The N-heterocyclic carbene-catalyzed [3 + 2] annulation of isoindigos with enals: the enantioselective construction of three contiguous stereogenic centers

Abstract

Constructing contiguous all-carbon quaternary stereogenic centers has posed a long-standing synthetic challenge in organic chemistry. In this work, the NHC-catalyzed enantioselective [3 + 2] annulation of enals with isoindigo was introduced as an efficient strategy for the construction of dimeric spirocyclic bisindoline alkaloid derivatives with moderate yields and good enantioselectivities. Remarkably, three contiguous stereogenic centers—including two congested all-carbon quaternary stereogenic centers—were successfully constructed in a simple one-step operation.