Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States.
Org Lett. 2014 Nov 7;16(21):5702-5. doi: 10.1021/ol502780w. Epub 2014 Oct 20.
The hexadehydro-Diels-Alder (HDDA) reactions between suitably substituted 1,3-diynes and alkynes produce highly reactive benzynes under thermal conditions without catalysts. DFT calculations and distortion/interaction analyses show that, for the activated substrates, the stepwise diradical pathway is more favorable than the concerted [4 + 2] process. One manifestation of this mechanism is that alkynyl substituents dramatically accelerate HDDA reactions, mainly by decreasing the distortion energy required to achieve the diradical transition state.
在热条件下，无需催化剂，适当取代的 1,3-二炔与炔烃之间的十六氢-Diels-Alder (HDDA) 反应会产生高反应性苯炔。DFT 计算和变形/相互作用分析表明，对于活化底物，分步双自由基途径比协同 [4 + 2] 过程更有利。该机制的一个表现是炔基取代基极大地加速了 HDDA 反应，主要是通过降低实现双自由基过渡态所需的变形能来实现。
