Abstract
A new method of synthesis of an analogue of Bolm's 2,2'-bipyridine ligand based on the catalytic [2 + 2 + 2] cyclotrimerization of 1-halodiynes with nitriles was developed. Crucial step of the whole synthesis turned out to be homodimerization of a substituted 2-bromopyridine to the corresponding bipyridine, that was studied and optimized. The newly prepared bipyridine (S,S)-2 was then tested as a chiral ligand in metalcatalyzed enantioselective reactions. Out of the studied reactions the most promising results were obtained in epoxide ring opening (82% yield, 98% ee) and Mukaiyama aldol reaction (> 96% yield, 99/1 dr, 92% ee). In the case of Mukaiyama-aldol reaction as well as in the Michael addition, novel ligand 2 proved its robustness compared to Bolm's ligand as it was less sensitive to the purity of used reagents.