[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.
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
A. Richard Chamberlin & James E. Sheppeck II
University of California, Irvine, CA, USA