Regioselective Olefination of 3‐Substituted Five‐Membered Heteroarenes
Hao Chen, Mirxan Farizyan, Manuel van Gemmeren
Abstract
Five‐membered heteroarenes constitute ubiquitous moieties in bioactive compounds and materials. It is thus not surprising that a direct and selective access to multiply substituted heteroarenes is considered as a highly attractive synthetic target. The direct olefination of such substrates, also known as cross‐dehydrogenative coupling has raised significant interest in this context. However, achieving site‐selectivity remains challenging with some substitution patterns such as 3‐substituted heteroarenes. Suitable catalyst systems and reaction conditions have to be identified, which enable the differentiation between the competing C2‐ and C5‐position. Over the last few years, substantial progress has been made to overcome this selectivity challenge mainly based on the use of novel ligand systems, which will be described herein.