Revisiting Classical Pummerer Cyclization Reaction: A Key Strategy for the Synthesis of (±)‐Quinagolide

Abstract

AbstractA formal synthesis of (±)‐quinagolide using β‐alanine as a starting material has been achieved. Late stage intramolecular classical Pummerer reaction has been used as a key synthetic tool to construct octahydrobenzo[g]quinoline skeleton of quinagolide. Conjugative reduction of olefin, regioselective C‐alkylation over O‐alkylation of β‐ketoester followed by retro‐Dieckmann/ Dieckmann reaction sequence has been used as a key reaction sequence to achieve prerequisite sulfoxide for the Pummerer reaction. While revisiting the classical Pummerer reaction, the one‐pot sequential thionium ion induced cyclocarbamation followed by N‐carbamate deprotection and Friedel‐Crafts type Pummerer cyclization was observed as an important finding of the present work.