Rhodium-catalyzed cross-coupling reactions of unactivated primary alkyl chlorides with diboron reagents have been developed as practical methods for the synthesis of alkylboronic esters. These reactions expand the concept and utility of Rh(I)-catalyzed cross-coupling of aliphatic electrophiles.

Recently the Chatani group reported the Rh(I)-catalyzed borylation of nitriles, which provided an efficient protocol for transformation of the C−CN bond to the C−B bond (J. Am. Chem. Soc. 2012, 134, 115). Although an unconventional β- carbon elimination mechanism was proposed in their study, the other previously proposed mechanisms, i.e., oxidative addition, deinsertion, and initial C−H bond activation, cannot be excluded. To clarify the dominant mechanism of this reaction, a density functional theory study on borylation of PhCN and BnCN catalyzed by [Rh(XantPhos)(B(nep))] (nep = neopentylglycolate, XantPhos = 4,5-Bis- (diphenylphosphino)-9,9-dimethylxanthene) was conducted. The computational results indicated that the deinsertion mechanism (2,1-insertion of the Rh−B bond into the C−N bond occurs first, followed by the insertion of the metal center into C−CN bond) is favored over oxidative addition, β-carbon elimination, and the initial C−H bond activation mechanism within all the inve

Cellulose is an important material for production of biofuel and refined chemicals. Pyrolysis is one of the most promising approaches for cellulose de-polymerization. Understanding the mechanism of cellulose pyrolysis is essential for development of efficient biomass conversion technologies. In this study, the thermodynamic energy change of cellulose pyrolysis through homolytic bond cleavage was studied with the aid of density functional theory method by using cellulose dimer as a model compound. The free energy changes of various homolytic bond dissociation of cellulose dimer were studied by the method of M06-2x at the temperature of 800 ℃ . To compare with experiment results of cellulose pyrolysis reported recently by Huber et al., the free energy changes of reaction pathways studied by Auerbach group via Car-Parrinello molecular dynamics calculations were also studied. Calculated results show that the free energy changes of homolytic dissociation of glucosidic bond varies in the ran

Ni-catalyzed addition of electron-deficient arenes and heteroarenes to olefin substrates through C−H activation provides an important method for the synthesis of diarylalkanes. This reaction usually generates Markovnikov adducts for aryl olefins, whereas anti-Markovnikov adducts are obtained for alkyl-substituted alkenes. To understand the mechanistic origin of this interesting regioselectivity, we conducted density functional theory calculations using the reactions of benzoxazole with styrene and 1-hexene as models. The calculation results are consistent with experimental observations, showing that the reaction proceeds through a mechanism involving Ar−H oxidative addition, hydronickelation, and C−C reductive elimination. Further calculations indicate that a better antiMarkovnikov regioselectivity can be obtained for olefins substituted with more bulky alkyl groups, whereas a better Markovnikov regioselectivity can be achieved for more electron-deficient para-substituted styrenes. Fur

Flavin-dependent catalysts are widely applied to aerobic monooxygenation/oxidation reactions. In contrast, flavin-catalyzed aerobic dioxygenation reactions exhibit higher atomic economy but are less reported, not to mention the relevant mechanistic studies. Herein, a density functional theory study on flavin-catalyzed aerobic epoxidation-oxygenolysis of alkenyl thio-esters was performed for the first time. Different from the previous mechanistic proposal, a pathway featuring two catalytic stages, monoanionic flavin-C(4a)-peroxide/oxide intermediates, and a reverse reaction sequence (epoxidation goes prior to oxygenolysis) was revealed. In comparison, the pathways involving dianionic flavin catalysts, monoanionic flavin-N(5)-(hydro)peroxide/C-(10a)-peroxide, or neutral flavin-C(4a)-hydroperoxide/hydroxide/N(5)-oxide, and the pathways where oxygenolysis goes prior to epoxidation are less favored. Epoxidation goes through intramolecular substitution of the O−O bond of anionic flavin-C(4a)

DFT calculations are carried out to investigate the hydroacylation mechanism based on copper-catalyzed A3- coupling tandem reaction of terminal alkynes, aldehydes and amines. The study reveals significant mechanistic differences between copper(I) and copper(II) catalysts. In the Cu(II)-catalyzed system, incorporation of a ligand is deemed necessary for facilitating reactivity, whereas no ancillary ligand is required in Cu(I) system. The ligand, through coordination with the Cu(II) center, stabilizes the key transition states and intermediates, resulting in a substantial reduction in the activation barrier. The ligand exhibits varying effect, with the order of activity being piperidine > pyridine > DMSO, correlating positively with the interaction energy between ligand and Cu complex. Additionally, the study sheds light on the pivotal roles played by the catalyst, ligand, base, and solvent DMSO in the reaction.

Developing applicable methods to forge linkages between sp3 and sp2-hydridized carbons is of great significance in drug discovery. We show here a new, Ni-catalyzed reductive crosscoupling reaction that forms Csp3−Csp2 bonds from aryl iodides and cyclic sulfonium salts. Notably, Csp3−Csp2 bonds can be forged selectively at the iodine-bearing carbon of bromo(iodo)arenes which is usually recognized as a huge challenge under the catalytic reductive cross-coupling (CRCC) conditions. Experimental and computational mechanistic studies support LNiIAr as an active species, while the untraditional anti-Markovnikov selective alkylation of asymmetric sulfonium salts is determined by the oxidative S-substitution of sulfonium salts with LNiIAr. This protocol further expands the range of alkyl electrophiles under the CRCC conditions and provides a new strategy for the construction of Csp3−Csp2 bonds.

An unprecedented transient promotion function (TPF) of CO2 in the electrochemical hydrogenation/deuteration of imines (especially α-iminonitriles) is reported. The TPF influence of CO2 results from the introduction of CO2 that disperses the negative charges of the imine radical anion intermediate. The resulting redistribution of electrons leads to a lower reduction potential of the CO2-substituted imine radical anion and thus facilitates the succeeding one-electron reduction. CO2 is finally released via spontaneous decarboxylation to complete the transient promotion process.

Flavin-dependent catalysts are widely applied to aerobic monooxygenation/oxidation reactions. In contrast, flavin-catalyzed aerobic dioxygenation reactions exhibit higher atomic economy but are less reported, not to mention the relevant mechanistic studies. Herein, a density functional theory study on flavin-catalyzed aerobic epoxidation-oxygenolysis of alkenyl thio-esters was performed for the first time. Different from the previous mechanistic proposal, a pathway featuring two catalytic stages, monoanionic flavin-C(4a)-peroxide/oxide intermediates, and a reverse reaction sequence (epoxidation goes prior to oxygenolysis) was revealed. In comparison, the pathways involving dianionic flavin catalysts, monoanionic flavin-N(5)-(hydro)peroxide/C-(10a)-peroxide, or neutral flavin-C(4a)-hydroperoxide/hydroxide/N(5)-oxide, and the pathways where oxygenolysis goes prior to epoxidation are less favored. Epoxidation goes through intramolecular substitution of the O−O bond of anionic flavin-C(4a)

DFT calculations are carried out to investigate the hydroacylation mechanism based on copper-catalyzed A3- coupling tandem reaction of terminal alkynes, aldehydes and amines. The study reveals significant mechanistic differences between copper(I) and copper(II) catalysts. In the Cu(II)-catalyzed system, incorporation of a ligand is deemed necessary for facilitating reactivity, whereas no ancillary ligand is required in Cu(I) system. The ligand, through coordination with the Cu(II) center, stabilizes the key transition states and intermediates, resulting in a substantial reduction in the activation barrier. The ligand exhibits varying effect, with the order of activity being piperidine > pyridine > DMSO, correlating positively with the interaction energy between ligand and Cu complex. Additionally, the study sheds light on the pivotal roles played by the catalyst, ligand, base, and solvent DMSO in the reaction.

Developing applicable methods to forge linkages between sp3 and sp2-hydridized carbons is of great significance in drug discovery. We show here a new, Ni-catalyzed reductive crosscoupling reaction that forms Csp3−Csp2 bonds from aryl iodides and cyclic sulfonium salts. Notably, Csp3−Csp2 bonds can be forged selectively at the iodine-bearing carbon of bromo(iodo)arenes which is usually recognized as a huge challenge under the catalytic reductive cross-coupling (CRCC) conditions. Experimental and computational mechanistic studies support LNiIAr as an active species, while the untraditional anti-Markovnikov selective alkylation of asymmetric sulfonium salts is determined by the oxidative S-substitution of sulfonium salts with LNiIAr. This protocol further expands the range of alkyl electrophiles under the CRCC conditions and provides a new strategy for the construction of Csp3−Csp2 bonds.

An unprecedented transient promotion function (TPF) of CO2 in the electrochemical hydrogenation/deuteration of imines (especially α-iminonitriles) is reported. The TPF influence of CO2 results from the introduction of CO2 that disperses the negative charges of the imine radical anion intermediate. The resulting redistribution of electrons leads to a lower reduction potential of the CO2-substituted imine radical anion and thus facilitates the succeeding one-electron reduction. CO2 is finally released via spontaneous decarboxylation to complete the transient promotion process.