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Titolo:
Substituted salen-Ru(II) complexes as catalysts in the asymmetric cyclopropanation of styrene by ethyl diazoacetate: the influence of substituents and achiral additives on activity and enantioselectivity
Autore:
Yao, XQ; Qiu, M; Lu, WR; Chen, HL; Zheng, Z;
Indirizzi:
Chinese Acad Sci, Dalian Inst Chem Phys, Dalian 116023, Peoples R China Chinese Acad Sci Dalian Peoples R China 116023 n 116023, Peoples R China
Titolo Testata:
TETRAHEDRON-ASYMMETRY
fascicolo: 2, volume: 12, anno: 2001,
pagine: 197 - 204
SICI:
0957-4166(20010219)12:2<197:SSCACI>2.0.ZU;2-7
Fonte:
ISI
Lingua:
ENG
Soggetto:
COPPER CARBENOID REACTION; BIS-OXAZOLINE LIGANDS; COBALT(II) COMPLEXES; RUTHENIUM PORPHYRIN; HIGHLY EFFICIENT; CHIRAL LIGANDS; OLEFINS; EPOXIDES; AZIRIDINATION; DERIVATIVES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
45
Recensione:
Indirizzi per estratti:
Indirizzo: Zheng, Z Chinese Acad Sci, Dalian Inst Chem Phys, Dalian 116023, Peoples RChina Chinese Acad Sci Dalian Peoples R China 116023 Peoples R China
Citazione:
X.Q. Yao et al., "Substituted salen-Ru(II) complexes as catalysts in the asymmetric cyclopropanation of styrene by ethyl diazoacetate: the influence of substituents and achiral additives on activity and enantioselectivity", TETRAHEDR-A, 12(2), 2001, pp. 197-204

Abstract

A series of alkyl-, halogen- and nitro-substituted salen ligands, 1, have been employed in the asymmetric cyclopropanation of styrene with ethyl diazoacetate by its ruthenium(II) complex with [RuCl2(p-cymene)](2) or RuCl2(PPh3)(3) as precursors. The introduction of appropriate electron withdrawing groups in the salen ligands benefited the enantioselectivity of the reaction. Some additives, including O-donor, N-donor and P-donor ligands, were added to the reaction to improve the enantioselectivity and activity, and e.e.s of up to 80% were achieved. In the salen/[RuCl2(p-cymene)](2) system, the(1R,2S)-isomer was obtained in 80.2% e.e. by using the salen ligand If derived from 3,5-dibrominated salicylaldehyde with Et3N as additive. E.e.s of up to 81.3% for (1S,2R)-isomers were achieved by using the complex 2 synthesized from the nitro-substituted ligand Im and RuCl2(PPh3)(3). A possible mechanism was also discussed. (C) 2001 Elsevier Science Ltd. All rights reserved.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 03/07/20 alle ore 01:30:16