Efficient Reductions of Nitroarenes with SnCl₂ in Ionic Liquid

Abstract

Mild, eco-friendly and fast reductions of nitroarenes to aminoarenes have been accomplished using stannous chloride dihydrate in ionic liquid tetrabutylammonium bromide (TBAB) that provides unsolvated nucleophilic bromide ion. Improved yields, lower reaction time, generality, and a less demanding work-up procedure are the notable features of this protocol.

reduction - nitroarenes - tin(II)chloride - TBAB - in situ ionic liquid

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Representative Procedure for Reduction of Nitroarenes with SnCl ₂ in Ionic Liquid: Nitroarene (2 mmol) was mixed with TBAB (1 g) with stirring and to this mixture was added SnCl₂·2H₂O (1350 mg, 6 mmol, 3 equiv). The mixture was stirred until a clear melt resulted. Then it was kept on water bath at 90 °C for completion (TLC monitoring) and extracted with Et₂O (3 × 5 mL). The combined organic layer was washed with H₂O, brine and dried over anhyd Na₂SO₄. Removal of solvent gave the crude product, which was purified by column chromatography over silica gel to furnish aminoarene exclusively.