Organocatalysis combines the concepts of molecular recognition as well as supramolecular chemistry with enzyme-like catalytic activity. Noting that about half of all enzymes do not carry a metal center it is obvious that this approach has long been underrated. Although this is a new and emerging field, it is already possible to catalyze many types of organic reactions with small, well-designed organic molecules. This circumvents the use of often toxic metals (leading to environmentally benign methods, green chemistry), and the preparation of the catalysts is much easier as it relies on the well-developed synthetic arsenal for tailor-making organic structures. In our group we have developed thiourea-based catalysts that are effective in catalyzing a variety of transformations such as Diels-Alder reactions, acetalization, THP-protection, stereoselective acyl transfer, reductions, epoxide openings and many more. Currently, we develop reactions and reaction sequences utilizing cooperative catalysis and multicatalysis.
TEMPO-functionalized mesoporous silica particles as heterogeneous oxidation catalysts. Julia Schulze, Julia Migenda, M. Becker, Sören M. M. Schuler, Raffael C. Wende, Peter R. Schreiner, Bernd M. Smarsly
J. Mat. Chem. A 2020, in press.
In Situ Switching of Site-Selectivity with Light in the Acetylation of Sugars with Azopeptide Catalysts. Dominik Niedek, Frederik R. Erb, Christopher Topp, Alexander Seitz, Raffael C. Wende, André K. Eckhardt, Jonas Kind, Dominik Herold, Christina M. Thiele and Peter R. Schreiner
J. Org. Chem. 2020, 85, in press. DOI: 10.1021/acs.joc.9b01913
We present a novel concept for the in situ control of site-selectivity of catalytic acetylations of partially protected sugars using light as external stimulus and oligopeptide catalysts equipped with an azobenzene moiety. The isomerizable azobenzene-peptide backbone defines the size and shape of the catalytic pocket, while the π-methyl-l-histidine (Pmh) moiety transfers the electrophile. Photoisomerization of the E- to the Z-azobenzene catalyst (monitored via NMR) with an LED (λ = 365 nm) drastically changes the chemical environment around the catalytically active Pmh moiety, so that the light-induced change in the catalyst shape alters site-selectivity. As a proof of principle, we employed (4,6-O-benzylidene)methyl-α-