An important challenge in enantioselective catalysis is developing strategies for the precise synthesis of neighboring congested all-carbon quaternary stereocenters. The well-defined transition states of [3,3]-sigmatropic rearrangements and their underlying stereospecificity render them powerful tools for the synthesis of such arrays. However, this type of pericyclic reaction remains notoriously difficult to catalyze, especially in an enantioselective fashion. Herein, we describe an enantioselective reductive Eschenmoser-Claisen rearrangement catalyzed by chiral 1,3,2-diazaphospholene-hydrides. This developed transformation enables full control of the two newly formed acyclic stereogenic centers, leading to amides with vicinal all-carbon quaternary-tertiary or quaternary-quaternary carbon atoms.

1,3,2-diazaphospholene hydrides (DAP-H) emerged as a nucleophilic main-group hydride able to promote smooth conjugate reduction of polarized double bonds. The transiently formed phosphorus-bound enolate provides a potential platform for reductive α-functionalizations. In this respect, asymmetric C-heteroatom bond forming processes are synthetically appealing but remain so far elusive. We report a 1,3,2-diazaphospholene-catalyzed three-step cascade transformation of α,β-unsaturated N-sulfinyl acrylamides comprised of a conjugate reduction, [2,3]-sigmatropic aza-Mislow-Evans rearrangement and subsequent S-O bond reductive cleavage. The obtained enantio-enriched α-hydroxyl amides are synthetically highly valuable and formed in good yields and excellent enantiospecificity. The stereo-defined P-bound N,O-ketene aminal ensures an excellent transfer of chirality from the sulfur stereocenter to α-carbon atom. The transformation operates under mild conditions at ambient temperature. Moreover, DAP hydrides are found to be competent reductants for the cleavage of the formed sulfenate ester, thus eliminating the required additional step like in traditional Mislow-Evans processes.

A new bifunctional ligand bearing chiral N-heterocyclic carbene (NHC) and prolinol moieties is presented. Utilizing the designed ligand, an in situ formed Cu/Zn hetero-bimetallic complex unlocks the asymmetric allylic alkylation reactions of allyl phosphates with zinc keto-homoenolates, leading to the formation of various gamma-vinyl ketones with good regio- and enantio-selectivity. DF sT calculation supports that the chelation of allyl phosphates with catalyst promotes the S(N)2' addition and the ligand-substrate steric interactions account for the stereoselective outcome.

The first total synthesis of the trimethyl ester of kadcoccinic acid A is described. The central structural element of our synthesis is a cyclopentenone motif that allows the assembly of the natural product skeleton. A gold(I)-catalyzed cyclization of an enynyl acetate led to efficient construction of the cyclopentenone scaffold. In this step, optimization studies revealed that the stereochemistry of the enynyl acetate dictates regioisomeric cyclopentenone formation. The synthesis further highlights an efficient copper-mediated conjugate addition, merged with a gold(I)-catalyzed Conia-ene reaction to connect the two fragments, thereby forging the D-ring of the natural product. The synthetic strategy reported herein can provide a general platform to access the skeleton of other members of this family of natural products.

Considering their unique electronic properties and diverse biological activities, regioselective access to fused aromatic compounds is significantly important in the field of organic materials and pharmaceutical science. Herein, we developed electrochemical oxidative [4+2] annulation reactions of heterobiaryl compounds with alkynes or alkenes, leading to the formation of several polycyclic heteroaromatic compounds. This electrosynthetic methodology serves for the straightforward π-extension of unfunctionalized heterobiaryl compounds. The requirements of additional oxidants and prefunctionalization of starting materials are obviated. Through the in situ generation of heterobiaryl radical cation intermediates, various fused aromatic compounds were obtained with good yields and excellent regioselectivity.

Polyketide natural products are an important class of biologically active compounds. Although substantial progress has been made on the synthesis of repetitive polyketide motifs through the iterative application of a single reaction type, synthetic access to more diverse motifs that require more than one type of carbon–carbon bond connection remains a challenge. Here we describe a catalytic, multicomponent method for the synthesis of the privileged polyketide 1,3-dienyl-6-oxy motif. The method allows for the formation of two new carbon–carbon bonds and two stereodefined olefins. It generates products that contain up to three contiguous sp3 stereocentres with a high stereoselectivity in a single operation and can be used to generate chiral products. The successful development of this methodology relies on the remarkable efficiency of the ruthenium-catalysed alkene–alkyne coupling reaction between readily available vinyl boronic acids and alkynes to provide unsymmetrical 3-boryl-1,4-diene reagents. In the presence of carbonyl compounds, these reagents undergo highly diastereoselective allylations to afford the desired 1,3-dienyl-6-oxy motif and enable complex polyketide synthesis in a rapid and asymmetric fashion. A ruthenium-catalysed multicomponent reaction provides rapid and tunable access to 1,3-dienyl-6-oxy polyketide motifs. An initial alkene–alkyne coupling produces unsymmetrical 3-boryl-1,4-dienes. Allylation of aldehydes and ketones with these products is highly diastereoselective and results in the formation of two carbon–carbon bonds, two stereodefined olefins and up to three contiguous sp3 stereocentres.

The ruthenium catalytic addition of alkenes to alkynes has been demonstrated as a powerful synthetic tool to form diene motifs and widely applied in the synthesis of complex molecules. However, except for the intramolecular coupling, trisubstituted alkenes are unsatisfactory coupling partners with alkynes, presumably due to the increased steric hindrance. Herein, we discovered that substituted vinyl 1,2-bisboronate derivatives can serve as the trisubstituted alkene equivalents to couple with alkynes, generating various boryl-substituted homoallylic alcohol motifs with good stereoselectivity through the sequential allylboration with aldehydes. In contrast to carbon substituents on the double bond, boron substituents accelerate the alkyne coupling.

The dehydrogenative aryl C-H/N-H cross-coupling is a powerful synthetic methodology to install nitrogen functionalities into aromatic compounds. Herein, we report an electrochemical oxidation induced intermolecular cross-coupling between aromatics and sulfonimides with high regioselectivity through N-radical addition pathway under external-oxidant-free and catalyst-free conditions. A wide variety of arenes, heteroarenes, alkenes and sulfonimides are applicable scaffolds in this transformation. In addition, aryl sulfonamides or amines (aniline derivatives) can be obtained through different deprotection process. The cyclic voltammetry mechanistic study indicates that the N-centered imidyl radicals are generated via proton-coupled electron transfer event jointly mediated by tetrabutylammonium acetate and anode oxidation process.

The sequenced Diels-Alder/oxidation reaction represents a powerful route for the construction of aromatic compounds in organic synthesis. The oxidative Diels-Alder reaction with H2 evolution would be a more ideal approach that can avoid the additional oxidation procedure and stoichiometric oxidant. Herein, an oxidative [4 + 2] annulation reaction of styrene derivatives with electron-rich dienophiles accompanying the H2 generation has been developed by using the synergistic merger of photoredox and cobaloxime catalyst. With respect to atom and step-economy ideals, this dual catalytic system enables the formation of high-value molecules from feedstock chemicals in a single step under room temperature.

The directly external oxidant-free oxytrifluoromethylation and aminotrifluoromethylation of alkenes have been developed through the constant current electrolysis synergizing with a Lewis-acid catalysis protocol. By using sodium trifluoromethanesulfinate as the trifluoromethyl source, the method enabled difunctionalization of C-C double bonds of a wide range of styrene derivatives.

Carbon monoxide is an abundant and cost-efficient C1 building block for the carbonylation industry. Transition-metal-catalyzed oxidative C–H/C(X)–H carbonylation with CO provides one of the most straightforward approaches to construct carbonyl compounds. However, the use of stoichiometric oxidants would bring several drawbacks such as high cost and undesired chemical waste. Especially, the explosion limit is a potential safety hazard in oxidative carbonylation using O2 as the oxidant. To overcome these issues, an electrochemical strategy for oxidative C–H/N–H carbonylation has been designed by taking advantage of anodic oxidation to recycle a cobalt catalyst, and H2 is generated at the cathode. The intra- and intermolecular carbonylation products can be achieved with good functional group tolerance in 31%–99% yields. A plausible reaction mechanism involving a CoII/CoIII/CoI catalytic cycle is proposed by the studies of XANES and CV.

The dehydrogenative cross-coupling of arenes and alkenes is a particularly ideal approach for the synthesis of aryl alkenes. Herein, we report a photo-induced C–H/C–H cross-coupling between electron-rich arenes and styrene derivatives using a dual catalytic system containing an acridinium photosensitizer and a cobaloxime proton-reducing catalyst. This catalytic system enables the Csp–Csp bond formation accompanying H2 evolution. Various substituted aryl alkenes can be afforded with good to excellent yields and high b-regioselectivity.

The dehydrogenative cross-coupling of arenes and alkenes is a particularly ideal approach for the synthesis of aryl alkenes. Herein, we report a photo-induced C-H/C-H cross-coupling between electron-rich arenes and styrene derivatives using a dual catalytic system containing an acridinium photosensitizer and a cobaloxime proton-reducing catalyst. This catalytic system enables the Csp2-Csp2 bond formation accompanying H2 evolution. Various substituted aryl alkenes can be afforded with good to excellent yields and high β-regioselectivity.

The oxidative [4+2] annulation reaction represents an elegant and versatile synthetic protocol for the construction of six-membered heterocyclic compounds. Herein, a photoinduced oxidative [4+2] annulation of NH imines and alkenes was developed by utilizing a dual photoredox/cobaloxime catalytic system. Various multisubstituted 3,4-dihydroisoquinolines can be obtained in good yields. This method is not only obviated the need of stiochiometric amounts of oxidants but also exhibited excellent atom economy by generating H2 as the only byproduct. Remarkably, high regioselectivity and trans diastereoselectivity can be achieved in this transformation even if the Z/E mixture of alkenes were employed.

Constructing carbon-carbon bonds through oxidative cross-coupling between two hydrocarbon compounds is regarded as a foundational issue in green chemistry. High atom-economy and mild conditions are long term pursued goals in this field. Herein, we developed a visible-light mediated direct cross-coupling between N-heterocycles and aldehydes without the requirement of a photocatalyst. Several N-heterocycles afforded the acylation products with aromatic or aliphatic aldehydes in good yields. The reaction can be conducted under room temperature and easily scaled up.

The cross-coupling of C(sp(3))-H and N-H represents one of the most straightforward approaches to construct saturated nitrogen-containing compounds. The additional oxidants or halogenated reagents are generally required in such processes. Herein, we developed an electrochemical oxidative intramolecular C(sp(3))-H amination of amides by employing a carbon rod anode and a platinum plate cathode in an undivided cell under constant-current electrolysis conditions. Tetrabutylammonium acetate was not only employed as an electrolyte, but also can form the intermolecular hydrogen bond with amide and promote cleavage of the N-H bond. The additional oxidants and N-halogenation step can be obviated in this methodology. A variety of benzylic and nonactivated tertiary, secondary, primary C(sp(3))-H amination can be achieved with good yields.

We have developed a photoinduced oxidative cross-coupling of thiophenols with alcohols for O–S bond formation. The protocol uses visible light, a metal-free photocatalyst, and oxygen as the oxidant for the selective synthesis of alkyl benzenesulfonates; no ligand co-additive is necessary. Mechanistic studies suggested that the disulfide and alkyl benzenesulfinate are involved as intermediates and that the transformation proceeds by a radical pathway.

Considering that stoichiometric borane and oxidant are required in the classical alkene anti-Markovnikov hydration process, it remains appealing to achieve the transformation in a catalytic protocol. Herein, a visible-light-mediated anti-Markovnikov addition of water to alkenes by using an organic photoredox catalyst in conjunction with a redox-active hydrogen atom donor was developed, which avoided the need for a transition-metal catalyst, stoichiometric borane, as well as oxidant. Both terminal and internal olefins are readily accommodated in this transformation to obtain corresponding primary and secondary alcohols in good yields with single regioselectivity. This procedure can be scaled up to gram scale with a 230 turnover number based on photocatalyst.

Research and industrial interest in radical C-H activation/radical cross-coupling chemistry has continuously grown over the past few decades. These reactions offer fascinating and unconventional approaches toward connecting molecular fragments with high atom- and step-economy that are often complementary to traditional methods. Success in this area of research was made possible through the development of photocatalysis and first-row transition metal catalysis along with the use of peroxides as radical initiators. This Review provides a brief and concise overview of the current status and latest methodologies using radicals or radical cations as key intermediates produced via radical C-H activation. This Review includes radical addition, radical cascade cyclization, radical/radical cross-coupling, coupling of radicals with M-R groups, and coupling of radical cations with nucleophiles (Nu).

An external oxidant-free cross-coupling of electron-rich arenes and styrenes was enabled by a dual photoredox-cobaloxime catalytic system.