环戊二烯与二氢呋喃类化合物Diels-Alder反应的理论研究

Theoretical study on the Diels-Alder reaction between cyclopentadiene and dihydrofuran compounds

采用量子化学密度泛函理论（DFT）在B3LYP／6—311＋＋G＊＊水平上对环戊二烯与2（5H）-呋喃酮，丁烯二酸酐和2，5-二氢呋喃的Diels—Alder反应机理进行了理论研究，并且考虑了溶剂化效应和取代基效应对反应机理及能垒的影响．结果表明，本文所涉及的环戊二烯与二氢呋喃类化舍物的Diels-Alder加成反应是以协同方式进行的；羰基取代基的吸电子作用是造成产物中C（1）-C（2）、C（3）-C（4）键键长增加的主要原因；反应所涉厦到的FMO相互作用主要是环戊二烯的HOMO与二氢呋喃类化合物的LUMO之间的相互作用，羰基对反应活化能的影响主要是通过降低呋喃类化合物的LUMO能级，减小与环戊二烯的HOMO的能级差异。从而有利于反应进行的；反应2的活化能垒最低，从动力学的角度考虑在室温下可以进行．

The Diels-Alder reactions between cyclopentadiene and 2 （5H）-furanone （butenedioic anhydride or 2,5-dihyrofuran） have been investigated theoretically using density functional theory at the B3LYP/6-311＋＋G＊＊ level. The influences of solvents and substituent groups on the mechanisms and activation energies of these reactions have been involved. The results indicate that all of these reactions are concerted. Increase of C （1）--C （2）, C （3）r--C （4） bond length in products may be relating to the carbonyl group. Moreover, the FMOs interaction involving in these reactions mainly occurs between the HOMO of cyclopentadiene and the LUMOs of dihydrofuran compounds. The main impact of carbonyl group on activation energies is that it would lower LUMO energy level of 2（5H）-furanone （butenedioic anhydride or 2,5-dihyrofuran）, reduce the energy barriers from them to the HOMO energy level of cyclopentadiene, and facilitate these reactions. From the kinetic point of view, the activation energy of reaction 2 is the lowest; it could be carried out at room temperature.