Electron ionization mass spectra of phosphorus-containing heterocycles. II. 1,2,3,4,4a,5,6,7,8,8a-decahydro-1,3,2-benzodiazaphosphinine 2-oxides.

The electron ionization mass spectra of cis- and trans-fused 1,2,3,4,4a,5,6,7,8,8a-decahydro-1,3,2-benzodiazaphosphinine 2-oxides (1-17) were recorded, and the fragmentation pathways were established and compared with those of 1,4,4a,5,6,7,8,8a-octahydro-2H-3,1,2-benzoxazaphosphinine 2-oxides. In general, the mass spectral behaviors of the isomeric compounds were very similar and it was mostly impossible to differentiate them from each other on the basis of the relative abundances of their characteristic fragment ions. The compounds in which R(2) = Ph or OPh exhibited a series of common fragments, e.g. [R(2)H](+), R(2)PONHR(1(3)+), [M-C(3)H(7)](+) and [M-C(4)H(9)](+), the latter two ions being present in the spectra of only two of the derivatives with an N(CH(2)CH(2)Cl)(2) substituent on the P atom. When R(2) = Ph, numerous other alkyl radicals, alkenes and a cycloalkane were also ejected and these compounds also lost NH(2), NH(3), CH(3)N, CH(4)N or CH(3)NH(2). The compounds with an N(CH(2)CH(2)Cl)(2) substituent on the P atom most closely resembled their 3,1,2-O,N,P analogs in respect of the dominant role of this substituent.