Dynamic stereochemistry of chiral axes. Design and synthesis of stable atropisomers.

In organic chemistry, dynamic processes involving the conformational exchange are ubiquitous phenomena that occur even in the simplest molecule. The study of the preferential disposition of functional groups and the definition of new interaction is therefore, of vital importance in order to foresee the spatial shape of organic molecules. In the following work, this has been accomplished by: first, an in silico DFT analysis of the conformers, second an experimental evaluation of the relative stability of the predicted conformers using the Dynamic-NMR, Dynamic-HPLC, and kinetic studies, and last the assessment of the potential absolute configuration by mean Electronic Circular Dichroism spectroscopy. The work herein reported finally aim to define the border between unstable conformations and stable ones (configurations). This border has been explored from both sides: 1) the stereodynamic side, that includes low energy process where the stereochemistry is not stable due to a low energy barrier. In this context are analysed molecules displaying long range interactions where only conformational changes are considered; 2) the stereostable side, where the energy barrier between conformers is high enough to generate distinct molecules. In this framework, the design and the synthesis of stereogenic axes in scaffold that cannot bear conventional stereogenic center are reported. This work gives a well-rounded view of the conformational analysis of organic molecules providing new insight in the interaction within stereolabile conformations as well as the generation of new stereostable conformers by the insertion of steric demanding groups.