1-Alkynyl-1,2-dihydrophosphetes, as prepared by reaction of the approp
riate titanacyclobutenes with alkynyldichlorophosphines, rearrange to
the corresponding phosphinines via an original 4 pi-cycloreversion-6 p
i-electrocyclization mechanism. The reaction of dimethyltitanocene wit
h 1,4-diphenylbutadiyne affords a new 3-vinyltitanacyclobut-3-ene that
can serve to prepare a 3-vinylphosphinine 6 by the same route. (C) 19
96 John Wiley & Sons, Inc.