1. From byproducts to NLO-active dyes: catalyst-free transfer hydrogenation in the modular synthesis of merocyanines.
- Author
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Zou, Jie, Pan, Yi, Zhang, Di, Zhang, Jie, Chen, Weilong, Sun, Hongyan, Lau, Kai-Chung, and Luo, Jingdong
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TRANSFER hydrogenation , *MEROCYANINES , *ELECTRON donors , *LEWIS acids , *DENSITY functional theory , *CHROMOPHORES synthesis - Abstract
We report an unexpected direct transfer hydrogenation (TH) from 8-alkoxyjulolidine as a strong electron donor to tricyanofuran-based hemicyanines and tandem condensation for the synthesis of push–pull chromophores. Density functional theory calculations identify the α-hydride transfer of julolidine derivatives, instead of nucleophilic addition, as the key initial step of reaction cascades, followed by efficient β-deprotonation to generate a nucleophilic enamine of isojuloline that condenses in situ with a second equivalent of hemicyanines as electrophiles. The scheme represents an exceptional example of TH reactions from 8-alkoxyjulolidine to highly polarizable hemicyanines, notably under simple reaction conditions without using potent catalysts of metal complexes or Lewis acids. The resulting products of isojuloline-based merocyanines exhibit strong near-infrared (NIR) absorption and large first hyperpolarizabilities. The study suggests that direct TH can be exploited to construct new NIR merocyanines by following rational, regioselective condensation pathways for photonic applications. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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