Acetic Acid-Catalyzed 1,6-Addition of Indolizine to para-Quinone Methides

This article describes the development of a metal and additive-free protocol that utilizes acetic acid (AcOH) as a catalyst for the C3-alkylation of indolizines using para-Quinone Methides (p-QMs) as an alkylation agent. The metal and additive free method offers an easy route to various substituted indolizine derivatives with good functional group tolerance and delivering acceptable good yields (up to 93%). A gram-scale synthesis and further product derivatization show the synthetic potential of this technique. The significance of these findings for medicinal chemistry makes this easy and green approach relevant to both medicinal and synthetic organic chemists, given the crucial role of indolizine in the pharmaceutical industry.