2-nitrodifuro[2,3-b:2',3'-d]pyridine InChI=1/C9H4N2O4/c12-11(13)7-3-5-4-10-9-6(1-2-14-9)8(5)15-7/h1-4 difuro[2,3-b:2',3'-d]pyridine, 2-nitro-