Development and application of efficient methods for extension of π-conjugated systems by catalytic substitution reactions via chelation-assisted cleavage of unreactive aromatic carbon bonds

Direct functionalization of unreactive bonds catalyzed by transition metal complexes has become a powerful tool in organic synthesis and has been studied extensively by many researchers. Our research group has been exploring regioselective functionalization via chelation-assisted cleavage of unreactive bonds by transition metal catalysts. Here we describe our recent efforts toward development of efficient methods for construction of π-conjugated systems by catalytic substitution via chelation-assisted cleavage of unreactive aromatic carbon-hydrogen and -heteroatom bonds. Ruthenium catalysts were employed to cleave aromatic carbon-hydrogen, carbon-oxygen, carbon-nitrogen, and carbon-fluorine bonds (aromatic carbon bonds) at ortho positions of directing groups and to introduce aryl, alkenyl, and carbonyl groups onto the aromatic rings. Application of these methods for short syntheses of substituted fused aromatic compounds such as twisted anthracenes, pentacenes, dibenzo[a,h] anthracenes, and picenes is also described.