Halogenation of Some Alkyl-Substituted 4-Aroyloxyimino- and 4-Arylsulfonyloxyimino-2,5-cyclohexadienones

The chlorination and bromination of 2,3-dimethyl-, 3-methyl-6-isopropyl-, and 2,6-diisopropyl-4-aroyl(or arylsulfonyl)oxyimino-2,5-cyclohexadienones follow the proposed rules of halogenation of 4-aroyl(or arylsulfonyl)oxyimino-2,5-cyclohexadienones: the reaction occurs preferentially at the cis-CÍC bond of the quinoid ring; simultaneous halogenation at both double bonds is not observed; halogen adds mainly across unsubstituted CÍC bond; no halogenation occurs at the double bond already substituted by a halogen; bromination of the CÍC bond with an alkyl substituent is more difficult than chlorination; the second halogen molecule adds only after regioselective dehydrohalogenation.