Sigmatropic rearrangement of ammonium ylideskey step in the synthesis of methyl 2-formylphenyl acetate
N-Cyanomethyl-N,N-dimethyl-N-(-methoxycarbonyl)benzylammonium salts 5 were synthesized and treated with different base/solvent systems, giving the products of sigmatropic rearrangements [2,3] 7 and [1,2] 8. In reactions carried out in liquid ammonia, [2,3] rearrangement definitively prevailed. Pure 7(or mixture of 7 and 8) were deprotected to afford methyl 2-formylphenyl acetate (9) in good yield.