Explore the vast range of titles available.

Chiral Brønsted acid-catalysed asymmetric synthesis has received tremendous interest over the past decades, and numerous efficient synthetic methods have been developed based on this approach. However, the use of chiral Brønsted acids in these reactions is mostly limited to the activation of imine and carbonyl moieties, and the direct activation of carbon–carbon triple bonds has so far not been invoked. Here we show that chiral Brønsted acids enable the catalytic asymmetric dearomatization reactions of naphthol-, phenol- and pyrrole-ynamides by the direct activation of alkynes. This method leads to the practical and atom-economic construction of various valuable spirocyclic enones and 2H-pyrroles that bear a chiral quaternary carbon stereocentre in generally good-to-excellent yields with excellent chemo-, regio- and enantioselectivities. The activation mode of chiral Brønsted acid catalysis revealed in this study is expected to be of broad utility in catalytic asymmetric reactions that involve ynamides and the related heteroatom-substituted alkynes.Chiral Brønsted acid catalysis is mostly limited to the activation of imine and carbonyl moieties. Now, by direct activation of alkynes, chiral Brønsted acids have been used to enable the catalytic asymmetric dearomatization of naphthol-, phenol- and pyrrole-ynamides for the construction of various spirocyclic enones and 2H-pyrroles bearing a chiral quaternary carbon stereocentre.

Copper-catalyzed radical transformations have seen extensive investigations over recent decades. Due to the complexity of controlling factors and the diversity of reaction components, accurately delineating the bond formation mechanisms—namely reductive elimination, outer-sphere radical substitution, and ion pair-type bond formation—poses a formidable challenge. This study reveals the linear free energy relationships (LFER) for the C–C bond formation of Cu-catalyzed radical transformations. Leveraging this discovery, we formulate an accurate LFER model for predicting radical bond formation mechanisms in this catalytic system. By establishing LFER scales for ligands, radicals, and nucleophiles, the bond formation mechanisms across 132,300 potential Cu-catalyzed radical transformations are revealed, offering a detailed mechanistic guide for future C–C bond designs. This research advances the mechanistic understanding of Cu-catalyzed radical transformations, providing systematic and quantitative insights into the mechanistic preference of radical bond formations. Due to the complexity of controlling factors and the diversity of reaction components, accurately delineating the bond formation mechanisms for copper-catalyzed radical transformations poses a challenge. Here, the authors reveal the linear free energy relationships for the C–C bond formation of Cu-catalyzed radical transformations.

In contrast with abundant methods for the asymmetric functionalization of alkyl radicals to generate stereogenic centres at reaction sites, catalytic enantioselective desymmetrizing functionalization of alkyl radicals for forging multiple stereocentres—including positions that are remote from the reaction sites—with both high enantio- and diastereoselectivity remains largely unexplored. The major challenge for such reactions is the high reactivity of open-shell alkyl radicals. Here, we describe a strategy to address this challenge: the use of Cu( ii ) phosphate to immediately associate with the in situ-generated reactive alkyl radical species, creating a compact and confined chiral microenvironment for effective stereocontrol. With this strategy, we have developed a general and efficient catalytic enantioselective desymmetrizing functionalization of alkene-tethered 1,3-diols. It provides various tetrahydrofurans and analogues bearing multiple stereocentres with remarkably high levels of enantio- and diastereocontrol. Density functional theory calculations and mechanistic experiments revealed a reaction mechanism involving an enantiodetermining outer-sphere C–O bond formation step. The high reactivity of open-shell alkyl radicals makes their use in asymmetric catalysis challenging. Here the authors report a catalytic enantioselective desymmetrizing reaction of alkyl radicals and diols, forming stereocentres at the reaction site and at sites remote from it.

Chiral amines are commonly used in the pharmaceutical and agrochemical industries 1 . The strong demand for unnatural chiral amines has driven the development of catalytic asymmetric methods 1 , 2 . Although the N -alkylation of aliphatic amines with alkyl halides has been widely adopted for over 100 years, catalyst poisoning and unfettered reactivity have been preventing the development of a catalyst-controlled enantioselective version 3 – 5 . Here we report the use of chiral tridentate anionic ligands to enable the copper-catalysed chemoselective and enantioconvergent N -alkylation of aliphatic amines with α-carbonyl alkyl chlorides. This method can directly convert feedstock chemicals, including ammonia and pharmaceutically relevant amines, into unnatural chiral α-amino amides under mild and robust conditions. Excellent enantioselectivity and functional-group tolerance were observed. The power of the method is demonstrated in a number of complex settings, including late-stage functionalization and in the expedited synthesis of diverse amine drug molecules. The current method indicates that multidentate anionic ligands are a general solution for overcoming transition-metal-catalyst poisoning. The chemoselective and enantioconvergent N -alkylation of aliphatic amines, including ammonia, is achieved using chiral tridentate anionic ligands and a copper catalyst; the method shows excellent enantioselectivity and functional-group tolerance.

In contrast with the well-established enantioconvergent radical C( sp 3 )–C cross-coupling of racemic secondary alkyl electrophiles, the corresponding coupling of tertiary electrophiles to forge all-carbon quaternary stereocentres remains underexplored. The major challenge arises from the steric hindrance and the difficult enantio-differentiation of three distinct carbon substituents of prochiral tertiary radicals. Here we demonstrate a general copper-catalysed enantioconvergent C( sp 3 )–C( sp ) cross-coupling of diverse racemic tertiary alkyl halides with terminal alkynes (87 examples). Key to the success is the rational design of chiral anionic N,N , N -ligands tailor-made for the computationally predicted outer-sphere radical group transfer pathway. This protocol provides a practical platform for the construction of chiral C( sp 3 )–C( sp / sp 2 / sp 3 ) bonds, allowing for expedient access to an array of synthetically challenging quaternary carbon building blocks of interest in organic synthesis and related areas. A general copper-catalysed enantioconvergent C( sp 3 )–C( sp ) cross-coupling of diverse racemic tertiary alkyl halides with terminal alkynes has been developed, forging all-carbon quaternary stereocentres. Key to the success is the rational design of chiral anionic N , N , N -ligands tailor-made for the computationally predicted outer-sphere radical group transfer pathway.

Although α-chiral C( sp 3 )–S bonds are of enormous importance in organic synthesis and related areas, the transition-metal-catalysed enantioselective C( sp 3 )–S bond construction still represents an underdeveloped domain probably due to the difficult heterolytic metal–sulfur bond cleavage and notorious catalyst-poisoning capability of sulfur nucleophiles. Here we demonstrate the use of chiral tridentate anionic ligands in combination with Cu(I) catalysts to enable a biomimetic enantioconvergent radical C( sp 3 )–S cross-coupling reaction of both racemic secondary and tertiary alkyl halides with highly transformable sulfur nucleophiles. This protocol not only exhibits a broad substrate scope with high enantioselectivity but also provides universal access to a range of useful α-chiral alkyl organosulfur compounds with different sulfur oxidation states, thus providing a complementary approach to known asymmetric C( sp 3 )–S bond formation methods. Mechanistic results support a biomimetic radical homolytic substitution pathway for the critical C( sp 3 )–S bond formation step. Methods for transition-metal-catalysed enantioselective C( sp 3 )–S bond construction are underdeveloped. Now, by taking advantage of the biomimetic radical homolytic substitution manifold, the copper-catalysed enantioconvergent C( sp 3 )–S cross-coupling of racemic secondary and tertiary alkyl halides with highly transformable sulfur nucleophiles has been realized. This reaction provides access to an array of α-chiral alkyl organosulfur compounds.

The transition-metal-catalysed cross-coupling reaction has established itself as one of the most reliable and practical synthetic tools for the efficient construction of carbon–carbon/heteroatom (p-block elements other than carbon) bonds in both racemic and enantioselective manners. In contrast, development of the corresponding heteroatom–heteroatom cross-couplings has so far remained elusive, probably due to the under-investigated and often challenging heteroatom–heteroatom reductive elimination. Here we demonstrate the use of single-electron reductive elimination as a strategy for developing enantioselective S–O coupling under Cu catalysis, based on both experimental and theoretical results. The reaction manifests its synthetic potential by the ready preparation of challenging chiral alcohols featuring congested stereocentres, the expedient valorization of the biomass-derived feedstock glycerol, and the remarkable catalytic 4,6-desymmetrization of inositol. These results demonstrate the potential of enantioselective radical heteroatomic cross-coupling as a general chiral heteroatom–heteroatom formation strategy.Heteroatom–heteroatom cross-couplings have so far remained elusive. Now, a copper-catalysed enantioselective S–O cross-coupling of diverse diols or triols with sulfonyl chlorides has been realized via a single-electron reductive elimination manifold. The reaction provides access to value-added chiral C3 building blocks and inositol phosphates through enantioselective desymmetrization of biomass-derived alcohols.

Transition-metal-catalysed enantioconvergent cross-coupling reactions of highly reactive alkyl radicals often suffer from reduced chemoselectivity, mainly due to side reactions with closed-shell reactants. A strategy to overcome this challenge has yet to be identified, posing substantial limitations on the synthetic utility of this method. Here we report a method for enantioconvergent radical carbon–carbon cross-coupling of highly reactive cyclopropyl radicals with terminal alkynes, using redox state-tuned copper catalysis, under mild conditions. Key to this method is the use of hard chiral N , N , N -ligands in combination with Cu(II) salts of hard ligands/counterions, which results in elevated concentrations of Cu(II) species and thus enhanced cross-coupling reactions. This protocol not only exhibits a broad substrate scope across a wide range of both racemic cyclopropyl halide and terminal alkyne coupling partners but also provides access to useful yet synthetically challenging enantioenriched cyclopropane building blocks. The synthetic use of highly reactive alkyl radicals typically results in low chemoselectivity due to competing side reactions. Now, a redox-state-tuned copper catalytic method is reported, which enables the enantioconvergent cross-coupling of cyclopropyl radicals and terminal alkynes with high chemo- and stereoselectivity.

Enhancing the guarantee of government supervision effectiveness on construction quality and intensifying the reform of supervision need continuous endeavors. Minister of Housing and Urban-Rural Development has established the Engineering quality supervision guidance ,based on basis principles on government supervision on construction quality of Supervision Rules on Construction Quality, which sets aims to refined and modern management .It proposes some new requirements about the government supervision on construction quality ,such as clearing demands of qualities, emphases and participants; planning projects in more scientific ways; refining supervision on quality behaviors; strengthening quality supervision on project entity; controlling strictly in project final acceptance; normalizing reports and files; and informationizing the methods to supervise. It is a consecutive task to improve efficiency in government supervision on construction quality, and guarantee successive improvements in construction quality.

The present study defines a low-latitude component （regionally averaged winter 1000-hPa V-winds over 10 25°N, 105 135°E） and a mid-high-latitude component （regionally averaged winter 1000-hPa V-winds over 30 50°N, 110 125°E） of the East Asian winter monsoon （EAWM）, which are denoted as EAWM-L and EAWM-M, respectively. The study examines the variation characteristics, reflecting variations in winter climate over eastern China, and associated atmospheric circulations corresponding to the two components. The main results are as follows： 1） the EAWM-L and EAWM-M have consistent variation in some years but opposite variations in other years; 2） the EAWM-M index mainly reflects the extensive temperature variability over eastern China, while the EAWM-L index better reflects the variation in winter precipitation over most parts of eastern China; and 3） corresponding to the variation in the EAWM-M index, anomalous winds over the mid-high latitudes of East Asia modulate the southward invasion of cold air from the high latitudes and accordingly affect temperatures over eastern China. In combination with the variation in the EAWM-L index, anomalous low-latitudinal winds regulate the water vapor transport from tropical oceans to eastern China, resulting in anomalous winter precipitation. These pronounced differences between the EAWM-L and the EAWM-M suggest that it is necessary to explore the monsoons＇ individual features and effects in the EAWM study.