The direct C3-functionalization of quinoxalin-2(1H)-ones via C–H bond activation has recently attracted considerable attention, due to their diverse biological activities and chemical properties.
The development of a methodology for the preparation of arylboronic acids or arylboronates is of significant interest to organic chemists. Classical synthetic methods to prepare these organoboron compounds are based on the reaction of Grignard or lithium reagents with trialkyl borates. In the past few decades, the transition‐ metal‐catalyzed borylation of aryl halides, or pseudohalides, and C–H bonds of hydrocarbons has been a powerful tool for the synthesis of arylboronates in modern organic synthesis. These transformations are generally considered to proceed via organometallic intermediates generated by oxidative addition or transmetalation processes from the boron reagent. Several reviews on this type of borylation catalyzed by transition metals have been published in the literature. Interestingly, there has been a novel recognition that the boron reagent can participate in free‐radical coupling via the homolytic cleavage of the boron‐boron bond in recent years. In this review, recent advances in this new area of boron chemistry are summarized and the reaction mechanisms are also discussed.
Chemical transformations via catalytic C-H bond activation have been established as one of the most powerful tools in organic synthetic chemistry. Transition-metal-catalyzed addition reactions of C-H bonds to polar C-X (X = N, O) multiple bonds, such as aldehydes, ketones, imines, isocyanates, nitriles, isocyanides, carbon monoxide and carbon dioxide, have undergone a rapid development in recent years. In this review, recent advances in this active area have been highlighted and their mechanisms have been discussed.
The transition-metal-catalyzed functionalization of arylboronic acids is the most powerful tool for the formation of carbon-carbon and carbon-heteroatom bonds in modern organic synthesis. These transformations are generally considered to proceed via organometallic intermediates generated by transmetalation from the boronic acids. Interestingly, there is a novel recognition that arylboronic acids can serve as aryl radical precursors via oxidative carbon-boron bond cleavage in recent years. Manganese(III) acetate, Ag(I)/persulfate and iron(II or III)/persulfate catalytic systems have been shown to be effective for this transformation. In this review, recent advances in this new area are highlighted and their mechanisms are also discussed.
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