Iron-Catalyzed Friedel-Crafts-type 3,5-Diacylation of Indoles

The exploration of remote functionalization of indoles is impeded by the inherently dominant reactivity intrinsic to the pyrrole moiety. Herein, we delineate a novel strategy facilitated by Lewis acid mediation, enabling the remote C-H functionalization, which culminates in the synthesis of an array of selectively functionalized indole derivatives, encompassing 3-trifluoroacetyl and 5-benzoyl motifs, utilizing trifluoroacetic anhydride and various acyl chlorides. Notably, the protocol exhibits versatility, as epitomized by the extension of C5-acylation to alkylation and sulfonation reactions. This methodology is distinguished by its exemplary regio- and chemo-selectivity, extensive substrate scope, commendable tolerance to a diverse array of functional groups, and the employment of comparatively mild reaction conditions.

Iodine-mediated oxidative triple functionalization of indolines with azoles and diazonium salts

We report an innovative synthetic strategy for the generation of polysubstituted indoles from indolines, aryldiazonium salts, and azoles. The methodology encompasses an electrophilic substitution reaction affording C5-indoline intermediates which undergo an iodine-mediated oxidative transformation coupled with C-H functionalization to yield the indole derivatives.

Site-Selective Synthesis of Antitumor C5-Aminated Indoles via Neighboring Aldehyde Group Assisted Catellani Reaction

A palladium/norbornene (NBE) cooperative catalytic system was developed to access C5-aminated indoles, starting from readily available C4-idonated indoles. Good yields and exclusive site selectivity were achieved for a broad substrate scope, including drug molecule core architectures. Control experiments found that both aldehyde on the C3 position and sulfonyl protecting group on the N1 position were vital for the transformation. Preliminary bioactivity evaluation identified a promising leading compound 3af with potent antitumor proliferative activity against several cancer cells.

Visible light-enabled regioselective chlorination of coumarins using CuCl2via LMCT excitation

An efficient, regioselective chlorination of coumarins using Earth-abundant and cost-effective CuCl₂ under visible light irradiation is reported. A key feature of this protocol is the photocatalytic dissociation of the copper(II) complex in acetonitrile through ligand-to-metal charge transfer (LMCT) to give the chlorine atom which then selectively chlorinates the coumarin. This method can chlorinate a broad scope of coumarins with either electron-withdrawing or electron-donating substituents to regioselectively afford 3-chlorocoumarins in good to excellent yields and can be further extended to other electron-deficient heterocycles and olefins such as flavones, 8-methoxypsoralen and naphthoquinones.

Switchable, Reagent-Controlled C(sp3)-H Selective Iodination and Acetoxylation of 8-Methylquinolines

An efficient Pd-catalyzed C(sp³)-H selective iodination of 8-methylquinolines is reported herein for the first time. Because of the versatility of organic iodides, the method offers a facile access to various C8-substituted quinolines. By slightly switching the reaction conditions, an efficient C(sp³)-H acetoxylation of 8-methylquinolines has also been enabled. Both approaches feature mild reaction conditions, good tolerance of functional groups, and a broad substrate scope.