DFT and ATR-IR insight into the conformational flexibility of cinchonidine adsorbed on platinum: Proton exchange with metal

Novel Evidence on the Role of the Nucleophilic Intermediate Complex in the Orito-Reaction: Unexpected Inversion in the Enantioselective Hydrogenation of 2,2,2-Trifluoroacetophenone on Pt-Cinchona Chiral Catalyst Using Continuous-Flow Fixed-Bed Reactor

“…In the case of TFAP bound to the protonated quinuclidine moiety, namely in solvent mixture with TFA the formation of the (R)-and (S)-products in excess are interpreted through the so-called O-H-N complexes (see Fig. 5, A1) [11,[70][71][72] or by the two point H-bonding model (A2 complex) [27,73]. Unexpected formation of the (R)-product in excess in higher amount in the presence of CN in solvent mixture without TFA may be envisaged by the formation of the less widely accepted nucleophilic complex illustrated in Fig.…”

Time-Lapse STM Studies of Diastereomeric Cinchona Alkaloids on Platinum Metals

“…Furthermore, the complexity is enhanced by structural changes, which are likely to occur in the molecule and the surface in the course of the adsorption process. 18 As a consequence the simple lattice gas model will not be able to describe the diffusion process adequately for our system. Nevertheless, to be able to compare the adsorption and diffusion behavior of the different surface species of CD and CN on both metal surfaces we had to define a method to quantify the surface mobility.…”

Enantioselective hydrogenation of activated ketones in the presence of Pt–cinchona catalysts. Is the proton transfer concept valid?

“…In this contribution experimental evidences are summarized, which strongly contradict to the proton transfer mechanism [5,15] proposed for the catalytic system Pt-cinchona alkaloids. If the quinuclidine nitrogen of the CD is involved in the hydrogen transfer, other tertiary amines would accomplish similar job.…”

“…It has also been demonstrated that both the first hydrogen transfer from the platinum surface to the quinuclidine N of CD and the second one of the same hydrogen atom to the [5,15]. Accordingly, a simplified scheme of hydrogen transfer was suggested (Scheme 2 in ref.…”