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首页> 外文期刊>Catalysis science & technology >Understanding the mechanism of transition metal-free anti addition to alkynes: the selenoboration case
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Understanding the mechanism of transition metal-free anti addition to alkynes: the selenoboration case

机译：理解的机制转变不含金属的抗除了炔烃:selenoboration案例

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The stereoselective anti-addition of selenoboranes to ,-acetylenic esters and amides was achieved in a transition metal-free context using catalytic amounts of PCy3. The reaction provides anti-3,4-selenoboration with concomitant delivery of -vinyl selenides by protodeboronation with MeOH. Interestingly, in the absence of phosphine the selenoboration switches towards the formation of -vinyl selenides. Theoretical calculations rationalize the regio- and stereoselectivity of the reaction by discovering a new mechanism for the anti-3,4-selenoboration. While the selenoborane is activated via the push-pull effect of B, the phosphine interacts with the position of the alkynoate switching the polarity of the triple bond and favoring 1,3-selenoboration which provides the -addition of the selenyl group. Then, the autocatalytic action of a second selenoborane reagent, which coordinates to the phosphorus ylide intermediate, determines the stereoselectivity and completes the catalytic process. Finally, the comparison of selenoborane reagents with diboranes and silaboranes, which have exhibited analogous reactivity, shows that the selenium moiety has a larger nucleophilic character favoring the performance of the reaction under mild conditions.
机译：的立体选择anti-addition selenoboranes乙炔的酯和酰胺实现不含金属的过渡使用催化上下文大量的PCy3。anti-3 4-selenoboration随之而来的交付的乙烯基化物通过protodeboronation甲醇。对形成selenoboration开关乙烯基的硒化物。合理化的地区——和立体选择性发现一个新的机制的反应anti-3 4-selenoboration。通过推拉selenoborane被激活B,磷化氢的影响与交互极性alkynoate开关的位置三键的支持1, 3-selenoboration提供补充selenyl集团。第二个selenoborane试剂的作用,坐标磷方面的中间,决定了立体选择性并完成催化过程。与乙硼烷和selenoborane试剂silaboranes,表现出类似反应活性,表明硒一半的更大的亲核的字符支持反应在温和的性能条件。

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