Synthesis of multi-substituted allenes from organoalane reagents and propargyl esters by using a nickel catalystElectronic supplementary information (ESI) available. See DOI: 10.1039/c8ob00781k

A highly efficient and simple route for the synthesis of multi-substituted allenes has been developed by a nickel catalyzed S N 2′ substitution reaction of propargyl esters with organic aluminium reagents under mild conditions, which gave the corresponding multi-substituted allenes in good to excellent yields (up to 92%) and high selectivities (up to 99%) at 60 °C for 6 h in THF. Aryls bearing electron-donating or electron-withdrawing groups in propargyl esters gave products in good yields. In addition, the multi-substituted allenes bearing a thienyl or a pyridyl group were obtained in 95-97% selectivities with isolated yields of 72-83%. Furthermore, the S N 2′ substitution reaction worked efficiently with propargyl carbonate compounds as well. On the basis of the experimental results, a possible catalytic cycle has been proposed. The S N 2′ substitution reaction of propargyl acetates with organoaluminum reagents mediated by Ni(PhP 3 ) 2 Cl 2 (4 mol%)/PPh 3 (8 mol%)/K 2 CO 3 in tetrahydrofuran afforded the corresponding product multi-substituted allenes in good yields (up to 92%) with high selectivities (up to 99%) at 60 °C for 6 h.