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ESPHOS

Related systems are the bis-diazaphospholane ligands of which ESPHOS has proved optimal. Best results were obtained upon hydroformylation of vinyl acetate with ee values up to 89% for the branched lactalde-hyde acetate (Scheme 23) [72], Even more efficient variations are bis-3,4-diazaphospholane ligands, which furnished up to 96% ee upon hydroformylation of vinyl acetate [73]. [Pg.161]

Rh(acac)(CO)2] in combination with ESPHOS (76a) was applied in the asymmetric hydroformylation of vinyl acetate with excellent results. ESPHOS was effective in styrene hydroformylation, but the product is essentially racemic.270... [Pg.172]

ESPHOS (178), a chiral bis(diazaphospholidine) ligand developed by the Wills group, has been found to be active in the asymmetric hydroformylation of vinyl acetate.231 (This ligand system is being commercialized by Stylacats.) Enantioselectivities of 87-89% ee and regioselectivities of 95/5 (b/1) have been obtained at 120 psig pressure of syn gas.232 Unfortunately, the substrate scope is not as broad as BINAPHOS. [Pg.237]

Hydrogenation, by far, has garnished the best results in homogeneous asymmetric catalysis, but efforts continue in the development of asymmetric hydroformylation. Several new ligands (Binaphos, Kelliphite, and ESPHOS) have been designed that have raised the level of enantioselectivities to 90-94% ee and regioselectivities to 88-99% in favor of the branched isomer. [Pg.240]

THE SYNTHESIS AND APPLICATION OF ESPHOS a new diphosphorus ligand for THE HYDROFORMYLATION OF VINYL ACETATE... [Pg.225]

The asymmetric hydroformylation of alkenes is an exceptionally atom-efficient method for the synthesis of enantiomerically-pure carbonyl-containing compounds.[1] The hydroformylation of vinylacetate, in particular, represents an excellent method for the preparation of ot-alkoxy aldehydes and, through their reduction, homochiral 1,2-diols. The use of the novel chiral ligand, ESPHOS (1),[2] in a rhodium(I) complex, results in hydroformylation of vinyl acetate in high branched linear selectivity and exceptional ee (Figure 12.1).[3]... [Pg.230]

ESPHOS (1) may be prepared in a 5-step procedure (Figure 12.2) from 2-bromoaniline (2), through diazotization to give (3), followed by decomposition and... [Pg.230]

Using the combination of ESPHOS with rhodium a catalytic hydroformylation of vinyl acetate may be achieved in high regio- and enantioselectivity using as little as... [Pg.237]

Given the temperature, 2 is usually obtained as the pure anti diastereoisomer following route B. One important example of a ligand obtained by this route is SEMI-ESPHOS, depicted in Scheme 3.2. [Pg.122]

Breeden and Wills " reported that SEMI-ESPHOS ligand is obtained as a... [Pg.123]

Both methodologies have been successfully extended for the preparation of diphosphorus ligands. An important example is ESPHOS (Scheme 3.3), prepared with total stereoselectivity in a 76% yield by Wills and Breeden. ... [Pg.123]


See other pages where ESPHOS is mentioned: [Pg.161]    [Pg.162]    [Pg.45]    [Pg.62]    [Pg.63]    [Pg.64]    [Pg.105]    [Pg.109]    [Pg.36]    [Pg.53]    [Pg.54]    [Pg.55]    [Pg.1017]    [Pg.225]    [Pg.231]    [Pg.231]    [Pg.235]    [Pg.236]    [Pg.237]    [Pg.153]    [Pg.153]    [Pg.123]    [Pg.124]    [Pg.128]    [Pg.129]    [Pg.444]    [Pg.447]    [Pg.464]    [Pg.221]    [Pg.222]   
See also in sourсe #XX -- [ Pg.153 , Pg.154 ]

See also in sourсe #XX -- [ Pg.123 ]




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SEMI-ESPHOS

Synthesis of ESPHOS

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