Aromatic nucleophilic substitution of hydrogen: mechanism of reaction of 6-nitroquinoline with cyanide ions, with and without participation of methylcyanoacetate

The mechanism of nucleophilic substitution of hydrogen (SNArH) in 6-nitroqu inoline 1 by action of cyanide ion in the presence or in the absence of met hyl cyanoacetate in dimethyl sulfoxide has been studied by means of H-1 NMR . The main reaction products and some side products have been identified an d their time-concentration dependences have been determined. An experiment with C-13 enriched potassium cyanide proved that the cyano group replaces h ydrogen at the 5-position of the starting compound 1. The two main products obtained from the reaction mixture of 6-nitroquinoline 1 and potassium cya nide are 6-hydroxyquinoline-5-carbonitrile 11 and 6,6'-azoquinoline-5,5'-di carbonitrile 13. On the basis of the data obtained, a mechanism has been su ggested for aromatic nucleophilic substitution of hydrogen by cyanide ion i n 6-nitroquinoline 1 involving a Meisenheimer adduct of 6-nitroquinoline 1 with cyanide ion and 6-nitrosoquinoline-5-carbonitrile 14 as unstable inter mediates.