Kemppainen Eeva K, Sahoo Gokarneswar, Piisola Antti, Hamza Andrea, Kótai Bianka, Pápai Imre, Pihko Petri M
Department of Chemistry, University of Jyväskylä, P. O. Box 35, 40014, University of Jyväskylä (Finland).
Chemistry. 2014 May 12;20(20):5983-93. doi: 10.1002/chem.201304240. Epub 2014 Apr 1.
The scope of the enantioselective Mukaiyama-Michael reactions catalyzed by trans-2,5-diphenylpyrrolidine has been expanded to include both α- and β-substituted enals. However, the rationalization of the observed enantioselectivity is far from obvious since the catalyst is not very sterically hindered. DFT calculations were carried out to rationalize the observed stereoselectivities. Transition states of the C-C bond formation between iminium intermediates and silyloxyfurans were located and their relative energies were used to estimate the stereoselectivity data. We find excellent agreement between the predicted and observed stereoselectivities. The analysis of intermolecular forces reveals that the enantioselectivity is mostly due to stabilizing noncovalent interactions between the reacting partners, not due to steric hindrance. The role of attractive noncovalent interactions in enantioselective catalysis may be underappreciated.
由反式-2,5-二苯基吡咯烷催化的对映选择性 Mukaiyama-Michael 反应的范围已扩大到包括 α-和 β-取代的烯醛。然而，鉴于催化剂的空间位阻不大，所观察到的对映选择性的合理化远非显而易见。进行了密度泛函理论（DFT）计算以合理化所观察到的立体选择性。确定了亚胺中间体与硅氧基呋喃之间 C-C 键形成的过渡态，并使用它们的相对能量来估计立体选择性数据。我们发现预测的和观察到的立体选择性之间有极好的一致性。分子间力的分析表明，对映选择性主要是由于反应伙伴之间稳定的非共价相互作用，而不是由于空间位阻。有吸引力的非共价相互作用在对映选择性催化中的作用可能未得到充分认识。
