(IC) undergo electrophilic attack by dimethyl acetylenedicartmxylate to reversibly form diradical or zwitterionic intermediates, which then evolve along different pathways. Thus initial attack at position 5 of the heteropentalene (path A, Scheme V) ends up in formal cycloaddition yielding the pyrazolo [1, 2-a] pyrazolo [l, 2-b] benzotriazole 2 from la and the triazolo [2, la] pyrazolo [l, 2-b] benzotriazole 10 from lb. The latter decomposes to dimethyl ...