Stereochemistry and kinetics of methoxide ion substitution in (Z)‐ and (E)‐O‐methylbenzohydroximoyl cyanides

Abstract

AbstractThe stereochemistry and kinetics of the methoxide ion substitution reactions (Z)‐ and (E)‐methylbenzohydroximoyl cyanidc [PhC(CN)NOCH3] were investigated. The reaction of the (Z)‐hydroximoyl cyanide with sodium methoxide in DMSO–methanol (9:1) solution at 44·8°C gives a mixture of methyl (Z)‐O‐methylbenzohydroximate [PhC(OCH3)NOCH3] and the O‐methyloxime of α‐ketophenylacetamide PhC(CONH2)NOCH3. The (E)‐hydroximoyl cyanide undergoes methoxide ion‐catalyzed isomerization to the E‐isomer faster than it undergoes nucleophilic substitution. These observations were interpreted in terms of an addition–elimination mechanism in which the rate‐limiting step is elimination of the nucleofuge (AN + DN#).