1997
DOI: 10.1021/ja963847x
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Transition States of Epoxidations:  Diradical Character, Spiro Geometries, Transition State Flexibility, and the Origins of Stereoselectivity

Abstract: The transition structures for the epoxidations of ethylene by performic acid, dioxirane, oxaziridine, and peroxynitrous acid have been located with density functional theory methods using the Becke3LYP functional and 6-31G* basis set. All of the epoxidations have spiro transition states; those with performic acid and dioxirane are early and involve synchronous oxygen transfer, while those with oxaziridine and peroxynitrous acid are later with asynchronous oxygen transfer. The results from Becke3LYP/6-31G* theo… Show more

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Cited by 186 publications
(127 citation statements)
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“…The stereochemical outcomes of epoxidations of transstilbene with ketones 3a-5a (leading to (À)-(S, S) stilbene oxide) and p-methoxy cinnamate with ketones 3a and 4a (leading to (À)-(2R, 3S) cinnamate oxide) have already been rationalized [7,9] by considering the model shown on Scheme 4: conformation K1 of the dioxirane (predicted to be the most populated because of the large i-Pr group equatorial); spiro geometry; [19][20][21][22] equatorial approaches of the olefin toward the dioxirane (with some contribution of the axial approaches, although less favored [9]) and n(F).p(Ar) or n(F).CH 3 repulsion in approach E-I (making the corresponding transition state more energetic than the one corresponding to approach E-II).…”
Section: Resultsmentioning
confidence: 99%
“…The stereochemical outcomes of epoxidations of transstilbene with ketones 3a-5a (leading to (À)-(S, S) stilbene oxide) and p-methoxy cinnamate with ketones 3a and 4a (leading to (À)-(2R, 3S) cinnamate oxide) have already been rationalized [7,9] by considering the model shown on Scheme 4: conformation K1 of the dioxirane (predicted to be the most populated because of the large i-Pr group equatorial); spiro geometry; [19][20][21][22] equatorial approaches of the olefin toward the dioxirane (with some contribution of the axial approaches, although less favored [9]) and n(F).p(Ar) or n(F).CH 3 repulsion in approach E-I (making the corresponding transition state more energetic than the one corresponding to approach E-II).…”
Section: Resultsmentioning
confidence: 99%
“…Moreover, these species are located in different cavities of the LDH structure (i.e., gallery, narrow and larger mesopores) and in different structural orientations. Obviuosly, some of these molecules are not able to act as catalytic active sites, if their environment is not large enough to allow the diffusion of the reactant molecules (i.e., trans-methylcinnamate) and the formation of the spirotransition state, in which the plane of the oxirane is perpendicular to the plane of the C C -system permeating the oxygen transfer [18,39] (Scheme 1). The kinetic diameter of trans-methylcinammate (6.7 Å) and the corresponding phenyl-glycinate product (7.1 Å) has been estimated from the molecular weight correlation, using the equation: For aromatic hydrocarbons (M w = molecular weight in g mol −1 ) [40].…”
Section: Resultsmentioning
confidence: 99%
“…In c [10,23]. In a work on photochemical and thermal rearrangement of oxaziridines bond lengths of N-O, C-O and C-N is 1.535Å, 1.428 Å and 1.456 Å respectively [24].…”
Section: CL Nh 2 and Methyl Derivatives Structuresmentioning
confidence: 99%
“…Research on synthesis and properties of 3, 3-disubstituted N-sulfonyloxaziridine [7] have been worked by Davis and et al Also they investigated the kinetics and mechanism of the oxidation of oxaziridines [8] and their applications in organic synthesis [9]. Transition states of epoxidation and stereo selectivity in oxaziridines were investigated by Houk and et al [10]. Oxaziridines have been studied as intermediate and their activation has been investigated [11,12].…”
Section: Introductionmentioning
confidence: 99%