TY - JOUR
T1 - Isotope effects and the distinction between synchronous, asynchronous, and stepwise Diels-Alder reactions
AU - Singleton, Daniel A.
AU - Schulmeier, Brian E.
AU - Hang, Chao
AU - Thomas, Allen A.
AU - Leung, Shun Wang
AU - Merrigan, Steven R.
N1 - Funding Information:
We thank NIH grant # GM-45617 and The Robert A. Welch Foundation for support.
PY - 2001/6/11
Y1 - 2001/6/11
N2 - A variety of symmetrical or nearly symmetrical Diels-Alder reactions are studied by a combination of experimental isotope effects, theoretical calculations, and rate observations. Becke3LYP calculations predicted highly asynchronous transition structures for Diels-Alder reactions of bis(boryl)acetylenes, dialkyl acetylenedicarboxylates, triazolinediones, and dialkyl maleates. Rate observations and kinetic isotope effects are consistent with these predictions, though the experimental support for the calculated structures is notably ambiguous in some cases. A concerted mechanism is supported for the retro-Diels-Alder reaction of norbornene. Overall, Diels-Alder reactions appear to be only very weakly biased toward synchronous transition states.
AB - A variety of symmetrical or nearly symmetrical Diels-Alder reactions are studied by a combination of experimental isotope effects, theoretical calculations, and rate observations. Becke3LYP calculations predicted highly asynchronous transition structures for Diels-Alder reactions of bis(boryl)acetylenes, dialkyl acetylenedicarboxylates, triazolinediones, and dialkyl maleates. Rate observations and kinetic isotope effects are consistent with these predictions, though the experimental support for the calculated structures is notably ambiguous in some cases. A concerted mechanism is supported for the retro-Diels-Alder reaction of norbornene. Overall, Diels-Alder reactions appear to be only very weakly biased toward synchronous transition states.
KW - Asynchronous transition state
KW - Diels-Alder reaction
KW - Isotope effect
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U2 - 10.1016/S0040-4020(01)00354-4
DO - 10.1016/S0040-4020(01)00354-4
M3 - Article
AN - SCOPUS:0035844684
SN - 0040-4020
VL - 57
SP - 5149
EP - 5160
JO - Tetrahedron
JF - Tetrahedron
IS - 24
ER -