Single‐Electron‐Transfer‐Induced Coupling of Alkylzinc Reagents with Aryl Iodides

Okura, Keisho; Shirakawa, Eiji

doi:10.1002/ejoc.201600367

Cited by 16 publications

(5 citation statements)

References 25 publications

(17 reference statements)

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“…In reference to literature reports ,,, and in light of the above mechanistic experimental results (Figure and Scheme ), an S RN mechanism illustrated in Figure is proposed for our photoreactions. Presumably, as a weak Lewis acid, one molecule of the Grignard reagent coordinates with bromopyridine and facilitates photoinduced single electron transfer (PET) from another molecule of the Grignard reagent to the complex.…”

Section: Resultssupporting

confidence: 74%

“…In 2012, thermal S RN reactions between aryl Grignard reagents and aryl or alkenyl iodides were developed by Shirakawa and Hayashi et al (Scheme b) . Thermal S RN reactions of aryl, alkyl, and alkynyl zinc reagents; organoboron compounds; arylaluminum reagents; and arylstannanes with organoiodides and organobromides (predominantly iodides) were reported by Shirakawa et al (Scheme b). Many of these reactions were conducted at 110 °C in toluene containing a small amount of tetrahydrofuran (THF) or in THF in a sealed tube, which is inconvenient and may raise safety concerns.…”

Section: Introductionmentioning

confidence: 99%

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Purple Light-Promoted Coupling of Bromopyridines with Grignard Reagents via SET

Lei,

Wang,

et al. 2024

J. Org. Chem.

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Alkyl- and arylpyridines and 2,2′-bipyridines are conventionally prepared by Minisci reactions of pyridines and transition metal-catalyzed coupling reactions of halopyridines. Herein, purple light-promoted radical coupling reactions of 2- or 4-bromopyridines with Grignard reagents in Et2O or a mixture of Et2O and tetrahydrofuran in regular glassware without the need for a transition metal catalyst were disclosed for the first time. Methyl, primary and secondary alkyl, cycloalkyl, aryl, heteroaryl, pyridyl, and alkynyl Grignard reagents were compatible with the protocol. As a result, alkyl- and arylpyridines and 2,2′-bipyridines were easily prepared. Single electron transfer from the Grignard reagent to bromopyridine was stimulated by purple light. An electron extruded from the dimerization of the Grignard reagent worked as the catalyst. Light on/off experiments indicated that constant irradiation was required for product formation. Studies of radical clock substrates verified the involvement of a pyridyl radical from bromopyridine and the noninvolvement of an alkyl or aryl radical from the Grignard reagent. The available proof supports a photoinduced SRN mechanism for the new coupling reactions.

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Section: Resultssupporting

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Purple Light-Promoted Coupling of Bromopyridines with Grignard Reagents via SET

Lei,

Wang,

et al. 2024

J. Org. Chem.

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“…In 2012, we reported the first electron-catalyzed crosscoupling reaction, which uses aryl Grignard reagents and aryl halides to obtain biaryls with no aid of a transition metal catalysis (6). The electron catalysis (7) has been further applied to the crosscoupling reaction of various organometallic reagents with aryl/ alkenyl halides (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21). As shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

Manipulation of an electron by photoirradiation in the electron-catalyzed cross-coupling reaction

et al. 2023

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An electron has recently been shown to catalyze the cross-coupling reaction of organometallic compounds with aryl halides. In terms of green and sustainable chemistry, the electron catalysis is much more desirable than the inevitably used transition metal catalysis but a high temperature of more than 100°C is required to achieve it. Here, we disclose that visible light photoirradiation accelerates the electron-catalyzed reaction of arylzinc reagents with aryl halides with the aid of a photoredox catalysis. Photoexcitation of a photoredox catalyst and an anion radical intermediate respectively affects the supply and transfer of the electron catalyst, promoting the cross-coupling reaction to proceed at room temperature. The supply of the electron catalyst by the photoredox catalysis makes the scope of aryl halides wider.

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“…Among these, Suzuki–Miyaura coupling, which employs arylboron compounds as arylmetals, is one of the most widely used due to the high stability and high availability of the reagents and the high functional‐group tolerance of the reaction . On the other hand, since our group reported the first electron‐catalyzed cross‐coupling, where aryl Grignard reagents are employed and an electron derived from them instead of a transition metal acts as a catalyst, we and other groups have reported transition‐metal‐free cross‐coupling of arylmetals (Zn/Al/Sn) as well as alkyl‐ and alkynylzinc reagents . Herein, we report for the first time that arylboron compounds can be utilized as aryl nucleophiles in the electron‐catalyzed cross‐coupling with the aid of a zinc reagent such as diethylzinc or zinc chloride/potassium tert ‐butoxide…”

Section: Effect Of the Amounts Of Diethylzinc And Lithium Chloride Inmentioning

confidence: 99%