Molecules 2012, 17(6), 6901-6915; doi:10.3390/molecules17066901

Catalytic Asymmetric Hydrogenation of 3-Substituted Benzisoxazoles

Department of Chemistry, Graduate School of Sciences, and International Research Center for Molecular Systems (IRCMS), Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
* Author to whom correspondence should be addressed.
Received: 17 April 2012; in revised form: 2 June 2012 / Accepted: 4 June 2012 / Published: 6 June 2012
(This article belongs to the Special Issue Asymmetric Catalysis)
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Abstract: A variety of 3-substituted benzisoxazoles were reduced with hydrogen using the chiral ruthenium catalyst, {RuCl(p-cymene)[(R,R)-(S,S)-PhTRAP]}Cl. The ruthenium-catalyzed hydrogenation proceeded in high yield in the presence of an acylating agent, affording a-substituted o-hydroxybenzylamines with up to 57% ee. In the catalytic transformation, the N–O bond of the benzisoxazole substrate is reductively cleaved by the ruthenium complex under the hydrogenation conditions. The C–N double bond of the resulting imine is saturated stereoselectively through the PhTRAP–ruthenium catalysis. The hydrogenation produces chiral primary amines, which may work as catalytic poisons, however, the amino group of the hydrogenation product is rapidly acylated when the reaction is conducted in the presence of an appropriate acylating agent, such as Boc2O or Cbz-OSu.
Keywords: ruthenium; catalytic asymmetric synthesis; hydrogenation; benzisoxazole; amine

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MDPI and ACS Style

Ikeda, R.; Kuwano, R. Catalytic Asymmetric Hydrogenation of 3-Substituted Benzisoxazoles. Molecules 2012, 17, 6901-6915.

AMA Style

Ikeda R, Kuwano R. Catalytic Asymmetric Hydrogenation of 3-Substituted Benzisoxazoles. Molecules. 2012; 17(6):6901-6915.

Chicago/Turabian Style

Ikeda, Ryuhei; Kuwano, Ryoichi. 2012. "Catalytic Asymmetric Hydrogenation of 3-Substituted Benzisoxazoles." Molecules 17, no. 6: 6901-6915.

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