The first example of the Wolff rearrangement of α-diazocyclobutanone, the title diazo ketone (2), into the three-membered cyclic ketene (4) was observed. The ketene intermediate (4) could be trapped by its reaction with alcohols, aniline, azobenzene, and N- benzylideneaniline to afford 1-alkoxycarbonyl-(5a–c) and 1-phenylcarbamoyl-2, 3-bis (diphenylmethylene) cyclopropane (5e), and 1, 2-bis (diphenylmethylene)-5, 6-diphenyl-5, ...
