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The Resolution of 1:2-Dimethylcinnamyl Alcohol, the Stereochemistry of Hydrogenation of this Alcohol and of 1-(alpha-Furyl)Ethanol.

Loc, Le Ba. (1959) The Resolution of 1:2-Dimethylcinnamyl Alcohol, the Stereochemistry of Hydrogenation of this Alcohol and of 1-(alpha-Furyl)Ethanol. Doctoral thesis, University of Surrey (United Kingdom)..

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Abstract

The resolution of (+/-)-1:2-dimethylcinnamyl alcohol has been carried out by fractional crystallisation of the brucine salt of the hydrogen phthalate, and has yielded the (-)-isomer. (+/-)-1:2-Dimethylcinnamyl alcohol has been hydrogenated over Raney nickel W-3 catalyst to (+/-)-2-methyl-l- phenylbutan-3-ol in which a new centre of asymmetry is generated at C[2]. Oxidation of the (+/-)-saturated alcohol has yielded (+/-)-2-methyl-l-phenylbutan-3-one in which the original asymmetric centre is eliminated. Attempts have been made, but failed, to separate the diastereoisomers of (+/-)-2-methyl-l-phenylbutan-3-ol, via their coloured p-phenylazobenzoates, by adsorption chromatography, both on silica gel and alumina. Attempts to replace the secondary alcohol group by a methylene group, both by reductive cleavage of the bromo-derivative with lithium hydride and lithium aluminium hydride, and by the preparation of the alkylmagnesium bromide, followed by reaction with ammonium chloride were not satisfactory, (-)-1:2-Dimethylcinnamyl alcohol has been smoothly hydrogenated to (+)-2-methyl-l-phenylbutan-3-ol, which on oxidation has yielded (-)-2-methyl-l-phenylbutan-3-one, the optical activity of the final ketone demonstrating that an asymmetric synthesis has been effected. Two sets of experiments were carried out. The percentage of asymmetric synthesis effected by hydrogenation of the optically active alcohol has been deduced by vapourphase chromatography of the (+)-saturated alcohol; the two diastereoisomeric alcohols were separated by this process, and it has been deduced from the chromatograms that 21.5% and 17.3% asymmetric synthesis was effected in the two acts of hydrogenation. Possible conformations of the 1:2-dimethyl-cinnamyl alcohol to the catalyst surface are discussed, one is considered to be somewhat more probable than others, and it is concluded that there is a preponderance of hydrogenation via this conformation, leading to asymmetric synthesis, (+/-)-1-(alpha-Furyl)ethanol has been hydrogenated over Raney nickel W-3 catalyst to (+/-)-1-(alpha-tetrahydro-furyl)ethanol, which, by the preparation and recrystallisation of the N-a-naphthylcarbamate, appears to contain two diastereoisoraeric racemates. Elimination of the original centre of asymmetry by oxidation has failed to give the expected (+/--alpha-acetotetrahydrofuran, The investigation has, therefore, not been extended to the optically active 1-(alpha-furyl)ethanol.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors :
NameEmailORCID
Loc, Le Ba.
Date : 1959
Contributors :
ContributionNameEmailORCID
http://www.loc.gov/loc.terms/relators/THS
Additional Information : Thesis (Ph.D.)--University of Surrey (United Kingdom), 1959.
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/848291

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