CBr4 catalyzed activation of α,β-unsaturated ketones.

We have shown here that weak interactions such as halogen bonding (XB) can be used to activate the carbonyl group of α,β-unsaturated ketones. Carbon tetrabromide (CBr4) has been used as the sole reagent for the selective synthesis of flavanones and aza-flavanones from the corresponding 2'-hydroxy- and 2'-aminochalcones under metal-free and additive-free conditions. DFT calculations support the catalytic role of XB between the oxygen of chalcones and CBr4 in these reactions.