Trimethylsilylcyanid als Umpolungsreagens, XVIII Nucleophile Acylierung von α‐Chlorcarbonyl‐Verbindungen – ein neuer und diastereoselektiver Zugang zu substituierten α,β‐Epoxyketonen

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.