Novel chiral diamino-oligothiophenes as valuable ligands in Pd-catalyzed allylic alkylations. On the "primary" role of "secondary" interactions in asymmetric catalysis

A new class of chiral C2-symmetrical diamino-oligothiophenes is described to be effective in catalyzing Pd-mediated asymmetric allylic alkylations in a highly enantioselective manner. The combination of experimental as well as crystallographic evidence revealed the key role played by sulfur-based heteroaromatic rings in the stereodiscriminating step of the procedure. In particular, unprecedented non-covalent secondary interactions between the inner thiophene and the metal center proved to be essential to create the stereochemical environment necessary in order to guarantee excellent levels of chemical and optical yields.