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Recently, with the boosted development of radical chemistry, enantioselective functionalization of C( sp 3 )–H bonds via a radical pathway has witnessed a renaissance. In principle, two distinct catalytic modes, distinguished by the steps in which the stereochemistry is determined (the radical formation step or the radical functionalization step), can be devised. This Perspective discusses the state-of-the-art in the area of catalytic enantioselective C( sp 3 )–H functionalization involving radical intermediates as well as future challenges and opportunities. Enantioselective functionalization of ubiquitous C(sp 3 )–H bonds via radical species has witnessed a renaissance in the past years. Here, the authors summarize the main achievements in the field by identifying two main reaction pathways determining the stereochemistry and give an outlook on future challenges and opportunities.

Organocatalysis—catalysis mediated by small chiral organic molecules—is a powerful technology for enantioselective synthesis, and has extensive applications in traditional ionic, two-electron-pair reactivity domains. Recently, organocatalysis has been successfully combined with photochemical reactivity to unlock previously inaccessible reaction pathways, thereby creating new synthetic opportunities. Here we describe the historical context, scientific reasoning and landmark discoveries that were essential in expanding the functions of organocatalysis to include one-electron-mediated chemistry and excited-state reactivity. This Review discusses recent developments in the combination of organocatalysis and photochemistry for the activation of molecules, which has enabled previously inaccessible reaction pathways and influenced many fields of chemical research. The rise of organocatalysis Organocatalysis uses small, chiral organic molecules as catalysts and has been widely applied to asymmetric reactions in the past few decades. In this Review, Mattia Silvi and Paolo Melchiorre look at how, in combination with photochemical reactivity, the field has moved from traditional two-electron-pair reactivity to include one-electron and excited-state chemistry. The merger of these two fields has expanded the scope of asymmetric organocatalysis substantially, providing access to previously unavailable synthetic prospects, and this combination shows promise for developing new stereocontrolled catalytic processes.

A promising solution to address the challenges in plastics sustainability is to replace current polymers with chemically recyclable ones that can depolymerize into their constituent monomers to enable the circular use of materials. Despite some progress, few depolymerizable polymers exhibit the desirable thermal stability and strong mechanical properties of traditional polymers. Here we report a series of chemically recyclable polymers that show excellent thermal stability (decomposition temperature >370 °C) and tunable mechanical properties. The polymers are formed through ring-opening metathesis polymerization of cyclooctene with a trans-cyclobutane installed at the 5 and 6 positions. The additional ring converts the non-depolymerizable polycyclooctene into a depolymerizable polymer by reducing the ring strain energy in the monomer (from 8.2 kcal mol–1 in unsubstituted cyclooctene to 4.9 kcal mol–1 in the fused ring). The fused-ring monomer enables a broad scope of functionalities to be incorporated, providing access to chemically recyclable elastomers and plastics that show promise as next-generation sustainable materials.Depolymerizable polymers can potentially address challenges in polymer sustainability, but most existing systems lack the useful thermomechanical properties of traditional ones. Now, it has been shown that depolymerizable polymers based on olefin metathesis show good thermal stability as well as versatile mechanical properties and that the monomers used to make them can be prepared from abundant materials.

The past decade has seen unprecedented growth in the development of new chemical methods that proceed by mechanisms involving radical intermediates. This new attention has served to highlight a long-standing challenge in the field of radical chemistry — that of controlling absolute stereochemistry. This Review will examine developments using a strategy that offers enormous potential, in which attractive non-covalent interactions between a chiral catalyst and the substrate are leveraged to exert enantiocontrol. In a simplistic sense, such an approach mimics the modes of activation and control in enzyme catalysis and the realization that this can be achieved in the context of small-molecule catalysts has had sizable impact on the field of asymmetric catalysis in recent years. This strategy is now starting to quickly gather pace as a powerful approach for control of enantioselectivity in radical reactions and we hope that this focused survey of progress so far will inspire future developments in the area.The past decade has seen unprecedented growth in the development of chemical methods that proceed by mechanisms involving radical intermediates, but controlling absolute stereochemistry has been a longstanding challenge in this area. This Review Article examines how attractive non-covalent interactions between a chiral catalyst and the substrate can exert enantiocontrol in radical reactions.

Chiral optical materials based on circularly polarized luminescence (CPL) have emerged rapidly due to their feasible applications in diverse fields of research. However, limited to the small luminescence dissymmetry factor ( g lum ), real application examples have rarely been reported. Here, we present a complex system, which show intense circularly polarized ultraviolet luminescence (CPUVL) with large g lum value, enabling a chiral UV light triggered enantioselective polymerization. By integrating sensitized triplet-triplet annihilation upconversion and CPL, both visible-to-UV upconversion emission and upconverted circularly polarized ultraviolet luminescence (UC-CPUVL) were obtained in the systems, built of chiral annihilator R ( S )-4,12-biphenyl[2,2]paracyclophane ( R -/ S -TP), and a thermally activated delayed fluorescence (TADF) sensitizer. After dispersing this upconversion system into room-temperature nematic liquid crystal, induced chiral nematic liquid crystal could significantly amplify the g lum value (0.19) of UC-CPUVL. Further, the UC-CPUVL emission has been used to trigger the enantioselective photopolymerization of diacetylene. This work paves the way for the further development of functional application of CPL active materials. Chiral functional materials with circularly polarized luminescence can be used in various applications but rarely reported. Here the authors show, a complex system, which show intense circularly polarized ultraviolet luminescence with large glum value, enabling a chiral UV light triggered enantioselective polymerization.

From the viewpoint of synthetic accessibility and functional group compatibility, photoredox-catalyzed sulfur dioxide insertion strategy enables in situ generation of functionalized sulfonyl radicals from easily accessible starting materials under mild conditions, thereby conferring broader application potential. Here we present two complementary photoinduced sulfur dioxide insertion systems to trigger radical asymmetric Truce–Smiles rearrangements for preparing a variety of chiral sulfones that bear a quaternary carbon stereocenter. This protocol features broad substrate scope and excellent stereospecificity. Aside from scalability, the introduction of a quaternary carbon stereocenter at position β to bioactive molecule-derived sulfones further demonstrates the practicality and potential of this methodology. The preparation of chiral sulfones featuring quaternary carbon stereocenters remains challenging. Here the authors report the synthesis of such compounds via a multicomponent reaction involving a photoinduced radical sulfur dioxide insertion followed by an asymmetric Truce–Smiles rearrangement.

The N−N atropisomer, as an important and intriguing chiral system, was widely present in natural products, pharmaceutical lead compounds, and advanced material skeletons. The anisotropic structural characteristics caused by its special axial rotation have always been one of the challenges that chemists strive to overcome. Herein, we report an efficient method for the enantioselective synthesis of N−N axially chiral frameworks via a cobalt-catalyzed atroposelective C-H activation/annulation process. The reaction proceeds under mild conditions by using Co(OAc) 2 ·4H 2 O as the catalyst with a chiral salicyl-oxazoline (Salox) ligand and O 2 as an oxidant, affording a variety of N−N axially chiral products with high yields and enantioselectivities. This protocol provides an efficient approach for the facile construction of N−N atropisomers and further expands the range of of N−N axially chiral derivatives. Additionally, under the conditions of electrocatalysis, the desired N−N axially chiral products were also successfully achieved with good to excellent efficiencies and enantioselectivities. Atropisomers are an important chiral system which are widely present in natural products but atropisomerism bearing a N−N bond remains largely underdeveloped. Here, the authors report an efficient method for the enantioselective synthesis of N−N axially chiral frameworks under mild conditions via a cobalt-catalyzed atroposelective C-H activation/annulation

Continued development of the Sonogashira coupling has made it a well established and versatile reaction for the straightforward formation of C–C bonds, forging the carbon skeletons of broadly useful functionalized molecules. However, asymmetric Sonogashira coupling, particularly for C( sp 3 )–C( sp ) bond formation, has remained largely unexplored. Here we demonstrate a general stereoconvergent Sonogashira C( sp 3 )–C( sp ) cross-coupling of a broad range of terminal alkynes and racemic alkyl halides (>120 examples) that are enabled by copper-catalysed radical-involved alkynylation using a chiral cinchona alkaloid-based P,N-ligand. Industrially relevant acetylene and propyne are successfully incorporated, laying the foundation for scalable and economic synthetic applications. The potential utility of this method is demonstrated in the facile synthesis of stereoenriched bioactive or functional molecule derivatives, medicinal compounds and natural products that feature a range of chiral C( sp 3 )–C( sp / sp 2 / sp 3 ) bonds. This work emphasizes the importance of radical species for developing enantioconvergent transformations. Asymmetric Sonogashira C( sp 3 )–C( sp ) couplings provide complementary approaches to established C( sp 3 )–C( sp 2 / sp 3 ) couplings for chiral C–C bond formation; however, relatively few reactions have been developed. Now, a versatile, enantioconvergent Sonogashira coupling via a radical intermediate has been developed. The approach uses a copper catalyst featuring a multidentate electron-rich cinchona alkaloid-derived ligand.

When faced with unfamiliar reaction space, synthetic chemists typically apply the reported conditions (reagents, catalyst, solvent and additives) of a successful reaction to a desired, closely related reaction using a new substrate type. Unfortunately, this approach often fails owing to subtle differences in reaction requirements. Consequently, an important goal in synthetic chemistry is the ability to transfer chemical observations quantitatively from one reaction to another. Here we present a holistic, data-driven workflow for deriving statistical models of one set of reactions that can be used to predict out-of-sample reactions. As a validating case study, we combined published enantioselectivity datasets that employ 1,1′-bi-2-naphthol (BINOL)-derived chiral phosphoric acids for a range of nucleophilic addition reactions to imines and developed statistical models. These models reveal the general interactions that impart asymmetric induction and allow the quantitative transfer of this information to new reaction components. This technique creates opportunities for translating comprehensive reaction analysis to diverse chemical space, streamlining both catalyst and reaction development. A workflow for deriving statistical models of one set of reactions that can be used to predict related reactions is presented, facilitating catalyst and enantioselective reaction development.

Absolute chiral environments are rare in regular polyhedral and prismatic architectures, but are achievable from self-assembly of metal–organic cages/containers (MOCs), which endow us with a promising ability to imitate natural organization systems to accomplish stereochemical recognition, catalysis and separation. Here we report a general assembly approach to homochiral MOCs with robust chemical viability suitable for various practical applications. A stepwise process for assembly of enantiopure ΔΔΔΔΔΔΔΔ - and ΛΛΛΛΛΛΛΛ- Pd 6 (RuL 3 ) 8 MOCs is accomplished by pre-resolution of the Δ / Λ -Ru-metalloligand precursors. The obtained Pd–Ru bimetallic MOCs feature in large D 4 -symmetric chiral space imposed by the predetermined Ru(II)-octahedral stereoconfigurations, which are substitutionally inert, stable, water-soluble and are capable of encapsulating a dozen guests per cage. Chiral resolution tests reveal diverse host–guest stereoselectivity towards different chiral molecules, which demonstrate enantioseparation ability for atropisomeric compounds with C 2 symmetry. NMR studies indicate a distinctive resolution process depending on guest exchange dynamics, which is differentiable between host–guest diastereomers. Homochiral molecular capsules offer potential applications in chiral separation and stereospecific catalysis. Here, by pre-resolution of Δ/Λ -metalloligand precursors, the authors are able to assemble enantiopure supramolecular cages capable of stereoselective host-guest behaviour.