[53777-75-6]  · C6H6N4O6S  · 2,4-Dinitrobenzenesulfonylhydrazide  · (MW 262.23)

(an effective reagent for preparing propargyl ketones and aldehydes via the Eschenmoser fragmentation2)

Alternate Name: DNSH.

Physical Data: mp 120 °C.

Solubility: sol most organic solvents.

Analysis of Reagent Purity: IR, NMR.

Preparative Method: by treatment of 2,4-dinitrobenzenesulfonyl chloride with 95% hydrazine in THF and crystallized from EtOH/THF.1

Handling, Storage, and Precautions: thermally labile; should be stored in a freezer. It is a toxic and potentially flammable solid that should be handled with gloves under inert atmosphere and freshly prepared as needed.

Eschenmoser Fragmentation.

Despite reports of the superiority of 2,4-dinitrobenzenesulfonyl hydrazide (DNSH) in the Eschenmoser fragmentation, this reagent has received very little attention as a mild alternative to p-Toluenesulfonylhydrazide and N-aminoaziridines.2,3 Condensation of DNSH with a,b-epoxy ketones in THF or dichloromethane gives smooth cleavage to alkynones and alkynals between 0 °C and rt (eqs 1-3) when treated with catalytic amounts of base (pyridine, sodium bicarbonate, or sodium carbonate). Yields are good to excellent. The fragmentation shown in eq 2 cannot be effected with p-Toluenesulfonylhydrazide, and N-aminoaziridines give low, irreproducible yields.1

Use of this reagent for synthesis of selenosulfonates has also been briefly examined, but Mesitylenesulfonylhydrazide is more efficient.4,5

1. Corey, E. J. JOC 1975, 40, 579.
2. Schreiber, J.; Felix, D.; Eschenmoser, M.; Winter, F.; Fautschi, K. H.; Schulte-Elte, E.; Sundt, G.; Ohloff, J.; Kalvoda, J.; Kaufmann, H.; Wieland, P.; Anner, G. HCA 1967, 50, 2101.
3. Felix, D.; Schreiber, J.; Piers, K.; Horn, U.; Eschenmoser, A. HCA 1970, 51, 1461.
4. Back, T. G.; Collins, S. TL 1980, 21, 2213.
5. Back, T. G.; Collins, S.; Krishna, M. V. CJC 1987, 65, 38.

A. Richard Chamberlin & James E. Sheppeck II

University of California, Irvine, CA, USA

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