Säurekatalysierte Umsetzungen von 2- Vinylanilin-Derivaten mit 1-Benzyl- und 1-Methylpiperidin-4-on: Eine Elegante Synthese Neuer Polycyclischer Indol-Derivate
✍ Scribed by Harald Walter; Hanspeter Sauter; Josef Schneider
- Publisher
- John Wiley and Sons
- Year
- 1993
- Tongue
- German
- Weight
- 465 KB
- Volume
- 76
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Acid‐Catalyzed Reactions of 2‐Vinylaniline Derivatives with 1‐Benzyl‐ and 1‐Methylpiperidin‐4‐one: An Elegant Synthesis of New Polycyclic Indole Derivatives
The reaction of 2‐vinylaniline derivatives with 1‐benzylpiperidin‐4‐one or 1‐methylpiperidin‐4‐one in toluene at temperatures between 115 and 120° with toluene‐4‐sulfonic acid as catalyst leads in good yields to a new class of polycyclic indole derivatives (Scheme 1, Table 1). The structure of the new diastereoisomerically pure racemic compounds 1–5 is determined by NMR‐spectroscopic methods. A reaction mechanism proceeding via cyclization of enamine 9, leading to a racemic, tricyclic reactive intermediate 10, and subsequent intramolecular 1,5‐dipolar cyclization as key steps in proposed for the formation of octahydropyrido[4′,3′:4]cyclobut[1,2‐b]indoles 1–5. The scope and limitations of the new method are discussed (see Table 2).