Reversal of oxaphosphetane formation in the reaction of benzaldehyde with benzylidene(2-N,N-dimethylaminophenyl)diphenylphosphorane ( ) and benzylidine(4-N,N-dlmethylamlnophenyl )diphenylphosphorane ( ), respectively, is found not to occur in tetrahydrofuran solution. The reason for this is that the rates of dissociation of the oxaphosphetanes to stilbenes and the corresponding triarylphosphine oxide are faster than reversal to the reagents. ... (e) BE Maryanoff, AB ...