Non-Catalyzed Reductions With Formate Salts: Conversion of Nitroaromatic Compounds to the Corresponding Primary Amines

Abstract

One of the more important transformations in aromatic chemistry involves nitration of the ring followed by reduction¹ of the nitro group to the corresponding primary amine. Despite its low cost, ease of handling, and known² property of being a convenient hydrogen donor, formic acid (or formate salts, which are even more active hydride donors²) was not utilized for this reduction until recently when Heck and Cortese reported ³ the palladium-catalyzed reduction of nitroaromatics using triethylammonium formate. Since the latter reagent in N,N-dimethylformamide (DMF) had previously⁴ been shown to reduce the carbon-carbon double bond in good Michael acceptors without the presence of a metal catalyst, we decided to examine non-catalytic systems involving formic acid⁵ for effecting reduction of the nitro group.