General Transition Metal-Free Synthesis of NH-Pyrroles from Secondary Alcohols and 2-Aminoalcohols.

A novel, transition metal-free and one-pot methodology to synthesize various substituted NH-pyrroles from readily available building blocks such as secondary alcohols and 2-aminoalcohols is described. The process is based on the venerable Oppenauer-Woodward oxidation, which uses benzophenone as an inexpensive reagent to achieve oxidation of secondary alcohols under mild condition to ketones, further in situ condensation with aminoalcohol, and oxidative cyclization to the target pyrrole ring. The reaction occurs under basic conditions, and features a broad substrate scope combined with very good tolerance for sensitive functional groups. This method can be used to synthesize various substituted pyrroles useful as a starting material for broad applications.