Exploring Methoxy-Activated Symmetric Alkynes in Click-Type [2+2] Cycloaddition-Retroelectrocyclization Reactions

Date

2024-6-12

Author

Kılıç, Murat Can

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Donor-acceptor-type chromophores are a compelling platform because of their strong charge-transfer bands. These chromophores have been utilized in many fields such as light-emitting diodes, colorimetric sensors, and solar cells. The [2+2] cycloaddition-retroelectrocyclization (CA-RE) of electron-deficient olefins (such as tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) with electron-rich alkynes is an excellent way for the synthesis of the corresponding push-pull chromophores. The [2+2] CA-RE between electron-deficient olefins and electron-rich alkynes is known to be thermally forbidden according to Woodward-Hoffmann's rules. Yet there are many contradicting examples in the literature that the reactions occur at room temperature with high yields. In this study, we investigate the relevant chemical transformations for substrates with 1,4-diethynyl-2,5-dimethoxybenzene core structure. The methoxy groups at the ortho and meta positions in the substrates mesomerically contribute to the electron density and activate the bound alkynes for [2+2] CA-RE. The CA-RE transformations of the selected substrates is particularly interesting due to its selective product distribution whether the reaction occurs at single alkyne or both. This distribution is selective in accordance with the electronic properties of alkynes and can be tailored by changing the substituents attached to the core structure. The aim of this project is to design a new family of electron-rich alkyne substrates that can be used in the [2+2] CA-RE reactions, and to investigate optical properties of the resulting products.

Subject Keywords

Chromophore, Donor Group Effect, [2+2] CA-RE, mono/di-TCBD

URI

https://hdl.handle.net/11511/110150

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Graduate School of Natural and Applied Sciences, Thesis