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Titolo:
Catalytic asymmetric epoxidation of enones using La-BINOL-triphenylarsine oxide complex: Structural determination of the asymmetric catalyst
Autore:
Nemoto, T; Ohshima, T; Yamaguchi, K; 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 Chiba Univ, Ctr Chem Anal, Inage Ku, Chiba 2630022, Japan Chiba Univ Chiba Japan 2630022 Chem Anal, Inage Ku, Chiba 2630022, Japan
Titolo Testata:
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
fascicolo: 12, volume: 123, anno: 2001,
pagine: 2725 - 2732
SICI:
0002-7863(20010328)123:12<2725:CAEOEU>2.0.ZU;2-G
Fonte:
ISI
Lingua:
ENG
Soggetto:
DIELS-ALDER REACTIONS; ENANTIOSELECTIVE EPOXIDATION; CHIRAL KETONES; DIOXIRANE; ALKENES; OLEFINS; SYSTEM;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Physical, Chemical & Earth Sciences
Citazioni:
27
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:
T. Nemoto et al., "Catalytic asymmetric epoxidation of enones using La-BINOL-triphenylarsine oxide complex: Structural determination of the asymmetric catalyst", J AM CHEM S, 123(12), 2001, pp. 2725-2732

Abstract

The catalytic asymmetric epoxidation of enones using the La-BINOL-Ph3As=O complex generated from La(O-i-Pr)(3), BINOL, and Ph3As=O in a ratio of 1:1:1 is described herein; Using 1-5 mol % of the asymmetric catalyst, a variety of enones, including a dienone and a cis-enone, were found to be epoxidized in a reasonable reaction time, providing the corresponding epoxy ketonesin up to 99% yield and with more than 99% ee. The possible structure of the actual asymmetric catalyst has been clarified by various methods, including X-ray crystal structure analysis. This is the first X-ray analysis of analkali-metal free lanthanoid-BINOL complex. Although La(binaphthoxide)(2)(Ph3As=O)(2) (7) was observed as the major complex in the complexes' solution, generated from La(O-i-Pr)(3), BINOL, and Ph3As=O in a ratio of 1:1:1, the possible active species turned out to be the La-BINOL-Ph3As=O complex in a ratio of 1:1:1. A probable reaction mechanism of the catalytic asymmetricepoxidation of enones is also proposed, suggesting that preferential formation of a heterochiral complex is the reason for asymmetric amplification. Moreover, the interesting role of La(O-i-Pr)(3) for accelerating the epoxidations while maintaining high ee's is discussed.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 04/07/20 alle ore 18:25:03