Synthetic Approaches to Benzothienoindole Frameworks: A Review

Polyacenes and their heteroatom‐containing analogs have become essential components in organic electronic materials due to their extended π‐conjugation, efficient charge transport, and tunable optoelectronic properties. Heteroacenes incorporating nitrogen and sulfur exhibit improved electronic modulation, enhanced stability, and superior solid‐state organization, thereby expanding their utility in advanced optoelectronic devices. Benzothienoindole is a unique class of nitrogen‐ and sulfur‐containing fused heteroacenes, formed by combining indole and benzothiophene units, and is available as four regioisomers with distinct structural and electronic properties. The review provides an extensive summary of the synthetic methodologies for constructing benzothienoindole frameworks, including one‐pot, multicomponent, multistep, and transition metal catalyzed approaches. Mechanistic insights into these transformations are examined, and the material applications of selected benzothienoindole derivatives are mentioned.