Copper-Catalyzed Difunctionalization of Propargylic Carbonates through Tandem Nucleophilic Substitution/Boroprotonation.

Highly functionalized organic molecules are in high demand, but their preparation is challenging. Copper-catalyzed transformation of alkynyl- and allenyl-containing substrates has emerged as a powerful tool to achieve this objective. Herein, an efficient copper-catalyzed difunctionalization of propargylic carbonates through tandem nucleophilic substitution/boroprotonation has been developed, affording the formation of thiol-, selenium-, and boron-functionalized alkenes with high yield and stereoselectivity. Two distinct catalytic mechanisms involving a single reaction without any requirement of catalyst change were successfully demonstrated.

New P,Nsp3 ligands for palladium-catalyzed asymmetric allylic substitutions.

New P,Nsp3 bidentate ligands containing two chiral carbon centers were developed and applied to palladium-catalyzed asymmetric allylic substitution reactions. Good generalities with various nucleophiles, including carbon, nitrogen and oxygen containing nucleophiles, were achieved with up to 96% ee and 98% yield. This reaction provides an efficient method for the asymmetric formation of C-C, C-N and C-O bonds.

Upgrading protected areas can improve or reverse the decline in conservation effectiveness: Evidence from the Tibetan Plateau, China.

Protected areas (PAs) are considered essential for maintaining biodiversity. Several governments would like to strengthen the management levels of their PAs (as shorthand for a hierarchy in PA administrative governance) to consolidate their conservation effectiveness. This upgrade (e.g., from provincial- to national-level PAs) means stricter protection and increased funds for PA management. However, confirming whether such an upgrade can produce the expected positive outcomes is key given limited conservation funds. Here, we used the Propensity Score Matching (PSM) method to quantify the impacts of upgrading PAs (i.e., from provincial to national) on vegetation growth on the Tibetan Plateau (TP). We found that the impacts of PA's upgrading can be divided into two impact types: 1) curbed or reversed declines in conservation effectiveness and 2) rapidly increased conservation effectiveness before the upgrade. These results indicate that the PA's upgrading process (including the pre-upgrade operations) can improve PA effectiveness. Nevertheless, the gains did not always occur after the official upgrade. This study demonstrated that in comparison to other PAs, those with more resources or stronger management policies were more effective.

Climate change mitigation potentials of biofuels produced from perennial crops and natural regrowth on abandoned and degraded cropland in Nordic countries.

Bioenergy expansion is present in most climate change mitigation scenarios. The associated large land use changes have led to concerns on how bioenergy can be sustainably deployed. Promising win-win strategies include the production of perennial bioenergy crops on recently abandoned cropland or on cropland prone to land degradation, as perennial crops typically reduce soil erosion rates. Natural vegetation regrowth is an alternative nature-based solution that can also co-deliver negative emissions and other environmental benefits. In this study, we explore the potential to deploy bioenergy crops in Nordic countries (Norway, Sweden, Finland, and Denmark) on abandoned cropland and on cropland threatened by soil erosion and compare the achievable climate change mitigation benefits with natural regrowth. We found 186 thousand hectares (kha) of abandoned cropland and 995 kha of cropland threatened by soil erosion suitable for bioenergy crop cultivation. The primary bioenergy potential in the region is 151 PJ (PJ) per year, corresponding to 67-110 PJ per year of liquid biofuels depending on biorefinery technology. This has a climate change mitigation potential from -6.0 to -17 megatons of carbon dioxide equivalents (MtCO2eq) per year over the first 20 years (equivalent to 14-40% of annual road transport emissions), with high-end estimates relying on bioenergy coupled to carbon capture and storage (BECCS). On the same area, natural regrowth can deliver negative emissions of -10 MtCO2eq per year. Biofuel production outperforms natural regrowth on 46% of abandoned cropland with currently available biorefinery technologies, 83% with improved energy conversion efficiency, and nearly everywhere with BECCS. For willow windbreaks, improved biorefinery technology or BECCS is necessary to ensure the delivery of larger negative emissions than natural regrowth. Biofuel production is preferable to natural regrowth on 16% of croplands threatened by soil erosion with the current biorefinery technology and on 87% of the land area with BECCS. Without BECCS, liquid biofuels achieve larger climate benefits than natural regrowth only when bioenergy yields are high. Underutilized land and land affected by degradation processes are an opportunity for a gradual and more sustainable bioenergy deployment, and local considerations are needed to identify case-specific solutions that can co-deliver multiple environmental benefits.

Development of spirocyclic phosphoramidite-based hybrid diphosphorus ligands for enantioselective iridium-catalyzed hydrogenation of imines.

Unsymmetrical hybrid chiral diphosphorus ligands bearing a spirocyclic phosphoramidite scaffold have been developed and successfully applied in the iridium-catalyzed asymmetric hydrogenation of imines. With this newly developed chiral iridium catalytic system, a wide range of imines including sterically hindered ones could be hydrogenated to give the corresponding optically active amines in high yields (up to >99%) and with excellent enantioselectivities (up to >99% ee). The utility of this hydrogenation has been demonstrated by the preparation of the chiral fungicide (S)-benalaxyl.

Highly Enantioselective Iridium-Catalyzed Hydrogenation of o-Amidophenyl Ketones Enabled by 1,2-Diphenylethylenediamine-Derived P,N,N-Ligands with Tertiary Amine Terminus.

A readily available and highly modular class of chiral P,N,N-ligands based on a structurally flexible nonchiral phosphine-amine framework with an optically active 1,2-diphenylethylenediamine unit bearing a tertiary amine terminus as the chiral source have been developed and successfully applied in the Ir-catalyzed asymmetric hydrogenation of o-amidophenyl ketones. These tridentate P,N,N-ligands exhibited excellent activity, enantioselectivity, and substrate tolerance, thus furnishing various optically active o-amidobenzhydrols in up to 99% yields and with >99% ee. The utility of this protocol has been proven by synthetically diverse product transformation and highly enantioselective production of a rice plant growth regulator, (S)-inabenfide.

Palladium-catalysed construction of butafulvenes.

Butafulvene is a constitutional isomer of benzene, comprising a cyclobutene skeleton bearing two exocyclic conjugated methylene units. As a result of the intrinsic high strain energy and anti-aromaticity, the preparation of butafulvene compounds has been a fundamental issue for the development of butafulvene chemistry. Here an efficient palladium-catalysed coupling protocol involving propargylic compounds has been developed, providing a solid and versatile strategy for the rapid assembly of symmetric butafulvene derivatives. Based on mechanistic studies, two complementary mechanisms, both involving palladium catalysis, have been confirmed. With the mechanism unveiled, the synthesis of non-symmetric butafulvenes has also been achieved. Advantages of this strategy include tolerance to a wide range of propargylic molecules, mild reaction conditions, simple catalytic systems and easy scalability. The synthetic potential of the products as platform molecules for cyclobutene derivatives has also been demonstrated.

Intramolecular Copper-Catalyzed Asymmetric Propargylic [4 + 2]- Cycloaddition toward Optically Active Tetrahydroisoindolo[2,1-a]quinoxalines.

An intramolecular Cu-catalyzed asymmetric propargylic [4 + 2] cycloaddition of bis-N-nucleophile-functionalized propargylic esters has been realized in the support of a chiral tridentate N-ligand, (S,S)-Pybox-diOAc, leading to chiral tetrahydroisoindolo[2,1-a]quinoxalines in high yields and with good to excellent enantioselectivities. The reaction features high efficiency, simplicity, and broad substrate scope, thus providing a powerful and concise strategy for stereoselective access to optically active polycyclic heterocycle frameworks that are otherwise difficult to synthesize.

Bicyclic Bridgehead Phosphoramidite-Based Hybrid Diphosphorus Ligands: Design, Synthesis, and Application in Catalytic Asymmetric Hydrogenation.

A strategy for chiral ligand design has been developed that allows for incorporation of an achiral bicyclic bridgehead phosphoramidite to generate a class of hybrid diphosphorus ligands for high activity and asymmetric control. Using this concept, a series of chiral phosphine-phosphoramidite ligands bearing the sole chirality at the ligand backbone have been prepared and successfully employed in the Rh-catalyzed asymmetric hydrogenation of 2-vinylanilides for the synthesis of optically active anilines bearing an ortho-tertiary benzylic stereocenter.

Sensitivity and future exposure of ecosystem services to climate change on the Tibetan Plateau of China.

CONTEXT: Climate change has imposed tremendous impacts on ecosystem services. Recent attempts to quantify such impacts mainly focused on a basin or larger scale, or used limited time periods that largely ignore observations of long-term trends at a fine resolution, thereby affecting the recognition of climate change's effect on ecosystem services. OBJECTIVES: This study conducts a detailed and spatially explicit recognition of climate change's effect on ecosystem services and provides an intuitive map for decision-making and climate change adaptation planning. METHODS: We used long-term time series of ecosystem service assessments and various future climate scenarios to quantify the sensitivity and future exposure of ecosystem services to climate change on the Tibetan Plateau. RESULTS: Carbon sequestration (CS) and habitat quality experience significant growth, while water retention did not show any trend. Sensitivity patterns of these ecosystem services vary largely. For CS, more than half of the pixels showed a positive sensitivity to climate change, even though the degree of sensitivity is not high. There is substantial spatial heterogeneity in the exposure of ecosystem services to future climate changes, and high levels of future climate change increase the intensity of exposure. CONCLUSIONS: This study illustrates the complex spatial association between ecosystem services and climatic drivers, and these findings can help optimize local response strategies in the context of global warming. For example, the existing protected areas have notable conservation gaps for disturbance of future climate change on ecosystem services, especially in the southeastern part of the study area. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10980-021-01320-9.

Enantioselective Copper-Catalyzed [3 + 3] Cycloaddition of Tertiary Propargylic Esters with 1H-Pyrazol-5(4H)-ones toward Optically Active Spirooxindoles.

A copper-catalyzed enantioselective [3 + 3] cycloaddition of 3-ethynyl-2-oxoindolin-3-yl acetates with 1H-pyrazol-5(4H)-ones for the construction of optically active spirooxindoles bearing a spiro all-carbon quaternary stereocenter has been realized. With a combination of Cu(OTf)2 and chiral tridentate ketimine P,N,N-ligand as the catalyst, the reaction displayed broad substrate scopes, good yields, and high enantioselectivities. This represents the first catalytic asymmetric propargylic cycloaddition with tertiary propargylic esters as the bis-electrophiles for access to chiral spirocyclic frameworks.

The catalyst-free decarboxylative dearomatization of isoquinolines with ß-keto acids and sulfonyl chlorides in water: access to dihydroisoquinoline derivatives.

An efficient and concise catalyst-free one-pot synthetic protocol for obtaining dihydroisoquinoline derivatives has been developed via the three-component condensation of isoquinolines with ß-keto acids and sulfonyl chlorides. This transformation involving decarboxylative dearomatization worked well under mild and water-mediated conditions. The protocol tolerates diverse functional groups, furnishing the dihydroisoquinoline products in good to excellent yields.

The unequal contribution to global energy consumption along the supply chain.

Reducing fossil fuel consumption is a top priority option for climate change mitigation, which requires collaborations of partners along the supply chain, such as energy suppliers, energy consumers and final consumers of goods and services. A comprehensive analysis of fossil fuel consumption is useful for policymakers to reduce demand but still absent. This study explores the national contribution to global energy consumption from different perspectives in the global supply chain and is designed to complement current energy reduction policies. For the developed countries, energy consumptions are stable from 2000 to 2014, while that of emerging countries almost doubled (e.g., China and India). Most of the developing countries are producers whose production-based and final production-based energy consumptions are higher than their consumption-based ones, except India after the global financial crisis. In contrast, the developed countries are consumers, whose consumption-based energy consumptions are higher. At the sectoral level, the service sector is the largest contributor to consumption- and income-based energy consumption. The analysis in this study can create opportunities for all the parties alongside the supply chain in reducing fossil fuel consumption.

Predominant regional biophysical cooling from recent land cover changes in Europe.

Around 70 Mha of land cover changes (LCCs) occurred in Europe from 1992 to 2015. Despite LCCs being an important driver of regional climate variations, their temperature effects at a continental scale have not yet been assessed. Here, we integrate maps of historical LCCs with a regional climate model to investigate air temperature and humidity effects. We find an average temperature change of -0.12 ± 0.20 °C, with widespread cooling (up to -1.0 °C) in western and central Europe in summer and spring. At continental scale, the mean cooling is mainly correlated with agriculture abandonment (cropland-to-forest transitions), but a new approach based on ridge-regression decomposing the temperature change to the individual land transitions shows opposite responses to cropland losses and gains between western and eastern Europe. Effects of historical LCCs on European climate are non-negligible and region-specific, and ignoring land-climate biophysical interactions may lead to sub-optimal climate change mitigation and adaptation strategies.

Copper-Catalyzed Asymmetric Propargylic Alkylation with Oxindoles: Diastereo- and Enantioselective Construction of Vicinal Tertiary and All-Carbon Quaternary Stereocenters.

A copper-catalyzed asymmetric propargylic alkylation of propargylic acetates with 3-substituted oxindoles for the stereoselective construction of vicinal tertiary and all-carbon quaternary stereocenters in a 3,3-disubstituted oxindole skeleton has been realized. The reaction proceeded smoothly under the catalysis of Cu(MeCN)4PF6 combined with a chiral tridentate ferrocenyl P,N,N ligand, leading to a broad range of optically active 3,3-disubstituted oxindoles in high yields and with excellent diastereo- and enantioselectivities.

Highly Diastereo- and Enantioselective Ir-Catalyzed Hydrogenation of 2,3-Disubstituted Quinolines with Structurally Fine-Tuned Phosphine-Phosphoramidite Ligands.

A highly diastereo- and enantioselective Ir-catalyzed hydrogenation of unfunctionalized 2,3-disubstituted quinolines, especially 3-alkyl-2-arylquinolines, has been realized. The success of this hydrogenation is ascribed to the use of a structurally fine-tuned chiral phosphine-phosphoramidite ligand with a (Sa)-3,3'-dimethyl H8-naphthyl moiety and (Rc)-1-phenylethylamine backbone. The hydrogenation displayed broad functional group tolerance, thus furnishing a wide range of optically active 2,3-disubstituted tetrahydroquinolines in up to 96% ee and with perfect cis-diastereoselectivity.

Rh-Catalyzed Asymmetric Hydrogenation of (Z)-ß-Phosphorylated Enamides: Highly Enantioselective Access to ß-Aminophosphines.

A catalytic asymmetric hydrogenation of ß-phosphorylated enamides for enantioselective access to optically active ß-aminophosphine derivatives is reported. Critical to the success of this method was the employment of rhodium catalysis in concert with an unsymmetrical hybrid chiral phosphine-phosphoramidite ligand. A wide range of aromatic ß-phosphorylated enamides could be hydrogenated in full conversion and with perfect enantioselectivity even at low catalyst loadings (S/C = 1000). ß-Aminophosphine oxides could be readily hydrolyzed and reduced, thus providing an efficient route to catalytically important chiral ß-aminophosphines.

Diastereo- and Enantioselective Copper-Catalyzed Decarboxylative Ring-Opening [3 + 2] Annulation of Tertiary Propargylic Carbamates through Regioselective α-Attack of γ-Butenolides.

A copper-catalyzed regio-, diastereo-, and enantioselective decarboxylative ring-opening [3 + 2] annulation of tertiary propargylic carbamates with γ-butenolides for the synthesis of optically active pyrrolidinones has been realized. The reaction proceeded through regioselective α-attack of γ-butenolide and generated highly congested vicinal tertiary and all-carbon quaternary stereocenters in pyrrolidinone scaffolds, featuring high stereoselective induction and broad functional group tolerance. Critical to the successful development of this method was the employment of copper catalysis in concert with a diPh-Pybox ligand.

Traceless-Activation Strategy for Rh-Catalyzed Csp2-H Arylation of Coumarins.

A traceless-activation strategy for the synthesis of 4-arylchroman-2-ones via a Rh(III)-catalyzed C-H activation of 2-arylpyridines and subsequent conjugated/decarboxylative addition to coumarin-3-carboxylic acids has been reported. The carboxyl group at C3 position of coumarin proved to be crucial to realize the reaction, which is spontaneously removed after the reaction by the release of CO2. The reaction displayed good substrate tolerance and gave various 4-arylchroman-2-ones in up to 90% yield.

Copper-catalyzed, silver-mediated formal [3+2] cycloaddition of simple alkynes with ß-ketoesters through propargylic C(sp3)-H functionalization.

A copper-catalyzed propargylic [3+2] cycloaddition of simple alkynes with ß-ketoesters through the propargylic C(sp3)-H functionalization has been realized. Under catalysis by CuI in combination with 1,10-phenanthroline hydrate as the ligand and Ag2CO3 as a bifunctional reagent (oxidant and base), the reaction proceeds smoothly with a broad substrate scope, thus providing a variety of highly functionalized furans in moderate to high yields. This represents the first successful example of the catalytic propargylic cycloaddition of simple alkynes with bisnucleophiles based on the propargylic C(sp3)-H functionalization strategy.