Mechanistic study of the Ni-catalyzed hydroalkylation of 1,3-dienes: The origins of regio- and enantioselectivities and a further rational design.

The development of the catalytic regio- and enantioselective hydrofunctionalization of 1,3-dienes remains a challenge and requires deep insight into the reaction mechanisms. We herein thoroughly studied the reaction mechanism of the Ni-catalyzed hydroalkylation of 1,3-dienes with ketones by density functional theory (DFT) calculations. It reveals that the reaction is initiated by stepwise oxidative addition of EtO-H followed by 1,3-diene migratory insertion to generate the alkylnickel(II) intermediate, rather than the experimentally proposed ligand-to-ligand hydrogen transfer (LLHT) mechanism.

Copper-catalyzed regioselective [3+2] annulation of malonate-tethered acyl oximes with isatins.

A copper-catalyzed regioselective [3+2] annulation of malonate-tethered acyl oximes with isatins was developed, affording valuable 2,3-dihydrooxazole-spirooxindoles in moderate to good yields with excellent diastereoselectivity. The reaction sequence involves Cu(i) initiated N-O bond cleavage, 1,5-HAT and C-N bond formation. The protocol features mild reaction conditions and broad substrate scope.

A Strained Ion Pair Permits Carbon Dioxide Fixation at Atmospheric Pressure by C-H H-Bonding Organocatalysis.

The cycloadditions of carbon dioxide into epoxides to afford cyclic carbonates by H-bond donor (HBD) and onium halide (X) cocatalysis have emerged as a key strategy for CO fixation. However, if the HBD is also a halide receptor, the two will quench each other, decreasing the catalytic activity. Here, we propose a strained ion pair tris(alkylamino)cyclopropenium halide (TAC·X), in which TAC repels X.

Directing Group-Promoted Inert C-O Bond Activation Using Versatile Boronic Acid as a Coupling Agent.

A simple Ni(cod) and carbene mediated strategy facilitates the efficient catalytic cross-coupling of methoxyarenes with a variety of organoboron reagents. Directing groups facilitate the activation of inert C-O bonds in under-utilized aryl methyl ethers enabling their adaptation for C-C cross-coupling reactions as less toxic surrogates to the ubiquitous haloarenes. The method reported enables C-C cross-coupling with readily available and economical arylboronic acid reagents, which is unprecedented, and compares well with other organoboron reagents with similarly high reactivity.