A New Type of Catalytic Tandem 1,4-Addition-Aldol Reaction Which Proceeds through an (Oxa-π-allyl)rhodium Intermediate
Kazuhiro Yoshida, Masamichi Ogasawara, and Tamio Hayashi*
*Department of Chemistry, Graduate School of Science, Kyoto University,
Sakyo, Kyoto 606-8502, Japan, Email: thayashi
kuchem.kyoto-u.ac.jp
K. Yoshida, M. Ogasawara, T. Hayashi, J. Am. Chem. Soc., 2002, 124, 10984-10985.
DOI: 10.1021/ja0271025
Abstract
The Rh-catalyzed reaction of 9-aryl-9-borabicyclo[3.3.1]nonanes with α,β-unsaturated ketones and aldehydes gave high yields of tandem 1,4-addition-aldol reaction products with high syn selectivity. The mechanism is discussed.
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Details
The document discusses a novel catalytic tandem 1,4-addition-aldol reaction facilitated by a rhodium complex, which catalyzes both carbon-carbon bond-forming steps. This reaction involves the 1,4-addition of an organorhodium species to an α,β-unsaturated ketone, followed by an aldol addition of the resulting (oxa-π-allyl)rhodium intermediate to an aldehyde. The study highlights the use of 9-aryl-9-borabicyclo[3.3.1]nonanes (B-Ar-9BBN) as organoboron reagents and [Rh(OMe)(cod)]2 as the catalyst, achieving high yields and syn selectivity. The reaction was tested with various enones and aldehydes, consistently producing high yields and selectivity. NMR experiments confirmed the involvement of a rhodium aldolate intermediate. The research also explored catalytic asymmetric synthesis using a chiral rhodium catalyst, yielding enantiomerically enriched products, though with lower catalytic activity. The study concludes that the rhodium complex effectively catalyzes both steps of the tandem reaction with high chemoselectivity, and future work will focus on optimizing the catalytic asymmetric tandem reaction. The research was supported by the Ministry of Education, Science, Sports, and Culture, Japan, and the Japan Society for the Promotion of Science.
Key Words
ID: J48-Y2002-1270
