Naslov
New pentacyclic ring system: intramolecular cyclization of o, o'-disubstituted bibenzothiazoles
(New pentacyclic ring system: intramolecular cyclization of o, o'- disubstituted bibenzothiazoles)

Autori
Racane, Livio ; Čičak, Helena ; Mihalić, Zlatko ; Karminski-Zamola, Grace ; Tralić-Kulenović, Vesna

Izvornik
Tetrahedron (0040-4020) 67 (2011), 15; 2760-2767

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
benzothiazole; benzo[c]cinnoline; carbazole; reduction; oxidation;

Sažetak
Efficient methods for preparation of isomeric o, o'-diaminobibenzothiazoles (8a and 11a) and o, o'-diamino-2, 2'-dimethylbibenzothiazoles (8b and 11b), potentially valuable building blocks for construction of hitherto unknown dithiazolo annulated pentacyclic heterocycles, has been developed. The dithiazolo annulated benzo[c]cinnolines 9a, 9b and 12a were prepared from corresponding diamines by oxidation with PhI(OAc)2 in a good yield. The dithiazolo annulated carbazoles 13 and 14 were efficiently prepared from corresponding diamines by thermal cyclization in H3PO4. Unusual course of reduction and product formation of o, o'-dinitrosubstituted bibenzothiazoles 6a and 6b with SnCl2 under acidic conditions was rationalized by DFT quantum-mechanical calculations. It was suggested that cyclic products are formed from dinitroso derivatives and open-shell species immediately following on a reduction path.

Izvorni jezik
Engleski

Znanstvena područja
Kemija, Tekstilna tehnologija

POVEZANOST RADA