An Efficient One‐Step Synthesis of Piperidin‐2‐yl and Pyrrolidin‐2‐yl Flavonoid Alkaloids through Phenolic Mannich Reactions

An efficient one‐step synthesis of piperidin‐2‐yl and pyrrolidin‐2‐yl flavonoid alkaloids was achieved in good to excellent yields by a highly regioselective phenolic Mannich reaction of chrysin with cyclic imines or iminium salts. Performing the reaction in a mixture of H 2 O/THF in the absence of an external reagent afforded the C‐6 alkylated product exclusively. The same reaction in water in the presence of NaOH provided the C‐8 alkylated flavonoid as a major product. The reaction has been successfully extended to simple phenols.