Furopyridines. XVII. 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).