Cycloadditions of Epoxy and Aziridinyl Enolsilanes and their Applications to Total Synthesis

Abstract

Epoxy and aziridinyl enolsilanes are versatile electrophiles for inter- or intramolecular (4+3) cycloadditions with common dienes such as furan and cyclopentadiene. However, even with less conventional dienes, they have also been effective for cycloadditions. Intramolecular (4+3) cycloadditions with substituted pyrroles have yielded for the first time fused tropanone frameworks, which we have used as a key step in the synthesis of the BCDEF core of the Type II galbulimima alkaloids (Scheme 1). Even benzenoid aromatics and thiophenes react readily as dienes in intramolecular (4+3) cycloadditions, culminating in an efficient dearomatization reactions overall (Scheme 2). This reaction could be used to construct both bridged and fused carbocycles towards the total synthesis of natural products.