Klomp Dirk, Maschmeyer Thomas, Hanefeld Ulf, Peters Joop A
Laboratory of Applied Organic Chemistry and Catalysis, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands.
Chemistry. 2004 Apr 19;10(8):2088-93. doi: 10.1002/chem.200305460.
The mechanism of hydrogen transfer from alcohols to ketones, catalysed by lanthanide(III) isopropoxides or zeolite Beta has been studied. For the lanthanide catalysed reactions, (S)-1-phenyl-(1-(2)H(1))ethanol and acetophenone were used as case studies to determine the reaction pathway for the hydrogen transfer. Upon complete racemisation all deuterium was present at the 1-position, indicating that the reaction exclusively takes place via a carbon-to-carbon hydrogen transfer. Zeolite Beta with different Si/Al ratios was applied in the racemisation of (S)-1-phenylethanol. In this case the racemisation does not proceed via an oxidation/reduction pathway but via elimination of the hydroxy group and its re-addition. This mechanism, however, is not characteristic for all racemisation reactions with zeolite Beta. When 4-tert-butyl cyclohexanone is reduced with this catalyst, a classical MPV reaction takes place exclusively. This demonstrates that zeolite Beta has a substrate dependent reaction pathway.
研究了由镧系（III）异丙醇盐或β-沸石催化的醇到酮的氢转移机理。对于镧系催化的反应，使用（S）-1-苯基-（1-（2）H（1））乙醇和苯乙酮作为案例研究来确定氢转移的反应途径。完全外消旋化后，所有氘都存在于1-位，表明反应仅通过碳到碳的氢转移发生。将具有不同硅铝比的β-沸石应用于（S）-苯乙醇的外消旋化反应。在这种情况下，外消旋化不是通过氧化/还原途径进行，而是通过羟基的消除及其重新加成进行。然而，这种机理并非所有β-沸石外消旋化反应的特征。当用该催化剂还原4-叔丁基环己酮时，仅发生经典的MPV反应。这表明β-沸石具有底物依赖性反应途径。
