Unprecedented Strong Lewis Bases—Synthesis and Methyl Cation Affinities of Dimethylamino-Substituted Terpyridines

摘要

A versatile method for the synthesis of functional-ized 2,2':6',2"-terpyridines by assembly of the terminal pyridine rings is presented. The cyclization precursors—bis-β-ketoena-mides—are prepared from 4-substituted 2,6-pyridinedicarbox-ylic acids and acetylacetone or its corresponding enamino ketone. Treatment with trimethylsilyl trifluoromethanesulfo-nate induces a twofold intramolecular condensation providing an efficient access to 4,4"-di- and 4,4',4"-trifunctionalized 6,6"-dimethy1-2,2':6',2"-terpyridines. Using this method, hitherto unknown 4,4"-bis(dimethylamino)- and 4,4',4"-tris(dimethyl-amino)terpyridines have been prepared that show remarkably high calculated Lewis basicities.