1-Oxa-4-azabutadienes proved to be prone to react with some heterocumulenes after 1, 3- cycloaddition patterns yielding various 5, 5-disubstituted derivatives of 1, 3-diaryl- hydanotoins as it was shown by the chemical and spectroscopic analysis. Relatively high yields, mild reaction conditions and a very weak effect of solvent polarity on the reaction rate suggested a synchroneous mechanism involving 1, 2-migration of a substituent.