Free Amine and Alcohol As the Director for Regioselective C(sp2)–H Bond Functionalization

Abstract

Transition-metal-catalyzed C(sp2)–H bond functionalization is recognized as a revolutionized strategy for mainstream organic synthesis to forge structurally complex biologically relevant heterocyclic frameworks in an efficient way. For this purpose, in the past decades, there have been significant developments in the realm, proclaiming improved site-selectivity by exploiting a class of directing groups (DGs). The DG installation, especially for the amine and alcohol and its further removal after the reaction, needs additional steps. In this regard, the use of free amine and alcohol as DGs in their native form is very advantageous. Due to its innate reactivity, the emergence of these potent DGs paves the way for a wide range of C–C and C–heteroatom bond formation as well as annulation cascades reaction. In this review, the aromatic sp2-C–H functionalization directed by free amine and hydroxyl is shown to be useful for the construction of three to seven-membered N- and O-heterocycle motifs.