Our group have developed an offspring of densely substituted unnatural L- and D- pyrrolidine derivatives 3 and 4 with endo- or exo- diastereoselectivity, respectively, in high enantioselectivities.[1] Encouraged by the efficiency of Proline-based organocatalysts in several C-C bond transformations, these novel densely substituted pyrrolidines (3 and 4) have been used as organocatalysts in the Michael reaction yielding the corresponding addition adduct 6.[2] These products may possess the same or opposite stereochemistry obtained under natural L-Proline organocatalysis depending on the stereochemistry of the catalyst used (endoL-3,4aa or L-Proline vs. exoL-3,4aa). Computational studies have been performed in order to gain insight into the mechanism and also, the influence of the substituents´ nature and additional side groups in the catalysts have been studied. As a coda, reactivity of the catalysts against a novel double electrophile is shown.
[1] Conde, E.; Bello, D.; de Cózar, A.; Sánchez, M.; Vázquez, M. A.; Cossío, F. P. Chem. Sci. 2012, 3, 1486-1491
[2] a) Xu, L. W.; Luo, J.; Lu, Y. Chem. Comm. 2009, 1807-1821. b) Vicario, J. L.; Badía, D.; Carrillo, L.; Reyes, E. Organocatalytic Enantioselective Conjugate Additions Reactions, RSC Publishing: Cambridge UK 2010
