Synthesis of the novel pyrrolo[2,1-d][1,2,5]benzotriazepine, pyrrolo[2,1-e][1,3,6]benzotriazocine and pyrrolo[1,2-a]tetrazolo[1,5-d][1,4]benzodiazepine ring systems. A new route to pyrrolo[1,2a]quinoxaline via transamination of in situ generated 1-(2-aminophenyl)-2-iminomethylpyrroles