Synthesis of cis-Octahydroindoles via Intramolecular 1,3-Dipolar Cycloaddition of 2?Acyl-5-aminooxazolium Salts

摘要

A concise method for the diastereoselectivensynthesis of octahydroindoles is presented. The productsncontain 2-amido and 7-hydroxyl substituents. A series of 2-nacyl-5-aminooxazoles were prepared in one step. Uponnmethylation of the oxazole nitrogen atom, the substratesnunderwent rapid intramolecular 1,3-dipolar cycloaddition with a tethered alkene and, after reduction with excess hydride,nproduced octahydroindoles with excellent diastereoselectivity. The method allows for the installation of α-quaternary stereogenicncarbon atoms.