Ring closing metathesis in the synthesis of sultones and sultams

Unsaturated sultones with normal, medium and large ring sizes were efficiently synthesized by ring closing metathesis (RCM) of sulfonates. The resulting alpha,beta-unsaturated sultones act as dienophiles in intermolecular Diels-Alder reactions. A first cyclic sulfate formation through RCM has been discovered, and a rapid access to beta-lactams fused to a sultam moiety of variable ring size was developed from inexpensive, commercially available starting materials using RCM as the key operation. An efficient RCM of 4-vinylazetidin-2-ones to give 1-aza-bicyclo[4.2.0]oct-4-en-8-ones is also described.