Harmony of CdI2 with CuBr for the one-pot synthesis of optically active α-allenols

A highly efficient one-pot synthesis of chiral α-allenols from propargylic alcohols, aldehydes and pyrrolidine induced by CuBr and (R,Ra)-N-PINAP or (R,Sa)-N-PINAP and CdI2 has been developed. Both the yields and enantioselectivities of the allenols of this one-pot procedure are practical. Comparison with ZnI2 control experiments revealed that CdI2 can convert propargylic amine to allene in the presence of CuBr efficiently.