Carbon-Bonding Metal Catalysis (CBMC): A Supramolecular Complex Directs Structural-Isomer Selection in Gold-Catalyzed Reactions

Carbon is a primary element to constitute organic molecules, while metal catalysis is a basic tool in organic synthesis. The establishment of a link between the ubiquitous carbon bonding and metal catalysis is thus a fundamentally important problem. However, there is yet no experimental example to introduce the role of carbon bonding in a metal catalysis process. Herein, we merged the topics of carbon bonding and metal catalysis together and demonstrated that a supramolecular carbon-bonding metal complex can not only give rise to catalytic activity but, more remarkably, direct structural-isomer selection events in gold-catalyzed reactions. The experimental results unveil the fact that the imposing of weak carbon-bonding interactions on a gold complex can alter the carbene as well as the Lewis acid property of these catalysts. These results illustrate a non-negligible role of weak carbon-bonding interactions in the modulation of metal catalysis. As such, carbon-bonding metal catalysis is suggested to be used as a routine tool not only in the development of reactions but more frequently in analyzing reaction processes in metal catalysis

Computational Insights into Palladium/Boron-Catalyzed Allylic Substitution of Vinylethylene Carbonates with Water: Outer-Sphere versus Inner-Sphere Pathway and Origins of Regio- and Enantioselectivities

Palladium/boron-catalyzed allylic substitution of vinylethylene carbonates with water provides a powerful approach for the enantioselective synthesis of the tertiary C–O bond. Density functional theory calculations in the present work show that the nucleophilic attack via a distinctive type of chelation-assisted inner-sphere pathway is responsible for the experimentally observed regio- and enantioselectivities. The chelation between the hydroxyl group of the boronate moiety and the Pd center in the nucleophilic attack enables the exclusive branched-regioselectivity. The enantioselectivity was rationalized in terms of the lone pair---π repulsive interaction between the O atom of the chelated hydroxyl group and the phenyl ring of the ligand

Mechanism and Origins of Regio- and Enantioselectivities of Iridium-Catalyzed Hydroarylation of Alkenyl Ethers

The iridium-catalyzed hydroarylation of alkenyl ethers developed by Nishimura and co-workers (Ebe, Y.; Onoda, M.; Nishimura, T.; Yorimitsu, H. <i>Angew. Chem. Int. Ed</i>. <b>2017</b>, <i>56</i>, 5607–5611) represents a rare example of regio- and enantioselective hydroarylation of challenging internal alkenes. In the present study, density functional theory calculations were performed in order to investigate the detailed reaction mechanism and the origins of the experimentally observed regio- and enantioselectivities. The computations show that the initial C–H oxidative addition and the isomerization between the allylic ethers and the 1-alkenyl ethers via the migratory insertion into the Ir–H bond/β-hydride elimination are both feasible. The reaction was found to proceed through the modified Chalk–Harrod-type mechanism via the migratory insertion into the Ir–C bond/C–H reductive elimination. The migratory insertion into the Ir–C bond constitutes the rate- and selectivity-determining step of the overall reaction. The calculations reproduced quite well the experimentally observed regio- and enantioselectivities. The enantioselectivity of the reaction was found to arise from the reactions of the (<i>E</i>)- and (<i>Z</i>)-1-alkenyl ethers, which afford the opposite enantiomers of product with the aryl group installed at the α-position to the alkoxy group. It turns out that the strong electron-donating character of the alkoxy group plays an important role in determining the regioselectivity, since it can stabilize the developed positive charge of the α-insertion transition state, leading to the aryl group being selectively installed at the α-position

Origin of Ligand Effects on Stereoinversion in Pd-Catalyzed Synthesis of Tetrasubstituted Olefins

The mechanism and origin of ligand effects on stereoinversion of Pd-catalyzed synthesis of tetrasubstituted olefins were investigated using DFT calculations and the approach of energy decomposition analysis (EDA). The results reveal that the stereoselectivity-determining steps are different when employing different phosphine ligands. This is mainly due to the steric properties of ligands. With the bulkier Xantphos ligand, the syn/anti-to-Pd 1,2-migrations determine the stereoselectivity. While using the less hindered P­(o-tol)3 ligand, the 1,3-migration is the stereoselectivity–determining step. The EDA results demonstrate that Pauli repulsion and polarization are the dominant factors for controlling the stereochemistry in 1,2- and 1,3-migrations, respectively. The origins of differences of Pauli repulsion and polarization between the two stereoselective transition states are further identified

Origins of Regioselectivity in CuH-Catalyzed Hydrofunctionalization of Alkenes

Factors controlling the regioselectivity in alkene hydrocupration were computationally investigated using energy decomposition analysis. The results demonstrate that the Markovnikov-selective hydrocupration with electronically activated mono-substituted olefins is mostly affected by the destabilizing Pauli repulsion, which is due to the electron delocalization effect. The anti-Markovnikov-selective hydrocupration with 1,1-dialkyl-substituted terminal olefins is dominated by the repulsive electrostatic interactions, which is because of the unequal π electron distribution caused by the induction effect of alkyl substituents

Divergent Rh Catalysis: Asymmetric Dearomatization Versus C–H Activation Initiated by C–C Activation

The divergent catalytic reactions based on C–C activation of benzocyclobutenones have been discovered, consisting of a highly enantioselective dearomatic “Cut & Sew” transformation and a cascade C–C/C–H activation/annulation process. The asymmetric dearomatization was achieved with 2.5 mol % [Rh(HQ)(cod)]BF4 and 3 mol % (S)-dtbm-Segphos, leading to a variety of highly enantioenriched polyfused rings (21 examples, up to 99% yield and 99% enantiometric excess (ee)). While the tandem C–C/C–H activation yields a series of amide-linked biaryl tricycles (29 examples, up to 89% yield) through a net C1–C2 bond and Caryl–H bond metathesis. A detailed density functional theory (DFT) computation revealed that an amide-directed regioselective C1–C2 activation with Rh complex is realized, in contrast to the known C1–C8 cleavage. The origins of asymmetric dearomatization were further elucidated

Divergent Rh Catalysis: Asymmetric Dearomatization Versus C–H Activation Initiated by C–C Activation

The divergent catalytic reactions based on C–C activation of benzocyclobutenones have been discovered, consisting of a highly enantioselective dearomatic “Cut & Sew” transformation and a cascade C–C/C–H activation/annulation process. The asymmetric dearomatization was achieved with 2.5 mol % [Rh(HQ)(cod)]BF4 and 3 mol % (S)-dtbm-Segphos, leading to a variety of highly enantioenriched polyfused rings (21 examples, up to 99% yield and 99% enantiometric excess (ee)). While the tandem C–C/C–H activation yields a series of amide-linked biaryl tricycles (29 examples, up to 89% yield) through a net C1–C2 bond and Caryl–H bond metathesis. A detailed density functional theory (DFT) computation revealed that an amide-directed regioselective C1–C2 activation with Rh complex is realized, in contrast to the known C1–C8 cleavage. The origins of asymmetric dearomatization were further elucidated

Divergent Rh Catalysis: Asymmetric Dearomatization Versus C–H Activation Initiated by C–C Activation

The divergent catalytic reactions based on C–C activation of benzocyclobutenones have been discovered, consisting of a highly enantioselective dearomatic “Cut & Sew” transformation and a cascade C–C/C–H activation/annulation process. The asymmetric dearomatization was achieved with 2.5 mol % [Rh(HQ)(cod)]BF4 and 3 mol % (S)-dtbm-Segphos, leading to a variety of highly enantioenriched polyfused rings (21 examples, up to 99% yield and 99% enantiometric excess (ee)). While the tandem C–C/C–H activation yields a series of amide-linked biaryl tricycles (29 examples, up to 89% yield) through a net C1–C2 bond and Caryl–H bond metathesis. A detailed density functional theory (DFT) computation revealed that an amide-directed regioselective C1–C2 activation with Rh complex is realized, in contrast to the known C1–C8 cleavage. The origins of asymmetric dearomatization were further elucidated

Divergent Rh Catalysis: Asymmetric Dearomatization Versus C–H Activation Initiated by C–C Activation

The divergent catalytic reactions based on C–C activation of benzocyclobutenones have been discovered, consisting of a highly enantioselective dearomatic “Cut & Sew” transformation and a cascade C–C/C–H activation/annulation process. The asymmetric dearomatization was achieved with 2.5 mol % [Rh(HQ)(cod)]BF4 and 3 mol % (S)-dtbm-Segphos, leading to a variety of highly enantioenriched polyfused rings (21 examples, up to 99% yield and 99% enantiometric excess (ee)). While the tandem C–C/C–H activation yields a series of amide-linked biaryl tricycles (29 examples, up to 89% yield) through a net C1–C2 bond and Caryl–H bond metathesis. A detailed density functional theory (DFT) computation revealed that an amide-directed regioselective C1–C2 activation with Rh complex is realized, in contrast to the known C1–C8 cleavage. The origins of asymmetric dearomatization were further elucidated