Synthesis of Flavones by Intramolecular O ‐Arylation of Unactivated Halogenated Aryl‐1,3‐diketones

Flavones are an important class of secondary metabolites in plants. Here we report a straightforward method for the conversion of unactivated halogenated 1,3‐biaryl‐1,3‐diketones into chromenone derivatives via intramolecular O ‐arylation under mild conditions. The resulting flavones were obtained in excellent to moderate yields. The synthesis typically proceeds according to a S N Ar mechanism under basic conditions without the requirement of any expensive catalyst. After successful implementation of fluorinated aryl diketones which lead to so far inaccessible fluoro‐substituted flavones, the scope of the reaction was also extended to chlorinated and brominated substrates as well as to substances with electron‐withdrawing or ‐donating substituents to demonstrate the functional group tolerance of the method. As an inverted reactivity was observed for bromo‐chloro diketones, quantum chemical calculations have been applied to support the proposed concerted mechanism (cS N Ar) for this case.