Cobalt-Catalyzed gem-Cross-Dimerization of Terminal Alkynes

Transition-metal-catalyzed dimerization of two different terminal alkynes provides an atom-economic synthesis of valuable conjugated 1,3-enynes. Despite many catalyst systems developed, the state-of-the-art solutions are still limited to special alkynes. A practical catalyst, which could be used to cross-dimerize general aryl alkynes and aliphatic alkynes, is still highly desired. Herein we present the earth-abundant Co(II)-catalyzed highly gem-selective cross-dimerization of aryl alkynes and aliphatic alkynes or gas acetylene under mild reaction conditions. Conjugated 1,3-enynes with various useful functional groups can be prepared in high yields. The applying of Co(OAc)2 and t-butyl group substituted triphos ligand is essential to distinguish the alkynes at different steps and realize the gem-selectivity.