27683-61-0Relevant articles and documents
Expanding the scope of alcohol dehydrogenases towards bulkier substrates: Stereo- and enantiopreference for α,α-dihalogenated ketones
Kedziora, Kinga,Bisogno, Fabricio R.,Lavandera, Ivan,Gotor-Fernandez, Vicente,Montejo-Bernardo, Jose,Garcia-Granda, Santiago,Kroutil, Wolfgang,Gotor, Vicente
, p. 1066 - 1072 (2014/05/06)
Alcohol dehydrogenases (ADHs) were identified as suitable enzymes for the reduction of the corresponding α,α-dihalogenated ketones, obtaining optically pure β,β-dichloro- or β,β-dibromohydrins with excellent conversions and enantiomeric excess. Among the different biocatalysts tested, ADHs from Rhodococcus ruber (ADH-A), Ralstonia sp. (RasADH), Lactobacillus brevis (LBADH), and PR2ADH proved to be the most efficient ones in terms of activity and stereoselectivity. In a further study, two racemic α-substituted ketones, namely α-bromo- α-chloro- and α-chloro-α-fluoroacetophenone were investigated to obtain one of the four possible diastereoisomers through a dynamic kinetic process. In the case of the brominated derivative, only the (1R)-enantiomer was obtained by using ADH-A, although with moderate diastereomeric excess (>99 % ee, 63 % de), whereas the fluorinated ketone exhibited a lower stereoselectivity (up to 45 % de). Bulking up: A series of β,β-dihalohydrins are obtained through alcohol dehydrogenase (ADH) catalyzed bioreduction of the synthesized α,α-dihalogenated ketones. Two racemic acetophenone derivatives are also subjected to this protocol to obtain stereoenriched alcohols through dynamic kinetic resolution (DKR).
Molecular Rearrangements. 13. Kinetics and Mechanism of Rearrangements of Some Ring-Substituted α-Chlorostyrene Oxides and trans-β-Chlorostyrene Oxides.
McDonald, Richard N.,Cousins, Raymond C.
, p. 2976 - 2984 (2007/10/02)
The synthesis of certain phenyl-substituted derivatives of the isomeric trans-β-chlorostyrene oxides (6) and α-chlorostyrene oxides (7) are reported.The kinetics of rearrangement of 6 (X = p-CH3, H, p-Br, m-Cl, p-NO2) to phenylchloroacetaldehydes (12) in CCl4 buffered by Na2HPO4 and 7 (X = p-CH3, H, p-NO2) to ω-chloroacetophenones in CCl4 were determined by following the rates of disappearance of the α-chloro epoxide and formation of the α-chloro carbonyl product.These substituent effects at 130 deg C were correlated with ?+ constants, yielding ρ values of-3.5 and -0.57 for the rearrangements of 6 and 7, respectively.In nitrobenzene solvent, the kC6H5NO2/kCCl4 for 6 was 180 and for 7 was 1740, the latter solvent effect attributed to nucleophilic solvent participation.It was concluded that these thermal rearrangements of 6 and 7 occur by disrotatory Cβ-O bond heterolysis to yield the corresponding α-keto carbonium-chloride ion pairs.