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The Stereochemistry of the Catalytic Hydrogenation of Cyclic Allylic Alcohols.

Sehgal, Raj Kumar. (1968) The Stereochemistry of the Catalytic Hydrogenation of Cyclic Allylic Alcohols. Doctoral thesis, University of Surrey (United Kingdom)..

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Abstract

2-Butylidenecyclopentanone, 2-butylidenecyclohexanone and 2-butylidenecycloheptanone were prepared by the Reformatsky reaction of 2-bromocyclopentanone, 2-bromocyclo-hexanone enol acetate and 2-bromocycIoheptanone respectively with n-butyraldehyde and their structure was confirmed by infrared and ultraviolet spectroscopy. Reduction of the exo-cyclic ketones with LiAlH4 gave the corresponding cyclic allylic alcohols which were purified chromatographically and characterised by their mass spectra. On catalytic hydrogenation of these cyclic allylic alcohols, over a number of catalysts, three components were obtained by chromatography. In each case the first components were shown to be the dehydrogenation products, by comparison of their retention times with authentic samples. The second and third components were shown to be cis- and trans-cyclic alcohols. The cis and trans-2-butyl-cyclopentanol were separated by preparative glc. The cis- and trans-2-butylcyclohexanol and 2-butylcycloheptanol were separated by column chromatography. They were assigned cis- and trans- configurations by n.m.r. in DMSO. The stereochemistry of the hydrogenation of these cyclic allylic alcohols is discussed. Hydrogenation of the exo-cyclic ketones in the presence of Pd/C gave the corresponding saturated ketones, characterised by the preparation of their derivatives. The saturated ketones in turn were reduced by LiAlH4 and hydrogenated in the presence of Raney Ni to the saturated cis- and trans-cyclic alcohols. 2-Benzylidenecyclopentanone, 2-benzylidenecyclo-hexanone and 2-benzylidenecycloheptanone were prepared by condensation of cyclopentanone,cyclohexanone,and cycloheptanone respectively with benzaldehyde under alkaline conditions and their structure confirmed by u.v., i.r., and n.m.r. spectroscopy. Reduction of the exo-cyclic ketones with LiAlH4 gave the corresponding cyclic allylic alcohols, characterised by u.v., i.r., and the preparation of derivatives. On catalytic hydrogenation of these cyclic allylic alcohols, over a number of catalysts, five components were obtained by chromatography. In each case the first components were shown to be the hydrogenolysis products, by their i.r. spectra. The second and third components were shown to be the cis- and trans-2-hexahydrobenzyl cyclic alcohols by their n.m.r. in DMSO. The fourth and fifth components were shown to be the cis- and trans-2-benzyl cyclic alcohols by the preparation of derivatives and by n.m.r. in DMSO. The hydrogenation products were separated on a preparative bentone 34-silicone oil column. The stereochemistry of the hydrogenation of these cyclic allylic alcohols is discussed. Hydrogenation of the exo-cyclic ketones in the presence of Pd/C gave the corresponding saturated ketones. The saturated ketones in turn were reduced by LiAlH[4] to the saturated cis-and trans-cyclic alcohols.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors :
NameEmailORCID
Sehgal, Raj Kumar.
Date : 1968
Contributors :
ContributionNameEmailORCID
http://www.loc.gov/loc.terms/relators/THS
Additional Information : Thesis (Ph.D.)--University of Surrey (United Kingdom), 1968.
Depositing User : EPrints Services
Date Deposited : 22 Jun 2018 15:15
Last Modified : 06 Nov 2018 16:54
URI: http://epubs.surrey.ac.uk/id/eprint/848323

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