Thiol radical addition to alkynes. Sulfanyl radical addition and hydrogen atom abstraction relative reaction rates
作者:Daniela Melandri、Pier Carlo Montevecchi、Maria Luisa Navacchia
DOI:10.1016/s0040-4020(99)00699-7
日期:1999.10
benzenethiol and benzeneethanethiol radical addition have been performed in order to determine the relative rate constants of the sulfanyl radical addition to the alkyne triple bond (k1) and the hydrogen abstraction reaction by the resulting vinyl radicals (kH). The k1 values are mainly determined by the vinyl radical stabilization provided by the C-(α) vinyl radical substituent, whereas the kH values
2-(甲苯硫基)-1和2-(苯硫基)-苯乙炔10在AIBN存在下分别于84和154°C与苯硫醇和甲苯硫醇反应,制得衍生自乙烯基2的产物,该产物进行氢抽象反应和5 -邻位和5- exo环化到两个相邻的苯环上,与β片段竞争。已经获得明确的证据,将烷硫烷基加到炔三键是不可逆的过程,而芳烃硫烷基则以可逆的方式加成。为了确定向炔烃三键(k 1)加成的硫烷基的相对速率常数和由所得乙烯基自由基引起的氢夺取反应(k H),已进行了涉及几个炔烃的竞争实验,涉及到苯硫醇和苯乙硫醇基团的加成。。k 1值主要由C-(α)乙烯基自由基取代基提供的乙烯基自由基稳定性决定,而k H值似乎主要由极性因素决定。就乙烯基的不同杂化而言,讨论了α-丙基和α-长链取代基之间出乎意料的不同行为。