THE MODIFICATION AND USE OF SUPPORTED PLATINUM CATALYSTS FOR ASYMMETRIC HYDROGENATION REACTIONS A Thesis Presented to die University of Glasgow for the Degree of Doctor of Philosophy by Elaine Allan October 1995 ProQuest Number: 11007860 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 11007860 Published by ProQuest LLC(2018). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 'fCiU l o z U CT 7 G la sg o w i UNIVERSITY ■ i t e y SUMMARY This thesis describes a study of the adsorption of chiral substituted binaphthalene molecules ( 2,2'-dihydroxy-l,l'-binaphthalene, 2,2'-diamino-l,l'-binaphthalene, 2,2- dimethoxy-1,1 '-binaphthalene and 2,2',7,7'-tetrahy droxy-1,1 ’-binaphthalene) on to supported Pt catalysts (1% w/w Pt/y-alumina, 1% w/w Pt/Grace silica CIO and 1% w/w Pt/Cab-O- Sil) with a view to establishing a system which could be capable of inducing asymmetric hydrogenation of prochiral starting materials. The 2,2'-dihydroxy-l,r-binaphthalene modifier was found to adsorb irreversibly on to the 1% w/w Pt/y-alumina and 1% w/w Pt/Grace silica CIO catalysts, prior to the ageing of the 1% w/w Pt/Grace silica CIO catalyst. The 2,2'-dihydroxy-l,r-binaphthalene modifier was also found to irreversibly adsorb on to the y-alumina support, to a similar extent as that on to the 1% w/w Pt/y-alumina catalyst. The 2,2'-diamino-l,r-binaphthalene modifier was adsorbed irreversibly on to the 1% w/w Pt/y-alumina, 1% w/w Pt/Grace silica CIO and 1% w/w Pt/Cab-O-Sil catalysts. In the case of the 1% w/w Pt/Cab-O-Sil catalyst, the 2,2'-diamino-l,l'-binaphthalene was found to undergo a chemical reaction which resulted in the formation of 2-hydroxy- 2'-amino-l,r-binaphthalene and 2,2'-dihydroxy-l,l'- binaphthalene. 2,2-Dimethoxy-l,r-binaphthalene modifier was found not to adsorb on to the (1% w/w Pt/y-alumina, 1% w/w Pt/Grace silica CIO and 1% w/w Pt/Cab-O-Sil catalysts. The 2,2',7,7'-tetrahydroxy-l,r-binaphthalene modifier was found to be adsorbed on to the 1% w/w Pt/y-alumina and 1% w/w Pt/Cab-O-Sil catalysts, with the y-alumina support adsorbing the 2,2',7,7'-tetrahydroxy-l,r-binaphthalene to a similar extent as that on to the 1% w/w Pt/y-alumina catalyst. Evidence is presented for the adsorption of 2,2'- dihydroxy-l,l'-binaphthalene, 2,2'-diamino-l,r-binaphthalene and 2,2',7,7'-tetrahydroxy- l,l'-binaphthalene modifiers are in a near vertical mode via their substituent groups, via the dissociation of a hydrogen atom. The adsorption of R-(-)-l-(9-anthryl)-2,2,2-trifluoroethanol was studied with respect to the 1% w/w Pt/y-alumina and 1% w/w Pt/Cab-O-Sil catalysts as well as the respective supports. It was found that only the 1% w/w Pt/y-alumina catalyst adsorbed this modifier. The adsorption of (S,S)-di-(2-propyl)-6,12-dioxa-2,5,13,16-tetraoxo-3,15,19- triazabicyclo [15.3.1] heneicosa-1 (21),17,19-triene and (S,S)-di-(2-propyl)-6,13-dioxa- 2,5,14,17-tetraoxo-3,16,20-triazabicyclo [16.3.1] docosa-1 (22),18,20-triene macrocycles were also studied, with the result that both the macrocycles were adsorbed on to both the 1% w/w Pt/y-alumina and 1% w/w Pt/Cab-O-Sil catalysts as well as the y-alumina support. The 1% w/w Pt/y-alumina and 1% w/w Pt/Cab-O-Sil catalysts were studied for their co-adsorption properties with respect to the 2,2'-dihydroxy-l, 1 '-binaphthalene and 2,2'- diamino-fl'-binaphthalene modifiers. In the case of the 1% w/w Pt/Cab-O-Sil catalyst, 2,2'-dihydroxy-l,l'-binaphthalene and 2-hydroxy- 2'-amino-l,T-binaphthalene were formed as well as 2,2'-diamino-l,r-binaphthalene being adsorbed. The hydrogenation of methyl tiglate and tiglic acid over the various modified supported Pt catalysts resulted in the formation of the racemate (methyl-2-methyl butyrate and 2-methyl butyric acid, respectively). However, the hydrogenation of 3-coumaranone over diamine modified supported Pt catalysts resulted in the inducement of enantioselectivity, that is, R-(+)-2,2'-diamino-l,r-binaphthalene modified supported Pt catalysts induced S-3-benzofuranol and S-(-)-2,2'-diamino-l,r-binaphthalene modified supported Pt catalysts induced R-3-benzofuranol. While the hydrogenation of 3- coumaranone over 2,2'-dihydroxy-l,r-binaphthalene modified supported Pt catalysts resulted in the racemate. Modification of the supported Pt catalysts with either (S,S)-di-(2- propy l)-6,12-dioxa-2,5,13,16-tetraoxo-3,15,19-triazabicyclo[ 15.3.1 Jheneicosa-1(21), 17,19- triene or (S,S)-di-(2-propyl)-6,13-dioxa-2,5,14,17-tetraoxo-3,16,20-triazabicyclo [16.3.1] docosa -1 (22),18,20-triene macrocycles led to the formation of the racemate with respect to the hydrogenation of 3-coumaranone. The hydrogenation of methyl tiglate and 3-coumaranone were studied over the supported Pt catalysts modified with L-histidine, R-(+)-N,N-dimethyl-l-phenylethylamine, L-tryptophan, R-(+)-a-methoxy-a-trifluoromethylphenylacetic acid, L-phenylalaninol, L- (+)-a-phenylglycinol and (+)-pseudoephedrine. The racemate was obtained from the hydrogenation of methyl tiglate over supported Pt catalysts modified with these modifiers, and the formation of methyl angelate was observed when the 1% w/w Pt/y-alumina catalyst was modified with L-histidine, R-(+)-N,N-dimethyl-l-phenylethylamine, (+)- pseudoephedrineandR-(+)-a-methoxy-a-trifluoromethylphenylacetic acid. An unidentified additional product was observed in the hydrogenation of 3-coumaranone over either the unmodified supported Pt catalysts or the modified supported Pt catalysts. ACKNOWLEDGEMENTS I would like to thank my academic supervisor Prof. Geoff Webb and industrial supervisor Dr. David Jackson for their help and the other members of research group Dr. E. Colvin, Miss N. Young and Mr. D. Hunter (University of Glasgow), Dr. W. Moss and Dr. G. Robinson (Zeneca Pharmaceuticals, Macclesfield), Dr. S. Korn (Zeneca Fine Chemicals Manufacturing Organisation, Huddersfield), Prof. Peter B. Wells, Dr. P. Johnston and Mr. S. R. Watson (University of Hull), Dr. A. Ibbotson and Dr. R. Sampson. I would also like to thank the Technical Staff in the Chemistry Department for all their help, especially Jim Mclver, Rose Millar and Victoria Yates. Thanks to the other members of the Inorganic Research Office. Thanks to Ian Dalgleish, Principle Teacher of Chemistry, Ardrossan Academy for scanning of some of the diagrams in the thesis. Thanks to EPSRC for funding and I.C.I. Katalco for providing me with sponsorship. Finally, I would like to thank my parents because without their support, encouragement and belief in my abilities, I could never have got this far. TABLE OF CONTENTS PAGE SUMMARY ACKNOWLEDGEMENTS TABLE OF CONTENTS Chapter 1 INTRODUCTION 1.1 INTRODUCTION 1 1.2 CATALYSIS 6 1.3 THE CATALYSTS 21 1.4 CATALYST CHARACTERISATION 26 Chapter 2 OBJECTIVES 33 Chapter 3 EXPERIMENTAL 3.1 INTRODUCTION 35 3.2 CATALYST PREPARATION 35 3.2.1 Pt/y-alumina 3.2.2 Pt/Grace silica CIO 3.2.3 Pt/Cab-O-Sil 3.3 CATALYST CHARACTERISATION 36 3.3.1 Ultra-violet-Visible spectroscopy 3.3.2 Temperature programmed reduction 3.3.3 Chemisorption 3.3.4 Transmission electron microscopy 3.4 ADSORPTION STUDIES 39 3.4.1 Materials 3.4.2 Reactor systems 3.4.3 Catalyst activation 3.4.4 Analysis of modifier solution after equilibration 3.4.5 Desorption studies 3.4.6 Calibration of polarimeter 3.4.7 Calibration of HPLC 3.5 HYDROGENATION REACTIONS 49 3.5.1 Materials 3.5.2 The reactor system 3.5.3 Experimental conditions 3.5.4 Analysis of the reaction mixture 3.5.5 Calibration of GC Chapter 4 RESULTS 4.1 CATALYST CHARACTERISATION 57 4.1.1 Ultra-violet-Visible spectroscopy 4.1.2 Temperature programmed reduction 4.1.3 Chemisorption 4.1.4 Transmission electron microscopy 4.2 ADSORPTION STUDIES OF CHIRAL MODIFIERS 60 4.2.1 Catalysts 4.2.2 Supports 4.2.3 Polarimetry studies 4.3 HYDROGENATION STUDIES 113 4.3.1 Methyl tiglate hydrogenation 4.3.2 Tiglic acid hydrogenation 4.3.3 3-Coumaranone hydrogenation Chapter 5 DISCUSSION 5.1 CATALYST CHARACTERISATION 117 5.1.1 Ultra-violet-Visible spectroscopy 5.1.2 Temperature programmed reduction 5.1.3 Chemisorption 5.1.4 Transmission electron microscopy 5.2 ADSORPTION STUDIES OF CHIRAL MODIFIERS 121 5.2.1 Adsorption of modifiers 5.2.2 Co-adsorption studies 5.2.3 Similarities/differences in the adsorption of resolved modifier 5.2.4 Effect of temperature on adsorption 5.2.5 Size of macrocycle methylene bridge 5.2.6 Strength of modifier adsorption 5.2.7 Mode of modifer adsorption 5.3 HYDROGENATION STUDIES 136 5.3.1 Hydrogenation of 3 -coumaranone 5.3.2 Hydrogenation of methyl tiglate and tiglic acid 5.3.3 Hydrogenation mechanism for 3-coumaranone 5.3.4 Hydrogenation mechanism for methyl tiglate and tiglic acid REFERENCES 150 APPENDICES CHAPTER 1 INTRODUCTION 1.1 INTRODUCTION 1.1.1 Chirality Stereochemistry, from the Greek word, stereos = solid, is the study in three dimensions of the relationship between molecular structure and properties of organic molecules.