Modular Syntheses of Star-Shaped Pyridine, Bipyridine, and Terpyridine Derivatives by Employing Sonogashira Reactions
D. Trawny, V. Kunz, H.-U. Reissig – 2014
A simple and flexible synthesis for a series of star-shaped pyridine, bipyridine, and terpyridine derivatives is reported by using a modular approach that combines the use of a ligand, spacer, and core unit. A fairly efficient method to prepare 4′-nonafloxy-functionalized terpyridine derivatives is described. The building blocks that contain the functionalized pyridine, bipyridine, or terpyridine derivatives were linked to different C3-symmetrical core units. In most cases, Sonogashira reactions were employed in the crucial final steps of the synthesis. A star-shaped dodecafluorinated compound was also prepared in a straightforward fashion. A simple procedure for the preparation of partially silylated 1,3,5-triethynylbenzene derivatives is presented, which provides an approach to C2-symmetrical star-shaped compounds that have only one terpyridine and two terphenyl units as “dummy” ligands. The absorption and emission spectra of the fully conjugated C3-symmetrical pyridine derivatives were systematically investigated, and fairly large Stokes shifts were observed.