FUROPYRIDINES .21. SYNTHESIS OF CYANO DERIVATIVES OF FURO[2,3-B]PYRIDINE, FURO[2,3-C]PYRIDINE AND FURO[3,2-C]PYRIDINE AND THEIR CONVERSION TO DERIVATIVES HAVING ANOTHER CARBON-SUBSTITUENT

Cyanation of furo[2,3-b]-, -[2,3-c]- and -[3,2-c]pyridine N-oxides 1a, 1b and 1c by the Reissert-Henze method, reaction with benzoyl chlorid e and trimethylsilyl cyanide in dichloromethane and the reaction with trimethylsilyl cyanide and triethylamine in acetonitrile afforded 6-cy anofuro[2,3-b]-2a, 7-cyanofuro[2,3-c]- 2b and 4-cyanofuro[3,2-c]pyridi ne 2c in moderate to excellent yield. The cyano group in 2a, 2b and 2c was converted to carboxamides 3a, 3b and 3c, ethyl imidates 5a, 5b an d 5c and ethyl carboxylates 6a, 6b and 6c. Reaction of the N-oxides wi th trimethylsily bromide in acetonitrile gave the deoxygenated furopyr idine 7a and 7d, bifuropyridyl 8b and 8c, and the N-oxide 9 of 8c.