Synthesis and Photophysical Properties of Polycarbo-Substituted Quinazolines Derived from the 2-Aryl-4-chloro-6-iodoquinazolines.

The reactivity of the 2-aryl-4-chloro-6-iodoquinazolines towards palladium catalyzed sequential (Sonogashira/Suzuki-Miyaura) and one-pot two-step cross-coupling (bis-Sonogashira, and successive Sonogashira/Stille) reactions to afford novel unsymmetrical polycarbo-substituted quinazolines has been evaluated. In contrast to the chloro-bromo substituted quinazolines in which selectivity has been previously found to generally favor substitution at the more activated C(4)-Cl bond over the weaker Csp(2)-Br bond, substitution in the case of the chloro-iodo derivatives favors cross-coupling through the intrinsically more reactive Csp(2)-I bond. The electronic absorption and emission properties of the prepared 2,3-diaryl-6-(phenylethynyl)quinazolines were studied in solvents of different polarity (dichloromethane, toluene, DMF, methanol) and CH2Cl2-TFA mixture using UV-Vis and emission spectroscopic techniques complemented with density functional theory method to establish the effect of substituents on intramolecular charge transfer properties.