Furopyridines. XXX [1]. Synthesis and reaction of difuro[3,2-c:- 3',2'- e]pyridine, a new tricyclic heterocycle

Difuro[3,2-c:3',2'-e]pyridine 1, a new tricyclic heteroaromatic, has been prepared for the first time. Bromination of 1 with molecular bromine gave 3-bromo 7, 8-bromo 7' and 3,8-dibromo derivative 8; nitration with fuming nitric acid yielded 2-nitro compound 9, while nitration with a mixture of fuming nitric acid and sulfuric acid gave 2,7-dinitro derivative 10; formylation with n-butyllithium and dimethylformamide gave 2-formyl 11, 7- formyl 11', and 2,7-diformyl compound 12. The N-oxide 14 of 1 afforded 4- cyano compound 15 by cyanation with trimethylsilyl cyanide, 4-chloro compound 16 by chlorination with phosphorus oxychloride, and 4-acetoxyl compound 17 by acetoxylation with acetic anhydride.