Atroposelective Nenitzescu Indole Synthesis

In the past decade, compounds bearing a stereogenic C– N axis have gained significant attention ranging from ligand to drug design. Yet, the atroposelective synthesis of these molecules remains a considerable challenge. In contrast to recent methods utilizing more advanced chiral catalysts, a most simply accessed Jacobsen-type Chromium(III)-salen complex was herein utilized as chiral enantiopure Lewis acid catalyst for a highly atroposelective Nenitzescu indole synthesis. Mild reaction conditions afforded various 5-Hydroxybenzo[g]indoles with up to 97% yield. Moreover, through a simple work-up, very high enantiomeric excesses of up to 99% could be obtained.