Highly Substrate‐Selective Macrocyclic Ring Closing Metathesis

A selective ring-closing metathesis (RCM) reaction for the formation of large macrocycles by using latent sulfur chelated ruthenium iodide benzylidenes, readily activated thermal and photochemical (UV-A visible light) stimuli, is reported. For dienes having one terminal alkene internal double bond, specific affinity diiodo alkylidenes unhindered terminus, combined with their reluctance to react olefins, favors RCM over oligomerization, providing high macrocyclic yields even at relatively concentrations. Alternatively, substrates containing two bonds, a sacrificial methylene donor can be used obtain desired products. With this methodology, lactones, lactams, ketones ranging from 13- 22-membered rings could synthesized in moderate yields. In addition, synthetic applications one-pot cyclization/reduction sequence produce Exaltolide, natural macrolide (commercial musk), Dihydrocivetone, other saturated have been explored. Thus, we disclose herein an important advantage benzylidene catalysts less dichloro counterparts provide more profound understanding mechanisms that enhanced cyclization outcome.