Solvent-Controlled Diastereoconvergent Synthesis of Spirochromeno[4,3-b][1,3]pyrrole-Cyclopropanes through 2,3-Rearrangement-Driven Cyclopropanation of O-Propargyl Oximes with Sulfur Ylides.

Abstract

Herein, a variety of spirochromeno[4,3-b][1,3]pyrrole-cyclopropanes bearing four contiguous stereocenters were prepared in moderate to good yields with high diastereoselectivity through copper(I)-catalyzed 2,3-rearrangement-driven cyclopropanation of O-propargylic oximes with sulfur ylides. Mechanistic studies revealed that the MeCN solvent played an important role in the control of the diastereoselectivity of products. The present method features a broad substrate scope, three-ring formation in one pot, the formation of four contiguous stereocenters, solvent-controlled diastereoselective cyclopropanation, and novel spirochromeno[4,3-b][1,3]pyrrole-cyclopropane scaffolds.