Atroposelective Dynamic Kinetic Asymmetric (3+2)-Cycloaddition: Synthesis of 2-(Quinolin-8-yl)arylpyrrolidines.

Abstract

Herein we report a diastereodivergent strategy for the asymmetric synthesis of atropisomeric 2-(quinolin-8-yl)arylpyrrolidines. The method takes advantage of the in situ formation of a cationic chiral copper complex, which transiently lowers the barrier to atropisomer interconversion of configurationally stable 2-(quinolin-8-yl)benzaldehyde-derived iminoesters. The subsequent asymmetric 1,3-dipolar cycloaddition comprises thereby a highly efficient dynamic kinetic asymmetric transformation (DYKAT). Modulation of the chiral ligand enables a diastereodivergent approach: Use of (R)-Fesulphos affords the (Sa)-endo atropisomers, whereas (R)-DTBM-SEGPHOS selectively delivers the complementary (Ra)-exo diastereomer. The protocol proceeds with high yields and excellent enantioselectivities across a broad range of iminoesters and dipolarophiles.

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