Nitrogen-containing aromatic compounds are extremely important in the synthesis of pharmaceuticals and commodity chemicals. As such, new methods for the construction of nitrogen substituted arenes are in high demand. To achieve aryl C—N bond formation, previous methodologies have generally required a pre-installed functional handle on the arene in order to introduce the amine via a cross-coupling strategy (Belfield et al. (1999) Tetrahedron 55, 11399; Surry and Buchwald (2011) Chem. Soc. 2, 27; Hartwig (2008) Acc. Chem. Res. 41, 1534). More recent work has demonstrated the utility of arene C—H functionalization as a comparatively expedient strategy for the construction of N-arylated products; however, these methodologies are limited by several factors. The regiochemical outcome is largely dictated by a pre-installed Lewis basic directing group, which typically results in ortho selectivity (Tsang et al. (2005) J. Am. Chem. Soc. 127, 14560; Antonchick et al. (2011) Angew. Chem. Int. Ed. 50, 8605; Matsubara et al. (2014) J. Am. Chem. Soc. 136, 646; Tran et al. (2013) Angew. Chem. Int. Ed. 52, 6043). In the rare examples of arene amination where ortho addition is suppressed, differentiation between meta and para positions is not observed (Shrestha et al. (2013) J. Am. Chem. Soc. 135, 8480). Additionally, these protocols often require superstoichiometric equivalents of both arene and a terminal oxidant in order to achieve synthetically useful yields (Allen et al. (2014) J. Am. Chem. Soc. 136, 5607; Brachet et al. (2015) Chem. Sci. Advance Article; Marchetti et al. Org. Lett. ASAP), limiting the value of this method as a tool for late stage functionalization. Despite recent advances in arene C—H functionalization, this methodology has continued to be restricted by the regioselectivity of the reaction and the substrate scope. Thus, there remains a need for direct aryl amination reactions that are tolerant to a wide range of substrates and that are regioselective.
USPTO Backgrounds
USPTO Backgrounds