A CONVENIENT SRN1 SYNTHESIS OF AROMATIC NITRILES FROM DIAZONIUM SALTS VIA DIAZOSULFIDES

Article abstract of DOI:10.1016/S0040-4020(01)86905-2

Properly substituted diazosulfides XC6H4-N=N-SPh (1) (either isolated or generated in situ from arenediazonium tetrafluoroborates and sodium benzenethiolate) react with tetrabutylammonium cyanide, in Me2SO under photon or electron stimulation, leading to nitriles XC6H4CN (2).Satisfactory yields of 2, comparable with those of the Sandmeyer reaction, are obtained when X= 3- or 4-CF3, 2-, 3-, or 4-CN, 4-F, 4-MeCO, 3-MeO, 4-NO2, 4-PhCO, and 4-PhSO2.For different reasons, the reaction practically fails as a useful nitrile synthesis when X= H, 4-MeO, 2-, or 3-NO2.The collected evidences agree well with the intervention of an S_RN1 mechanism to which diazosulfides 1, given their easy reducibility followed by a prompt fragmentation of the C-N and N-S bonds, are convenient participating substrates.An important consequence of the mechanism involved is the behaviour of bromo and chloro derivatives (1: X= Br, Cl) which lead, through the contemporaneous introduction of two cyano functionalities, to more than satisfactory yields of the corresponding dicyanobenzenes.