Theoretical Study On Intermolecular Hetero-Alder-ene Reactions

The Alder-ene reaction, firstly definded by Alder in1945, is also known as enereaction. It is a useful method for C C bond formation and also widely used inasymmetric synthesis. In this thesis, the mechanism, selectivity and substituent effect offive hetero-Alder-ene reactions which include carbonyl-ene, imine-ene, thio-carbonyl-ene,metallo-ene and pure sulfuric acid ene reactions were studied respectively using densityfuncational theory (DFT) at B3LYP level.1. For the carbonyl-ene reaction, the influences of twelve kinds of Lewis acids andeleven substituent groups have been studied. The calculation results show that in thepresence of a Lewis acid, the activation energy greatly decreases and so does the reactionenergy. And AlCl3is the most efficient promoter among the selected Lewis acids. Thefrontier molecular orbital energies were investigated to evaluate the influence of Lewisacids. The electron withdrawing group (EWG) on R1is favorable in energy, while theinfluence of group on R2can be ignored. The p-π or π-π conjugation effect on R3or R4isfavorable in activation energy or reaction energy, respectively.2. For imine-ene reaction, the energy surfaces of stepwise and concerted pathwayshave been compared, the results show that a concerted mechanism with an exoconfiguration six-membered TS is favorable. The influences of seventeen kinds of Lewisacids and nine substituent groups were studied. For the reactions, there are two goodlinear correlations, the barrier is linear with polar character of the TS and the activationenergy is linear with electrophilicity (ω).3. The thio-carbonyl-ene reaction goes through a concerted mechanism. Thesubstituents play important role on the barrier height and the regio-selectivity. Thereactions with EWG(s) on enophile prefer the sulfide path and have lower activationenergies, while the reactions with strong electron donating group (EDG) prefer the thiolpath with higher barrier. The frontier molecular orbital, reactivity indices and distortionenergies give good explanations on the promotion role of the substituent, and there aregood linear relationships between the distortion energy and activation energy.4. For the metallo(Al)-ene reaction, the concerted mechanism was found to be the favorable mechanism. The AIM and FMO results show that the Al moiety migration andC C bond formation occur synchronously, and the electron transferred from ene toenophile moiety during the reaction. The different group R affects the cationic property ofthe transferring Al in allyl-AlR2while the activation energy of the reaction gets alongwith the cationic property of Al. And the influence of the substituent on ethylene was alsostudied.5. A new concerted mechanism of the addition between pure H2SO4and alkeneswas proposed. During the reaction, the electron transfers from the enophile to ene moiety.An electron donating group on ethene facilitates the addition, and the reaction obeys theMarkovnikov’s rule, while an electron withdrawing group hampers the reaction and thereaction obeys the anti-Markovnikov regio-selectivity. The results show that theactivation energy mainly depends on the corresponding FMO gap, and there is a linearrelationship between them.