Benzylic carbocations bearing an ortho- or para-hydroxyl group can be stabilized by forming quinone methides, which have been explored in enantioselective synthesis. However, those with a meta-hydroxyl group have remained almost unexplored in organic synthesis. The lack of resonance stabilization by a typical quinone methide form renders them not only difficult to generate, but also challenging to control for asymmetric bond formation. Here we report an efficient catalytic enantioselective reaction between meta-hydroxyl triarylmethanols and indoles, via triaryl carbocations, for the synthesis of tetraarylmethanes with excellent enantiocontrol. Control experiments reveal that the meta-hydroxyl group is essential for both reactivity and stereocontrol. Ortho-directing groups (alkoxyl, sulfenyl or fluoro) benefit enantiocontrol through secondary hydrogen-bonding interactions, but are not required for reactivity. The resulting tetraarylmethane products show anticancer activities, through a mechanism distinct from that of classical anticancer drugs.

带有邻位或对位羟基的苄基碳阳离子可以通过形成醌甲基化物来稳定，这已在对映选择性合成中得到探索。然而，那些具有间位羟基的化合物在有机合成中几乎仍未得到探索。典型的醌甲基化物形式缺乏共振稳定性使得它们不仅难以生成，而且还难以控制不对称键的形成。在这里，我们报告了间羟基三芳基甲醇和吲哚之间通过三芳基碳阳离子进行的有效催化对映选择性反应，用于合成具有出色对映体控制的四芳基甲烷。对照实验表明元-羟基对于反应性和立体控制都是必不可少的。邻位基团（烷氧基、硫基或氟）通过二次氢键相互作用有利于对映体控制，但不是反应性所必需的。由此产生的四芳基甲烷产物通过不同于经典抗癌药物的机制显示出抗癌活性。