Copper(I)-Catalyzed Three-Component Selenosulfonation of Maleimides with Sulfonyl Hydrazides and Diselenides via Radical Relay.

By employing Cu(CH3CN)4PF6 as the catalyst and tert-butyl hydroperoxide as the oxidant, we realized a three-component radical selenosulfonation of substituted maleimides, sulfonyl hydrazides, and diphenyl diselenides, providing a series of 3,4-selenosulfonylated succinimides in moderate to good yields. This reaction features broad substrate scopes, high functional-group tolerability, and feasibility of gram-scale synthesis, enabling one-step construction of C-SO2 and C-Se bonds under mild reaction conditions. Preliminary mechanistic studies support the free-radical-induced pathway.

Transition-Metal-Free Radical-Triggered Hydrosulfonylation and Disulfonylation Reaction of Substituted Maleimides with Sulfonyl Hydrazides.

A convenient and practical hydrosulfonylation and disulfonylation of substituted maleimides was realized using sulfonyl hydrazides as the sulfur reagent and tert-butyl hydroperoxide as the oxidant. The advantages of the reactions include mild and transition-metal-free reaction conditions, good functional group tolerance, and readily available starting materials. The radical species-induced pathway is also demonstrated by mechanistic studies.

Copper(I)-Catalyzed Direct Oxidative Annulation of 1,3-Dicarbonyl Compounds with Maleimides: Access to Polysubstituted Dihydrofuran Derivatives.

An efficient annulation method for the synthesis of polysubstituted dihydrofurans from 1,3-dicarbonyl compounds and maleimides is described. The reactions can afford furo[2,3-c]pyrrole derivatives with satisfactory yields. The developed strategy realizes the direct oxidative double C(sp3)-H functionalization in the presence of copper(I) salts and 2-(tert-butylperoxy)-2-methylpropane. Meanwhile, this protocol features a mild reaction condition and simple catalytic system. A reaction mechanism involving a single electron oxidation is also proposed.

Catalyst-free visible-light-induced condensation to synthesize bis(indolyl)methanes and biological activity evaluation of them as potent human carboxylesterase 2 inhibitors.

A mild strategy for visible-light-induced synthesis of bis(indolyl)methanes was developed using aromatic aldehydes and indole as substrates. This reaction could be performed at room temperature under catalyst- and additive-free conditions to synthesize a series of bis(indolyl)methanes in good to excellent yields. In addition, all synthesized bis(indolyl)methanes together with ß-substituted indole derivatives synthesized according to our previous work, were evaluated for their inhibitory effect against human carboxylesterase (CES1 and CES2). Primary structure-activity relationship analysis of all tested compounds showed that the modifications of ß-substituted indole at the ß-site with another indolyl group led to a significant enhancement of the inhibitory effect on CES2, and the bisindolyl structure is essential for CES2 inhibition. These results demonstrated that these bis(indolyl)methanes are potent and selective CES2 inhibitors, which might be helpful for medicinal chemists to design and develop more potent and selective CES2 inhibitors for biomedical applications.