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 ).