Copper-catalyzed reactions of α,β-unsaturatedN-tosylhydrazones with diaryliodonium salts to constructN-arylpyrazoles and diaryl sulfones

Abstract

Herein, an economic copper-catalyzed reaction of α,β-unsaturated N-tosylhydrazones with diaryliodonium salts to constract both N-arylpyrazoles and diaryl sulfones, has been developed. Both p-toluenesulfonyl anion and 3-arylpyrazole intermediates were formed in...

Copper‐Catalyzed Synthesis of Diaryl Sulfones via Cross‐Coupling of Boronic Acids and p‐Toluenesulfonyl Hydrazide

“…(entries [11][12][13][14][15]. Further, different solvents were tested for the reaction, among the screened solvents trifluoroethanol (TFE) was identified as the best solvent yielding the desired product in 86 % yield (entries [16][17][18][19][20][21][22][23]. After that, a control reaction was performed without any additive and no conversion of the starting materials was observed by TLC, indicating that the additive is required for this reaction (entry 24).…”

“…The [(phen)CuIBr] complex was also observed to catalyze cross‐coupling of tosyl chloride and phenylboronic acid for the synthesis of diaryl sulfones (Scheme 1e) [17] . Additionally, a copper‐catalyzed reaction of α , β ‐unsaturated N‐ tosyl hydrazones with diaryliodonium salts was observed to produce both N‐ aryl pyrazoles and diaryl sulfones (Scheme 1f) [18] . However, this transformation requires multiple steps and gave a mixture of products rather than a single product.…”

“…[17] Additionally, a copper-catalyzed reaction of α,βunsaturated N-tosyl hydrazones with diaryliodonium salts was observed to produce both N-aryl pyrazoles and diaryl sulfones (Scheme 1f). [18] However, this transformation requires multiple steps and gave a mixture of products rather than a single product. As a less harmful alternative, third-row transition metal-catalyzed coupling reactions involving aryl-halides/-boronic acids and aryl-sulfinic acid salts/-sulfonyl chlorides have recently been developed.…”