Photoinduced intramolecular S-α-C(sp³)-H functionalization enabled by an electron donor-acceptor complex-Mediated...

Area of Science:

• Organic Chemistry
• Photochemistry
• Synthetic Methodology

Background:

• Electron donor-acceptor (EDA) complexes are increasingly utilized in organic synthesis.
• Photoactivation offers a mild and efficient route for chemical transformations.
• Developing streamlined synthetic pathways for heterocyclic compounds is of significant interest.

Purpose of the Study:

• To develop a novel, one-step synthesis for 3-(4-pyridylbenzyl)benzothiophenes and benzoselenophenes.
• To explore the utility of photoactivated EDA complexes in consecutive organic reactions.
• To investigate the mechanism of the proposed synthetic route.

Main Methods:

• Consecutive reaction of 2-alkynylthioanisoles with 4-cyanopyridine.
• Photoactivation of EDA complexes formed between thioethers and 4-cyanopyridine.
• Analysis of reaction intermediates and products using spectroscopic methods.

Main Results:

• Successful synthesis of various 3-(4-pyridylbenzyl)benzothiophenes and benzoselenophenes.
• Demonstration of sequential S-α-C(sp3)-H bond activation, cyclization, and radical coupling.
• Identification of EDA complexes as crucial intermediates in the reaction pathway.

Conclusions:

• Photoactivated EDA complex catalysis provides an efficient single-step method for synthesizing substituted benzothiophenes and benzoselenophenes.
• The reaction proceeds under mild conditions, highlighting its practical applicability.
• Mechanistic studies confirm the pivotal role of EDA complexes in enabling this transformation.