The first example of enantioselective carbenoid addition to organochalcogen atoms: application to [2,3]sigmatropic rearrangement of allylic chalcogen ylides

In the presence of a catalytic amount of chiral copper(I) or rhodium(II) compounds the enantioselective addition of a carbenoid, derived from ethyl diazoacetate, to chalcogen atoms of aryl cinnamyl chalcogenides affords a diastereoisomeric mixture of ethyl 2-arylchalcogeno-3-phenylpent-4-enoates via[2,3]sigmatropic rearrangement of the intermediate chalcogen ylide with up to 41% ee.