One-pot synthesis of nitrones from nitro compounds by in situ trapping of arylhydroxylamines

Abstract

Highly efficient, convenient, simple procedure and a highly chemoselective method has been described for the conversion of nitroarenes to their corresponding nitrone derivatives by employing SnCl2·2H2O and Na2CO3 in the grinding apparatus in solvent-free conditions. Biaryl nitrones can be achieved via the condensation of an aldehyde with an unstable arylhydroxylamine which is prepared in situ through the reduction of the corresponding nitro aromatic compound. Interestingly, the slow and nonselective reduction of nitroarene to arylhydroxylamine step was directed with the condensation of in situ-prepared arylhydroxylamine with aromatic aldehyde (second step). Moreover, this protocol was successfully used for preparation of valuable dinitrones from dialdehyde and nitro aromatic compounds. For dinitrone preparation, dialdehyde compounds were first synthesized by the reaction of salicylaldehyde and glycol derivatives. Then, dialdehydes were reacted with reduced nitro compounds in optimal conditions that we used for synthesis of biaryl nitrones.