Synthesis of 1, 3-Dioxin-4-ones and Their Use in Synthesis. XI. : 2, 2-Dimethyl-1, 3-dioxin-4-one as a Synthetic Equivalent of Formylketene : Synthesis of Heterocyclic Compounds

Cycloaddition of formylketene generated in situ by thermolysis of 2, 2-dimethyl-1, 3-dioxin-4-one with N-benzhydrylidenebenzylamine yields 3-benzyl-2, 2-diphenyl-1, 3-oxazin-4-one. Analogous reactions with a carbodiimide, cyanamide, and keteneacetal afford the corresponding 4+2 cycloadducts. Reaction of formylketene with 3-amino-2-butenamides affords 4-hydroxy-2-pyridones having a C-2 unit at the 3-position.