Furopyridines .17. Cyanation, chlorination and nitration of furo[3,2-b]pyridine N-oxide

The N-oxide 2 of furo[3,2-b]pyridine (1) was cyanated by the Reissert-Henze reaction with potassium cyanide and benzoyl chloride to give 5-cyano derivative 3, which was converted to the carboxamide 4, carboxylic acid 5, ethyl ester 6 and ethyl imidate 8. Chlorination of 2 with phosphorus oxychloride yielded 2-9a, 3-9b, 5-9c and 7-chloro derivative 9d. Reaction of 9d with sodium methoxide, pyrrolidine, N,N-dimethylformamide and ethyl cyanoacetate afforded 7-methoxy-10, 7-(1-pyrrolidyl)-11 and 7-dimethylaminofuro[3,2-b]pyridine (14) and 7-(1-cyano-1-ethoxy-carbonyl)methylene-4,7-dihydrofuro[3,2-b]pyridine (12). Nitration of 2 with a mixture of fuming nitric acid and sulfuric acid gave 2-nitrofuro[3,2-b]pyridine N-oxide (15).