Asymmetric Synthesis of cis-5-tert-Butylproline with Metal Carbenoid NH Insertion

Abstract
The highly stereoselective intramolecular metal carbenoid insertion reaction of sulfinimine-derived δ-amino α-diazoesters is used to prepare cis-5-tert-butylproline. A concerted or nearly concerted metal carbenoid N−H insertion reaction mechanism is proposed.