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

The 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#).