A convergent, modular approach to functionalized 2,1-borazaronaphthalenes from 2-aminostyrenes and potassium organotrifluoroborates.

Azaborines are an important class of compounds with applications in both medicinal chemistry and materials science. The first borazaronaphthalene, 2-chloro-2,1-borazaronaphthalene, was reported in 1959; however, access to more highly functionalized substructures has been limited because of the harsh reaction conditions required to displace the chloride on boron. A convergent approach has been developed to synthesize disubstituted 2,1-borazaronaphthalenes from N-substituted 2-aminostyrenes and potassium organotrifluoroborates, where the potassium organotrifluoroborate is converted to the active R-BX2 species (X = Cl or F) in situ by addition of a fluorophile. Starting from aryl-, heteroaryl-, alkynyl-, alkenyl-, and alkyltrifluoroborates, a library of highly functionalized 2,1-borazaronaphthalenes were synthesized in one step under mild, transition-metal-free conditions.