MONOCARBOXYLATION AND DICARBOXYLATION OF ALPHA-HALOALKYNES CATALYZED BY NICKEL CYANIDE UNDER PHASE-TRANSFER CONDITIONS

Alpha-Haloalkynes react with carbon monoxide to give either allenic monoacids or unsaturated diacids in 70-96% overall yields. The reaction is catalyzed by nickel cyanide under phase-transfer conditions (4-methyl-2-pentanone, 5 N NaOH, tetraalkylammonium halide). It is shown that the carbonylation occurs stepwise: first to the allenic monoacid via a nucleophilic substitution, followed by a second carbonylation of this latter. The diacid is obtained with high stereoselectivity.