Decyanative Heteroarylations of Glycine Derivatives.

Amino acids and aromatic nitrogen heterocycles are widely used in pharmaceuticals. Herein, we present an effective visible-light-driven thiobenzoic acid (TBA)-catalyzed decyanative C(sp3)-H heteroarylation of glycine derivatives. This process occurs under mild and straightforward conditions, affording a range of valuable yet challenging-to-obtain α-heteroaryl amino acid derivatives. Moreover, this organocatalytic C(sp3)-C(sp2) bond formation reaction is applicable to the late-stage modification of various short peptides.

Oxidative Tandem Cyclization of Glycine Esters with Propargyl Alcohols.

A facile and efficient aerobic oxidative (4 + 2)-cyclization/aromatization/lactonization tandem reaction of N-aryl glycine esters with propargyl alcohols to access quinoline-fused lactones is reported. The reaction can be extended to homopropargylic alcohols too. The transformation is straightforward to perform under mild conditions and scalable, and both reaction components are readily available.

Photosensitized Anti-Markovnikov Hydroesterification of Unactivated Alkenes.

Hydrofunctionalization of alkenes represents a fundamental strategy in synthetic organic chemistry. Herein, we describe a visible-light-promoted approach for the anti-Markovnikov hydrooxygenation of unactivated alkenes. Our protocol features the utilization of a cost-effective, bench-stable, and easy-to-handle oxime ester as the reagent, enabled by energy-transfer catalysis. This methodology exhibits excellent functional group tolerance and mild reaction conditions, rendering it suitable for the hydroesterification of pharmaceutically relevant molecule-derived alkenes.

C(sp3)-H/C(sp3)-H Dehydrogenative Radical Coupling of Glycine Derivatives.

Here we report a general C(sp3)-H/C(sp3)-H dehydrogenative coupling strategy for the preparation of various natural or unnatural amino acids from readily available glycine derivatives and hydrocarbons through a combination of SET and HAT process.

Synthesis of 10H-indolo[1,2-a]indol-10-ones via palladium-catalyzed C-H bond activation and difluorocarbene transfer.

A Pd-catalyzed annulation between 1-(2-iodophenyl)-1H-indoles and sodium difluorochloroacetate has been developed to synthesize 10H-indolo[1,2-a]indol-10-one derivatives via C-H bond activation and difluorocarbene transfer. Our route enables facile access to the targeted products with various substituents in moderate to high yields. This method features high reactivity, good functional group tolerance, a simple operation procedure, and mild reaction conditions. The reaction can be carried out on a gram scale.

Recent progress in organophotoredox reaction.

In the past decade, visible light photoredox catalysis has been established as a gentle and powerful strategy for the activation of organic molecules. As an important part of this, organic photocatalysts are widely used in chemical synthesis due to their attributes, such as cheapness and relatively high redox potential. In this article, we review the related organic reactions promoted by visible light in the presence of various organic photocatalysts over the past 5 years. The reaction mechanisms involving single electron transfer, energy transfer and proton-coupled electron transfer are also discussed. The recovery and reuse of some supported organic photocatalysts are highlighted. Moreover, prospects for the development of organic photocatalysts are emphasized.

Photocatalytic Redox-Neutral Approach to Diarylmethanes.

We report a visible-light induced redox-neutral decarboxylative cross coupling reaction of indole-3-acetic acid NHPI esters with indoles using a Ru photosensitizer to deliver a wide range of symmetrical and unsymmetrical 3,3'-bisindolylmethane derivatives. Furthermore, the reaction is readily adapted to the preparation of a wide variety of diarylmethane derivatives.

Visible-Light-Induced Intermolecular Oxyimination of Alkenes.

An intermolecular vicinal O-N difunctionalization reaction of olefins with oxime esters through energy transfer catalysis has been developed.

Ultrafast Detection of Sulfur Dioxide Derivatives by a Distinctive "Dual-Positive-Ion" Platform that Features a Doubly Activated but Irreversible Michael Addition Site.

Sulfur dioxide (SO2) is a gaseous signaling molecule and widely used as a preservative for foods, but its excessive intake is closely related to a series of diseases. Therefore, the development of a potent fluorescence probe for the detection of SO2 in foods and biological systems is of great significance. Herein, we report for the first time a "dual-positive-ion" platform-based fluorescence probe CMQ, designed by a doubly activated but irreversible strategy, which results in its ultrafast response to SO2 within 5 s in pure aqueous solution together with a low detection limit as 15.6 nM. In addition, the probe was successfully applied for imaging of SO2 in mitochondria of living cells and zebrafish and prepared as a reagent kit for convenient and instantaneous quantification of HSO3- in real food samples.

Visible-Light-Promoted Diboron-Mediated Transfer Hydrogenation of Azobenzenes to Hydrazobenzenes.

A visible-light-promoted transfer hydrogenation of azobenzenes has been developed. In the presence of B2pin2 and upon visible-light irradiation, the reactions proceeded smoothly in methanol at ambient temperature. The azobenzenes with diverse functional groups have been reduced to the corresponding hydrazobenzenes with a yield of up to 96%. Preliminary mechanistic studies indicated that the hydrogen atom comes from the solvent and the transformation is achieved through a radical pathway.

Cyanation of glycine derivatives.

We report a catalytic oxidative C-H cyanation of glycine derivatives using a simple copper(i) catalyst with NFSI as an oxidant via a radical process to furnish α-cyano glycine derivatives, which are useful intermediates for organic synthesis. CuCl acted as both a one-electron reductant and a transition-metal catalyst in this transformation. NFSI served as a one-electron oxidant and generated a N-centered radical as a H-abstractor. The reaction displayed broad substrate scope and mild reaction conditions.

Visible-light promoted α-alkylation of glycine derivatives with alkyl boronic acids.

A visible-light-mediated aerobic α-alkylation reaction of glycine derivatives with alkyl boronic acids has been established in the presence of a Ru/Cu catalyst system, giving the desired radical coupling products efficiently. The transformation features mild reaction conditions and broad substrate scope, delivering a wide range of complex unnatural α-amino-acid derivatives.

Visible-light-promoted selective O-alkylation of 2-pyridones with α-aryldiazoacetates.

A visible-light-promoted O-H insertion reaction between 2-pyridones and α-aryldiazoacetates has been developed. Upon visible light irradiation, the reaction proceeds smoothly under mild and catalyst-free conditions. A wide scope of 2-pyridones and α-aryldiazoacetates are well tolerated, and various O-alkylated 2-pyridones are obtained with perfect selectivity and good functional group tolerance. A photoinduced radical process is probably responsible for the excellent selectivity.

Catalyst-free, visible-light-promoted S-H insertion reaction between thiols and α-diazoesters.

A visible-light-promoted S-H insertion reaction between thiols and α-diazoesters was developed. The reaction proceeded smoothly at room temperature with a broad substrate scope, affording various thioethers in moderate to excellent yields. The catalyst- and additive-free nature, sustainable energy source and mild reaction conditions make this strategy more eco-friendly.

Visible-Light-Mediated Hydroacylation of Azobenzenes with α-Keto Acids.

A visible-light-mediated protocol for the hydroacylation of azobenzenes with α-keto acids has been developed. In the absence of any catalyst or additive, decarboxylative hydroacylation proceeded smoothly under visible-light irradiation at room temperature. A wide range of azobenzenes and α-keto acids were well-tolerated and afforded hydroacylation products in high to excellent yields. Preliminary investigations indicated that photoactive azobenzenes absorb visible light to enable the transformation.

Diastereoselective synthesis of spiro-cyclopropanyl-cyclohexadienones via direct sulfide-catalyzed [2 + 1] annulation of para-quinone methides with bromides.

An efficient sulfide-catalyzed [2 + 1] annulation of para-quinone methides (p-QMs) with diverse bromides has been achieved. This catalytic strategy provides an efficient and straightforward protocol for accessing a variety of spiro-cyclopropanyl-cyclohexadienone compounds in good to excellent yields (64% to 96% yields) with outstanding diastereoselectivities (>20 : 1 dr), displaying good functional group tolerance as well as gram-scale capacity.

Peroxidation of 3,4-dihydro-1,4-benzoxazin-2-ones.

The sp3-C-H peroxidation of 3,4-dihydro-1,4-benzoxazin-2-ones was achieved under mild and simple catalyst-free reaction conditions. A range of biologically important alkylated benzoxazinone peroxides are synthesized in high yield with a good functional group tolerance. The C(sp3)-OO bond was constructed efficiently and could be further converted into C(sp3)-C(sp3), C(sp3)-C(sp2), C(sp3)-C(sp), C-P and C[double bond, length as m-dash]O bonds by late-stage functional group transformations.

Visible-light-promoted acyl radical cascade reaction for accessing acylated isoquinoline-1,3(2H,4H)-dione derivatives.

A visible-light-promoted decarboxylative acyl radical acylation/cyclization cascade reaction of N-methacryloylbenzamides for accessing acylated isoquinoline-1,3(2H,4H)-dione derivatives was described. In this report, α-keto acids were used for generating acyl radicals and inducing radical acylations. This protocol features mild reaction conditions, operational practicality and a broad substrate scope.

Iodine promoted cascade cycloisomerization of 1-en-6,11-diynes.

An iodine promoted cascade cycloisomerization of 1-en-6,11-diynes is presented for the easy preparation of tetrahydrobenzo[f]isoquinolines. This developed reaction system is identified as having good functional-group applicability and can be scaled up to gram quantities. In this transformation, two new cyclic frameworks and one carbonyl group are formed with four new bonds constructed. Additionally, the resulting iodo-substituted compounds could be further derived through simple elimination reactions.

Double C-N bond cleavages of N-alkyl 4-oxopiperidinium salts: access to unsymmetrical tertiary sulfonamides.

In this paper, regiospecific, double intraannular C-N bond cleavages of N-alkyl 4-oxopiperidinium salts are presented. The reaction sequence involves a charge-transfer complex, in situ formed between sulfonyl chloride and N-methylmorpholine, which induces S-Cl bond homolysis of sulfonyl chloride, yielding a reactive sulfonyl radical that further induces the double C-N bond cleavages of N-alkyl 4-oxopiperidinium salt. The secondary amine thus produced was trapped by sulfonyl chloride to yield the desired sulfonamide product. The key feature of this protocol is that two intraannular C-N bonds of the 4-oxopiperidine ring are cleaved in one step under metal- and oxidant-free conditions.