Stereospecific addition of organocopper(I) reagents to 1‐alkynylphosphines. A new example of α‐hetero‐substituted vinylcopper(I) compounds

Homocuprates R2CuMgX and heterocuprates [RCuBr]MgX can be reacted easily with 1‐alkynylphosphines R′‐C≡C‐P(C6H5)2 (R′ = H or CH3), leading exclusively to vinylic phosphines RR′CCHP(C6H5)2 after protonation, in almost quantitative yields. The additions proved to be stereospecific, only cis‐additions were observed as was shown by 1H‐NMR and GLC.