Transformations of gem-dichloroarylcyclopropanes in the reaction with NOCl·2SO3. Synthesis of 3-aryl-5-chloroisoxazoles

Nitrosation with complex NOCl·2SO3 of gem-dichloroarylcyclopropanes containing acceptor substituents in the aromatic ring proceeded chemo- and regioselectively affording 3-aryl-5-chloroisoxazoles in high yields. The presence of donor substituents complicated the reaction by the occurrence of competing processes.