Abstract: Stable, ylide-substituted 1, 3-~ yclobutanediones 4 were synthesized from triphenylphosphoranylidene-ketene, Ph, P= C= C= O (l), and aldehydes or active ketones, presumably through formation of unusual methyleneketene intermediates, RR'C= C= C= O(3). Related cyclobutanediones 5 were formed directly from 1 and ketenes in a one-step reaction. Structure identifications were made principally by nmr and mass spectra. ...
