Electrophilic Reactivities of Substituted Cyclopropanes

Cyclopropanes are small three-membered all-carbon rings. The making of cyclopropanes costs some extra energy because of the strain introduced by the compressed chemical bonds in these molecules. The energy stored in the three-membered ring is not lost, however, but can be used to promote reactions, in which the ring is opened. This is why synthetic chemists have been able to utilize cyclopropanes for many decades to produce a broad range of new products. However, the ability to predict if (and how fast) reactions of cyclopropanes take place has remained challenging and is not well explored to date. This project is going to investigate the physicochemical properties of cyclopropanes to enhance the fundamental understanding of their reactivity in ring-opening reactions. In an effort to enable informed planning of syntheses with cyclopropanes, this project will systematically study the factors that govern their polar reactivity. To achieve this, several cyclopropanes with additional functional groups will be prepared. The functional groups attached to the cyclopropanes are used to tune their reactivity, and the rates of cyclopropane reactions with reaction partners will be measured. To gain deeper insights into the individual steps in the molecular transformations, the experimentally observed rates will then be compared with modelled data from quantum-chemical computational methods. At the end of the first phase of the project (24 months at the LMU München), it is anticipated that the results can be used to predict straightforwardly whether cyclopropanes will react under certain conditions with a diverse set of reaction partners. The approach path of reaction partners to the cyclopropanes can be directed by interactions with catalyst molecules. Thus, the spatial structure of the products can be controlled. On the basis of the fundamental understanding of the cyclopropane reactivity, synthetic methods that use cyclopropanes in combination with catalysts will be developed to achieve sophisticated molecular architectures. The application of catalysts in cyclopropane reactions will be explored during the return phase of the project (12 months at the JKU Linz).