82027-28-9Relevant academic research and scientific papers
Transition-Metal-Free Reduction of α-Keto Thioesters with Hydrosilanes at Room Temperature: Divergent Synthesis through Reagent-Controlled Chemoselectivities
Maity, Rajib,Das, Bhanuranjan,Das, Indrajit
supporting information, p. 2347 - 2353 (2019/04/17)
The combination of hydrosilanes with a Br?nsted or Lewis acid as a promoter can be used for the reagent-controlled chemoselective reduction at room temperature of conjugated C=C bond, enone moiety, or the carbonyl of (β,γ-unsaturated) α-keto thioesters, providing facile access to β,γ-saturated α-keto thioesters, α-hydroxy thioesters, or silyl ethers. The reaction pathway and the chemoselectivity can be fine-tuned through the judicious choice of the hydrosilane or the reaction conditions. The reactions tolerate a wide range of functional groups including labile thioesters and the products are generally obtained in moderate to excellent yields. Unsymmetrical thioethers can also be synthesized using PMHS and catalytic B(C6F5)3 via reductive deoxygenation of both the carbonyl groups. The applicability has been highlighted by the amine-mediated and coupling reagent-free syntheses of saturated α-keto amides from β,γ-unsaturated α-hydroxy thioesters and β,γ-saturated α-keto thioesters. (Figure presented.).
Model Studies of the Glyoxalase I Reaction. Buffer-catalysed Rearrangement to α-Hydroxyacyl Thiolesters of Hemithioacetals from 2-Mercaptoethanol with Substituted Arylglyoxals
Douglas, Kenneth T.,Demircioglu, Husniye
, p. 1951 - 1956 (2007/10/02)
A model system for the reaction catalysed by the enzyme glyoxalase I has been studied kinetically.A series of substituted arylglyoxals was synthesised.The hemithioacetals formed between these α-ketoaldehydes and β-mercaptoethanol in aqueous solutions at pH 9.2 underwent smooth rearrangement to the corresponding α-hydroxyacyl thiolester.The kinetics of this rearrangement were studied anaerobically and rate constants showed saturation dependence on thiol concentration obs=kmax Kh/(1+Kh)>, where kmax refers to the limiting value of kobs at high thiol concentrations and Kh is the equilibrium constant for the hemithioacetal equilibrium.The rearrangement was catalysed by diazabicyclo octane and second-order rate constants for this process followed a Hammett ? relationship with a p value of +0.90.Isotope effects in H2O- and D2O-based media for PhCOCHO and PhCOCDO, respectively, were measured at 30 deg C to give kmax (H/D)=5.9+/-0.9; Kh (H/D)=0.24+/-0.08.Activation parameters were obtained for isolated kmax and Kh terms for phenylglyoxal with mercaptoethanol.The data obtained, along with literature information, allowed assignement of the rate-determining step to base-catalysed deprotonation at the C(1)-H site of the hemithioacetal (i.e. at the caron α to the sulphur atom).
