NICKEL-CATALYZED CARBONYLATION OF ALPHA-KETO ALKYNES UNDER PHASE-TRANSFER CONDITIONS

alpha-Keto alkynes are carbonylated in the presence of Ni(CN)(2) under phase transfer conditions (toluene, 5 N NaOH, tetrabutylammonium bromide) to give either unsaturated hydroxybutyrolactones or 2-alkynylidene 3-keto carboxylic acids depending on. the presence or absence of an alpha-H on the carbon alpha to the alkynyl group. This is rationalized, in the second case, by a rearrangement following abstraction of this alpha-H by base. A rearrangement to an allenic intermediate prior to carbonylation is excluded.