Organocatalytic Enantioconvergent Synthesis of Tetrasubstituted Allenes via Asymmetric 1,8-Addition to aza-para-Quinone Methides

In contrast to the well-explored quinone methides (QMs) and aza-ortho-QMs, aza-para-QMs have been rarely studied in terms of their asymmetric transformations. Herein, a highly efficient enantioconvergent asymmetric 1,8-addition of aza-para-QMs is described. Featuring remarkable remote stereocontrol, this reaction provides expedient access to chiral tetrasubstituted allenes bearing an adjacent all-carbon quaternary stereocenter with high enantioselectivity and diastereoselectivity.