Heteropentalenes. The Thermal Addition of Pyrazolo- and Triazolobenzotriazoles to Dimethyl Acetylenedicarboxylate

Article abstract of DOI:10.1021/jo00189a003

Pyrazolo<1,2-a>benzotriazole (1a), 1,2,3-triazolo<2,1-a>benzotriazole (1b), and 1,2,3-triazolo<1,2-a>benzotriazole (1c) undergo electrophilic attack by dimethyl acetylenedicarboxylate to reversibly form diradical or zwitterionic intermediates, which then