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Enantioselective Aza-Sakurai Cyclizations: Dual Role of Thiourea as H-Bond Donor and Lewis Base.

An enantioselective, catalytic aza-Sakurai cyclization of chlorolactams has been developed as an efficient entry into indolizidine and quinolizidine frameworks. Structure-enantioselectivity relationship studies and mechanistic analysis point to a dual role of the catalyst wherein the thiourea moiety of the catalyst is engaged in both anion binding and Lewis base activation of a substrate.