Selective Synthesis of Highly Functionalized Bicyclic Pyridinone and 1,3-Oxazinane Derivatives

Two types of novel bicyclic compounds such as pyridinone 3 and 1,3-oxazinane derivatives 4 have been synthesised via the regioselective condensation reaction of heterocyclic ketene aminals (HKAs) with ethyl 2-cyano-3,3-bis(methylthio)-acrylate or 2-(bis(methyl-thio)methylene)-malononitrile in xylene at refluxing temperature. The bicyclic pyridinone compounds 3 can be efficiently obtained using catalyst-free conditions whereas 1,3-oxazinane derivatives 4 are obtained by adding Cs2CO3 under the same conditions. The reactions have the advantage of excellent yield, inexpensive raw materials and convenient final treatment.