A novel synthesis of bis(benzoxazole) derivatives via tandem Claisen rearrangement

The one-pot thermal reaction of 1,3-bis(o-acylamino phenyloxy)-2-methylene propane derivatives gave either the bis(benzoxazole) derivatives or the benzodihydrofuran derivatives via tandem Claisen rearrangement in good yields. The reaction courses strongly depend upon the reaction conditions such as the solvent or the substituent of the carbamoyl moiety. The resulting bis(benzoxazole) derivative having a 2-aromatic substituent emits blue fluorescence and has almost the same fluorescence quantum yield as the model mono(benzoxazole) compound.