Michael additions with an enaminoester: Reaction of phenyl 4-chromone-3-sulfonate with methyl 3-amino-2-pentenoate

The novel benzoxathiinopyridines 5 and 8 and the hitherto unknown oxathiinobenzopyran 17 were synthesized by ring transformations of phenyl 4-chromone-3-sulfonate ( 1 ) with methyl 3-amino-2-pentenoate ( 2 ). The structures of 5, 8 and 17 were determined by spectroscopic methods and the reaction pathways for the formation of these compounds are discussed.