Lewis Acid Catalyzed Benzylic Bromination

Shibatomi, Kazutaka; Zhang, Yanhua; Yamamoto, Hisashi

doi:10.1002/asia.200800087

Cited by 37 publications

(18 citation statements)

References 24 publications

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“…63 Lewis acids, such as ZrCl 4 , exclusively provided the benzylic brominated product. 63 Lewis acids, such as ZrCl 4 , exclusively provided the benzylic brominated product.…”

Section: Differences In Chemoselectivity Between Brønsted and Lewis Amentioning

confidence: 99%

Super Brønsted acid catalysis

2011

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Brønsted acid catalysis has emerged as a new class of catalysis in modern organic synthesis. However, in order to make the utility of the Brønsted acid catalysis as broad as the well-developed Lewis acid catalysis, it is desirable to develop Brønsted acids demonstrating both high reactivities and selectivities. In this feature article, we will present our achievement in the design and development of strong Brønsted acids and their application to organic reactions. Furthermore, we will describe the Tf(2)NH-catalyzed Mukaiyama aldol reaction of super silyl enol ethers. We also will highlight the differences in reactivity and chemo- and stereo-selectivity between Brønsted and Lewis acid catalysis.

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“…63 Lewis acids, such as ZrCl 4 , exclusively provided the benzylic brominated product. 63 Lewis acids, such as ZrCl 4 , exclusively provided the benzylic brominated product.…”

Section: Differences In Chemoselectivity Between Brønsted and Lewis Amentioning

confidence: 99%

Super Brønsted acid catalysis

2011

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“…Use of a longer propyl spacer provided the tribrominated products 6 g , h without cyclization. Control experiments indicated again that free non‐guided radical bromination– was not competitive with the Hofmann‐Löffler reactions in the cases for 6 a – h . Although all products 6 a – h form in high yields, their tendency for decomposition reduced the isolated yields.…”

Section: Figurementioning

confidence: 93%

Multiple Halogenation of Aliphatic C−H Bonds within the Hofmann–Löffler Manifold

Castillo

Martínez

Bosnidou

et al. 2018

Chemistry A European J

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An innovative approach to position-selective polyhalogenation of aliphatic hydrocarbon bonds is presented. The reaction proceeded within the Hofmann-Löffler manifold with amidyl radicals as the sole mediators to induce selective 1,5- and 1,6-hydrogen-atom transfer followed by halogenation. Multiple halogenation events of up to four innate C-H bond functionalizations were accomplished. The broad applicability of this new entry into polyhalogenation and the resulting synthetic possibilities were demonstrated for a total of 27 different examples including mixed halogenations.

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“…1 Consequently, many methods for the bromination of aromatics have been reported in the literature. 2,3 In contrast to direct bromination by toxic elemental bromine or HBr used as a bromine source, oxidation of a bromide anion using a suitable oxidant such as hydrogen peroxide under nearly neutral solution would be atom efficient and environmental friendly. 4,5 In order to overcome these problems, several safe systems for oxybromination have been developed.…”

Section: Introductionmentioning

confidence: 99%

Highly Regioselective Oxybromination in an Aqueous System Using SBA‐15 Supported Sulfated Zirconia Catalyst

Chen

Mou

2010

J Chinese Chemical Soc

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SBA-15 supported sulfated zirconia (SZ) catalysts were employed in many acid-catalysis of reactions under mild condition because it is a strong solid acid with various Lewis and Brønsted acid sites. An oxybromination of aromatic substrates using hydrogen peroxide and ammonium bromide in the aqueous phase under mild temperature and near-neutral pH condition over SZ was achieved. A good to excellent para-selectivity was observed. The mesoporous silica SBA-15 supported SZ possessed higher catalytic activity than self-supported SZ because of larger surface area and pore size. The effect of the calcinations temperature was also investigated. The good catalytic performance of the SZ/SBA-15 materials was attributed to high degree of dispersion of sulfate groups to give sulfated silica-zirconia of (1) very good redox property and (2) high strength and high density of acid sites. The SZ/SBA-15 catalyst may be re-used several times without substantial loss of activity.

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Lewis Acid Catalyzed Benzylic Bromination

Cited by 37 publications

References 24 publications

Super Brønsted acid catalysis

Super Brønsted acid catalysis

Multiple Halogenation of Aliphatic C−H Bonds within the Hofmann–Löffler Manifold

Highly Regioselective Oxybromination in an Aqueous System Using SBA‐15 Supported Sulfated Zirconia Catalyst

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