TRIP, catalysis

Bringing together the concept of aminocatalysis and the activation mode of chiral phosphoric acids. List and co-workers introduced the concept of asymmetric counter anion directed catalysis (ACDC) and they applied this idea to the asymmetric reduction of enals 47 (Scheme 23) [ 135]. The catalytic species is formed by an achiral ammonium ion 60 and a chiral phosphate anion 59 derived from 3,3 -bis(2,4,6-triisopropylphenyl)-1,1 -binaphthyl-2,2 -diyl hydrogen phosphate 9 (TRIP). 

In the same year, Zhou and List reported a novel one-pot tandem reaction which, for the first time, combined chiral Bronsted acid catalysis with enamine and iminium catalysis. Later, on the basis of control experiments and ESI-MS/MS analysis, a reasonable mechanism was proposed (Scheme 2.2). The initial step of this tandem reaction was mediated by achiral /j-ethoxyaniline (PEP-NH2) and chiral phosphoric acid (R)-TRIP either reagent alone was inefficient in promoting this aldol condensation to afford the first iminium intermediate. The following step was a conjugate reduction which was also Bronsted acid and amine co-catalysed, and no further conversion took place in the absence of either catalyst. The final step was an acid-catalysed reductive amination. This novel sequence allowed the highly enantioselective synthesis of pharmaceutically active chiral ds-3-substituted cyclohejyl or heterocyclohexyl amines in high diastereo- and... 

We traveled through several basic kinetic concepts applied to catalysis, with some emphasis on organometaUic systems. In this trip, several misconceptions ( myths ) have been reviewed, trying to make some sense in the analysis of catalytic cycles. As said before, most of these misconceptions have been corrected a long time ago, and many researchers certainly know how to handle them (there is nothing new under the sun after all). However, that does not mean that they were uprooted from the textbooks, and consequently they are too common in research papers. Let us discuss one last myth. 

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