Density functional theory study of the mechanism of zinc carbenoid promoted cyclopropanation of allenamides

Xu, Huiying; Zhang, Xiting; Ke, Zhuofeng; Li, Zhifeng; Xu, Xian‐Yan; Su, Cheng‐Yong; Phillips, David Lee; Zhao, Cunyuan

doi:10.1039/c3ra42168f

Cited by 9 publications

(4 citation statements)

References 79 publications

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“…50 Most previous mechanistic studies employed simplied, achiral catalyst model, such as dirhodium(II) tetraformate Rh 2 (O 2 CH) 4 or dirhodium(II) tetraacetate Rh 2 (OAc) 4 . [52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69] However, to the best of our knowledge, no theoretical study on the Rh 2 (S-PTTL) 4 -catalyzed cyclopropanation of diazooxindoles has ever been reported. Indeed, recent studies have demonstrated the importance of considering interactions between the Rhcomplex and carbene, as well as the conformational mobility of the ligand in these systems.…”

Section: Introductionmentioning

confidence: 99%

Mechanism and stereoselectivity of the Rh(ii)-catalyzed cyclopropanation of diazooxindole: a density functional theory study

2015

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The mechanism and origin of stereoselectivity of rhodium(II)-catalyzed cyclopropanation reactions with diazooxindole and styrene has been studied using density functional theory calculations. The catalyzed reactions by achiral Rh 2 (OAc) 4 and chiral Rh 2 (S-PTTL) 4 as well as the uncatalyzed model were comparatively studied. The computational results indicate that the cyclopropanation step in both Rh 2 (OAc) 4 and Rh 2 (S-PTTL) 4 models is a single concerted but asynchronous process. The nitrogen extrusion step is found to be the rate-limiting step of the catalytic cycle, whereas the cyclopropanation step is the stereoselectivity-determining step. The diastereomeric ratios (dr) and the enantiomeric excess (ee) values are successfully predicted, which are in good agreement with the experimental values. The high trans-diastereoselectivity might be governed by the p-p interactions between the syn indole ring in carbenoid ligand and the phenyl group in styrene, whereas the good enantioselectivity can be ascribed to the steric interaction between the phenyl ring in styrene and the phthalimido group in the catalyst as well as the aromatic interactions (p-p and CH-p) in the transition states. Additionally, the methodological study using different functionals demonstrated the importance of considering the dispersion interactions in the current reaction systems. This theoretical study will help in understanding the mechanism of the asymmetric cyclopropanations of olefins through carbene-transfer reactions. † Electronic supplementary information (ESI) available: Comparison of different DFT methods (Table S1), calculated relative free energies with and without BSSE correction (Table S2), NBO analysis of TS11a and TS11b (Table S3), natural charge analysis (Tables S4 and S5), energy prole for the uncatalyzed cyclopropanation in Re-face pathway (Fig. S1), comparison between the DFT and X-ray structure of Rh 2 (OAc) 4 (Fig. S2), and other gures and tables, and xyz le giving the Cartesian coordinates for all structures. See Scheme 1 Rh 2 (S-PTTL) 4 catalyzed cyclopropanation of styrene and diazooxindole.Scheme 2 Proposed catalytic cycle for the asymmetric cyclopropanation.57782 | RSC Adv., 2015, 5, 57781-57791This journal is

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Section: Introductionmentioning

confidence: 99%

Mechanism and stereoselectivity of the Rh(ii)-catalyzed cyclopropanation of diazooxindole: a density functional theory study

2015

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“…All calculations were carried out using the Gaussian 09 program . The hybrid density functional M06, which has been shown to give reasonable predictions on the mechanism and selectivity in many transition metal‐catalyzed reactions, was used in combination with the standard 6‐31G(d,p) basis set for C, H, N, O, F, S, and P and the Los Alamos National Laboratory (Lanl) basis sets, also known as Lanl‐2‐double zeta (LanL2DZ) for Zn, Au, and Br. All structures were fully optimized in chlorobenzene solvent ( ε = 5.6968) using the SMD method of Truhlar and Cramer .…”

Section: Computational Detailsmentioning

confidence: 99%

Metal‐catalyzed alkyne oxidation/CH functionalization: Effects of oxidant, temperature, and metal catalyst on chemoselectivity

Wang

Kai

et al. 2018

J Comput Chem

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Gold-catalyzed intermolecular alkyne oxidation has attracted much synthetic attention, but mostly suffering undesired overoxidation. Recent experiments demonstrated that overoxidation could be dramatically suppressed in zinc(II)-catalyzed intermolecular alkyne oxidation/C H functionalization. By means of first-principle density functional theory calculations, we explored the mechanism of the M-catalyzed intermolecular alkyne oxidations (M = Zn(OTf ) 2 and Au + PR 3 ) as well as the effects of oxidants, temperature, and metal catalysts on chemoselectivity, in an effort to disclose the origin of the extraordinary chemoselectivity pertaining to zinc catalysis. Our calculations indicate that the Zn-catalyzed intermolecular alkyne oxidation/C H functionalization proceeds by a Friedel-Crafts alkylation mechanism rather than metal carbene insertion mechanism. The chemoselectivity of C H functionalization against over-oxidation in Zn catalysis, in comparison with gold catalysis, can be jointly controlled by four factors: (1) the use of less nucleophilic N-oxide, (2) the enhanced electrophilicity and carbocationic nature of the carbenic site in the α-oxo metal carbenoid intermediate, (3) enhanced steric repulsion to incoming oxidant exerted by bulky ancillary ligand in the close nearby of the carbenic site to disfavor intermolecular over-oxidation and (4) the large negative value of activation entropy in the intermolecular over-oxidation pathway, that jointly give rise to lower activation free energy for the intramolecular cyclization/C H functionalization pathway than for the intermolecular overoxidation pathway.

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“…However, we found that the energy barriers of the alkene aziridination reactions calculated by the BPW91 functionals are always overestimated by about 5 kcal/mol, when compared with the M06L level of calculations (see farther below). The M06L pure functional was found to be accurate for the thermochemistry predictions and weak interaction descriptions for systems of both transition metals and main group elements. , Finally, the M06L pure functionals were also employed to optimize and feature key reaction species. Minimum-energy crossing points (MECPs) between singlet–triplet potential energy surfaces (PES) were located with the MECP program developed by Harvey and co-workers .…”

Section: Computational Detailsmentioning

confidence: 99%

Mechanistic Investigation of Dirhodium-Catalyzed Intramolecular Allylic C–H Amination versus Alkene Aziridination

Zhang

Zhao

2014

J. Org. Chem.

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The reaction mechanisms and chemoselectivity on the intramolecular allylic C-H amination versus alkene aziridination of 4-pentenylsulfamate promoted by four elaborately selected dirhodium paddlewheel complexes are investigated by a DFT approach. A predominant singlet concerted, highly asynchronous pathway and an alternative triplet stepwise pathway are obtained in either C-H amination or alkene aziridination reactions when mediated by weak electron-donating catalysts. A singlet stepwise C-H amination pathway is obtained under strongly donating catalysts. The rate-determining step in the C-H amination is the H-abstraction process. The subsequent diradical-rebound C-N formation in the triplet pathway or the combination of the allylic carbocation and the negative changed N center in the singlet pathway require an identical energy barrier. A mixed singlet-triplet pathway is preferred in either the C-H insertion or alkene aziridination in the Rh2(NCH3CHO)4 entry that the triplet pathway is initially favorable in the rate-determining steps, and the resultant triplet intermediates would convert to a singlet reaction coordinate. The nature of C-H amination or alkene aziridination is estimated to be a stepwise process. The theoretical observations presented in the paper are consistent with the experimental results and, more importantly, provide a thorough understanding of the nature of the reaction mechanisms and the minimum-energy crossing points.

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Density functional theory study of the mechanism of zinc carbenoid promoted cyclopropanation of allenamides

Cited by 9 publications

References 79 publications

Mechanism and stereoselectivity of the Rh(ii)-catalyzed cyclopropanation of diazooxindole: a density functional theory study

Mechanism and stereoselectivity of the Rh(ii)-catalyzed cyclopropanation of diazooxindole: a density functional theory study

Metal‐catalyzed alkyne oxidation/CH functionalization: Effects of oxidant, temperature, and metal catalyst on chemoselectivity

Mechanistic Investigation of Dirhodium-Catalyzed Intramolecular Allylic C–H Amination versus Alkene Aziridination

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