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Titolo:
Direct catalytic asymmetric aldol reaction
Autore:
Yoshikawa, N; Yamada, YMA; Das, J; Sasai, H; Shibasaki, M;
Indirizzi:
Univ Tokyo, Grad Sch Pharmaceut Sci, Bunkyo Ku, Tokyo 1130033, Japan Univ Tokyo Tokyo Japan 1130033 ceut Sci, Bunkyo Ku, Tokyo 1130033, Japan
Titolo Testata:
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
fascicolo: 17, volume: 121, anno: 1999,
pagine: 4168 - 4178
SICI:
0002-7863(19990505)121:17<4168:DCAAR>2.0.ZU;2-H
Fonte:
ISI
Lingua:
ENG
Soggetto:
SILYL KETENE ACETALS; ALPHA-AMINO PHOSPHONATES; METHYL-BETA-HYDROXY; PURE ANTI-ALDOLS; ENANTIOSELECTIVE SYNTHESIS; HETEROBIMETALLIC COMPLEXES; ENOLATE EQUIVALENTS; TITANIUM ENOLATE; BINOL COMPLEXES; ACID-ESTERS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Physical, Chemical & Earth Sciences
Citazioni:
80
Recensione:
Indirizzi per estratti:
Indirizzo: Shibasaki, M Univ Tokyo, Grad Sch Pharmaceut Sci, Bunkyo Ku, Tokyo 1130033, Japan Univ Tokyo Tokyo Japan 1130033 kyo Ku, Tokyo 1130033, Japan
Citazione:
N. Yoshikawa et al., "Direct catalytic asymmetric aldol reaction", J AM CHEM S, 121(17), 1999, pp. 4168-4178

Abstract

The direct catalytic asymmetric aldol reaction using aldehydes and unmodified ketones is described for the first time herein. This reaction was firstfound to be promoted by 20 mol % of anhydrous (R)-LLB (L = lanthanum, L = lithium, B = (R)-binaphthol moiety) at -20 OC, giving a variety of aldol products in ee's ranging from 44 to 94%. This asymmetric reaction has been greatly improved by developing a new heteropolymetallic asymmetric catalyst [(R)-LLB, KOH, and H2O]. Using 3-8 mol % of this catalyst, a variety of direct catalytic asymmetric aldol reactions were again found to proceed smoothly, affording aldol products in ee's ranging from 30 to 93% and in good to excellent yields. Interestingly, the use of this new heteropolymetallic asymmetric catalyst has realized a diastereoselective and enantioselective aldol reaction using cyclopentanone for the first time. It is also noteworthy that a variety of aldehydes, including hexanal, can be utilized for the current direct catalytic asymmetric aldol reaction. Chiral aldehydes containingalpha-hydrogen including (S)-hydrocinnamaldehyde-alpha-d have been found to produce the corresponding aldol products with negligible racemization (0-4%) at the a-position One of the aldol products has been successfully converted to the key synthetic intermediates of epothilone A and bryostatin 7. The possible structure of the heteropolymetallic catalyst is also discussed. Finally, mechanistic studies have revealed a characteristic reaction pathway, namely that the reaction is kinetically controlled and the rate-determining step is the deprotonation of the ketone. This is consistent with the fact that the reaction rate is independent of the concentration of the aldehyde.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 29/11/20 alle ore 17:07:16