Cyclic Anti-Azacarboxylation of 2‑Alkynylanilines with Carbon Dioxide

Direct anti-azacarboxylation of 2-alkynylanilines with CO2 mediated by ZnEt2 was observed to afford indole-3-carboxylic acids, a class of important compounds for the synthesis of many biologically active compounds, efficiently under 1 atm of CO2. The readily available nature of the different starting materials and tolerance of various functional groups provide vast opportunities for the efficient construction of diversified libraries for bioactive compounds listed in Figure 1. As an example, this methodology has been applied to the synthesis of Lotronex, a drug molecule used for the treatment of irritable bowel syndrome.