Trimethylsilylcyanid als Umpolungsreagens, XXII. Nucleophile Acylierung α,β‐ungesättigter Aldehyde durch umgepolte α,β‐ungesättigte Aldehyde

Abstract

Trimethylsilyl Cyanide — A Reagent for Umpolung, XXII. — Nucleophilic Acylation of α,β‐Unsaturated Aldehydes by Umpolung of α,β‐Unsaturated AldehydesAmbident anions 1aA → 1dA, obtained from 1a — d by LDA, are treated with α,β‐unsaturated aldehydes 2a — c. In all cases the kinetically controlled 1,2/α adducts 3 are formed which in contrast to 1,2/α adducts with α,β‐unsaturated ketones do not rearrange to the thermodynamically stable 1,4/α‐ or 1,4/γ products 4a and 6. Adducts 4 are smoothly formed if imines of 2 are applied. A thermal oxy‐Cope rearrangement transforms adducts 3 into 6. Substantial proportions of 1,2/γ adducts 5 are produced from 1A and 2 in the presence of magnesium bromide.