The reactivity of quinoneimines towards ketene and diphenylketene was examined.
N-Phenylbenzoquinoneirnines (I), (2) and also N-phenylnaphthoquinoneimine
react with ketene to give the spiro-adducts (5), (7) and (1 1) respectively.
These adducts were stable even after prolonged heating in high boiling
solvent. Reaction of the above imines with diphenylketene also afforded 13-
lactam spiro-adducts (6), (8) and (12), but they rearranged to oxindole derivatives
(9), (10) and (13) by heating in boiling ethanol. N-Phenyl-9, 10-
anthraquinoneirnine, however, was inert towards ketene or diphenylketene under
the same reaction conditions