Phosphorus-Nitrogen Centres

The kinetics of the nucleophilic monosubstitution of imidazole by /7-nitrophcnolate in hexaimidazolylcyclotriphosphazene (265) in water-THF have been studied.242 A two-step mechanism involving the cleavage of a pentacoordinated intermediate to (266) in a general acid-catalysed reaction is proposed. As expected for such a mechanism, a change in the slow step occurs at pH 7 when the [buffer] increases and L0bs becomes independent of [buffer]. 

The kinetics and mechanism of hydrolysis of monobutylaniline phosphate (267) in acidic media have been reported on.243 The mechanism of hydrolysis of mono-phenylhydrazophosphate, as its barium salt, was investigated.244 

The rearrangement of the /V-phosphinoyl-O-sulfonylhydroxylamine (268) (with 57% enrichment with one 180 atom in the SO2 group) to the sulfonamide (269) (43.7% enriched with one 180 atom) occurs with BfrNFL in dichloromethane via the phosphonamidic-sulfonic anhydride intermediate (270).245 The rearrangement of the O-phosphinoyl compound (271) with /-butoxidc gives the phosphonamidic-phosphinic 

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Optical activity was first observed with organic compounds having one or more chiral carbon atoms (or centres) (i.e. a carbon substituted with four different groups). In the structures (1) to (17) the chiral carbons are specified with an asterisk. Subsequently compounds having chiral centres at suitably substituted heteroatoms (e.g. silicon, germanium, nitrogen, phosphorus, arsenic, sulphur, etc.) were also synthesised. Molecular dissymmetry, and hence chirality, also... 

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