9-硅蒽和9-锗蒽与烯烃杂Diels-Alder反应的理论研究

Theoretical Study on the Hetero-Diels-Alder Reactions of 9-silaanthracene and 9-germaanthracene with Alkenes

采用密度泛函理论方法在B3LYP/6-311G**水平研究了9-硅蒽和9-锗蒽与烯烃的杂Diels-Alder反应的微观机理、势能剖面,考察取代基对反应势能剖面的影响.计算结果表明,所研究反应均以协同非同步的方式进行,且Si(Ge)—C键总是先于C—C键形成.乙烯分子中C原子上的苯基取代基在热力学上对反应不利,但在动力学上的影响取决于产物中苯基与Si(Ge)原子之间的相对位置.9-硅(锗)蒽分子中Si(Ge)原子上的2,4,6-三甲基苯基取代基在热力学和动力学上均对反应不利.

The mechanism and potential energy surface of the hetero-Diels-Alder reactions of 9-silaanthracene or 9- germaanthracene with alkenes were investigated using density functional theory （DFT） at the B3LYP/6-311G＊ ＊ level and the influences of some substituents on the potential energy surface were explored. The obtained results were com- pared with those of the corresponding reactions of silabenzene or germabenzene. The results show that all reactions oc- cur in a concerted but nonsynchronous way and the formation of Si（ Ge）--C bond always keeps ahead the formation of C--C bond. The phenyl group at C atom of ethylene molecules is not in favor of the hetero-Diels-Alder reactions ther- modynamically, however, its influence on the kinetic properties of the reaction are determined by the relative position of phenyl with Si（Ge） atom in products. The mesityl substituent at Si （Ge） atom of 9-silaanthracene or 9-germaan- thracene molecules has an unfavorable effect on the reactions both thermodynamically and kinetically.