# Rh(iii)-catalyzed heteroannular-selective heteroarylation of biaryls: facile access to heteroacenes with sulfur-embedded 5–7 ring topology

## TL;DR

This paper presents a new rhodium-catalyzed method to create sulfur-containing heteroacenes with unique ring structures, which could be useful in organic semiconductors.

## Contribution

A novel Rh(III)-catalyzed method for synthesizing sulfur-embedded heteroacenes with 5–7 ring topology is introduced.

## Key findings

- The method enables efficient synthesis of thioether- and seleno-ether-substituted biheteroaryl compounds.
- Heteroacenes with sulfur-embedded 5–7 or 5–6 ring topologies can be switchably constructed.
- Crystal and photophysical studies suggest potential for high-performance organic semiconductors.

## Abstract

Acenes with non-benzenoid 5–7 ring topology have drawn significant attention. Nevertheless, introducing sulfur atoms into 5/7-membered rings of acenes has not yet been achieved owing to synthetic challenges. Disclosed herein is a rhodium-catalyzed heteroannular-selective C–H/C–H oxidative cross-coupling reaction of 2-substituted biaryls with heteroarenes, which provides a convenient approach to heteroacenes with sulfur-embedded 5–7 ring topology. This protocol demonstrates excellent regioselectivity and broad functional group tolerance, enabling the efficient synthesis of a diverse library of thioether- and seleno-ether-substituted biheteroaryl compounds. Heteroacenes featuring sulfur-embedded 5–7 or 5–6 ring topologies can be switchably constructed through further intramolecular cyclization involving directing groups. Crystal structure analysis, along with studies on photophysical properties and aromaticity, indicates that heteroacenes with sulfur-embedded 5–7 ring topology have the potential as high-performance organic semiconductor materials.

The heteroacenes with sulfur-embedded 5–7 or 5–6 ring topologies are switchably obtained via heteroannular-selective oxidative cross-coupling of biaryls with heteroarenes, followed by directing group-involved intramolecular cyclization.