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Synlett 2006(18): 3013-3016  
DOI: 10.1055/s-2006-951518
LETTER
© Georg Thieme Verlag Stuttgart · New York

RuHCl(CO)(PPh3)3-Catalyzed Reductive Dimerization of α,β-Unsaturated Aldehydes Leading to α-Hydroxymethyl Ketones

Takashi Doi, Takahide Fukuyama, Satoshi Minamino, Ilhyong Ryu*
Department of Chemistry, Graduate School of Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan
Fax: +81(72)2549695; e-Mail: ryu@c.s.osakafu-u.ac.jp;
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Publication History

Received 26 April 2006
Publication Date:
25 October 2006 (online)

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Abstract

The reductive dimerization α,β-unsaturated aldehydes to give saturated ketones was achieved using RuHCl(CO)(PPh3)3 as a catalyst in the presence of secondary alcohols as hydrogen source. The reaction is likely to proceed via the hydroruthenation of α,β-unsaturated aldehydes followed by aldol reaction of the resultant ruthenium enolates with α,β-unsaturated aldehydes to give unsaturated α-hydroxymethyl ketones, which undergo transfer hydrogenation to give α-hydroxymethyl ketones.

Key words

ruthenium enolates - aldol reaction - α-hydroxymethyl ketones - α,β-unsaturated aldehydes - transfer hydrogenation

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After 15 min, 3a contained ca. 17% of double-bond isomers.

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General Procedure for the RuHCl(CO)(PPh 3 ) 3 -Catalyzed Reductive Dimerization of α,β-Unsaturated Aldehyde. A mixture of 1a (103 mg, 1.03 mmol), 2-PrOH (63 mg, 1.05 mmol), and RuHCl(CO)(PPh3)3 (96.0 mg, 0.1 mmol) in benzene (6 mL) was stirred at reflux for 10 h under an atmosphere of N2. Purification by silica gel column chromatography and preparative HPLC equipped with GCP column gave α-hydroxymethyl ketone 2a (59.0 mg, 59%).