Furopyridines .24. Nitration, chlorination, acetoxylation and cyanation of 2,3-dihydrofuro[2,3-b]-, -[3,2-b]-, -[2,3-c]- and -[3,2-c]pyridine N-oxides

Nitration of 2,3-dihydrofuro[3,2-b]- N-oxide 3b and -[2,3-c]pyridine N-oxide 3c afforded the nitropyridine compounds 4b, 5b and 6 from 3b and 4c, 5c, 5'c and 7 from 3c, while -[2,3-b]- N-oxide 3a and -[3,2-c]pyridine N-oxide 3d did not give the nitro compound. Chlorination of 3b and 3c with phosphorus oxychloride yielded mainly the chloropyridine derivatives 15b, 15'b from 3b and 15c and 15'c from 3c, whereas 3a and 3d gave pyridine derivatives formed through fission of the 1-2 ether bond of the furopyridines 13a, 14 and 13d. Acetoxylation of 3b and 3c gave 3-acetoxy derivatives 18b and 18c and the parent compound Ib and Ic. Acetoxylation of 3a yielded compounds formed through fission of the 1-2 bond 16 and 17 and 3d gave furopyridones 19 and 19'. Cyanation of 3b and 3c yielded mainly the cyanopyridine compounds 20b, 20c and 20'c. Cyanation of 3a and 3d gave the cyanopyridine compounds 2)a, UM and 20'd accompanying formation of the pyridine derivatives 21a, 21d and 21'd.