- (o-Phenylenediamino)borylstannanes: Efficient Reagents for Borylation of Various Alkyl Radical Precursors
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(o-Phenylenediamino)borylstannanes were newly synthesized to achieve radical boryl substitutions of a variety of alkyl radical precursors. Dehalogenative, deaminative, decharcogenative, and decarboxylative borylations proceeded in the presence of a radica
- Suzuki, Kensuke,Nishimoto, Yoshihiro,Yasuda, Makoto
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supporting information
p. 3968 - 3973
(2020/12/30)
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- Metal-free photoinduced C(sp 3)–H borylation of alkanes
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Boronic acids and their derivatives are some of the most useful reagents in the chemical sciences1, with applications spanning pharmaceuticals, agrochemicals and functional materials. Catalytic C–H borylation is a powerful method for introducing these and other boron groups into organic molecules because it can be used to directly functionalize C–H bonds of feedstock chemicals without the need for substrate pre-activation1–3. These reactions have traditionally relied on precious-metal catalysts for C–H bond cleavage and, as a result, display high selectivity for borylation of aromatic C(sp2)–H bonds over aliphatic C(sp3)–H bonds4. Here we report a mechanistically distinct, metal-free borylation using hydrogen atom transfer catalysis5, in which homolytic cleavage of C(sp3)–H bonds produces alkyl radicals that are borylated by direct reaction with a diboron reagent. The reaction proceeds by violet-light photoinduced electron transfer between an N-alkoxyphthalimide-based oxidant and a chloride hydrogen atom transfer catalyst. Unusually, stronger methyl C–H bonds are borylated preferentially over weaker secondary, tertiary and even benzylic C–H bonds. Mechanistic studies indicate that the high methyl selectivity is a result of the formation of a chlorine radical–boron ‘ate?? complex that selectively cleaves sterically unhindered C–H bonds. By using a photoinduced hydrogen atom transfer strategy, this metal-free C(sp3)–H borylation enables unreactive alkanes to be transformed into valuable organoboron reagents under mild conditions and with selectivities that contrast with?those of established metal-catalysed protocols.
- Shu, Chao,Noble, Adam,Aggarwal, Varinder K.
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p. 714 - 719
(2020/11/02)
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- Allylboronates from vinyl triflates and α-chloroboronates by reductive nickel catalysis
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Allylboronates are unique building blocks widely used in organic synthesis, but the construction of cyclic allylboranates remains a challenging subject. We demonstrate here a mild and efficient access to this type of compound through the cross-electrophile coupling of vinyl triflates and α-chloroboronates. The reaction proceeded with a good substrate scope and good functional group compatibility. The ready availability of vinyl triflates from ketones, as well as the rich chemistry of allylboranates, makes our method suitable for the divergent modification of biologically active compounds. Preliminary mechanistic studies revealed that α-chloroboronates were activated via a radical process.
- Qiao, Jin-Bao,Zhao, Zhen-Zhen,Zhang, Ya-Qian,Yin, Kai,Tian, Zhi-Xiong,Shu, Xing-Zhong
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supporting information
p. 5085 - 5089
(2020/07/16)
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- A photocatalytic sp3 C-S, C-Se and C-B bond formation through C-C bond cleavage of cycloketone oxime esters
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The photocatalytic thiolation, selenylation and borylation of cycloketone oxime esters through iminyl radical-triggered C-C bond cleavage were described. The reactions provide a unified approach to alkyl sulfur, selenium and boron compounds tethered to a
- Anand, Devireddy,He, Yuwei,Li, Linyong,Zhou, Lei
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p. 533 - 540
(2019/01/24)
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- Transition-metal free C-C bond cleavage/borylation of cycloketone oxime esters
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An efficient transition-metal free C-C bond cleavage/borylation of cycloketone oxime esters has been described. In this reaction, the B2(OH)4 reagent not only served as the boron source but also acted as an electron donor source through formation of a complex with a DMAc-like Lewis base. This complex could be used as an efficient single electron reductant in other ring-opening transformations of cycloketone oxime esters. Free-radical trapping, radical-clock, and DFT calculations all suggest a radical pathway for this transformation.
- Zhang, Jin-Jiang,Duan, Xin-Hua,Wu, Yong,Yang, Jun-Cheng,Guo, Li-Na
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p. 161 - 166
(2019/01/04)
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- Addition of a B-H Bond across an Amido-Cobalt Bond: CoII-H-Catalyzed Hydroboration of Olefins
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This paper describes a well-defined cobalt(II) half-sandwich complex bearing a phosphinoaminato ligand, Cp Co(1,2-Ph2PC6H4NH) (1), that can activate pinacolborane (HBpin) for catalytic terminal hydroboration of olefins. Th
- Pang, Maofu,Wu, Chengjuan,Zhuang, Xuewen,Zhang, Fanjun,Su, Mincong,Tong, Qingxiao,Tung, Chen-Ho,Wang, Wenguang
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p. 1462 - 1467
(2018/05/24)
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- Iridium-catalyzed hydroboration of alkenes with pinacolborane
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Hydroboration of terminal and internal alkenes with pinacolborane (1.2 equiv) was carried out at room temperature in the presence of an iridium(I) catalyst (3 mol%). Addition of dppm (2 equiv) to [Ir(cod)Cl]2 gave the best catalyst for hydroboration of aliphatic terminal and internal alkenes at room temperature, resulting in addition of the boron atom to the terminal carbon of 1-alkenes with more than 99% selectivities. On the other hand, a complex prepared from dppe (2 equiv) and [Ir(cod)Cl]2 resulted in the best yields for vinylarenes such as styrene. These complexes exhibited higher levels of catalyst activity and selectivity than those of corresponding rhodium complexes. Graphical Abstract.
- Yamamoto, Yasunori,Fujikawa, Rhyou,Umemoto, Tomokazu,Miyaura, Norio
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p. 10695 - 10700
(2007/10/03)
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- A highly enantioselective and diastereoselective synthesis of cyclobutanes via boronic esters
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(equation presented) Deprotonation of enantiopure (R,R)-1,2-dicyclohexyl-1,2-ethanediol 1-chloro-4-cyanobutylboronates 5 with LDA followed by treatment with anhydrous magnesium bromide yields (R)-(trans-2-cyanocyclobutyl)boronic esters 7 in high diastereomeric and enantiomeric purity. No cyclobutane formation has been observed in the absence of at least a catalytic amount of magnesium halide.
- Man, Hon-Wah,Hiscox, William C.,Matteson, Donald S.
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p. 379 - 381
(2008/02/11)
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