Chiral 1,2,3‐Triazolium Salt Catalyzed Asymmetric Mono‐ and Dialkylation of 2,5‐Diketopiperazines with the Construction of Tetrasubstituted Carbon Centers

Abstract

Novel asymmetric mono‐ and dialkylation reactions of α‐substituted 2,5‐diketopiperazines catalyzed by new chiral spirocyclic‐amide‐derived triazolium organocatalysts have been developed, resulting in a range of enantioenriched 2,5‐diketopiperazine derivatives containing one or two tetrasubstituted carbon stereocenters. The reactions feature high yields (up to 98%), and excellent cis‐diastereo‐ and enantioselectivities (up to >20:1 dr, >99 % ee), and they provide a new asymmetric synthetic approach to important functionalized 2,5‐diketopiperazine skeletons. Furthermore, a possible reaction mechanism was proposed based on both control experiments and extensive DFT calculations.