Reductive alkylation of nitrobenzene promoted by zinc and tin in protic solvents

Barbier-type organometallic reactions of nitrobenzene with organic halides in protic solvents produce directly N,N-dialkylanilines. With allyl bromide, best yields are obtained using zinc in an aqueous monobasic sodium phosphate solution in the presence of cuprous iodide or tin in methanol. The latter procedure is also successful in the case of benzyl bromide and primary alkyl iodides. Control experiments exclude a mechanism of reduction followed by nucleophilic alkylation and show that the reaction is initiated by a nucleophilic attack of the organometallic species on the nitro group. Similar reactions with Grignard reagents under anhydrous conditions are reported to have a completely different outcome