Cohen Revital, Graves Christopher R, Nguyen SonBinh T, Martin Jan M L, Ratner Mark A
Department of Organic Chemistry, Weizmann Institute of Science, 76100 Rechovot, Israel.
J Am Chem Soc. 2004 Nov 17;126(45):14796-803. doi: 10.1021/ja047613m.
The mechanistic details of the Meerwein-Schmidt-Ponndorf-Verley (MSPV) reduction of ketones to the corresponding alcohols were investigated both experimentally and computationally. Density functional theory (DFT) was used to assess the energetics of several proposed pathways (direct hydrogen transfer, hydridic, and radical). Our results demonstrate that a direct hydrogen transfer mechanism involving a concerted six-membered ring transition state is the most favorable pathway for all calculated systems starting from a small model system and concluding with the experimentally investigated BINOLate/Al/(i)PrOH/MePhC=O system. Experimental values for the activation parameters of acetophenone reduction using the BINOLate/Al/(i)PrOH system (DeltaG# = 21.8 kcal/mol, DeltaH# = 18.5 kcal/mol, DeltaS# = -11.7 au) were determined on the basis of kinetic investigation of the reaction and are in good agreement with the computational findings for this system. Calculated and experimental kinetic isotope effects support the concerted mechanism.
对Meerwein-Schmidt-Ponndorf-Verley（MSPV）将酮还原为相应醇类反应的机理细节进行了实验和计算研究。采用密度泛函理论（DFT）评估了几种提出的反应途径（直接氢转移、氢负离子转移和自由基途径）的能量学。我们的结果表明，对于从小模型体系开始并以实验研究的联萘酚盐/铝/异丙醇/甲基苯乙酮体系结束的所有计算体系，涉及协同六元环过渡态的直接氢转移机理是最有利的途径。基于对该反应的动力学研究，确定了使用联萘酚盐/铝/异丙醇体系还原苯乙酮的活化参数的实验值（ΔG# = 21.8 kcal/mol，ΔH# = 18.5 kcal/mol，ΔS# = -11.7 au），并且与该体系的计算结果高度吻合。计算和实验得到的动力学同位素效应支持协同机理。
