Convenient decagram scale preparation of ethyl 3,4-diethylpyrrole-2-carboxylate, a versatile precursor for pyrrole-based macrocycles and chromophores

Abstract

Herein, we describe a detailed preparation of the versatile pyrrole building block 3,4-diethylpyrrole-2-carboxylate (1), a key structural feature in various porphyrins, porphyrinoids, and other chromophores. 1 was prepared via a one-pot DBU catalyzed Henry reaction and acid catalyzed acetylation followed by an aqueous workup and telescoping through an adapted Magnus-Schöllkopf-Barton-Zard cyclization protocol from commercial starting materials. The three-step preparation utilized new chemistry, requires only one formal purification step, and affords 1 at 86% yield and >99% purity on a decagram scale.