Synthesis of Phosphinamides in the 5,6-Oxaphosphabicyclo(2.2.2)octene Series as Possible Precursors of Metaphosphoramidates

摘要

The readily dimerizable 1-aminophosphole oxides were found to function as dienes in the Diels-Alder reaction with N-phenylamaleimide, thereby providing phosphinamides with the 7-phosphanorbornene structure. The dimers also possess this structural feature, which has been subjected to the oxygen-insertion reaction with m-chlorperbenzoic acid. The Diels-Alder adducts react cleanly to provide the insertion product at the Phosphorus-Carbon bond, providing the 5,6-oxaphosphabicyclo octene ring system; the dimers undergo reaction first at the phosphinamide nitrogen of the -phospholene ring and then at the 7-phosphanorbornene P-C bond. Stereochemical features of an aminophosphole oxide dimer and of the O-insertion product of a Diels-Alder adduct were unequivocally established by X-ray crystal structure analyses. The O-insertion occurred with retention of the configuration at phosphorus. P and C NMR spectra were also of value in structure assignments.