Iron-catalyzed C(sp²)-H and C(sp³)-H arylation by triazole assistance

Modular 1,2,3-triazoles enabled iron-catalyzed C-H arylations with broad scope. The novel triazole-based bidentate auxiliary is easily accessible in a highly modular fashion and allowed for user-friendly iron-catalyzed C(sp ²)-H functionalizations of arenes and alkenes with excellent chemo- and diastereoselectivities. The versatile iron catalyst also proved applicable for challenging C(sp³)-H functionalizations, and proceeds by an organometallic mode of action. The triazole-assisted C-H activation strategy occurred under remarkably mild reaction conditions, and the auxiliary was easily removed in a traceless fashion. Intriguingly, the triazole group proved superior to previously used auxiliaries. With a little help: A versatile iron catalyst allows the arylation of C(sp²)-H and C(sp³)-H bonds in the presence of a modular and removable triazolyldimethylmethyl (TAM) auxiliary, whose structure can be varied through 1,3-dipolar azide-alkyne cycloadditions.