# Regioselective Stepwise Synthesis of Unsymmetrical 1,2,5-Triarylpyrroles via Palladium-Catalyzed Decarboxylative Cross-Coupling and C–H Arylation

## TL;DR

This paper introduces a new method to synthesize complex pyrrole molecules used in medicine, using a stepwise chemical process.

## Contribution

A modular, regioselective synthesis of unsymmetrical 1,2,5-triarylpyrroles via decarboxylative cross-coupling and C–H arylation is presented.

## Key findings

- A stepwise synthesis of unsymmetrical 1,2,5-triarylpyrroles was successfully achieved.
- The method uses pyrrole ester building blocks and palladium-catalyzed reactions.
- The scope and limitations of the synthetic sequence were experimentally determined.

## Abstract

Pyrrole derivatives are natural organic molecules that are important to the pharmaceutical industry due to their occurrence in nature and their use in a wide range of medical applications. In general, non-symmetric, 1,2,5-triaryl-substituted pyrroles are prepared either by Paal–Knorr condensation or cycloaddition that present synthetic challenges particularly if late-stage functionalization is required. The present study describes a modular approach to synthesizing 1,2,5-triarylpyrroles containing three different arene substituents. Using pyrrole ester building blocks, a sequence of decarboxylative cross-coupling and C–H arylation provides unsymmetrical 1,2,5-triarylpyrroles in a regioselective, stepwise manner; the scope and limitations of the sequence are disclosed.