Copper-Catalyzed Reaction of N-Monosubstituted Hydrazones with CBr4: Unexpected Fragmentation and Mechanistic Study

The copper catalyzed reaction of N-monosubstituted hydrazones with carbon tetrabromide leads to formation of expected dibromodiazadienes and unexpected dibromostyrenes. The experimental and theoretical study of the reaction revealed a key role of N-centered radicals, which can eliminate aryl radicals to form the corresponding dibromostyrenes. Alternatively, the oxidation of intermediate N-centered radicals by Cu(II) results in the corresponding diazadienes. These two reaction pathways are competitive directions of the reaction. Consequently, the reaction can be useful for the synthesis of both dibromostyrenes and rare dibromodiazadienes.

Automated summary

The copper catalyzed reaction of N-monosubstituted hydrazones with carbon tetrabromide leads to the formation of expected dibromodiazadienes and unexpected dibromostyrenes. The key role of N-centered radicals in the reaction was revealed through experimental and theoretical studies, where they can eliminate aryl radicals to form dibromostyrenes. Alternatively, the oxidation of intermediate N-centered radicals by Cu(II) results in the formation of diazadienes. These two reaction pathways are competitive directions of the reaction, making it useful for the synthesis of both dibromostyrenes and rare dibromodiazadienes.