Synthesis of Cyclic and Macrocyclic Ethers Using Metathesis Reactions of Alkenes and Alkynes

✍ Scribed by Elisabetta Groaz; Donatella Banti; Michael North

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 330 KB
• Volume: 2007
• Category: Article
• ISSN: 1434-193X
• DOI: 10.1002/ejoc.200700291

✦ Synopsis

Abstract

The metathesis transformations of cyclohexanes and cyclohexenes bearing allylic and/or propargylic ether substituents has been investigated. A range of products containing fused 6,8‐bicyclic ring systems resulting from alkene and/or enyne metatheses were obtained using first and second generation, well defined alkylidene ruthenium catalysts. However, the unstrained cyclohexene unit did not participate in any of these metathesis processes, even though doing so would have led to a thermodynamically more stable product. This contrasts with previous results on similar compounds and on the corresponding amino‐substituted cyclohexenes. The synthesis of dienes and dihydrofurans by metathesis processes involving the side chains of suitable cyclohexene ethers is also reported. When the unstrained cyclohexene unit was replaced by a norbornene group, the strained alkene did participate in a cascade of alkene and enyne metatheses. This chemistry was extended to alkyne metatheses of cyclohexene and norbornene esters, leading to 6,12‐fused cycloalkynes which would subsequently undergo further enyne and/or alkene metatheses. This culminated in the development of the first one‐pot metathesis process in which alkyne, enyne and alkene metathesis reactions initiated by two different catalysts all occur sequentially to form a 5,12‐fused bicyclic diene product. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)