14898-87-4Relevant articles and documents
SN2 type hydrolysis of secondary alkyl halides and sulfonates in hydrothermal water
Yamasaki, Yuki,Hirayama, Takaharu,Oshima, Koichiro,Matsubara, Seijiro
, p. 864 - 865 (2004)
Optically active secondary alkyl halides and sulfonates were treated with alkaline hydrothermal water at 250°C in sealed vessel. The hydrolysis mostly proceeded with inversion of stereochemistry.
Selective Reductions. 32. Structural Effects on the reduction of Epoxides by Lithium Triethylborohydride. A Kinetic Study
Brown, Herbert C.,Narasimhan, S.,Somayaji, Vishwanatha
, p. 3091 - 3096 (1983)
An analytical procedure for the estimation of lithium triethylborohydride utilizing iodimetry has been developed.The rates of reduction of a number of epoxides are studied.The reaction exhibits second-order kinetics, first order with respect to each reactant.Methyl substitution decreases the reactivity of the epoxide by a factor of 8-10.In the case of aliphatic derivatives, the cis epoxide reacts 12 times faster than the trans.On the other hand, cis- and trans-β-methylstyrene oxides exhibit the opposite trend.A remarkable change in the regioselectivity of reduction of these two epoxides was observed.A possible explanation is presented.The kinetic isotope effect has been established both by rate studies and by determination, by mass spectrometry, of the deuterium incorporation in a competitive reaction between LiEt3BH, LiEt3BD, and the epoxide.A value of kH/kD ca. 1.4-1.5 is obtained by both methods.A mechanism is proposed to account for these results.
Instantaneous SmI2-H2O-mediated reduction of dialkyl ketones induced by amines in THF
Dahlén, Anders,Hilmersson, G?ran
, p. 7197 - 7200 (2002)
Reduction of various ketones to their corresponding alcohols is shown to be instantaneous, i.e. completed in less than 10 s, by samarium diiodide (2.5 equiv.) in the presence of water (6.25 equiv.) and an amine (5 equiv.) in THF. The rates of reduction of ketones in this mixture exceed by far the rates determined by an amine or water alone. Rate enhancement is at least 100 000 compared to the reduction without a proton source, or at least 100 times faster than the rate of the widely used HMPA/alcohol accelerated reductions. This new method is therefore suggested to be an excellent replacement of the toxic HMPA/alcohol method.
Synthesis of (R)-selegiline via hydrolytic kinetic resolution
Kondekar, Nagendra B.,Kumar, Pradeep
, p. 1301 - 1308 (2011)
A short and enantioselective formal synthesis of (R)-selegiline has been achieved using Jacobsen's hydrolytic kinetic resolution (HKR) of phenyl propylene oxide.
Chemo-enzymatic synthesis of the active enantiomer of the anorressant 2- benzylmorpholine
D'Arrigo, Paola,Lattanzio, Maria,Fantoni, Giuseppe Pedrocchi,Servi, Stefano
, p. 4021 - 4026 (1998)
Baker's yeast reduction of (Z)-α-bromocinnamaldehyde 1 in the presence of absorbing resins allows the easy preparation of the corresponding saturated bromo-alcohol 2 in high yields and enantiomeric excess. The absolute configuration is assigned through conversion into the (R)-phenyl oxirane 3 and 1-phenyl-2-propanol 4 of (S) absolute configuration. The (R)- epoxide is transformed into 6, the pharmacologically active enantiomer of the appetite suppressant 2-benzylmorpholine, to which the (R) configuration is assigned.
Discovery and Redesign of a Family VIII Carboxylesterase with High (S)-Selectivity toward Chiral sec-Alcohols
Park, Areum,Park, Seongsoon
, p. 2397 - 2402 (2022/02/17)
Highly enantioselective lipase has been widely utilized in the preparation of versatile enantiopure chiral sec-alcohols through kinetic or dynamic kinetic resolution. Lipase is intrinsically (R)-selective, and it is difficult to obtain (S)-selective lipase. Recent crystal structures of a family VIII carboxylesterase have revealed that the spatial array of its catalytic triad is the mirror image of that of lipase but with a catalytic triad that is distinct from lipase. We, therefore, hypothesized that the family VIII carboxylesterase may exhibit (S)-enantioselectivity toward sec-alcohols similar to (S)-selective serine protease, whose catalytic triad is also spatially arrayed as its mirror image. In this study, a homologous enzyme (carboxylesterase from Proteobacteria bacterium SG_bin9, PBE) of a known family VIII carboxylesterase (pdb code: 4IVK) was prepared, which showed not only moderate (S)-selectivity toward sec-alcohols such as 3-butyn-2-ol and 1-phenylethyl alcohol but also (R)-selectivity toward particular sec-alcohols among the substrates explored. Furthermore, the (S)-selectivity of PBE has been significantly improved by rational redesign based on molecular modeling. Molecular modeling identified a binding pocket composed of Ser381, Ala383, and Arg408 for the methyl substituent of (R)-1-phenylethyl acetate and suggested that larger residues may increase the enantioselectivity by interfering with the binding of the slow-reacting enantiomer. As predicted, substituting Ser381with larger residues (Phe, Tyr, and Trp) significantly improved the (S)-selectivity of PBE toward all sec-alcohols explored, even the substrates toward which the wild-type PBE exhibits (R)-selectivity. For instance, the enantioselectivity toward 3-butyn-2-ol and 1-phenylethyl alcohol was improved from E = 5.5 and 36.1 to E = 2001 and 882, respectively, by single mutagenesis (S381F).
The solvent determines the product in the hydrogenation of aromatic ketones using unligated RhCl3as catalyst precursor
Bartling, Stephan,Chakrabortty, Soumyadeep,De Vries, Johannes G.,Kamer, Paul C. J.,Lund, Henrik,Müller, Bernd H.,Rockstroh, Nils
, p. 7608 - 7616 (2021/12/13)
Alkyl cyclohexanes were synthesized in high selectivity via a combined hydrogenation/hydrodeoxygenation of aromatic ketones using ligand-free RhCl3 as pre-catalyst in trifluoroethanol as solvent. The true catalyst consists of rhodium nanoparticles (Rh NPs), generated in situ during the reaction. A range of conjugated as well as non-conjugated aromatic ketones were directly hydrodeoxygenated to the corresponding saturated cyclohexane derivatives at relatively mild conditions. The solvent was found to be the determining factor to switch the selectivity of the ketone hydrogenation. Cyclohexyl alkyl-alcohols were the products using water as a solvent.
