Versatile Bis‐Propargylic Reactivity of Acetylenedicarbonyl−Cobalt Complexes with Neutral C‐Nucleophiles: Direct Synthesis of a Furyl‐α‐pyrone

Abstract Double aldol reactions of the Co 2 (CO) 6 complex of acetylenedicarbaldehyde with several enol ethers have been carried out and compared with the double Nicholas reactions of the corresponding bis(diethyl acetal) complex. The selectivity was found to depend on (i) the nucleophile, (ii) the solvent, and (iii) the number of equivalents of the auxiliary BF 3 ·OEt 2 . While silyl enol ethers give mono‐ and 1,4‐bis‐dialkylation products …