Distortion-Controlled Reactivity and Molecular Dynamics of Dehydro-Diels-Alder Reactions.
We report density functional theory (M06-2X) studies of a series of dehydro-Diels-Alder (DDA) reactions. For these and the parent reaction, the stepwise mechanisms have similar barriers, whereas the barriers of the concerted mechanisms differ significantly. The reactivity of DDA reactions is controlled by distortion energy. The concerted and stepwise mechanisms of the hexadehydro-Diels-Alder (HDDA) reaction are competitive with activation barriers of ∼36 kcal/mol. This is because a large distortion energy (∼43 kcal/mol) is required to achieve the concerted transition state geometry. MD simulations reveal that productive concerted trajectories display a strong angle bending oscillation (∼25° oscillation amplitude), while the stepwise trajectories show only a chaotic pattern and less pronounced bending vibrations.
Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States.
Peiyuan
P
Yu
Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States.
Zhongyue
Z
Yang
Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States.
Yong
Y
Liang
Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States.
Xin
X
Hong
Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States.
Yanwei
Y
Li
Department of Chemistry and Biochemistry, University of California , Los Angeles, California 90095, United States.
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KN
Houk