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The stereochemistry of the catalytic hydrogenation of compounds containing an asymmetric carbon atom.

Howard, Terence John. (1960) The stereochemistry of the catalytic hydrogenation of compounds containing an asymmetric carbon atom. Doctoral thesis, University of Surrey (United Kingdom)..

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4-Phenylpent-3-en-2-one has been prepared by the reaction of dimethyl cadmium with beta-methylcinnamoyl chloride, and its structure confirmed by a haloform degradation to trans-beta-methylcinnamic acid. Reduction of the ketone with aluminium isopropoxide gave (+/-)-4-Phenylpent-3-en-2-ol, characterised by the preparation of the N- a-naphthyl and N-4-diphenylyl-carbamates. On catalytic hydrogenation (+/-)-4-phenylpent-3-en-2-ol gave a mixture of the two diastereoisomeric racemates of (+/-)-4-phenylpentan-2-ol in which a new centre of asymmetry has been generated at C[4]. On vapour-phase chromatography the two racemates separated; from the chromatogram the ratio in which they are present has been determined, and hence the degree of asymmetric synthesis calculated and found to be: (i) 5%, (ii) 57%. By oxidation the original centre of asymmetry at C[2] has been removed to yield (+/-)-4-phenylpentan-2-one. The stereochemistry of the hydrogenation is discussed. (+)-alpha-Pinene has been hydrogenated over a Raney nickel catalyst to give almost exclusively (+)-cis-pinane, and the stereochemistry of this hydrogenation is also discussed. The possibility of purifying (+)-alpha-pinene by the technique of progressive freezing has been examined. (+/-)-beta-Naphthylmethylcarbinol has been hydrogenated over a platinum oxide catalyst, and over active and stabilized Raney nickel catalysts. In all cases a mixture of isomers of 1,2,3,4-tetrahydro-2-ethylnaphthalene and 1,2,3,4-tetrahydro-6-ethylnaphthalene was the exclusive, or predominating, product. In the hydrogenation with a stabilized catalyst a small quantity of a tetrahydro-beta-naphthylmethylcarbinol was isolated, and the presence of two isomeric 2-ethyldecalins was also detected. The hydrogenation of beta-naphthylmethylcarbinyl acetate, and of the methyl ether, produced in each case, exclusively, a mixture of the two isomeric ethyltetralins. p-Cymene has been acetylated to give a mixture of two acetyl cymenes in which 2-acetyl-p-cymene predominates. Aluminium isopropoxide reduction gave a mixture of two cymyl alcohols, the hydrogenation of which, under various conditions, gave in all cases an isomeric mixture of ethylcymenes, generally as the major product. With a stabilized Raney nickel catalyst a small quantity of the menthyl alcohols was obtained, and vapour-phase chromatography showed that hydrogenation had produced a mixture of four diasterio-isomeric racemates of the menthyl alcohols, which were present in unequal amounts, indicating that an asymmetric hydrogenation had occurred. The stereochemistry of the hydrogenation is discussed.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors :
Howard, Terence John.
Date : 1960
Contributors :
Additional Information : Thesis (Ph.D.)--University of Surrey (United Kingdom), 1960.
Depositing User : EPrints Services
Date Deposited : 22 Jun 2018 14:27
Last Modified : 06 Nov 2018 16:53

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