The Modification and Use of Supported Platinum Catalysts for Asymmetric Hydrogenation Reactions

Allan, Elaine (1995) The Modification and Use of Supported Platinum Catalysts for Asymmetric Hydrogenation Reactions. PhD thesis, University of Glasgow.

Abstract

This thesis describes a study of the adsorption of chiral substituted binaphthalene molecules (2,2'-dihydroxy-l,l'-binaphthalene, 2,2'-diamino-1,1'-binaphthalene, 2,2- dimethoxy-1,1 '-binaphthalene and 2,2',7,7'-tetrahydroxy-1,1 '-binaphthalene) on to supported Pt catalysts (1% w/w Pt/gamma-alumma, 1% w/w Ft/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,l'-binaphthalene modifier was found to adsorb irreversibly on to the 1% w/w Pt/?-alumma 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'-dihy droxy-l,l'-binaphthalene modifier was also found to irreversibly adsorb on to the yalumina support, to a similar extent as that on to the 1% w/w Pt/gamma-alumina catalyst. The 2,2'-diamino-1,1'-binaphthalene modifier was adsorbed irreversibly on to the 1% w/w Pt/gamma-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-1,1'-binaphthalene and 2,2'-dihydroxy-1,1'- binaphthalene. 2,2-Dimethoxy-1,1'-binaphthalene modifier was found not to adsorb on to the (1% w/w Pt/gamma-alumina, 1% w/w Pt/Grace silica CIO and 1% w/w Pt/Cab-O-Sil catalysts. The 2,2',7,7'-tetrahydroxy-1,1'-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 gamma-alumina support adsorbing the 2,2',7,7'-tetrahydroxy-1,1'-binaphthalene to a similar extent as that on to the 1% w/w Pt/gamma-alumina catalyst. Evidence is presented for the adsorption of 2,2'- dihydroxy-1,1'-binaphthalene, 2,2'-diamino-1,1'-binaphthalene and 2,2',7,7'-tetrahydroxy- 1,1'-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/gamma-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/gamma-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/gamma-alumina and 1% w/w Pt/Cab-O-Sil catalysts as well as the yalumina support. The 1% w/w Pt/gamma-alumina and 1% w/w Pt/Cab-O-Sil catalysts were studied for their co-adsorption properties with respect to the 2,2'-dihydroxy-1,1 '-binaphthalene and 2,2'-diamino-l,l'-binaphthalene modifiers. In the case of the 1% w/w Pt/Cab-O-Sil catalyst, 2,2'-dihydroxy-l,r-binaphthalene and 2-hydroxy-2'-amino-1,1'-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,l'-binaphthalene modified supported Pt catalysts induced S-3-benzofuranol and S-(-)-2,2'-diamino-l,l'-binaphthalene modified supported Pt catalysts induced R-3-benzofuranol.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: Geoff Webb
• Keywords: Organic chemistry, Inorganic chemistry, Molecular chemistry
• Date of Award: 1995
• Depositing User: Enlighten Team
• Unique ID: glathesis:1995-74939
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 27 Sep 2019 15:05
• Last Modified: 27 Sep 2019 15:05
• URI: https://theses.gla.ac.uk/id/eprint/74939