Oxidative Coupling Reactions Mediated by MoCl5 Leading to 2,2′-Cyclolignans: The Specific Role of HCl

✍ Scribed by Beate Kramer; Roland Fröhlich; Siegfried R. Waldvogel

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 175 KB
• Volume: 2003
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/ejoc.200300263

✦ Synopsis

Abstract

The scope and performance of oxidative coupling reaction using MoCl~5~ can be significantly improved by employing Lewis‐acidic additives such as TiCl~4~, SnCl~4~, or SiCl~4~. Since the by‐product, HCl, plays a particular function as an inhibitor for MoCl~5~ by forming chloro complexes, exploiting typical chloride scavengers, like silver salts or molecular sieves, is also successful. A variety of differently substituted 1,4‐diarylbutanes 4a−g, which were easily synthesized by a modular approach, were subjected to the dehydrodimerization reaction. For the oxidative coupling reaction, a para‐substitution pattern — with a donor group on the aryl system — is pivotal for allowing access to the 2,2′‐cyclolignans 5a,e−g. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)