Furopyridines. VII. Preparation and hydrolysis of 2‐cyano and 3‐cyano derivatives of furo[3,2‐b]‐, furo[2,3‐c]‐ and furo[3,2‐c]pyridine

This paper describes the preparation and hydrolysis of 2‐cyano and 3‐cyano derivatives of furo[3,2‐b]‐, furo[2,3‐c]‐ and furo[3,2‐c]pyridine. Treatment of furopyridines 1a, 1b and 1c with n‐butyllithium in hexane‐tetrahydrofuran at ‐70° and subsequent addition of N,N‐dimethylformamide yielded 2‐formyl derivatives 2a, 2b and 2c. Dehydration of the oximes 4a, 4b and 4c of 2a, 2b and 2c gave 2‐cyano compounds 5a, 5b and 5c, which were hydrolyzed to give 2‐carboxylic acids, 6a, 6b and 6c, respectively. Reaction of 3‐bromo compounds 7a, 7b and 7c with copper(I) cyanide in N,N‐dimethylformamide afforded 3‐cyano derivatives 8a, 8b and 8c. Alkaline hydrolysis of 8a, 8b and 8c gave compounds formed by fission of the 1‐2 bond of furopyridines 9a, 9b and 9c, while acidic hydrolysis gave the corresponding carboxamides, 10a, 10b and 10c.