Dibenzoacridines: synthesis by alkyne-carbonyl-metathesis and properties.

Dibenzo[,]acridines and regioisomeric dibenzo[,]acridines were synthesized from a common starting material, 2,3,5,6-tetrachloropyridine, by combination of site-selective cross-coupling reaction followed by ring-closing alkyne-carbonyl metathesis using simple Brønsted acids. The two regioisomeric series were accessed by change of the order of Sonogashira and Suzuki-Miyaura reactions. The optical properties of the products were studied by steady-state absorption spectroscopy and time-resolved emission measurements. The electronic properties of the products were further elucidated by DFT calculations.