Application of carbene reactive intermediates in organic synthesis——Ⅲ.Reaction of difluorocarbene with trimethylsilyl enol ethers

The addition of difluorocarbene generated from phenyl(trifluoromethyl)mercury and anhydrous sodium iodide,with trimethylsilyl enol ethers derived from cyclohexanone,cycloheptanone, 3-pentanone and acetophenone was described.The corresponding 2,2-difluoro-1-trimethylsilyloxy- cyclopropanes were obtained in good yields.The thermal stability of these cyclopropyl derivatives was affected by the molecular strain and the nature of their substituents.Thus,1-trimethylsilyloxy- cyclopentene reacted with difluorocarbene to give only 2-fluoro-2-cyclohexen-1-one instead of the expected 1-trimethylsilyloxy-6,6-difluorobicyclo[3.1.0]hexane,and a mechanism for its formation was proposed.

Analysis of Equilibrium and Kinetics of Chromium-Fluoride Complexation from Spectroscopic Data via Chemometrics Methods

The complexation of Cr^3＋ with F^- undergoes a muhistep reversible process. An approach to research the involved equilibria and kinetics using suitable chemometrics methods to the online measured UV-Vis spectra is proposed. By investigating the equilibrium spectra of the complexes at different molar ratios of M to L（ metal to ligand） and 50 ℃, the result of Principal Component Analysis（PCA） shows that three complexes, ML, ML2 and ML3, can be formed under the research conditions. The spectrum of each complex was then analyzed and the accumulated equilibrium constants were calculated by applying Target Testing Factor Analysis（TITA）. Meanwhile, a reactive intermediate was observed before the formation of MLx during the specific kinetic study at 15℃. The equilibrium constant and spectrum of the intermediate as well as the rate constants were all resolved by using TTFA.

Recent Advances in Real-Time Analysis of Electrochemical Reactions by Electrochemical Mass Spectrometry

Electrochemical mass spectrometry(EC-MS)is a powerful tool to capture and analyze the intermediates and products during elec-trochemical reactions.This hyphenated technique combines electrochemistry with mass spectrometry using specific apparatuses,which helps researchers study mechanisms of redox reactions by in situ detecting chemical composition changes.Recently,various EC-MS methods have been applied in a series of electrochemical reactions to reveal the mechanisms,mainly in the areas of electro-chemical sensors,organic electrochemistry,and electrocatalysis.In this review,we intend to summarize the recent advances in re-al-time analysis of different types of electrochemical reactions by EC-MS and offer an outlook on the perspectives in these areas.

Mechanistic Applications of Nonlinear Effects in First-Row Transition-Metal Catalytic Systems

Knowledge of asymmetric catalytic reaction mechanism is very important for rational design and synthesis of new chiral catalysts or catalytic systems with high catalytic activity and stereoselectivity.The studies of nonlinear effect have attracted wide attentions as a simple and practical mechanistic tool to probe complex asymmetric catalytic reactions.

Exploring the Far Side of Glycosyl Sulfoxide Activation Process

The discovery of Kahne glycosylation forwards a big step in the carbohydrate chemistry.Despite an extensive series of studies,the precise mechanism of this powerful glycosylation is still not fully understood.To address these 30-year puzzles,the far side of Kahne glycosylation is explored in this study.After a series of control and tracking experiments,a number of important intermediates including glycosyl oxo-sulfonium ion and sulfenic anhydride(Crich's intermediate)are suggested to be responsible for the complex reaction pathway.It also reveals that in addition to the conventional ionic glycosylation pathway,a novel free radical pathway is very likely to contribute to the various side-and co-products.This study provides further understanding of Kahne glycosylation,and it also sheds light on how to improve the efficiency of sulfoxide-based glycosylation reactions.

Polymer Synthesis Based on Self-Accelerating 1,3-Dipolar Cycloaddition Click Reactions

This review reports our recent work on developing polymer synthesis methods based on a self-accelerating double-strain-promoted 1,3-dipole-alkyne cycloaddition(DSPDAC)click reaction.In DSPDAC,the cycloaddition of 1,3-dipole with the first alkyne of sym-dibenzo-1,5-cyclooctadiene-3,7-diyne(DIBOD)activates the second unreacted alkyne,which reacts with 1,3-dipole much faster than the original alkyne of DIBOD.When using DIBOD and bis-dipole compounds as monomer pairs,the self-accelerating property of DSPDAC allows us to develop a stoichiometric imbalance-promoted step-growth polymerization method.It could produce polymers with ultrahigh molecular weight in the presence of excess DIBOD monomers.When using DIBOD to ring-close linear polymers with 1,3-dipole end groups,the self-accelerating property of DSPDAC facilitates us to develop a unique bimolecular ring-closure method.It could efficiently prepare pure cyclic polymers in the presence of excess DIBOD small linkers to linear polymer precursors.