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Please login to access the full content or check if you have access via Variation 4: Aldols via Boron Enolates from the Addition of Sulfur Nucleophiles to ­Monoalkylketenes

DOI: 10.1055/sos-SD-023-00535

Tidwell, T. T.Science of Synthesis, (200623596.

Methylketene (2) prepared by dehalogenation of 2-bromopropanoyl bromide reacts with dibutyl(tert-butylsulfanyl)borane (156) by addition of the sulfur nucleophile anti to the methyl group of the ketene to form the intermediate enol borinate 157, which reacts with aldehydes 158 [R1=Ph, iPr, (CH2)2Ph] to form aldol products 159 in 6578% yield and with erythro/threo ratios of 93:3 to >95:5 (Scheme 49).[‌109‌] Enol borinates prepared by enolization of S-tert-butyl propanethioate have the opposite stereochemistry and react to form the threo-products preferentially.[‌109‌]

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