O, red; C, gray) shown in ball-and-stick and polyhedral representations of trigonal prismatic geometry (blue) and (b)

ditopic links, 1,4-benzenedicarboxylate (BDC) [53]

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primary hexagonal channel (along the z-axis) is 6.7 Å The images of basic unit of

MOF-235 in solvent and activated MOF-MOF-235 are illustrated in Figure 1.14, respectively

1.2 3 Synthesis and structure of Fe 3 O(BPDC) 3

The iron-based metal±organic framework Fe3O(BPDC)3 was synthesized according to a slightly modified procedure reported in the literature [45] This MOF have been obtained with iron salt FeCl3.6H22 DQG ¶-biphenyldicarboxylate using N,N-

dimethylformamide as a solvent (24 h, at 100 °C) The Fe3O(BPDC)3 single crystal structure uses a sHWXS RI D QRYHO LQWHUZRYHQ IRUP RI WKH LURQ,,,  ¶-biphenyldicarboxylate [Fe3O(H2O)2(OH)[(BPDC)3].n(solvent) (solvent is dimethyl

formamide and/or water) (Figure 1.15) This structure exhibits a tetragonal symmetry,

a=21.800(3) Å and c=35.407(7) Å, and is built up from oxo-centered trimers of iron

(III) octahedra linked together via ¶-biphenyldicarboxylate linkers The

Fe3O(BPDC)3 with Fe(III) ions bear four oxygen atoms from the carboxylates, one (µ3O) oxygen atom and two types of terminal ligands, namely water (2/3) and hydroxyl groups (1/3) [45]

Figure 1.14 The basic unit of MOF-235 in solvent (a) and activated (b) [53]

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1 3 Application of MIL-68 (In), MOF-235 and Fe 3 O(PBDC) 3 in catalysis

In fact, there are many studies investigating the structure as well as properties of MOFs but most of them are M2+ based MOFs (M2+: Cu2+, Ni2+, Zn2+« ZKLOHWKRVHRI03+

based MOFs (M3+: Al3+, Fe3+, Cr3+, In3+, V3+, Sc3+, Vn3+« [54-57] are still rare Especially, among the possible trivalent metals, indium (III) is a highly promising candidate due to its low toxicity and redox properties [58] However, reports on applications of these frameworks (MIL-68(In)) in catalysis have been very uncommon

in the literature In this thesis, a literature review of structure, properties, synthesis, characterization, and catalytic activity of MIL-68, a kind of indium (III) based MOFs,

is presented

The development of novel mode for transition-metal-catalyzed transformation of ketoximes for the synthesis of useful structures is still highly desirable We hypothesized WKDW HQYLURQPHQWDOO\ IULHQGO\ DQG DEXQGDQW LURQ VDOWV PD\ SURPSW WKH 1í2 ERQGcleavage of the ketoxime carboxylate, thus implying that Fe-MOF catalyzed coupling

of ketoximes and the Į-C(sp3 í+ERQGRIWHUWLDU\DPLQHVPD\RFFXU [59]

The &í+ DFWLYDWLQJ HVWHULILFDWLRQ KDV DOVR DWWUDFWHG DWWHQWLRQV LQ the past few years, which proceeds through oxidative coupling reactions from common starting materials with high atom economy Several transition-metal catalysts, including palladium,

Figure 1.15 Organization of the two orthogonally interpenetrated trigonal bipyramidal

building units of of Fe3O(BPDC)3 [45]

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copper, rhodium, and platinum have been GHYHORSHG IRU WKLV QHZ &í+ DFWLYDWLQJesterification reaction [60] However, to the best of our knowledge, no reports of Fe-MOF catalyzed oxidative C(sp3 í+DFWLYDWLQJHVWHULILFDWLRQRIHWKHUV are known

As the previous reports, the In-MOF and Fe-MOFs including MIL-68(In),

Fe3O(BPDC)3 and MOF-235 show high activity for many reactions due to their unsaturated open metal sites The synthesis have already described in chapter 2

The high surface areas, flexible pore metrics, and high density of active sites within the very open structures of MOFs offer many advantages to their use in catalysis [29] The nodes of most MOFs are reasonably good Lewis acids, these acid sites will tend to be exposed at MOF surfaces and may well function as catalysts [19] Besides the unsaturated metal centers (Lewis acidic sites) present as responsible active sites, the presence of ether oxygen atoms (Lewis basic sites) of organic linkers can also contribute

to catalyze reaction Both organic linkers and metal points could contribute to catalytic activity of the framework, and consequently, the diversity of active sites in MOFs would offer a new approach towards catalysis of numerous organic transformations [61-63] In

2014, a new indium coordination polymer, In(OH)(H2O)(BDC) has been prepared under solvothermal conditions using a mixture of rigid organic linker and inorganic

heteropolyacid (12-phosphotungstic acid) template by Zheng et al [64] This compound

exhibits good catalytic activity for the cyanosilylation of aromatic aldehydes and can be reused three times without losing activity or significant mass Because of the small pore

size, its activity took place on the surface Zheng et al has also been researched that

In-MOFs (not included MIL-68(In)) is high-performance heterogeneous catalysts for the synthesis of amino acid derivatives [65] The In-MOFs were initially evaluated in the

Strecker reaction between N-Boc-phenylaldimine and TMSCN at room temperature

(Figure 1.16)

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In 2015, Monge et al formerly performed the acetalization of carbonyl compounds [66],

and the reduction transformations of nitroarenes [8, 67] using indium based organic framework (not include MIL-68(In)) as catalyst [8, 63] Reports on applications

metal-of In-MOF, especially MIL-68(In) in catalysis have been very uncommon in the literature In 2016, Phan and coworkers reported that the transformation could proceed readily to produce 4-(1,3-diphenylprop-2-ynyl)morpholine in the presence of a catalytic amount of MIL-68(In) [68] This MOF was used as a recyclable catalyst for the one-pot three-component coupling of aldehydes, alkynes, and amines to form 4-(1,3-

diphenylprop-2-ynyl)morpholine via C±H bond activation In this report, toluene was

found to be the solvent of choice for the transformation (Scheme 1.1)

Figure 1.16 Proposed mechanisms for the Strecker reaction catalyzed by In-MOF [65]

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Recently, iron-based metal±organic frameworks have been synthesized and used as heterogeneous catalysts for some oxidation reactions [69-73] For catalytic studies, metal iron active sites in MOF-235 catalyst will act as Lewis acid Furthermore, the defects in MOFs could also play a major role in the catalytic transformation In 2016, Phan and coworkers has reported that MOF-235 could be used as a reusable solid

catalyst for 1,5-benzodiazepine synthesis via cyclocondensation of 1,2-diamines with

ketones (Scheme 1.2) [74] Especially, MOF-235 showed better catalytic activity than conventional homogeneous catalysts as SiO2/ZnCl2 and silica gel-supported sulfuric acid and those of other MOFs

Phan and coworkers also revealed the direct CíC coupling of indoles with alkylamides

via oxidative CíH functionalization with MOF-235 (Scheme 1.3) [75] The catalyst expressed higher catalytic efficiency for the direct CíC coupling transformation than that of other MOFs and that of other homogeneous iron catalysts

Scheme 1.1 The synthesis of 4-(1,3-diphenylprop-2-ynyl)morpholine via C±H bond

activation using the MIL-68(In) catalyst [68]

Scheme 1.2 The cyclocondensation of 1,2-phenylenediamine with acetone to form dihydro-2,2,4-trimethyl-1H-1,5-benzodiazepine using MOF-235 as catalyst [74]

2,3-22

In 2017, the direct arylation of benzoazoles with aldehydes utilizing MOF-235 as a recyclable heterogeneous catalyst were explored by Phan and coworkers [61] The catalyst disclosed higher catalytic productivity for the formation of aryl-substituted azoles than various MOFs and miscellaneous iron salts The direct arylation between benzothiazole and benzaldehyde to generate 2-phenylbenzo[d]thiazole as the major product (Scheme 1.4) This transformation was substantially controlled by the solvent

and the oxidant, and the combination of N-methyl-2-pyrrolidone as solvent with

di-tert-butyl peroxide as oxidant furnished the best result

Beside MOF-235, the catalytic activities of Fe3O(BPDC)3 was discovered Phan and coworkers applied Fe3O(BPDC)3 as highly efficient heterogeneous catalyst for one-pot oxidative synthesis of quinazolinones directly from alcohols and 2-aminobenzamides (Scheme 1.5) [46] In this report, the Fe3O(BPDC)3 catalyst could be recovered and reused several times without a significant degradation in catalytic activity Especially,

quinazolinones could be prepared directly from alcohols instead of using aldehydes via

a one-pot procedure under heterogeneous catalyst Fe3O(BPDC)3 conditions, offering advantages over conventional approaches

Scheme 1.3 The direct CíC coupling of 1-methylindole with N,N-dimethylacetamide

via oxidative CíH functionalization using MOF-235 catalyst [75]

Scheme 1.4 The arylation between benzothiazole and benzaldehyde utilizing

MOF-235 catalyst [61]