Sulfonylpyrazole- and pyrazole-directed ortho-selective C-H functionalization/alkenylation and desulfenylative olefination of aryl(sulfonyl)pyrazoles

ortho-Selective C-H alkenylation of arenes was achieved using sulfonylpyrazoles and pyrazoles as directing groups, favored by a combination of a Pd(OAc)(2) catalyst, Boc-Sar-OH and silver acetate. A wide variety of mono-alkenylated products of aryl-sulfonylpyrazoles and pyrazoles were synthesized with complete site-selectivity under mild reaction conditions. This transformation tolerated several electron-withdrawing and electron-donating groups on the aryl ring and the yields ranged from 52% to 70%, producing highly decorated/valuable alkenylated sulfonylpyrazole and pyrazole derivatives. Amazingly, switching of the oxidant, with the use of AgBF4 in place of AgOAc, offered cinnamic acid derivatives through de-sulfonylation followed by alkenylation at the same position with good yields in the case of aryl-sulfonylpyrazoles. These kinds of molecules have great biological importance and target predictions indicate that they may serve as potential antifungal and anti-tumor agents.

Automated summary

The ortho-selective C-H alkenylation of arenes using sulfonylpyrazoles and pyrazoles as directing groups has been achieved, leading to the synthesis of a variety of highly decorated alkenylated sulfonylpyrazole and pyrazole derivatives. These compounds have shown significant biological potential as potential antifungal and anti-tumor agents.