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Catalysts 2013, 3(2), 486-500; doi:10.3390/catal3020486
Article

Mechanistic Studies for Synthesis of Bis(indolyl)methanes: Pd-Catalyzed C–H Activation of Indole–Carboxylic Acids with Benzyl Alcohols in Water

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Received: 27 March 2013; in revised form: 9 May 2013 / Accepted: 10 May 2013 / Published: 16 May 2013
(This article belongs to the Special Issue Palladium Catalysts for Cross-Coupling Reaction)
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Abstract: A method for synthesis without protecting groups of bis(indolyl)methanes by the (η3-benzyl)palladium system generated from a palladium catalyst and benzyl alcohol in water is developed. This domino protocol involves C3–H bond activation/benzylation of indole–carboxylic acids and benzylic C–H functionalization. Mechanistic studies indicate that the (η3-benzyl)palladium(II) complex, which is formed via oxidative addition of benzyl alcohol 2 to a Pd(0) species, activates the C–H bond at the C3-position of indole 1. Notably, water plays an important role in our catalytic system for sp3 C–O bond activation and stabilization of OH by hydration for the smooth generation of the activated Pd(II) cation species, as well as for nucleophilic attack of indoles to hydrated benzyl alcohols.
Keywords: palladium; C–H activation; water; indole; benzyl alcohol palladium; C–H activation; water; indole; benzyl alcohol
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Hikawa, H.; Suzuki, H.; Yokoyama, Y.; Azumaya, I. Mechanistic Studies for Synthesis of Bis(indolyl)methanes: Pd-Catalyzed C–H Activation of Indole–Carboxylic Acids with Benzyl Alcohols in Water. Catalysts 2013, 3, 486-500.

AMA Style

Hikawa H, Suzuki H, Yokoyama Y, Azumaya I. Mechanistic Studies for Synthesis of Bis(indolyl)methanes: Pd-Catalyzed C–H Activation of Indole–Carboxylic Acids with Benzyl Alcohols in Water. Catalysts. 2013; 3(2):486-500.

Chicago/Turabian Style

Hikawa, Hidemasa; Suzuki, Hideharu; Yokoyama, Yuusaku; Azumaya, Isao. 2013. "Mechanistic Studies for Synthesis of Bis(indolyl)methanes: Pd-Catalyzed C–H Activation of Indole–Carboxylic Acids with Benzyl Alcohols in Water." Catalysts 3, no. 2: 486-500.


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