High-Rate Accelerations in Oxy-Cope Rearrangements Induced by Sulfur Substitution:  Kinetic Study Involving Electronically and Geometrically Differentiated 1-Alkenyl-2-(<i>Z</i>-1-propenyl)-7,7-dimethyl-<i>exo</i>-norbornan-2-ols

Paquette, Leo A.; Reddy, Y. Jayasudhan; Vayner, and Grigoriy; Houk, K. N.

doi:10.1021/ja0025402

Cited by 16 publications

(7 citation statements)

References 43 publications

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“…This is evident in Houk's calculations,28a which indicate that thiyl (−SH) is more efficient than hydroxyl (−OH) in stabilizing methyl anion by about 15.1 kcal/mol (B3LYP/ 6-31+G*), comparable with the 11 kcal/mol difference in activation energy difference for the RORC steps of reactions I and III. Another related support is the experimental observation that a thioalkoxy substituent is more efficient than an alkoxy substituent in accelerating anionic oxy-Cope rearrangements …”

Section: Discussionmentioning

confidence: 88%

A Theoretical Study of the Mechanisms and Regiochemistry of the Reactions of 5-Alkoxyoxazole with Thioaldehydes, Nitroso Compounds, and Aldehydes

2002

J. Org. Chem.

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A theoretical study based on B3LYP/6-31G calculations has been applied to the mechanisms and regiochemistry of reactions of 5-alkoxyoxazole with thioaldehydes, nitroso compounds, and aldehydes. All three reactions adopt similar mechanisms, which start with Diels-Alder (DA) reactions, followed by either a novel, concerted ring-opening-ring-closing (RORC) step to transfer the DA adduct to 2-alkoxycarbonyl-3-thiazoline and 2-alkoxycarbonyl-3-oxazoline for thioaldehydes and aldehydes, respectively, or stepwise ring-opening and ring-closing steps to generate 1,2,4-oxadiazoline for nitroso compounds. The reactions of 5-alkoxyoxazole with thioaldehydes and nitroso compounds can be conducted under thermal reaction conditions due to the 10 kcal/mol activation barriers for their rate-determining DA reactions. By contrast, the reaction of 5-alkoxyoxazole with aldehydes cannot take place under thermal conditions, since this bimolecular reaction has the rate-determining RORC transition state higher than the reactants by 30.5 kcal/mol.

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Section: Discussionmentioning

confidence: 88%

A Theoretical Study of the Mechanisms and Regiochemistry of the Reactions of 5-Alkoxyoxazole with Thioaldehydes, Nitroso Compounds, and Aldehydes

2002

J. Org. Chem.

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“…Very early on, substituent effects were observed. While sulfur-substituted diene alkoxides undergo the rearrangement under very mild conditions, the presence of bulky alkyl groups on the termini positions may completely impede the transposition. For instance, crowded substituted dienes are unreactive under typical anionic oxy-Cope conditions.…”

mentioning

confidence: 99%

Rate Acceleration of Anionic Oxy-Cope Rearrangements Induced by an Additional Unsaturation

et al. 2003

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[reaction: see text] In sharp contrast to their isopropyl counterparts, a variety of (Z)-isopropenyl tertiary bicyclo[2.2.2]octenols undergo facile anionic oxy-Cope rearrangements allowing the stereoselective incorporation of an isopropenyl group into polycyclic skeletons such as the tricyclic system of vinigrol, bicyclo[5.3.1]undecane, and cis-decalin frameworks. This rate acceleration is probably due to the stabilization of the transition state by the additional unsaturation on the terminal position.

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“…Cope rearrangements of 3-hydroxy-1,5-hexadienes are accelerated by deprotonation of the hydroxyl-substituent: anionic oxy-Cope rearrangements are very rapid .…”

Section: Computational Studiesmentioning

confidence: 99%

Demonstrating the Synergy of Synthetic, Mechanistic, and Computational Studies in a Regioselective Aniline Synthesis

Davies

Marcoux²,

Kuethe³

et al. 2004

J. Org. Chem.

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Tri- and tetrasubstituted anilines are formed in good to excellent yields by the addition of ketones to vinamidinium salts (up to 98%). The reaction proceeds via the formation of dienone intermediates, which react to form an enamine with the liberated amine. In the case of a nitro, or dimethylaminomethylene substituent, the enamines undergo a facile electrocyclic ring closure to form a cyclohexadiene, which goes on to form anilines with a high degree of selectivity (up to 50:1) with a minor competing pathway proceeding via the enol providing phenols. Competition experiments using isotopic substitution reveal that the rate determining step en route to dienone is enol/enolate addition to the vinamidinium salt, which is characterized by an inverse secondary isotope effect (k(H/D) 0.7-0.9). Computational studies have been used to provide a framework for understanding the reaction pathway. The original proposal for a [1,5]-H shift was ruled out on the basis of the calculations, which did not locate a thermally accessible transition state. The minimum energy conformation of the enamine is such that a facile electrocyclic ring closure is ensured, which is corroborated by the experimental studies. A framework for understanding the reaction pathway is presented.

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High-Rate Accelerations in Oxy-Cope Rearrangements Induced by Sulfur Substitution: Kinetic Study Involving Electronically and Geometrically Differentiated 1-Alkenyl-2-(Z-1-propenyl)-7,7-dimethyl-exo-norbornan-2-ols

Cited by 16 publications

References 43 publications

A Theoretical Study of the Mechanisms and Regiochemistry of the Reactions of 5-Alkoxyoxazole with Thioaldehydes, Nitroso Compounds, and Aldehydes

A Theoretical Study of the Mechanisms and Regiochemistry of the Reactions of 5-Alkoxyoxazole with Thioaldehydes, Nitroso Compounds, and Aldehydes

Rate Acceleration of Anionic Oxy-Cope Rearrangements Induced by an Additional Unsaturation

Demonstrating the Synergy of Synthetic, Mechanistic, and Computational Studies in a Regioselective Aniline Synthesis

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