摘要
The development of intermolecular [2+2] cycloadditions between allenamides and diarylketenes is described. α-Aryldiazo arylketones are employed as ketene precursors that react smoothly with allenamides in the presence of a P(C <sub>6</sub> F <sub>5</sub> ) <sub>3</sub> promoter. High diastereoselectivity (dr > 20 : 1) with endo-regioselectivity can be achieved when two aryl groups of ketenes have opposite electronic properties. The role of P(C <sub>6</sub> F <sub>5</sub> ) <sub>3</sub> is to increase the reaction yields, but also enhancing stereoselectivity.