Hydrazine monohydrate (Fluka),
2-nitrobenzenesulfonyl chloride (Aldrich),
THF (distilled from sodium benzophenone ketyl),
Ethyl acetate,
10% aqueous sodium chloride,
Hexane

Hydrazine hydrate (12.1 mL, 0.25 mol, 2.5 equiv) was added dropwise to a solution of 2-nitrobenzenesulfonyl chloride (22.2 g, 0.1 mol, 1 equiv) in THF (100 mL) at -30^oC under an inert atmosphere. After stirring at -30^oC for 30 minutes, ice-cold ethyl acetate (200 mL) was added to the cold reaction mixture and the mixture was washed repeatedly with ice-cold 10%aqueous sodium chloride (5x150 mL). The organic layer was dried over sodium sulfate at 0^oC then was added slowly to a stirring solution of hexanes(1.2 L) over 5 minutes. 2-Nitrobenzenesulfonyl hydrazide precipitated as a white solid and was collected by vacuum filtration. The filter cake was washed with hexanes (2x50 mL) and then dried in vacuo yielding the title compound as a white solid (17.61 g, 81 %)

During the addition of hydrazine hydrate the reaction goes brown and a white solid (hydrazine hydrochloride) is deposited around the sides of the flask. The workup procedure is quite specific and if altered in any way will reduce both the yield and purity of the reagent. The contact time for washing with the salt solution must be less than 1 minute per wash as this contact decomposes the product but is necessary for removal of residual 2-nitrobenzenesulfinic acid. NBSH can be stored in a freezer for up to 2 months without serious degradation. Further, NBSH can be recrystalised from ethyl acetate/hexane to afford pure material. On addition of THF to pure NBSH a clear colourless solution is expected. If the solution is yellow the purity of NBSH is questionable and should not be used. This procedure can be used to prepare 20g batches of material and has been carried out 3 times at the above scale within the group.

mp 100-101 ^oC ¹H nmr (300MHz, CD₃CN) 3.90 (2H,bs), 5.97 (1H, bs), 7.78-7.91 (3H, m), 8.03-8.17 (1H, m)

Myers, A.G.; Zheng, B.; Movassaghi, M.; J. Org. Chem. 1997, 62, 7507

Dann, A.T.; Davies, W.; J. Chem. Soc. 1929, 1050