Selective Photoactivation: From a Single Unit Monomer Insertion Reaction to Controlled Polymer Architectures

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• 作者：Jiangtao Xu ; Sivaprakash Shanmugam ; Changkui Fu ; Kondo-Francois Aguey-Zinsou ; Cyrille Boyer
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：March 9, 2016
• 年：2016
• 卷：138
• 期：9
• 页码：3094-3106
• 全文大小：917K
• ISSN：1520-5126

文摘

Here, we exploit the selectivity of photoactivation of thiocarbonylthio compounds to implement two distinct organic and polymer synthetic methodologies: (1) a single unit monomer insertion (SUMI) reaction and (2) selective, controlled radical polymerization via a visible-light-mediated photoinduced electron/energy transfer-reversible addition–fragmentation chain transfer (PET-RAFT) process. In the first method, precise single unit monomer insertion into a dithiobenzoate with a high reaction yield (>97%) is reported using an organic photoredox catalyst, pheophorbide a (PheoA), under red light irradiation (λ_max = 635 nm, 0.4 mW/cm²). The exceptional selectivity of PheoA toward dithiobenzoate was utilized in combination with another catalyst, zinc tetraphenylporphine (ZnTPP), for the preparation of a complex macromolecular architecture. PheoA was first employed to selectively activate a dithiobenzoate, 4-cyanopentanoic acid dithiobenzoate, for the polymerization of a methacrylate backbone under red light irradiation. Subsequently, metalloporphyrin ZnTPP was utilized to selectively activate pendant trithiocarbonate moieties for the polymerization of acrylates under green light (λ_max = 530 nm, 0.6 mW/cm²) to yield well-defined graft co-polymers.