On-Water Vinylogous Mukaiyama–Michael Addition of Heterocyclic 2-Silyloxydienes to 1,2-Diaza-1,3-dienes: One-Pot Three-Step Entry to Functionality-Rich Pyrroles

✍ Scribed by Lucia Battistini; Luca Dell'Amico; Andrea Sartori; Claudio Curti; Giorgio Pelosi; Giovanni Casiraghi; Orazio A. Attanasi; Gianfranco Favi; Franca Zanardi

• Publisher: John Wiley and Sons
• Year: 2011
• Tongue: English
• Weight: 378 KB
• Volume: 353
• Category: Article
• ISSN: 1615-4150
• DOI: 10.1002/adsc.201100296

✦ Synopsis

Abstract

Densely substituted pyrrole‐carboxylates have been prepared in good yields in a highly practical one‐pot three‐step procedure. The key reaction of this process, which involves an uninterrupted sequence of reactions on‐water, is a diastereoselective vinylogous Mukaiyama–Michael addition reaction (VMMcR) of heterocyclic 2‐silyloxydienes to 1,2‐diaza‐1,3‐dienes mediated by water itself. Subsequent in situ addition of catalytic aqueous sodium carbonate promotes an intramolecular aza‐Michael addition with final ring‐opening and aromatization. The superior use of water in the VMMcR as both reaction medium and promoter vis‐à‐vis deployment of conventional Lewis acids in organic solvents is highlighted, which provides the best results in terms of reaction rate, efficiency, stereoselectivity, and overall practicality.