Thermolysis of polyazapentadienes. Part 10. Flash vacuum pyrolysis of azoalkenes and some azocarbonyl compounds

Abstract

Thermolysis of the azoalkenes (1) and (6)–(8) takes place by 4π-electron electrocyclisation, followed by elimination of HCN to give imines. Decomposition of the related compounds (9)–(12) is less well defined, though the indole (22) has been identified from the thermolysis of (10) at high temperature. Alternatively, the azo ketones (15)–(18) undergo homolysis of the central C–N bond at 750 °C, and low yields of biaryls, formed by intermolecular radical coupling are generally found. Decarbonylation of intermediate aroyl radicals is extremely rapid under these conditions.