A Novel Coupling 1,3-Dipolar Cycloaddition Sequence as a Three-Component Approach to Highly Fluorescent Indolizines

✍ Scribed by Alexandru V. Rotaru; Ioan D. Druta; Thomas Oeser; Thomas J. J. Müller

• Book ID: 102261000
• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: German
• Weight: 362 KB
• Volume: 88
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.200590141

✦ Synopsis

Abstract

Indolizines 4 and biindolizines 6 can be synthesized in moderate yields in a consecutive one‐pot three‐component process by a coupling/1,3‐dipolar cycloaddition sequence of a (hetero)arenecarbonyl chloride 1, a terminal alkyne 2, and a suitable 1‐(2‐oxoethyl) pyridinium bromide 3 or 5, respectively (Schemes 1 and 2). After the Sonogashira coupling, a [2+3] cycloaddition of the in situ formed pyridinium ylide, an allyl‐type 1,3‐dipole, furnishes a cycloadduct that is instantaneously oxidatively aromatized to give the highly fluorescent indolizine derivatives that were unambiguously characterized by an X‐ray‐structure analysis of compound 4d (Fig. 1). Additionally, fluorescence studies with pyridinyl‐substituted representatives reveal not only that indolizines and biindolizines are highly interesting fluorescence dyes but that their fluorescence color can also be reversibly switched upon altering the pH of the medium.