Generating conjugated boron heterocycles from Boroles.

Much of the existing methodology for the construction of cyclic systems does not translate for boron-containing rings. With both limited routes and the restricted amount of commercially available reagents, significant progress is necessary to expand the library of known boracycles. Boroles, highly reactive four π-electron heterocycles, are a family of compounds with the potential to serve to as effective reagents to produce boron heterocycles with extended conjugation. The current work capitalizes on this ring expansion methodology to access six- and seven-membered heterocycles via 1,1- and 1,2-insertion reactions, respectively. These findings demonstrate that boroles, and their benzofused relatives 9-borafluorenes, are synthons for the construction of unique boracyclic architectures.