TRIMETHYLSILYL CYANIDE - A REAGENT FOR UMPOLUNG .18. NUCLEOPHILIC ACYLATION OF ALPHA-CHLOROCARBONYL COMPOUNDS - A NOVEL AND DIASTEREOSELECTIVE APPROACH TO SUBSTITUTED ALPHA,BETA-EPOXY KETONES

Trimethylsilyl Cyanide ‐ A Reagent for Umpolung, XVIII. ‐ Nucleophilic Acylation of α‐Chlorocarbonyl Compounds ‐ a Novel and Diastereoselective Approach to Substituted α,β‐fl‐Epoxy Ketones The addition products of trimethylsilyl cyanide and benzaldehyde (1a), furfural (1b), and α,β‐unsaturated aldehydes 2a‐c, respectively, react after deprotonation with α‐chloroaldehydes and ‐ketones 3a‐d. By 1,4‐O,O‐silyl rearrangement and cyanide elimination O‐trimethylsilyl acyloins 4 and 9, respectively, are formed. With fluoride, 4 and 9 react to α,β‐epoxy ketones 5 and 10 in high yield and with E/Z selectivities from 80:20 to >95: 5. By this novel route even α,β‐unsaturated epoxy ketones (10) become available. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim