Weakly bounded intermediates as a previous step toward's highly-enantioselective iminium type additions of beta-keto-sulfoxides and -sulfones

作者：Arpa Enrique M; Frias Maria; Alvarado Cuauhtemoc; Aleman Jose^*; Diaz Tendero Sergio^*

来源：Journal of Molecular Catalysis A: Chemical , 2016, 423: 308-318.

DOI：10.1016/j.molcata.2016.03.013

• Aminocatalysis
• Iminium ion
• Computational homogenous catalysis
• Beta-ketosulfoxides
• Beta-ketosulfones

A joined experimental and theoretical study on the addition of beta-keto-sulfoxides and -sulfones to enals catalyzed with amine compounds of the Jorgensen-Hayashi type is presented. Theoretically, density functional theory calculations are used to explore the potential energy surface of the reactions, providing insight into the mechanisms. Our combined approach allows us to show that the reactions with the sulfoxides take place with the enolate instead of the enol intermediates. The addition mechanisms are evaluated computing the transition states of the reactions between enolates of beta-ketosulfones and beta-ketosulfoxides with the iminium ion of different catalysts. In the reactions with beta-ketosulfoxides, the experiments found a high enantio - and diastereoselectivity; this is explained with the kinetic control exerted by the difference in the energetic barriers as given by the calculations. In the case of beta-ketosulfones a low diastereoselectivity was experimentally observed. In this case, similar energy barriers in the two studied pathways are obtained. In both cases (beta-keto-sulfones and -sulfoxides), the interaction of both reactants leads to a weakly bounded complex previous to the reaction, in which the orientation determines the stereoselectivity obtained in the products.

• 出版日期2016-11