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 H2O/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.

中文翻译：

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酚类曼尼希反应一步法合成哌啶-2-基和吡咯烷-2-基黄酮类生物碱

通过白杨素与环状亚胺或亚胺盐的高度区域选择性酚类曼尼希反应，实现了哌啶-2-基和吡咯烷-2-基黄酮类生物碱的高效一步合成，收率良好至极好。在不存在外部试剂的情况下在 H2O/THF 的混合物中进行反应，仅提供 C-6 烷基化产物。在 NaOH 存在下在水中的相同反应提供 C-8 烷基化黄酮类化合物作为主要产物。该反应已成功扩展到简单的酚类。