Aromatic nucleophilic substitution of hydrogen: reactions of 6-nitroquinoline with potassium cyanide and nitroalkanes
The reactions of 6-nitroquinoline 1 and potassium cyanide with methyl nitroacetate, nitroethane, 1-nitropropane, and 2-nitropropane have been carried out in the medium of dimethyl sulfoxide. 1H NMR has been used to identify the reaction products from 6-nitroquinoline 1 with methyl nitroacetate and potassium cyanide and to determine the proportions of products in the reaction mixture. The main reaction products are 6-(methoxalylamino)quinoline-5-carbonitrile 6 and 1-aminoisoxazolo[4,3-f]quinoline 9. The reactions of 6-nitroquinoline 1 with potassium cyanide and primary nitroalkanes give, as the main products, 3-substituted pyrido[3,2-f]quinazolin-1(2H)-ones 12a,b. The reaction of 6-nitroquinoline 1 and potassium cyanide with 2-nitropropane produces 3-(1-cyano-1-methylethyl)-2,3-dihydro-1H-pyrazolo[4,3-f]quinolin-1-one 14 as the chief product. In all cases the reaction involves substitution of the 5-hydrogen of quinoline skeleton with concomitant lowering of oxidation number of the nitrogen atom in the original nitro group of 1. A mechanism is suggested for the reactions investigated involving 6-nitrosoquinoline-5-carbonitrile 3 as a likely common intermediate.