Enantioselective Synthesis of Pyridines with All‐Carbon Quaternary Carbon Centers via Cobalt‐Catalyzed Desymmetric [2+2+2] Cycloaddition

Abstract

AbstractA Co‐catalyzed enantioselective desymmetric [2+2+2] cycloaddition for synthesis of pyridines with all‐carbon quaternary carbon centers has been developed. The regio‐ and enantioselectivities are controlled by the inherent nature of terminal alkynes and the substituents on the bisoxazolinephosphine ligands. Pyridines with 5‐substitutents could be obtained with >20:1 regioselectivity and up to 94 % ee when terminal alkyl, alkenyl or silyl alkynes and DTBM/Ph‐based NPN* ligand L6 were used. Terminal aryl alkynes and Ph/Bn‐based ligand L4 leads to formation of pyridines with 6‐substitutents in up to 99 % ee.