Phosphoranes Thioxophosphoranes

The P=C bond of ), a -phosphoranes is also accessible to a 1,3-dipolar cycloaddition reaction. The formation of 97 (Scheme 8.23), of 3,5-dihydro-1,2,4-diazaphosphole sulfide 132 from an amino(methylene)thioxophosphorane (190) and of phosphirane imine 133 from an amino(imino)alkylidenephosphorane (191) (Scheme 8.29) illustrate the chemical behavior of phosphaalkenes containing a A, a -phosphoms atom. 

Some R-P=NR type compounds will add O or S directly to produce trigonal planar imino oxo-phosphoranes (7.535a) or thioxophosphoranes (7.535b). 

Phosphinylidene thioxophosphoranes are obtained by direct addition of S to diphosphenes, and methylene(thioxo)phosphoranes occur as intermediates in the formation of thiaphosphirene sulphides from methylene phosphoranes (9.642). Only a few of these compounds have so far been found stable enough for isolation. 

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