Furopyridines. XXIX. Reactions of furo[2,3-b : 4,5-c ']-, -[3,2-b : 4,5-c ']-, -[2,3-c : 4,5-c']- and -[3,2-c : 3,2-c ']dipyridine

Furo[2,3-b:4,5-c']- 1a, -[3,2-b:4,5-c']- 1b, -[2,3-c:4,5-c']- 1c and -[3,2- c:4,5-c']dipyridine 1d were derived to the N-oxides 2a-d, N'-oxides 2'b, 2' c or N,N'-dioxide 3b-d by N-oxidation with m-chloroperbenzoic acid. Chlorin ation of these N-oxides, hr-oxide and N,hr-dioxides with phosphorus oxychlo ride afforded compounds chlorinated at the alpha-position(s) to the ring ni trogen 4a-d, 4'c, 14b-d and 14'b. Acetoxylation of N-oxides 2a-d and 2'c wi th acetic anhydride gave the corresponding pyridone compounds 6a-d and 6'c in good yields, while the acetoxylation of N,N'-dioxides gave a complex mix ture from which no compound could be isolated. Cyanation of 2a-d, 2'c and 3 b-d with trimethylsilyl cyanide yielded the cyano compounds 7a-d, 7'c, cyan o-N-oxides 15b-d and dicyano compounds 15'c and 15'd. Monocyano compounds 7 a-d and 7'c were converted to the imino eaters 8a-d and 8'c by treatment wi th sodium ethoxide. Imino eaters were derived to the carboxylic esters 9a-d and 9'c, from which the corresponding aldehydes 10a-d and 10'c were obtain ed by reduction with diisobutylaluminum hydride. Dicyanide 15'c was convert ed to dialdehyde 19 by the treatment with sodium ethoxide, and the subseque nt hydrolysis of the imino ester and reduction of the carboxylic eater with diisobutylaluminum hydride.