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Title: Diphenylphosphinoyl ketals
Author: Cornish, C. A.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1982
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This thesis describes the synthesis of some diphenylphosphinoyl ketals and the reactions of their anions with aldehydes, ketones and esters. Starting from ethyl acetoacetate anion and an epoxide, the synthesis of γ-diphenylphosphinoyl (Ph2P0) ketals (98) was readily accomplished via the 5-bromo pentan-2-one ethylene acetals. Since γ-Ph2PO ketals may be alkylated adjacent to the phosphorus, this allows the range of substitution patterns to be expanded. The anions of γ-Ph2PO ketals reacted with aldehydes to give mixtures of diastereoisomeric alcohols (167, 175) which were usually separable by chromatography. An excess of the erythro alcohol (167) was formed. The alcohols were converted stereospecifically into unsaturated ketals (176, 177) with sodium hydride (Wittig-Horner Reaction). When the anion of the γ-Ph2PO ketal(98, R1 = R2 = H) reacted with esters, the ketones (174) were produced, reduction of which with sodium borohydride also gave a mixture of the alcohols (167, 175), this tine with the threo alcohol (175) predominating. When the anion of (98) reacted with a ketone, mixtures of the tertiary alcohols (163) were produced, which when separated could be converted stereospecifically into the trisubstituted olefins (183). These methods allow the first synthesis of a general γδ-unsaturated ketal that is connective, stereospecific and regiospecific on each component. In an analogous manner, the δ-Ph2PO ketal (194) was prepared and used in the formal total synthesis of Brevicomin, an insect sex pheromone. The anion of (98) reacted with diphenyl disulphide to give (203). This compound was converted to the corresponding sulphoxide and pyrolysed to give the vinyl phosphine oxide (205). The anion of (205) was made at low temperature, but only the deprotected enone (252) was isolated on work up. The anion of (203) also reacts with aldehydes to give vinyl sulphides (264) which are convertible into cyclcpentenones.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available