C–H Amination of Unactivated 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 of-ten, 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 be-tween 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 di-verse range of arylamines with a broad substrate scope. The synthetic versatility of this approach was show-cased in the late-stage amination of natural products, pharmaceuticals, agrochemicals, and functional organic materials. Comparison with electrophilic halogenation / Buchwald-Hartwig amination or Ir-catalyzed boryla-tion / 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.