Site-selective [4 + 2] and [4 + 3] annulations of arylboronic acids with cyclic diaryliodoniums for polycyclic arene synthesis

Abstract

A facile access to functionalized triphenylenes through tandem Suzuki–Miyaura and intramolecular C–C coupling between arylboronic acids and cyclic diaryliodonium salts is disclosed. More importantly, this protocol can be extended to large-sized boronic acids involving naphthalene, anthracene, pyrene, triphenylene, dibenzo[b,d]thiophene, and carbazole units bearing two competitive C(sp²)–H bonds, and all these cases show good α-selectivity. This α-selective [4 + 2] annulation provides a fast access to π-extended polycyclic arenes including [4]- and [5]carbohelicenes as well as their aza-/thia-hybrids. Moreover, the double annulation version on diboronic acids is presented as an efficient and fast route toward (helical) nanographenes. In addition, a selective Suzuki coupling and N–H activation cascade has been realized through the [4 + 3] annulation of (9H-carbazol-1-yl)boronic acids and cyclic iodoniums, providing nonalternant molecules bearing N-doped pentagon–heptagon pairs in good yields.