2-Substituted and 2,6-disubstituted 1,4-benzoquinone 4-oxime acetates

Abstract

The preparation and physical properties of 19 compounds in the title series are described. The acetates were prepared by treatment of the corresponding benzoquinone oximes or p-nitrosophenols with acetic anhydride in the presence of catalytic amounts of pyridine. The syn and anti isomers can be equilibrated in acetic anhydride solutions containing traces of sulphuric acid. The effect of substituents at C2 on the position of the syn-anti equilibria is very similar to their effect in the corresponding 1,4-benzoquinone 4-oximes. N.m.r. parameters, electronic and infrared data, photochemical syn-anti conversions, and the probable mechanism of the acid-catalysed equilibration are discussed.