Copper-catalyzed silylation of aryl and alkenyl triflates with silylboronic esters avoiding base-mediated borylation.

Silylation of aryl and alkenyl triflates is found to occur readily with silylboronic esters as a silicon source under copper catalysis. The silyl moieties are exclusively installed into the organic frameworks through the preferential generation of a silylcopper species, wherein base-mediated direct borylation is totally suppressed. The combined use of tri-n-butylphosphine and 4,4'-diphenyl-2,2'-bipyridine as a ligand combination turned out to be indispensable for achieving the high catalytic activity.

Synthesis of Deuterated Compounds by Flow Chemistry.

Development of the efficient and practical method for the synthesis of deuterated compounds which occupies the broadest area among stable isotopes is one of the most essential issues toward the industrial advance and building a sustainable society. This review describes recent advances in deuteration reactions, where the continuous flow chemistry plays pivotal roles for the successful installation of deuterium atom into diverse organic frameworks, opening new fields of isotope-based synthetic chemistry.

Flow-Chemistry-Enabled Synthesis of 5-Diethylboryl-2,3'-bipyridine and Its Self-Assembly Dynamics.

5-Diethylboryl-2,3'-bipyridine (1), which is inaccessible by conventional batch methods, was synthesized by using a flow microreactor. Compound 1 was obtained as an equilibrium mixture of a cyclic trimer and a cyclic tetramer in solution, the latter of which was crystallized in benzene by vapor diffusion of hexane at 7 °C. The dynamic nature of this system was confirmed by solvent- and concentration-dependent experiments. Notably, the dynamics was verified by using flow NMR spectroscopy, which revealed that the time required to reach equilibrium was influenced by the solvent ratio (<18 s, 24-28 s, and 34-42 s in 2 : 1, 1 : 1, and 1 : 2 mixtures of [D6 ]acetone and C6 D6 , respectively). Compound 1 and 3-[4'-(diethylboryl)phenyl]pyridine (2) exhibited different self-assembly behavior in solution and crystals. Density functional theory calculations suggested that this difference was largely due to enhanced planarity between two consecutive aromatic rings.

Transition metal-free B(dan)-installing reaction (dan: naphthalene-1,8-diaminato): H-B(dan) as a B(dan) electrophile.

H-B(dan) was demonstrated to serve as a B(dan) electrophile, despite its highly diminished boron-Lewis acidity, leading to direct and transition metal-free approach to R-B(dan) of high synthetic utility upon treatment with Grignard reagents. Iterative cross-coupling of 5-bromo-2-pyridyl-B(dan), synthesized by the present method, was also achieved.

Anthranilamide (aam)-substituted arylboranes in direct carbon-carbon bond-forming reactions.

Anthranilamide (aam)-substituted arylboranes, which were reported to serve as masked boranes in the Suzuki-Miyaura coupling, have been found to be directly cross-coupled just by use of an aqueous medium. The excellent stability of 2-pyridyl-B(aam) toward protodeborylation allowed their smooth cross-coupling.

Anthranilamide (aam)-substituted diboron: palladium-catalyzed selective B(aam) transfer.

An unsymmetrical diboron bearing an anthranilamide (aam) substituent was synthesized and was found to be coupled with aryl halides through the palladium-catalyzed Miyaura-Ishiyama-type reaction. The selective transfer of aam-substituted boryl moiety led to exclusive formation of diverse Ar-B(aam).