A versatile synthesis of allenic hydrocarbons. Evidence for an organocopper(III) intermediate

Abstract

Abstract A number of allenes RR 1 CCCHR 2 2 have been prepared by interaction between acetylenic tosylates R 1 C≡CCHR 2 OTs, 1 (R 1 = H, alkyl, aryl, H 2 CC(CH 3 ) or CH 3 C≡C; R 2 = H or t ‐C 4 H 9 ) and organocopper(I) compounds “RCu” (formed from Grignard compounds RMgCl or RMgBr with R = alkyl, aryl or 2‐thienyl and copper(I) bromide in tetrahydrofuran). If R = t ‐C 4 H 9 the reaction with catalytic amounts of CuBr also gives good results. Significant amounts of C 6 H 5 CHCCH 2 or C 6 H 5 CDCCH, are formed if C 6 H 5 CCCH 2 OTs is reacted with “CH 3 Cu” (from CH 3 MgCl and CuI) at −60° in tetrahydrofuran and the reaction mixture is quenched at low temperatures with methanol or deuteriomethanol. This finding is considered as evidence for the intermediate occurrence of a copper(III) derivative.