Synthesis and Thermolysis of Pentacoordinate 1,2-Azaphosphetidines

Pentacoordinate 1,2-azaphosphetidines bearing the Martin ligand were synthesized by the intramolecular dehydration of the corresponding β-amino phosphine oxides with Mitsunobu reagent (Ph3P-EtO2CN=NCO2Et). The X-ray crystallographic analysis of 1,2,4,4-tetraphenyl derivative shows that it has a distorted trigonal bipyramidal structure with oxygen and nitrogen atoms at apical positions. Their thermolyses gave the corresponding olefins along with a cyclic iminophosphorane, which was readily hydrolyzed to give the cyclic phosphinate and aniline.