Selective synthesis of 2,5-disubstituted furan-3-carboxylates and the isomeric 2,4-disubstituted furan-3-carboxylates

An unprecedented Ag2CO3 and DBU mediated cyclization of 3-substituted 2-(2-bromoallyl)-3-oxo-1-carboxylates leading to the formation of 2,5-disubstituted furan-3-carboxylates has been reported. In the absence of a silver salt, the isomeric 2,4-disubstituted furan-3-carboxylates are obtained.