Construction of 2‐Methylindoles Using Solid Calcium Carbide as a Substitute for Gaseous Acetylene.

An efficient method for the construction of 2‐methyl‐1‐sulfonylindoles and 2,3‐dimethyl‐1‐sulfonylindoles using solid calcium carbide as an alkyne source and o‐sulfonamidobenzaldehyde hydrazones or o‐sulfonamidoacetophenone hydrazones as starting materials is described. This protocol has the salient feature of the use of an inexpensive, abundant and easy‐to‐handle solid alkyne source, effectively avoiding the use of flammable and explosive gaseous acetylene as an original alkyne source. Noble‐metal‐free conditions, wide substrate scope, high yield, and simple workup procedures are advantages of this method. The transformation can also be carried out on a gram scale. [ABSTRACT FROM AUTHOR]