Facile Synthesis of Alternating Benzene–Pyrrole Oligomers by Cyclization of Propargylic Dithioacetals and Imines and Their Fluorescent Properties

Alternating benzene–heteroaryl oligomers possess fascinating optoelectronic properties and a wide range of applications. This article presents the facile synthesis of benzene–pyrrole oligomers with diverse functional groups and the elongated alternating heterocycle–benzene–pyrrole oligoaryls. The syntheses are based on a one‐pot, three‐step reaction of propargylic dithioacetals and imines. The subtle influence of functional groups, such as ether, ester, hydroxy, and dithiacetal groups on the peripheral benzene rings, on the reaction, has been explored and the reaction conditions were finely changed accordingly to achieve reasonable yields. The elongation could be accomplished by using a similar procedure. The fluorescent properties of original and elongated alternating benzene–pyrrole oligomers were determined. Theoretical calculations preliminarily reveal that the fluorescent intensity is closely related to the molecular geometry and to the HOMO/LUMO energy difference in the ground state.