Mild Iron-Catalyzed Oxidative Cross-Coupling of Quinoxalinones with Indoles.

Utilizing iron chloride as a Lewis acid catalyst, we developed a straightforward and mild oxidative cross-coupling reaction between quinoxalinones and indoles, yielding a series of versatile 3-(indol-3-yl)quinoxalin-2-one derivatives. This approach allows for the incorporation of a wide array of functional groups into the final products, demonstrating its synthetic versatility. Notably, the method was successfully scaled up to gram-scale reactions while maintaining high yields. Our mechanistic investigation indicates that iron chloride serves as a catalyst to facilitate the formation of key intermediates which subsequently undergo oxidation to afford the desired products. The merits of this protocol include its cost effectiveness, operational simplicity, and the ease of product isolation via filtration.

Visible-Light-Promoted Fe(III)-Catalyzed N-H Alkylation of Amides and N-Heterocycles.

The combination of the radical chemistry of ligand-to-metal charge transfer with metal catalysis by a single iron salt helps to realize the visible-light-promoted N-H alkylation of amides and N-heterocycles. A wide variety of amides and nitrogen-containing heterocycles were tolerated in our protocol to give N-alkylated products. The applicability of this protocol was further demonstrated by late-stage alkylation of N-H-containing pharmaceuticals. Moreover, N-H-alkylated α-amino tetrahydrofurans could be transformed into versatile ring-opened amino alcohols under reducing conditions. A mechanistic study revealed that hydrogen atom transfer by a tert-butoxyl radical and a chlorine radical was responsible for the activation of C(sp3)-H precursors.

Light-enabled alkenylation of iodocarboranes with unactivated alkenes.

The synthesis of alkenylated-o-carboranes via photoalkenylation of iodocarboranes with unactivated alkenes has been achieved. This strategy features a transition metal-free protocol, a light-promoted reaction under mild reaction conditions, broad substrate scope and good functional group tolerance. Control experiments suggest that the reaction may involve the cage C-centered radical species.

Redox-neutral rhodium(III)-catalyzed chemo- and regiospecific [4 + 1] annulation between benzamides and alkenes for the synthesis of functionalized isoindolinones.

Herein, using electron-deficient alkenes embedded with an oxidizing function/leaving group as a rare and nontraditional C1 synthon, we have achieved the redox-neutral Rh(III)-catalyzed chemo- and regioselective [4 + 1] annulation of benzamides for the synthesis of functionalized isoindolinones. This method features broad substrate scope, good to excellent yields, excellent chemo- and regioselectivity, good tolerance of functional groups and mild external-oxidant-free conditions.

Redox-Neutral Rhodium(III)-Catalyzed Chemospecific and Regiospecific [4+1] Annulation between Indoles and Alkenes for the Synthesis of Functionalized Imidazo[1,5-a]indoles.

Exploiting internal alkenes embedded with an oxidizing function/leaving group as a rare and unconventional one-carbon unit, a redox-neutral rhodium(III)-catalyzed chemo- and regiospecific [4+1] annulation between indoles and alkenes for the synthesis of functionalized imidazo[1,5-a]indoles has been achieved. Internal alkenes employed here can fulfill an unusual [4+1] annulation rather than normal [4+2] annulation/C-H alkenylation. This method is characterized by excellent chemo- and regioselectivity, broad substrate scope, good functional group tolerance, good to high yields, and redox-neutral conditions.

Additive-Controlled Divergent Synthesis of Tetrasubstituted 1,3-Enynes and Alkynylated 3H-Pyrrolo[1,2-a]indol-3-ones via Rhodium Catalysis.

Herein, we report the additive-controlled divergent synthesis of tetrasubstituted 1,3-enynes and alkynylated 3H-pyrrolo[1,2-a]indol-3-ones through rhodium-catalyzed C-H alkenylation/DG migration and [3+2] annulation, respectively. This protocol features rare directing group migration in 1,3-diyne-involved C-H activation, excellent regio- and stereoselectivity, excellent monofunctionalization over difunctionalization, broad substrate scope, moderate to high yields, good functional group compatibility, and mild redox-neutral conditions.

Rhodium(III)-Catalyzed C-H Alkenylation/Directing Group Migration for the Regio- and Stereoselective Synthesis of Tetrasubstituted Alkenes.

An efficient Rh(III)-catalyzed C-H alkenylation/directing group migration cascade between indoles and alkynes for the assembly of tetrasubstituted alkenes is reported. The carbamoyl directing group migrates to the carbon of the alkene moiety of the products through rare Rh-catalyzed C-N bond cleavage after the C-H alkenylation step and thus acts as an internal amidation reagent. This protocol shows broad substrate scope, excellent regio/stereoselectivity, and good to excellent yields.

Transition-Metal-Free Cross-Coupling Reaction of Iodocarboranes with Terminal Alkynes Enabled by UV Light: Synthesis of 1-Alkynyl-o-Carboranes and Carborane-Fused Cyclics.

A transition-metal-free coupling protocol between iodocarboranes and terminal alkynes enabled by light at room temperature has been developed, leading to the synthesis of a variety of 1-alkynyl-o-carboranes. Moreover, following this strategy, the introduction of 1-I-3-aryl-o-carboranes or 1-I-2-aryl-o-carboranes results in the formation of o-carborane-fused cyclics. Interestingly, when 1-I-3-(p-R-C6H4)-o-carboranes are chosen as coupling partners, unexpected R-group migration products are also isolated. On the basis of the results of control experiments and isolation of the key intermediates, a possible reaction mechanism is then proposed, involving the formation of spiro radical species.

Metal-free C3-H acylation of quinoxalin-2(1H)-ones with α-oxo-carboxylic acids.

Direct C3-H acylation of quinoxalin-2(1H)-ones with α-oxocarboxylic acids under thermo conditions promoted by PIDA has been achieved in a moderate to good yield in a very fast manner. Mechanistic study revealed that the reaction proceeds via a radical process. In addition, this method could be applied to a gram-scale reaction and antitumor agent synthesis. This work represents a simple, convenient and efficient synthesis of 3-acylated quinoxalin-2(1H)-ones.

Facile and clean synthesis of dihydroxylatopillar[5]arene-stabilized gold nanoparticles integrated Pd/MnO2 nanocomposites for robust and ultrasensitive detection of cardiac troponin I.

In this work, a novel, facile, clean synthesis of monodisperse Au nanoparticles (AuNPs) with an average diameter of 5 nm was achieved by reducing HAuCl4 with dihydroxylatopillar[5]arene (2HP5) in basic solution without the use of harsh reagents and/or external energy. Accordingly, toluidine blue (TB), one electrochemcial indicator, could enter into the cavity of 2HP5 to fabricate host-guest complex through strong electrostatic interaction and charge-transfer interaction, which significantly enhanced the loading quantity of TB and effectively suppressed the leaking of TB resulting in an ultrasensitive and robust electrochemical response. More importantly, the integration of 2HP5-stabilized AuNPs and Pd-decorated MnO2 nanocomposites (2HP5@Au-Pd/MnO2) might usually obtain a novel functional-enhanced materials and lead to new properties and improving the analytical performance and robustness of electrochemical devices. Therefore, we construct a sandwich-type electrochemical immunosensor using TB-2HP5@Au-Pd/MnO2 nanocomposites as the transducing materials for robust and ultrasensitive detection of cardiac troponin I (cTnI), a significant biomarker of acute myocardial infarction. As anticipated, this immunosensor had remarkable robustness, sensitivity, stability, specificity, and corresponded linearly to the concentration of cTnI over a wide range from 0.005 to 20 ng mL-1 with a low detection limit of 2 pg mL-1 (S/N = 3). The proposed electrochemical immunosensor showed acceptable recoveries in human serum, indicating that macrocycle-stabilized metal nanoparticle might be a promising emerging transducer material for the detection of biological markers.

Photoarylation of Iodocarboranes with Unactivated (Hetero)Arenes: Facile Synthesis of 1,2-[(Hetero)Aryl]n -o-Carboranes (n=1,2) and o-Carborane-Fused Cyclics.

Photoarylation of iodocarboranes with unactivated arenes/heteroarenes at room temperature has been achieved, for the first time, thus leading to the facile synthesis of a large variety of cage carbon mono(hetero)arylated and di(hetero)arylated o-carboranes. This work represents a clean, efficient, transition-metal-free, and cheap synthesis of functionalized carboranes, which has significant advantages over the known methods.

One-pot three-component approach to the synthesis of polyfunctional pyrazoles.

A simple, multicomponent, and straightforward reaction of vinyl azide, aldehyde, and tosylhydrazine affords the construction of 3,4,5-trisubstituted 1H-pyrazoles regioselectively in the presence of base with moderate to excellent yields. A range of functionality could be tolerated in this methodology, and a possible mechanism is proposed.