Abstract
Conformational dynamics can define the function of organocatalysts. While the accepted mechanism of Schreiner's catalyst features a double hydrogen bond to the substrate that only forms with the anti-anti conformation of its central thiourea group, our electronic-structure theory study reveals that binding of the model substrate methyl vinyl ketone prefers syn-anti conformations. We find a new mechanism featuring π stacking interactions and highlight the need for extensive structure searches for flexible molecules, especially when aiming for structure-based design of catalytic activity.
Highlights
C atalysts speed up reactions by binding substrates and by stabilizing transition states, thereby lowering reaction barriers
An example is illustrated in Figure 1a: Schreiner’s catalyst 1 catalyzes the Diels−Alder reaction of the dienophile methyl vinyl ketone (2) with cyclopentadiene (3) to the endo product 4.1 The established mechanism exploits the capability of NH protons in the anti-anti conformation of the central thiourea moiety to form a double hydrogen bond to the keto group of 2 (Figure 1b)
To enzymes,[3] their function is directly linked to their structure and their activity may be regulated via their conformational dynamics
Summary
C atalysts speed up reactions by binding substrates and by stabilizing transition states, thereby lowering reaction barriers. An example is illustrated in Figure 1a: Schreiner’s catalyst 1 catalyzes the Diels−Alder reaction of the dienophile methyl vinyl ketone (2) with cyclopentadiene (3) to the endo product 4.1 The established mechanism exploits the capability of NH protons in the anti-anti conformation of the central thiourea moiety to form a double hydrogen bond to the keto group of 2 (Figure 1b).
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