Journal of the American Chemical Society
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“operationally” achiral.1 Most ‘memory effects’ impact stere-
Experimental and computational perspectives. J. Phys. Org. Chem. 2018, 31,
e3888.
(8) Debbert, S. L.; Carpenter, B. K.; Hrovat, D. A.; Borden, W. T. The
Iconoclastic Dynamics of the 1,2,6-Heptatriene Rearrangement. J. Am.
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properties of reaction coordinates. J. Chem. Phys. 1974, 61, 3200-3209. (b)
Valtazanos, P.; Elbert, S. T.; Ruedenberg, K. Ring Opening of Cyclopropy-
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Internal Motions, Steric Hindrances, and Long-Range Dipolar Interac-
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oselectivity through the time persistence of conformations.18
On shorter, sub-picosecond time scale, dynamic matching
arises when the symmetry of a short-lived formally symmet-
rical intermediate is broken by the retained non-symmetrical
momentum of the atoms as they enter the area of the inter-
mediate. The general idea here is the same, but it is taken to
its logical extreme since 14 is not an intermediate and since
the molecular asymmetry is both energetic and geomet-
rical.19
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When the products of a reaction are selected within a suffi-
ciently short time, symmetry all but disappears. As a result,
molecular events that are separated in time can be intercon-
nected by short-lived dynamical differences. This possibility
is not new,2,3 but here it affects the stereochemistry of an or-
dinary reaction in solution. This dynamical asymmetry com-
plicates the understanding of stereochemical observations
and their origin, since stereospecificity in formally concerted
concomitant bonding changes would not necessary require
any degree of temporal overlap. We are continuing to ex-
plore the impact of dynamical effects on the understanding
of selectivity in reactions.
(12) Hare, S. R.; Tantillo, D. J. Post-Transition State Bifurcations Gain
Momentum – Current State of the Field. Pure Appl. Chem. 2017, 89, 679–
698.
(13) (a) Singleton, D. A.; Hang, C.; Szymanski, M. J.; Meyer, M. P.;
Leach, A. G.; Kuwata, K. T.; Chen, J. S.; Greer, A.; Foote, C. S.; Houk, K.
N. Mechanism of Ene Reactions of Singlet Oxygen. A Two-Step No-
Intermediate Mechanism. J. Am. Chem. Soc. 2003, 125, 1319–1328. (b)
Patel, A.; Chen, Z.; Yang, Z.; Gutierrez, O.; Liu, H. –w.; Houk, K. N.; Sin-
gleton, D. A. Dynamically Complex [6+4] and [4+2] Cycloadditions in the
Biosynthesis of Spinosyn A. J. Am. Chem. Soc. 2016, 138, 3631-3634.
(14) (a) Thomas, J. R.; Waas, J. R.; Harmata, M.; Singleton, D. A. Con-
trol Elements in Dynamically-Determined Selectivity on a Bifurcating
Surface. J. Am. Chem. Soc. 2008, 130, 14544-14555. (b) Bogle, X. S.; Single-
ton, D. A. Dynamic Origin of the Stereoselectivity of a Nucleophilic Substi-
tution Reaction. Org. Lett. 2012, 14, 2528-2531. (c) Kelly, K. K.; Hirschi, J.
S.; Singleton, D. A. Newtonian Kinetic Isotope Effects. Observation, Pre-
diction, and Origin of Heavy-Atom Dynamic Isotope Effects. J. Am. Chem.
Soc. 2009, 131, 8382-8383. (d) Wang, Z.; Hirschi, J. S.; Singleton, D. A.
Recrossing and Dynamic Matching Effects on Selectivity in a Diels-Alder
Reaction Angew. Chem. Int. Ed. Engl. 2009, 48, 9156-9159. (e) Singleton,
D. A.; Hang, C.; Szymanski, M. J.; Greenwald, E. E. A New Form of Kinetic
Isotope Effect. Dynamic Effects on Isotopic Selectivity and Regioselectivi-
ty. J. Am. Chem. Soc. 2003, 125, 1176-1177.
(15) As is common for secondary cations. Hong, Y. J.; Tantillo, D. J. A
Maze of Dyotropic Rearrangements and Triple Shifts: Carbocation
Rearrangements Connecting Stemarene, Stemodene, Betaerdene,
Aphidicolene, and Scopadulanol. J. Org. Chem. 2018, 83, 3780–3793.
(16) Seeman, J. I. Effect of Conformational Change on Reactivity in
Organic Chemistry. Evaluations, Applications, and Extensions of Curtin-
Hammett/Winstein-Holness Kinetics. Chem. Rev. 1983, 83, 83–134.
(17) Dewar, M. J. S. Multibond Reactions Cannot Normally be Syn-
chronous. J. Am. Chem. Soc. 1984, 106, 209-219.
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the ACS
Publications website.
Complete descriptions of experimental and computational pro-
cedures and structures (PDF).
AUTHOR INFORMATION
Corresponding Author
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
DAS thanks the NIH (Grant GM-45617) for financial support. Finan-
cial support to OVL by the Welch Foundation (AX-1788) and the NSF
(CHE-1455061 and CHE-1625963) is gratefully acknowledged.
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