Selective Functionalization of Aminoheterocycles by a Pyrylium Salt

Article abstract of DOI:10.1002/anie.201806271

The functionalization of aminoheterocycles by using a pyrylium tetrafluoroborate reagent (Pyry-BF₄) is presented. This reagent efficiently condenses with a great variety of heterocyclic amines and primes the C?N bond for nucleophilic aromatic substitution. More than 60 examples for the formation of C?O, C?N, C?S, or C?SO₂R bonds are disclosed herein. In contrast to C?N activation through diazotization and polyalkylation, this method is characterized by its mild conditions and impressive functional-group tolerance. In addition to small-molecule derivatization, Pyry-BF₄ allows the introduction of functional groups in a late-stage fashion to furnish highly functionalized structures.