Origin of Proposed Mechanistic Models in Heterogeneous Catalytic Enantioselective Hydrogenation of Pyruvates Comes from the Conformation Properties of Internal Rotation of Cinchona Alkaloids

Abstract

The main orientations of methyl pyruvate in the force field of cinchonia alkaloids have been fully mapped and analyzed using molecular mechanics building techniques and density functional theory methods. Beside the known “open (3), (4)” and “closed (1), (2)” forms of cinchonidine, its group of “open (10), (11)” conformation is also analyzed, as well as the potential surface of isocinchonines. In this way an origin of different mechanistic models by different authors for the hydrogenation of activated ketones on cinchona alkaloid modified platinum is revealed: All models can be originated from the conformational properties of the internal rotation of the two-ring system in cinchona alkaloids (particularly cinchonidine, α and β-isocinchonine) with and without methyl pyruvate adduct formation.