Fragmentation of methyl hydrogen α-hydroxyiminophosphonates to monomeric methyl metaphosphate: Stereochemistry and mechanism

Methyl α-(hydroxyimino)benzylphosphonates [(E)-(2) and (Z)-(2)] undergo fragmentation in alcohols to benzonitrile and a (mixed) phosphodiester. Kinetic studies of the behaviour of (E)-(2) and (Z)-(2) in a series of alcohols indicate that (Z)-(2) undergoes acid catalysed isomerization to (E)-(2) which subsequently undergoes fragmentation via a concerted, dissociative bond cleavage to benzonitrile and monomeric methyl metaphosphate (7). The latter is trapped by the solvent in the second step of the reaction to give the final phosphodiester product.