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Titolo:
Preparation and use of sterically hindered organobis(2,4,6-triisopropylphenyl)hydroborates and their polystyrene derivatives for the diastereoselective reduction of ketones
Autore:
Smith, K; El-Hiti, GA; Hou, DJ; DeBoos, GA;
Indirizzi:
Univ Wales, Dept Chem, Swansea SA2 8PP, W Glam, Wales Univ Wales Swansea W Glam Wales SA2 8PP m, Swansea SA2 8PP, W Glam, Wales ZENECA Huddersfield Works, Huddersfield HD2 1FF, W Yorkshire, England ZENECA Huddersfield Works Huddersfield W Yorkshire England HD2 1FF ngland Tanta Univ, Fac Sci, Dept Chem, Tanta, Egypt Tanta Univ Tanta EgyptTanta Univ, Fac Sci, Dept Chem, Tanta, Egypt
Titolo Testata:
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 1
fascicolo: 19, , anno: 1999,
pagine: 2807 - 2812
SICI:
0300-922X(1999):19<2807:PAUOSH>2.0.ZU;2-7
Fonte:
ISI
Lingua:
ENG
Soggetto:
ALKALI-METAL HYDRIDES; ORGANIC-SYNTHESIS; ADDITION-COMPOUNDS; ORGANOBORON GROUPS; POTASSIUM HYDRIDE; STEREOCHEMISTRY; REAGENT; CYCLOHEXANONES; BOROHYDRIDE; POLYMERS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Physical, Chemical & Earth Sciences
Citazioni:
28
Recensione:
Indirizzi per estratti:
Indirizzo: Smith, K Univ Wales, Dept Chem, Swansea SA2 8PP, W Glam, Wales Univ WalesSwansea W Glam Wales SA2 8PP a SA2 8PP, W Glam, Wales
Citazione:
K. Smith et al., "Preparation and use of sterically hindered organobis(2,4,6-triisopropylphenyl)hydroborates and their polystyrene derivatives for the diastereoselective reduction of ketones", J CHEM S P1, (19), 1999, pp. 2807-2812

Abstract

Preparations of benzyl and phenylbis(2,4,6-triisopropylphenyl)hydroborates[organoditripylhydroborates] are outlined. The lithium and potassium benzylditripylhydroborates reduce substituted cyclohexanones with diastereoselectivities comparable to those obtained with the most selective reagents known (e.g. 99% cis-4-methylcyclohexanol from 4-methylcyclohexanone). Lithium phenylditripylhydroborate also reduces ketones with significant selectivity. For example, 4-methylcyclohexanone is reduced to cis-4-methylcyclohexanol in 88% isomeric purity. Unlike with most other highly selective reagents the reactions take place at room temperature and have the additional advantage that the boron reagent can be recovered quantitatively. Coupling of Merrifield's resin with ditripylfluoroborane in the presence of lithium naphthalenide affords (ditripylborylmethyl)polystyrene. Similarly, coupling of bromopolystyrene with ditripylfluoroborane in the presence of n-BuLi affords (ditripylboryl)polystyrene. Reactions of these polymeric organoboranes with t-BuLi give the corresponding polymer-supported lithium hydroborates. Lithium ditripylhydroboratylmethylpolystyrene reduces cyclic ketones in identicalfashion to its non-polymeric counterpart, giving the corresponding thermodynamically less stable alcohols in 99% or better isomeric purity. Similarly, lithium ditripylhydroboratylpolystyrene behaves like its non-polymeric counterpart and reduces 4-methylcyclohexanone to cis-4-methylcyclohexanol in 89% isomeric purity. Recovery and reuse of the organoboranes are even easier for the polymeric reagents.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 28/09/20 alle ore 04:27:22