Fürstner Indole Synthesis

Abstract

Abstract This reaction is the low‐valent titanium‐induced or ‐mediated intramolecular reductive alkylidenation of alkyl (or aryl) 2‐ N ‐acylamidophenyl ketones to afford 2,3‐disubstituted indoles and is known as titanium‐induced intramolecular oxoamide coupling or the zipper reaction. This reaction is referred to as the Fürstner indole synthesis. In theory, the Fürstner indole synthesis is an extension of the McMurry coupling. However, the Fürstner indole synthesis is different from the normal McMurry coupling in both reaction scope and mechanism and an in‐depth comparison has been presented. The Fürstner indole synthesis has been successfully used in the synthesis of 2,3‐disubstituted indoles on a multigram scale as well as a series of indole‐containing compounds, but it has been found to be problematic for substrates with two branched alkyl groups at C‐2 and C‐3, and for the preparation of 3‐unsubstituted indoles from o ‐ N ‐acylated benzaldehydes.