Organozinc pivalates, a recently developed air-and moisturestable organozinc species, were found for the first time as excellent organometallic species in the monoorganylation of trialkyl borates whereby boronic acids were prepared in high yields. The significant advantage of organozinc pivalates over another previously employed organometallic reagents, e. g., organolithium reagents, Grignard reagents and organozinc halides, is that the generation of multiorganylation byproducts such as borinic acids and trialkylboranes were completely suppressed. Additionally, the in situ generated boronates could be directly arranged into Suzuki-Miyaura type cross-coupling reactions to produce biaryls in high yields.The great success of organylboronic acids and their derivatives in organic synthesis, [1] pharmaceuticals [2] and material chemistry [3] has inspired dramatic synthetic interests [4] on these privileged molecules. Thus, a range of protocols have been developed to convert aryl [5] and alkyl [6] halides, carboxylic acid derivatives, [7] anilines, [8] diaryliodonium salts, [9] arenes, [10] alkenes [11] and quaternary ammonium salts [12] etc. into boronic acids or their esters. However, due to the employment of unaffordable expensive borylating agents or expensive transitional metal catalysts, most of these protocols are rarely employed in the practical boronic acids synthesis. Thus, the conventional approach, the electrophilic trapping of organometallics (generally the lithium reagents, [13] Grignard reagents [14] and organozinc reagents [15] ) with trialkyl borates, still occupies a large portion in modern factory manufacture. The common defects involved in this approach are, cryogenic conditions demanding, poor functional groups tolerance (largely due to high reactivity of organometallics), unavoidable borinic acid and borane byproducts (arise from second and third additions of the organometallic reagents into the borate esters), low isolated yields. To avoid multiple addition of organometallics to borate esters, Wang et al. [14d] reported that bis [2-(N,N-dimethylamino) ethyl] ether could be employed as a ligand to suppress these side reactions. Alternatively, Leermann et al. [14b] reported that excellent yields of boronic acids were obtained via reactions of Grignard's with B(OMe) 3 in the presence of LiCl.Organozinc pivalates [16] are a privileged class of organometallics particularly known to their air-and moisture-stability and broad spectrum of functional groups tolerance. These reagents exhibit excellent reactivity in reactions, e. g., Negishi cross coupling reactions [17] and were successfully used in the synthesis of complex molecules [18] Based on our interests on expanding the applicability of organozinc reagents in organic synthesis, [19] we here first describe a CuI-catalyzed chemospecific borylation of organozinc pivalates with trialkyl borates to afford boronic acids in high yields.Initially, p-TolZnBr·MgCl 2 ·LiCl (2a'), in situ prepared from ptolylbromide (1 a) via magnesium insertion-Z...
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