Heterole-Fused [20]- and [22]Smaragdyrins and Fused-Heterole-Bridged [20]- and [22]Smaragdyrin Dimers

Abstract

In order to examine the effects of the fused heterole on the electronic properties of aromatic and antiaromatic smaragdyrins, 2,3-thiophene- and 2,3-indole-fused [20]smaragdyrins were synthesized by Suzuki-Miyaura coupling and subsequent oxidative fusion reaction, and were reduced with NaBH₄ to the corresponding [22]smaragdyrins. Fused-thiophene- and fused-pyrrole-bridged [20]- and [22]smaragdyrin dimers were also synthesized in the similar manner. The installed fused heteroles mitigate the paratropic ring current of the [20]smaragdyrin but exert only minor effects on the diatropic ring current of the [22]smaragdyrin. Similar features are also observed for the fused-heterole-bridged [20]- and [22]smaragdyrin dimers.