THERMAL ISOMERIZATION OF 1-MORPHOLINO-3-PHEHYL (OR VINYL)-ALLENES: SYNTHESIS OF THE OXAZINOAZEPINE FRAMEWORK

Article abstract of DOI:10.1016/0040-4039(92)88051-6

1-Morpholino-3-phenylallenes isomerize to 3,4,6,12b-tetrahydro-1H-<1,4>oxazino<4,3-a><2>benzazepines at >/= 105 deg C.Similarly, 1-morpholino-3-vinylallenes are transformed into 3,4,10,10a-tetrahydro-1H-<1,4>oxazino<4,3-a>azepines.Formation of these novel heterocycles is rationalized by a 1,3-proton shift in the morpholinoallenes, followed by 1,7-electrocylization of the α,β,γ,δ-unsaturated azomethine ylide thus formed.