Abstract: Reaction of hydridophosphoranes 2 with benzensulfenic esters 3 provides a series of substituted spirobicyclic alkoxyphosphoranes 4.The pseudorotation process of compound 4 was observed by the variable temperature ³¹PNMR spectra. The free energy of activation for this process was calculated. Coalescence for 4_a,4_boccurred at 130℃ ,4_cand 4_dat 140℃.The △G≠ for 4_a,4_b,4_c,4_dare 81.8,81.8,85.8,84. 99kJ/mol,respectively.The results have indicated that pseudorotation process is subject to steric infltiences.

Key words: Alkoxyphosphoranes, Pseudorotation, Pentacoordinated phosphorus, Benzene sulfenic esters, Hydridophosphoranes