Regioselective synthesis of optically active (pyrazolyl)pyridines with adjacent quaternary carbon stereocenter: chiral N,N-donating ligands

Novel optically active 2-(pyrazol-1-yl)pyridines have been prepared using resolved the O-methyl ether of atrolactic acid as a source of the adjacent quaternary carbon stereocenter. Different regioisomers were formed selectively in the reaction of 2-hydrazinopyridines with the chiral 1,3-diketone and in the nucleophilic substitution of 2-chloropyridines with the potassium salt of the chiral pyrazole. The second route gave 2-(pyrazol-1-yl)pyridines with the stereogenic center neighboring the coordinating nitrogen in the pyrazole ring. Also, new C2-symmetric chiral ligands based on 2,6-bis(pyrazolyl)pyridine and 6,6′-bis(pirazolyl)-2,2′-bipyridine structures were obtained.