Benzothiazole derivatives R 0270Synthesis of Novel Pyrazolo[5,1-b]benzothiazoles: A New Pericyclic Pathway. -N-Amination of the benzylbenzothiazoles (I), followed by reaction of the N-amino salts (III) with ethyl orthoformate (IV) afford derivatives (V) of the pyrazolobenzothiazole ring system. The ring closure may proceed via deprotonation of the N-amino salt and subsequent electrocyclization to provide the tricyclic ring system. From a theoretical point of view, the pericyclic nature of the ring-closure step is of importance. -(TEKINER-GULBAS, B.; FILAK, L.; VASKO, G. A.; EGYED, O.; YALCIN, I.; AKI-SENER, E.; RIEDL, Z.; HAJOS*, G.; Heterocycles 75 (2008) 8, 2005-2012; Chem. Res. Cent., Hung. Acad. Sci., H-1025 Budapest, Hung.; Eng.) -H. Hoennerscheid 50-123