Generation of o-quinone α-carbomethoxymethide by photolysis of methyl 2-hydroxyphenyldiazoacetate in aqueous solution

Abstract

Flash photolysis of methyl 2-hydroxyphenyldiazoacetate (8) in dilute aqueous perchloric acid solution and acetic acid and biphosphate ion buffers produced a transient species that was identified as o-quinone α-carbomethoxymethide (9). This structural assignment is based upon solvent isotope effects, the form of buffer catalysis, UV absorption maxima, and the identity of decay rate constants with those determined for the transient obtained by flash photolysis of other, more conventional, quinone methide precursors, namely the benzyl alcohol methyl 2-hydroxy mandelate (10) and its acetate, 2′-acetoxy-2-hydroxyphenylacetate (11).