Furopyridines. XXVII. Reactions of 2‐methyl and 2‐cyano derivatives of furo[2,3‐b]‐, ‐[3,2‐b]‐, ‐ [2,3‐c]‐ and ‐[3,2‐c]pyridine

Abstract

AbstractBromination of 2‐methylfuropyridines 1a‐d‐Me gave the 3‐bromo derivatives 2a‐d, while the 2‐cyano compounds 1a‐d‐CN resulted in the recovery of the starting compounds. Nitration of 1a‐d‐Me and 1a‐d‐CN did not yield the corresponding nitro derivative, except for 1‐c‐CN giving 3‐nitro derivative 3c in 7% yield. N‐Oxidation of 1a‐d‐Me and 1b‐d‐CN with m‐chloroperbenzoic acid yielded the N‐oxides 4a‐d‐Me and 4b‐d‐CN, whereas 1a‐CN did not afford the N‐oxide. Cyanation of N‐oxides 4a‐d‐Me and 4b‐d‐CN with trimethylsilyl cyanide gave the corresponding α‐cyanopyridine compounds 5a‐d‐Me and 5b‐d‐CN. Chlorination of 4a‐d‐Me and 4b‐d‐CN with phosphorus oxychloride also gave the α‐chloropyridine compounds 6b‐d‐Me and 6b‐d‐CN, accompanying formation of γ‐chloropyridine 6a‐Me, 6′b‐Me and 6′b‐CN, β‐chloropyridine 6′b‐CN, and α'‐chloropyridine derivatives 6′c‐Me and 6′c‐CN. Acetoxylation of 4a‐d‐Me and 4b‐d‐CN with acetic anhydride yielded α‐acetoxypyridine compounds 7a‐Me and 7b‐CN, pyridone compounds 11d‐Me, 11c‐CN and 11d‐CN, 3‐acetoxy compounds 8, 9b, 9c, and 2‐acetoxymethyl derivatives 10b and 10c.