Abstract Cumulenic ethers of the type R′ R ″C= C= C= CHOMe 1 (R′, R ″= H, H; H, Me or Me, Me) are readily convertible into 3-alken-1-ynes R′ R ″C= CR− C≡ C− H 2 (R= alkyl or Ph) upon treatment with Grignard reagents, RMgX, in the presence of small amounts of CuBr. Interaction of substrates 1 with homocuprates [RCuR] MgX results generally in mixtures of 2 and 1-methoxy-1, 3-butadienes R′ R ″C= CR [BOND] CH= CHOMe 3, ...
