Enantioselective a-chalcogenation

Several natural products, as well as many versatile synthetic intermediates, have a carbon-oxygen bond at the a-position of the carbonyl compound. Therefore, synthetic strategies aiming to perform the stereoselective introduction of this carbon-oxygen bond are of great importance, and several organocatalytic methods have been developed recently. 

---

It is worth noting that Doyle and co-workers have reported quite recently a Rh-catalyzed highly enantioselective [2,3]sigmatropic rearrangement of allylic oxonium ylides in place of the allylic chalcogen ylides [51]. 

---