An array of nitroaryls with various functionality were treated with freshly-prepared aluminum amalgam in aqueous THF. In most cases the products were the corresponding arylamines, and in select cases, the arylamine products were accompanied by the corresponding hydroxylamine. The reductions are relatively rapid with consumption of the amalgam and disappearance of starting material occurring over 20-30 minutes. The workup of the reductions involves only removal of the aluminum by-products by filtration followed by concentration. Gravity or flash-column chromatography of the crude product was the most efficient purification procedure where necessary. The desired arylamines were furnished in quantities of 50-100mg, which in some cases, could be taken on to the next reaction with minimal purification. Reductions of 4-nitrobenzyl derivatives of carbohydrates or nucleosides are selective in affording the corresponding 4-aminobenzyl products and do not affect ester or ketal protection of the carbohydrate or nucleoside. Reduction of 4-nitrobenzyl groups which are connected to natural products through ether bonds result in the corresponding aminobenzyl derivatives which are azidated and are click-reaction ready. The reduction of select compounds and the application of the reduction in multi-step sequences will be presented.

Aluminum amalgam reduction of arylnitro groups

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