DIELS-ALDER REACTIONS OF PYRIDINE O-QUINODIMETHANE ANALOGS GENERATED FROM FUNCTIONALIZED O-BIS(CHLOROMETHYL)PYRIDINES

The polyfunctional 2,3- and 3,4-o-bis(chloromethyl)pyridines 3, produc ed vip cycloaddition of the oxazinones 2 with propargyl chloride and 1 ,4-dichloro-2-butyne, were used as precursors of various pyridine o-qu inodimethane analogues. The 2,3- and 3,4-dimethylenepyridine systems w ere generated via reductive 1,4-elimination with iodide and trapped in situ with various dienophiles to form the tetrahydroquinoline and -is oquinoline type adducts. A regiospecific cycloaddition was observed fo r the 3,4-dimethylenepyridine system with electron-rich dienophiles, i .e. dihydrofuran and ethyl vinyl ether, in contrast to the reaction wi th methyl acrylate. Copyright (C) 1996 Elsevier Science Ltd.