Sulfonyl Hydrazides in Organic Synthesis: A Review of Recent Studies

The clean preparation of multisubstituted pyrroles under metal- and solvent-free conditions

Oxidative Sulfonylation of Multiple Carbon‐Carbon bonds with Sulfonyl Hydrazides, Sulfinic Acids and their Salts

The direct C-H methylsulfonylation of alkenes using inorganic sodium metabisulfite as the sulfur dioxide surrogate is described. This method provides convenient access to (E)-2-methyl styrenyl sulfones in good yields. In general, the in situ generated methyl radical from di-tert-butyl peroxide undergoes a methylsulfonylation process with the combination of sulfur dioxide.

Direct C–H Methylsulfonylation of Alkenes with the Insertion of Sulfur Dioxide

The tandem C–H bond trifluoromethylation and chromone annulation reactions of o-hydroxyphenyl enaminones have been realized for the practical synthesis of 3-trifluoromethyl chromones. The reactions are performed efficiently with the promotion of K2S2O8 without using any transition metal catalyst or additive. In addition, the 3-trifluoromethyl chromone products have been successfully used for the synthesis of 3-trifluoromethyl pyrimidines by reacting with guanidine/amidine substrates.

Transition metal-free synthesis of 3-trifluoromethyl chromones via tandem C–H trifluoromethylation and chromone annulation of enaminones

The cascade reactions between NH2-functionalized enaminones and sulfonyl hydrazines have been developed for the synthesis of fully substituted pyrazoles. By making use of the hydrophilic primary amino group in the enaminones, the reactions proceed well in the medium of pure water in the presence of molecular iodine, TBHP, and NaHCO3 via cascade C-H sulfonylation and pyrazole annulation. The cleavage of the C–N bond in enaminones is confirmed by the experiment using 15N-labeled enaminone.

Guodong Wang

Papers

Domino C-H Sulfonylation and Pyrazole Annulation for Fully Substituted Pyrazole Synthesis in Water Using Hydrophilic Enaminones

Synthesis of 2,3,5,6-tetrasubstituted pyridines via selective three-component reactions of aldehyde and two different enaminones