6948-02-3Relevant academic research and scientific papers
Screening of liver acetone powders in the resolution of 1-phenylethanols and 1-phenylpropanols derivatives
Solis, Aida,Garcia, Susana,Perez, Herminia I.,Manjarrez, Norberto,Luna, Hector
, p. 549 - 553 (2008/09/20)
Hydrolases from the liver acetone powders (LAPs) of bovine, cat, chicken, turkey, lamb, pig, rabbit, and rat were assessed for the enantioselective hydrolysis of acetates of 1-(4-chlorophenyl)ethanol, 1-(3-bromophenyl)ethanol, 1-(4-chlorophenyl)propanol, 1-(4-bromophenyl)propanol, and 1-(3-bromophenyl)propanol. The enantioselectivity of the hydrolytic reaction was dependent upon the liver hydrolase, substrate, pH of the reaction media, and the cosolvent. The most ester selective LAP was from chicken, and the resulting alcohols had the highest ee (80% to >99%). All of the LAPs tested catalyzed the hydrolysis of 1-(4-chlorophenyl)ethanol, except for lamb LAP.
Immobilized Manihot esculenta preparation as a novel biocatalyst in the enantioselective acetylation of racemic alcohols
Machado, Luciana L.,Lemos, Telma L.G.,de Mattos, Marcos Carlos,de Oliveira, Maria da Conceicao F.,de Gonzalo, Gonzalo,Gotor-Fernandez, Vicente,Gotor, Vicente
, p. 1418 - 1423 (2008/12/20)
The enzymatic preparation obtained from a discard of Manihot esculenta roots has been successfully immobilized on calcium alginate hydrogels. This preparation has been tested as a chiral biocatalyst in the enzymatic acylation of a set of racemic aromatic alcohols. Depending on the reaction conditions, excellent enantioselectivities can be achieved. Some parameters that can alter the biocatalytic properties of the enzyme, such as solvent, temperature, acyl donor and substrate structure have been studied exhaustively in order to establish a deeper knowledge of this novel biocatalyst.
Solvolysis of 1-Arylethyl Tosylates. Kinetic and Stereochemical Tests for Solvent Participation
Allen, Anette D.,Kanagasabapathy, V. M.,Tidwell, Thomas T.
, p. 4513 - 4519 (2007/10/02)
Solvolytic studies of the 1-arylethyl tosylates 8a (Ar=3-BrC6H4), 8b (Ar=3-CF3C6H4), and 8c (Ar=3,5-(CF3)2C6H3) show that in relatively nonnucleophilic solvents all three substrates have polarimetric rates markedly faster than rates of product formation.These products are largely racemic, but solvolysis of 8c in CF3CO2H gives 6percent net retention.In the more nucleophilic solvents the rates of product formation are close to the polarimetric rates and the products show extensive inversion of configuration.The results are interpreted in terms of an ion-pair mechanism in which nucleophilic solvent attack on the ion pair plays a major role.In the less nucleophilic solvents this attack is rate limiting, whereas attack of the more nucleophilic solvents is fast and initial ionization is rate limiting.Direct displacement by the solvent could contribute to the reactions in the more nucleophilic solvents but is not required by any of the results.The ion-pair mechanism provides a single consistent explanation for the results in all the solvents with all the substrates, and also readily accommodates a variety of other results in the literature, particularly the findings of oxygen and deuterium scrambling, and elimination during solvolysis.
Concerted Bimolecular Substitution Reactions of 1-Phenylethyl Derivatives
Richard, John P.,Jencks, William P.
, p. 1383 - 1396 (2007/10/02)
Substituted 1-phenylethyl derivatives with ?+ > -0.08 exhibit bimolecular substitution reactions with azide ion in 20percent acetonitrile in water.The reactions with 1-phenylethyl chlorides follow a Hammett correlation with ρ = -2.9, compared with ρ = -5.6 (r+ = 1.15) for solvolysis.Swain-Scott correlations give values of s = 0.46 and 0.22 for 1-(4-nitrophenyl)ethyl chloride and tosylate, respectively; there are large positive deviations for azide ion and water and negative deviations for cyanide ion.The value of βnuc is 0.09 for reactions of substituted acetates with the chloride.The reactions exhibit ''synergism'' between the nucleophile and leaving group that favors the bimolecular reaction with Me2S, Br- > Cl- > OTs- leaving groups.The bimolecular reaction with azide follows the Grunwald-Winstein Y correlation with m = 0.8 in methanol-water mixtures.Bimolecular reactions with less reactive nucleophiles in the series N3-, CN-, AcO-, and ROH appear at progressively larger ? values, as the carbocation becomes less stable.It is concluded that these reactions are SN2 displacements that proceed through an open, ''exploded'' transition state that closely resembles a carbocation.Specific salt effects are small in water but are significant in acetonitrile-water mixtures and could be mistaken for normal or induced common ion rate depressions.No evidence was obtained for nucleophilic assistance to the formation of a carbocation intermediate.Concurrent SN1 and SN2 pathways occur in the reactions with solvent and azide of dimethylsulfonium ion, 1-(4-fluorophenyl)ethyl chloride, 1-(3-methoxyphenyl)ethyl chloride, and, probably, 1-(3-nitro-4-methoxyphenyl)ethyl chloride.Crude estimates of the lifetime of the carbocation intermediate in the presence of the nucleophile are consistent with the hypothesis that the concerted reactions are enforced by the absence of a significant lifetime of the carbocation in the presence of the nucleophile and that stepwise mechanisms are followed when the intermediate has a significant lifetime; the change from a stepwise to a concerted mechanism occurs when the intermediate ceases to have a lifetime in the presence of a nucleophile.
