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Investigation of the relative reactivity of bonds in fullerenes will provide fundamental theory for the design of fullerene-based materials. We have theoretically investigated the reactivity of the (DA) of cis-1,3-butadiene to all types of bonds in C60 and C70 using the M06-2X hybrid density functional theory (DFT) calculations ( J. Phys. Org. Chem. 2012, 25 850-855) and have pointed out that the DA of cis and trans forms of 1,3-butadiene to ethylene have a specially intimate relationship ( J. Phys. Org. Chem. 2014, 27 652-660). For the aim of telling a whole story of the DA concerning C60 and C70, the DA of trans-1,3-butadiene to all types of bonds in C60 and C70 were explored at the same theoretical level as those of the cis-1,3-butadiene. The calculated results related with the trans- and cis-1,3-butadienes were compared. The potential energy curves of DA of trans- and cis-1,3-butadiene to C60 and C70 were discussed. The distortion-interaction energy model was employed to elucidate the origin of different reactivity of all kinds of CC bonds. The solvent effects were examined using the continuum solvent model. These current results, along with our previous research, will help to obtain an overall view of the DA of 1,3-butadiene to C60 and C70. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Endohedral metallofullerene has novelproperties because of the interaction between the encapsulated metalatom or cation and fullerene. Experiments have demonstrated that theinsertion of Li+into C60can greatly promotethe reactivity of the Diels–Alder (DA) cycloaddition of cyclopentadiene(CpH) to C60. However, the reaction is sufficiently fastthat its quantitative kinetic data cannot be obtained experimentally.In addition, knowledge regarding the effects of other alkali metalcations and metal cations with more charges on the reactivity andregioselectivity of C60is almost nonexistent. In the currentstudy, DA cycloadditions of CpH to M+@C60(whereM = Li, Na, K, Rb, and Cs) and Ca2+@C60wereinvestigated via density functional theory in the gas phase and insolvent. Via careful discussion and comparison with the results ofC60, we concluded the following for the DA reaction ofCpH to C60and, more generally, for DA reactions of otherfullerenes: (1) the encapsulated metal cations enhance the reactivity;(2) among alkali metal cations, Na+could be the best catalyst;(3) Ca2+is more favorable in promoting the reactivitythan any alkali metal cation; (4) encapsulated metal cations withmore positive charges enhance the reactivity of the 6–5 bondin C60, which is significant when the 6–5 adductis the target product. [ABSTRACT FROM AUTHOR]

The (DA) reaction is one of the most important reactions in organic chemistry. The controversy surrounding this reaction as to whether it follows a concerted or stepwise mechanism has existed for a long time. The reaction of 1,3-butadiene and ethylene is the paradigmatic example of the DA reaction. We have reinvestigated the mechanism of this reaction using density functional theory. The theoretical study considered all types of possible pathways for the reaction of 1,3-butadiene and ethylene using six functionals at different rungs of Jacob's ladder. Therefore, a complete picture is given for a thorough understanding of the iconic DA reaction, and a new stationary point during the reaction processes has been reported for the first time. The calculated results indicated that three functionals, ωB97X-D, M06-2X, and B2-PLYP, of the fourth and fifth rungs of Jacob's ladder performed well in the investigation of the mechanism of this reaction and that the reliable basis set should be larger than 6-311+G(2d,p). The cis-1,3-butadiene more easily reacted with ethylene compared with 1,3-butadiene in the trans conformation. The concerted mechanism was found to be energetically favorable, whose energy barrier is around 10 kcal/mol lower than that of the stepwise mechanism. Two investigated solvents, toluene and CH3CN, had little impact on this simple DA reaction. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

All possible types of Diels-Alder cycloadditions of 1,3- cis-butadiene to C60 (2 in total) and to C70 (8 in total) were theoretically investigated by the M06-2X density functional method in gas phase and solutions. An intermediate between the reactant and the transition state was located for each reaction. These intermediates except one have not been experimentally or theoretically reported before. The reactivities of the 10 reactions in both the gas phase and solutions were systematically compared based on the calculated results. The present conclusion agrees with the experimental observations and partly disagrees with the previously theoretical conclusion. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

All possible types of Diels-Alder cycloadditions of 1,3- cis-butadiene to C60 (2 in total) and to C70 (8 in total) were theoretically investigated by the M06-2X density functional method in gas phase and solutions. An intermediate between the reactant and the transition state was located for each reaction. These intermediates except one have not been experimentally or theoretically reported before. The reactivities of the 10 reactions in both the gas phase and solutions were systematically compared based on the calculated results. The present conclusion agrees with the experimental observations and partly disagrees with the previously theoretical conclusion. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]