Thermal rearrangement of some 3-alkyl-2-aryltetrahydro-1,3-oxazine N-oxides. Synthesis of 2-alkyl-7-aryltetrahydro-1,6,2-dioxazepines

Several 2-alkyl-7-aryltetrahydro-1,6,2-dioxazepines 5a-i have been synthesized by a Meisenheimer-type rearrangement of 3-alkyl-2-aryltetrahydro-1,3-oxazine N-oxides 4a-i . These dioxazepines have not been previously described and for the first time compounds with the tetrahydro-1,6,2-dioxazepine ring-system have been made available. The structure assigned to members of this novel heterocycle is based on elemental analysis, infrared, and ¹H nmr spectral evidence. Further definitive evidence for the structure of these heterocycles is provided by an X-ray crystallographic analysis of 5c .