Heterogeneous asymmetric reactions, 14. Epicinchona alkaloids in the enantioselective hydrogenation of ethyl pyruvate over Pt/alumina. What determines the sense of enantioselection?

The enantioselective hydrogenation of ethyl pyruvate to (R)-and (S)-ethyl lactate over Pt/Al₂O₃ catalyst was investigated using epiquinine (42% ee) and epiquinidine (22% ee) as modifiers and the results were compared with those found for quinine (85% ee) and quinidine (81% ee). The experimental results show that the sense of enantioselection is determined by the conformation of the entire alkaloid, and the structure of the intermediate is a 1∶1 complex of the pyruvate and the ‘anti open’ conformer of the cinchona alkaloid.     

Functionalization op saturated hydrocarbons in the presence of aprotic organic superacids. 2. Single-stage synthesis of thioesters R1CO-SR from n-alkanes or cycloalkanes (RH), elemental sulfur,and complexes R1COBr·-2AlBr3

It has been found for the first time that n-alkanes and cycloalkanes (RH) can interact with elemental sulfur at 20°C. These reactions go forward in the presence of aprotic organic superacids with the composition R¹COBr·2AlBr₃, leading to the formation of thioesters R¹-CO-SR in satisfactory yields.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 105–108, January, 1991.