Reaction Rates and Mechanisms for Radical, Photoinitated Addition of Thiols to Alkynes, and Implications for Thiol-Yne Photopolymerizations and Click Reactions
Reaction Rates and Mechanisms for Radical, Photoinitated Addition of Thiols to Alkynes, and Implications for Thiol-Yne Photopolymerizations and Click Reactions
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DOI：
10.1021/ma1002968
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发表时间：
2010-05-11
期刊：
影响因子：
5.5
通讯作者：
Bowman, Christopher N.
中科院分区：
文献类型：
--
作者：
Fairbanks, Benjamin D.;Sims, Evan A.;Bowman, Christopher N.
由于其在网络聚合、树枝状聚合物合成和单体开发中的实用性，硫醇与炔的光引发加成已迅速成为聚合物科学家的重要工具。然而，因为这种化学方法最近才被应用于交联聚合物的开发，所以对于炔结构如何影响反应的性质的理解以及关于带有各种取代基的炔的相对反应性的信息是不可用的，因为与乙烯基硫化物相比，硫醇对炔的相对加成速率也是不可用的。在此，探索了光引发的辛烷硫醇对各种炔的加成。硫醇与炔的最快加成是与环辛炔的加成，尽管所得的乙烯基硫化物不允许随后的硫醇加成。此外，在不存在自由基引发剂和光的情况下，硫醇自发地加成到环辛炔上，这表明对应变促进的无铜叠氮化物、炔环加成的正交性的限制。两种硫醇的加成反应按反应速率递减的顺序为脂肪族1-辛炔>炔丙基乙酸酯>甲基炔丙基醚> 2-辛炔。丙炔酸乙酯和甲基炔丙胺与硫醇的反应速率非常小，并且没有观察到连续加成。
Because of its utility in network polymerization, dendrimer synthesis, and monomer development, the photoinitiated addition of thiols to alkynes has rapidly become an important tool for polymer scientists. Yet, because this chemistry has only recently been applied to cross-linked polymer development, understanding of the nature of how the yne structure affects the reactions and information on the relative reactivities of alkynes bearing various substituents is unavailable as is the relative addition rate of the thiol to the yne as compared to the vinyl sulfide. Herein, the photoinitiated addition of octanethiol to various alkynes is explored. The most rapid addition of thiols to alkynes is that to cyclooctyne, although the resulting vinyl sulfide does not permit subsequent thiol addition. Furthermore, in the absence of radical initiators and light, thiols add spontaneously to cyclooctynes, suggesting limitations to the orthogonality of the strain-promoted copper-less azide, alkyne cycloadditions. In order of decreasing reaction rates, the consecutive addition of two thiols occurs with the aliphatic 1-octyne > propargyl acetate > methyl propargyl ether > 2-octyne. Ethyl propiolate and methyl propargylamine exhibit very small reaction rates with thiols, and no consecutive addition is observed.