Metal-Free Directed Diastereoselective C2,C3-Cyclopropanation of Substituted Indoles with Diazoesters.

A metal-free directed C2,C3-cyclopropanation of suitably substituted indoles with α-diazo esters has been accomplished for the diastereoselective synthesis of cyclopropane-fused indolines in good yield. This method works well with a wide range of differently substituted α-diazo esters as well as indole derivatives and shown excellent compatibility for diverse directing group like pyridyl, pyrimidyl, acyl, and urea derivatives. Furthermore, the preliminary mechanistic investigation revealed the importance of directing group for the developed transformation.