Synthesis of 1,2,3,5-tetrasubstituted-1,2-azaborines

Tetrasubstituted arenes are important building blocks in many bioactive compounds. The development of 1,2-dihydro-1,2-azaborine, a surrogate of quintessential benzene that substitutes a C=C bond with isoelectronic and isostructural B–N bond, extends the chemical space of the compounds relevant to biomedical research and materials science. To further investigate the potential applications of 1,2-dihydro-1,2-azaborines, we herein disclose the synthesis of 1,2,3,5-tetrasubstituted-1,2-azaborines. N-TBS-B-Cl-1,2-azaborine, developed by Liu group in 2009, was halogenated at C3 and C5 positions and underwent transitionmetal-catalyzed cross-coupling reactions to yield 1,2,3,5-tetrasubstituted-1,2-azaborines. The 1, 2, 3, and 5 positions of 1,2,3,5-tetrasubstituted-1,2-azaborines could be selectively functionalized by varieties of groups. The preparation of 1,2,3,5-tetrasubstituted-1,2-azaborines opens the possibility of incorporating 1,2-azaborines in biologically active molecules, which may provide new opportunities in drug design.