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Titolo:
The asymmetric addition of trimethylsilyl cyanide to aldehydes catalyzed by chiral (salen)titanium complexes
Autore:
Belokon, YN; Caveda-Cepas, S; Green, B; Ikonnikov, NS; Krustalev, VN; Larichev, VS; Moscalenko, MA; North, M; Orizu, C; Tararov, VI; Tasinazzo, M; Timofeeva, GI; Yashkina, LV;
Indirizzi:
Russian Acad Sci, Inst Organoelement Cpds, Moscow 117813, Russia Russian Acad Sci Moscow Russia 117813 lement Cpds, Moscow 117813, Russia Univ Coll N Wales, Dept Chem, Bangor LL57 2UW, Gwynedd, Wales Univ Coll N Wales Bangor Gwynedd Wales LL57 2UW LL57 2UW, Gwynedd, Wales
Titolo Testata:
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
fascicolo: 16, volume: 121, anno: 1999,
pagine: 3968 - 3973
SICI:
0002-7863(19990428)121:16<3968:TAAOTC>2.0.ZU;2-7
Fonte:
ISI
Lingua:
ENG
Soggetto:
BINAPHTHOL-TITANIUM COMPLEX; SCHIFF-BASE COMPLEXES; CARBONYL-ENE REACTION; C BOND FORMATION; ENANTIOSELECTIVE ADDITION; LEWIS-ACID; UNFUNCTIONALIZED OLEFINS; (SALEN)MANGANESE(III) COMPLEXES; CYANOHYDRIN SYNTHESIS; HYDROGEN-CYANIDE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Physical, Chemical & Earth Sciences
Citazioni:
82
Recensione:
Indirizzi per estratti:
Indirizzo: Belokon, YN Russian Acad Sci, Inst Organoelement Cpds, Moscow 117813, Russia Russian Acad Sci Moscow Russia 117813 Moscow 117813, Russia
Citazione:
Y.N. Belokon et al., "The asymmetric addition of trimethylsilyl cyanide to aldehydes catalyzed by chiral (salen)titanium complexes", J AM CHEM S, 121(16), 1999, pp. 3968-3973

Abstract

The use of chiral (salen)TiCl2 complexes to induce the asymmetric additionof trimethylsilyl cyanide to aldehydes has:been investigated. The complexes are catalytically active at substrate-to-catalyst ratios as high as 1000:1, and the optimal catalyst (2e) which is derived from (R,R)-1,2-diaminocyclohexane and 3,5-di-tert-butyl-2-hydroxybenzaldehyde produces trimethylsilyl ethers of cyanohydrins with up to 90% enantiomeric excess at ambient temperature. Water plays a key role in these reactions since under strictly anhydrous conditions much lower enantiomeric excesses are produced. The role of water has been shown to be to generate dimeric complexes of the form [(salen)Ti(mu-O)](2) (4) which are the real catalyst precursors. A structure for one of these complexes (4a derived from (R,R)-1,2-diaminocyclohexane and 2-hydroxybenzaldehyde) has been determined by X-ray crystallography. The dimeric complexes are more active than the dichloride precursors, and at substrate-to-catalyst ratios between 100 and 1000:1 give cyanohydrin trimethylsilyl ethers with up to 92% enantiomeric excess in less than 1 h at ambient temperature.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 20/09/20 alle ore 01:07:00