查看更多>>摘要：Dibenzo[b,f][1,5]diazocines are a class of eight-membered heterocycles,which exhibit unique rigid saddle-shaped structure and pos-sess inherent chirality.In this study,we report a convenient and straightforward method for the catalytic enantioselective synthesis of these unique chiral molecules through chiral phosphoric acid-catalyzed dimerization of 2-acylbenzoisocyanates.Notably,the addition of corresponding 2-acylaniline as the co-catalyst significantly improved the efficiency of these reactions,and a simple phase separa-tion operation resulted in products with excellent enantiopurity.Experimental studies were performed to elucidate the mechanism behind these reactions,leading to the proposal of a plausible reaction mechanism based on the study findings.
查看更多>>摘要：Covalent organic frameworks(COFs)driven photocatalytic organic transformations especially photooxidation reactions have become a fertile topic and attracted numerous research attentions.Boosting the charge generation and transport process is the key factor for achieving high catalytic efficiencies.As one of the most effective strategies,the introduction of"heavy atoms"into the long-range or-dered conjugated backbones can effectively facilitate the intersystem crossing(ISC)process and hence improve the generation of ac-tive oxygens,which is beneficial for the oxidation.In this work,we designed and synthesized a benzoselenadiazole based covalent or-ganic framework(COF)material,BSe-COF with heavy atom of selenium(Se),and a benzothiadiazole based BT-COF with isomorphic backbone for comparison.Compared to BT-COF,BSe-COF exhibits broader absorption range,stronger photocurrent response and en-hanced intersystem crossing(ISC)with higher singlet oxygen(1O2)generation efficiency.When applied in photocatalytic organic trans-formation,BSe-COF presents remarkably higher photocatalytic activity in the oxidation of sulfides than BT-COF under the irradiation of blue LED lamp.Furthermore,BSe-COF can be used as efficient photocatalyst for the window ledge reaction with high yields(over 84％)of various sulfoxides from a wide range of thioether substrates scope.
查看更多>>摘要：Bond dissociation energy(BDE),which refers to the enthalpy change for the homolysis of a specific covalent bond,is one of the basic thermodynamic properties of molecules.It is very important for understanding chemical reactivities,chemical properties and chem-ical transformations.Here,a machine learning-based comprehensive BDE prediction model was established based on the iBonD ex-perimental BDE dataset and the calculated BDE dataset by St.John et al.Differential Structural and PhysicOChemical(D-SPOC)de-scriptors that reflected changes in molecules'structural and physicochemical features in the process of bond homolysis were de-signed as input features.The model trained with LightGBM algorithm gave a low mean absolute error(MAE)of 1.03 kcal/mol on the test set.The D-SPOC model could apply to accurate BDE prediction of phenol O—H bonds,uncommon N-SCF3 and O-SCF3 reagents,and β-C—H bonds in enamine intermediates.A fast online prediction platform was constructed based on the D-SPOC model,which could be found at http://isyn.luoszgroup.com/bde_prediction.
查看更多>>摘要：Catechol-formaldehyde resin(CFR)is very attractive for H2O2 production via the catalytic process.However,the H2O2 formation is ac-companied by the oxidation of catechol groups to o-benzoquinone groups on CFR,which will cause irreversible damage to CFR and greatly limit its long-term stable catalytic activity.Herein,CdS/CFR composite photocatalyst with a core-shell structure was synthe-sized by hydrothermal method.The photogenerated electrons of CdS are used as a powerful driving force for the reversible redox conversion between catechol groups and o-benzoquinone groups on the CFR,which not only achieves the long-term stability of CFR-catalyzed production of H2O2,but also promotes the separation efficiency of photogenerated e-and h+in CdS,greatly inhibiting their recombination,so as to maintain CdS stability.The H2O2 yield of CdS/CFR can accumulate to 1.65 mmol·L-1 under visible light for 6 h without sacrificial agent,which is about 3.1 and 2 times that of CdS and CFR,respectively,and CdS/CFR can persist for 10 cycles of photocatalysis(60 h).CdS/CFR also improves the yield of photocatalytic H2O2 by increasing the selectivity of H2O2 and inhibiting its decomposition.This work offers a novel tactic for expanding the application of CFR in photocatalytic generation of H2O2.
查看更多>>摘要：The rhodium-catalyzed C—H bond activation and cyclization of 3-oxopent-4-enenitriles with alkynes proceed efficiently.Various 2H-pyrans with multiple substituents are achieved in good yields through regioselective formation of C—O and C—C bonds.Trans-formations involving hydroxy-alkynoates resulted in products with a furo[3,4-b]pyran skeleton via further intramolecular ester ex-change processes.Different from the traditional"1-oxatrienes pathway",this method for the synthesis of useful 2H-pyrans possesses certain highlights in terms of readily available substrates,stable and easily derivatized products,gentle and convenient operation process,and step and atom economy.
查看更多>>摘要：The stereochemical synthesis of highly substituted Danishefsky-type dienes remains unsolved in organic chemistry.We describe a sim-ple and efficient approach for the stereoselective synthesis of Danishefsky-type trisubstituted dienes from readily available propargylic esters via Pd-catalyzed dienylation reaction through the key intermediate metallacyclobutene in a regio-,chemo-and stereoselective fashion.This method facilitates a broad range of challenging trisubstituted dienes with a high level of stereocontrol.The synthetic util-ities of oxygenated trisubstituted dienes have been demonstrated by the downstream chemistry,which notably undergoes Diels-Alder reaction with a variety of electron-deficient dienophiles to furnish multisubstituted cyclohexenes in good yields with excellent stere-oselectivity.
查看更多>>摘要：We report herein the first observation of MOF nanozyme enabling dual-functional photo-induced charge transfer and biomimetic pre-cipitation for advanced organic photoelectrochemical transistor(OPECT)bioanalysis.Specifically,Fe/Co-MIL-88,serving simultaneous-ly as the semiconductor and nanozyme,was explored as a dual-functional gating module in OPECT.Upon light illumination,it could accelerate the charge transfer of the photogate to produce enhanced photo-induced voltage.Meanwhile,its catalytic property could efficiently produce biomimetic precipitation to block the nanopores in Fe/Co-MIL-88 and thus alter the device characteristics.The ge-neric bioanalytical potential of such a rationale was then demonstrated with an aptasensing assisted by magnetic separation.This work represents the first exploration of biomimetic precipitation from MOF nanozymes for generic OPECT bioanalysis,it is expected to attract more interest in various nanozymes for novel optoelectronic bioanalytics.
查看更多>>摘要：Chiral BINAM-derived selenide/achiral acid co-catalyzed atroposelective electrophilic sulfenylation of pyrrole derivatives has been re-alized for the first time.A variety of C-N axially chiral sulfur-containing pyrrole derivatives were readily obtained in moderate to good yields with moderate to excellent enantioselectivities.This catalytic system involves sequential desymmetrization and kinetic resolu-tion.
查看更多>>摘要：We detail the generation of a pulsed atomic oxygen(AO)broad beam with a high flux-density via collision-induced dissociation of O2 to support practical industrial exploitation of AOs,particularly for facilitating 2-dimenstional oxidation/etching at a fast rate of one-monolayer per second in an area ≥ 1000 cm2.This innovation fuses the following interdisciplinary concepts:(a)a high density of O+can be produced in an electron-cyclotron-resonance(ECR)O2 plasma;(b)O+can be extracted and accelerated with an aper-ture-electrode in the plasma;(c)O+with adequate kinetic energy can initiate a cascade of gas-phase collisions in the presence of O2;(d)collision-induced dissociation of O2 yields AOs with adequate kinetic energy which can cause additional collision-induced dissocia-tion of O2.Computational simulations of such collisions,with both ab initio molecular dynamics and direct simulation Monte Carlo methods,are used to guide the experimental generation of the proposed AO-beam.We experimentally demonstrate the highest known AO mean flux-density of about 1.5 × 1016 atoms·cm-2·s-1 in a broad-beam,and use it to oxidatively modify a self-assembled molecular layer of siloxane on a silicon wafer.In addition,we also demonstrate the growth of Al2O3 through an AO-assisted atomic layer deposition process at room temperature.
查看更多>>摘要：The development of catalytic asymmetric methods that enable access to value-added functionalities or structures,exemplified by allylic alcohols,is a highly interesting yet challenging topic from both academic and industrial perspectives.However,before recent advances in chemical catalysis,there were scarce protocols toward constructing enantioenriched tertiary allylic alcohol scaffolds.In this context,peptide-mimic phosphonium salts were found to be highly efficient in catalytic asymmetric α-hydroxylation ofα,β-unsaturated and/or β,Y-unsaturated compounds with satisfactory regio-and stereochemical outcomes(up to 97％yield and 95％ee).This methodology tolerates a broad array of substrates and thus provides an expeditious and unified platform for the assembly of enantioenriched tertiary allylic alcohols by avoiding the use of additional reductants and expensive metal catalysts.Furthermore,the power of this protocol is enlarged by simple conditions and the use of air as a source of hydroxyl functionality.
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