Efficient synthesis of (Z)- and (E)-methyl 2-(methoxyimino)-2-phenylacetate

Abstract Direct oximation of 2-oxo-2-phenylacetate ( 3 ) gave the ( Z )-methyl 2-(methoxyimino)-2-phenylacetate ( 1 ) in 71% yield, while the E oxime 2 was prepared from 3 in 65% yield via oxime isomerization of 2-(methoxyimino)-2-phenylacetic acid ( 5 ). Computational studies suggest that the isomerization of 5 is thermodynamically driven, while the direct oximation of ketoester 3 is kinetically controlled.