C-H Amination of Arenes and Heteroarenes through a Dearomative (3 + 2) Cycloaddition.

The C-H amination of arenes offers a path for the synthesis of important arylamines that precludes the need for the prior functionalization of arene substrates, for example through halogenations or metalations. Most often, the direct C-H amination of arenes was achieved using transition metal or photoredox catalysis, through mechanisms ranging from electrophilic substitution to radical additions or nitrene insertions. Here, we report that azidium ions enabled the telescoped C-H amination of unactivated arenes and heteroarenes through a cycloaddition and C-N/N-N bond cleavage sequence. First, a dearomative (3 + 2) cycloaddition reaction between aromatic substrates and azidium ions generated fused triazolinium adducts. Subsequent treatment of the latter with a mild base, followed by thermolysis at moderate temperatures, achieved the synthesis of a diverse range of arylamines with a broad substrate scope. The synthetic versatility of this approach was showcased in the late-stage amination of natural products, pharmaceuticals, agrochemicals, and functional organic materials. Comparison with electrophilic halogenation/Buchwald-Hartwig amination or Ir-catalyzed borylation/Chan-Lam amination sequences revealed that the new C-H amination can provide a regio- or site-selectivity that complements these most widely used approaches for the synthesis of arylamines. Employing this protocol, uniquely regioselective postsynthetic double C-H aminations of coronene and [9]cycloparaphenylene were achieved for the first time.