Cross-metathesis–based approaches to heteroaromatics: Combining catalysts for furan formation

Abstract

Ring-closing olefin metathesis (RCM) is an effective method for the formation of cyclic alkenes (1). Recently, the aromatization of RCM products has emerged as a topic of intensive investigation (2). In this context, a variety of regiocontrolled protocols have been developed for the synthesis of diverse heteroaromatic compounds, such as pyridines, pyridazines, pyrroles, quinolines, and furans (2). In all reported approaches, a key strategic consideration relates to the requirement of intermolecular fragment union in advance of the key RCM event. Strategies based on the use of intermolecular alkene metathesis, termed cross-metathesis, would potentially streamline access to aromatic structures by uniting the key steps of fragment coupling and alkene formation. However, the use of cross-metathesis in the synthesis of aromatic heterocycles is prohibited by the fact that trans-alkene products predominate (3, 4), which are unsuitable for cycloaromatization. A report by Donohoe and Bower (3) in this issue of …