Selective Functionalization of Arenes and Heteroarenes via S _E Ar and Related Transformations

Abstract

Electrophilic aromatic substitution (S E Ar) is among the classic routes toward the functionalization of aromatic CH bonds. There are a myriad of functionalities that can be introduced into aromatic systems via S E Ar, including but not limited to halogens, perfluoroalkyl, sulfenyl, alkyl, acyl, and nitro substitutions. S E Ar has become increasingly common in modern synthetic chemistry as many of the potential products, particularly halogenated arenes, have become important building blocks in drug discovery and other endeavors. Despite its widespread application, S E Ar is hindered by several issues that have historically prevented its use on more complex systems. These issues include a reliance on strongly acidic conditions and a lack of regioselectivity. In this article, we will discuss recent advances, from the past vicennial, in S E Ar methodology with a focus on new reagents and catalytic strategies that alleviate many of these issues for halogenation, sulfenylation, and perfluoroalkylation.