Reversal of .pi.-facial diastereoselection upon electronegative substitution of the substrate and the reagent

Cieplak, Andrzej Stanislaw; Tait, Bradley D.; Johnson, Carl R.

doi:10.1021/ja00204a018

Cited by 261 publications

(118 citation statements)

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“…These include steric effects, complexation between diene and dienophile, secondary orbital interactions, polarizability, electrostatic interactions, orbital mixing, and transition state hyperconjugation. This latter interpretation proposed by Cieplak for reactions of cyclohexanones is based on the concept of transition state stabilisation by a donation from an adjacent a bond into the vacant a * orbital associated with the incipient bond (26,27). This explanation was used to account for the syn approach of 2,3-dimethylbutadiene to C5-fluoroadamantane-2-thione (28) and rationalize the preference observed for addition anti to the antiperiplanar a bond that is the better donor in the reactions of dienophiles with C5-substituted pentamethylcyclopentadienes (29,30) and 2,5-dimethylthiophene oxide (15).…”

Section: Introductionmentioning

confidence: 99%

An AM1 calculational study of the Diels–Alder addition of maleic anhydride to C5-substituted pentamethylcyclopentadienes and 2,5-dimethylthiophene oxide. An attempt to ascertain the factors controlling the π-facial selectivities and relative reactivities

Ma¹

1994

Can. J. Chem.

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NICK HENRY WERSTIUK and JIANGONG MA. Can. J. Chem. 72,2493 (1 994).The Diels-Alder reactions of maleic anhydride (1) with a group of C5-substituted cyclopentadienes and 2,5-dimethylthiophene oxide (5) have been studied with the semi-empirical method AM1. We find that the facial selectivities and relative reactivities found experimentally for six dienes (2n-2f) are accurately reproduced at this level of theory. The results of the calculational study provide no concrete support for the proposal that a-a* hyperconjugation in the transition state -an interaction between a a bond at C5 of the cyclopentadiene and the incipient a bonds anti to it (the Cieplak effect) -is the major source of the syn facial selectivity observed for 2a-2d. In addition, the relative reactivities and facial selectivities are predicted for a number of cyclopentadienes which will be synthesized and studied experimentally.NICK HENRY WERSTIUK et JIANGONG MA. Can. J. Chem. 72,2493Chem. 72, (1994. Faisant appel 2 la methode semi-empirique AM I, on a CtudiC les rkactions de Diels-Alder de l'anhydride maleique (I) avec un certain nombre de cyclopentadiknes substituCs en position 5 et avec l'oxyde du 2,5-dimCthylthiophkne (5). On a trouvC que, h ce niveau de la thCorie, il est possible de reproduire fidklement les sClectivitCs faciales et les rCactivitCs relatives observCes expCrimentalement pour les six diknes (2n-2f). Les rCsultats de I'Ctude par calculs ne fournit aucun support concret pour la proposition qui a CtC faite selon laquelle de l'hyperconjugaison a** dans I'Ctat de transition -une interaction entre une liaison a au niveau C5 du cyclopentadibne et les liaisons a qui se forment anti par rapport h elles (effet Cieplak) -serait la cause principale de la sClectivitC faciale syn observCe avec les composCs 2n-2d. De plus, on a prCdit les rCactivitCs relatives et les sClectivitCs faciales d'un certain nombre de cyclopentadiknes qui seront synthCtisCs et CtudiCs expCrimentalement.[Traduit par la redaction] Introduction The synthetic utility of the Diels-Alder reaction is well established although the ability to control the facial selectivity which would render the reaction enantioselective with asvmmetric planar 1,3-dienes and potentially generate five or more chiral centres in one operation, is limited in the absence of chiral auxiliaries. In the reaction of C5-substituted cyclopentadienes where n-facial diastereoselectivity has been observed in the absence of chiral auxiliaires, the origin of the selectivity is still imperfectly understood even though a wide range of substrates have been studied experimentally (1-16) and computationally (17-25). These investigations revealed that a number of factors are important and various suggestions have been advanced as possible sources of the pattern observed. These include steric effects, complexation between diene and dienophile, secondary orbital interactions, polarizability, electrostatic interactions, orbital mixing, and transition state hyperconjugation. This latter interpretation proposed by Ci...

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Section: Introductionmentioning

confidence: 99%

An AM1 calculational study of the Diels–Alder addition of maleic anhydride to C5-substituted pentamethylcyclopentadienes and 2,5-dimethylthiophene oxide. An attempt to ascertain the factors controlling the π-facial selectivities and relative reactivities

Ma¹

1994

Can. J. Chem.

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“…The conformation of monosulfone 10 avoids severe allylic strain which would arise from a flipped-chair conformation. This is supported by stereoelectronic effects described above and by evaluation of the 13 C NMR spectra: 13 C shifts in position C-5 of thiane-and 1,3-dithiane-derived S-oxides are strongly dependent from the number of b-sulfoxides with S=O groups in axial position (g-gauche effect). [32] Axial S=O groups which are part of a sulfone moiety do not contribute to this effect and compounds bearing a sulfilimine group behave inconsistently in that context.…”

Section: A Normal Perlin Effect Was Observed For Position C-5 a C H Tmentioning

confidence: 73%

“…[9][10][11][12] In other words, an n O !s* ax-CÀH hyperconjugation leads to a weakening of the axial CÀH bond. [13] An anomalous pattern in the magnitude of the coupling constants has been found for similar systems containing sulfur atoms. [7,[10][11][12]14] Here, a hyperconjugation from the s CÀS bond into the s* eq-CÀH is responsible for smaller coupling constants of the adjacent equatorial C À H bonds (reverse Perlin effect, Figure 1, bottom).…”

Section: Introductionmentioning

confidence: 89%

Stereoelectronic Effects in Cyclic Sulfoxides, Sulfones, and Sulfilimines: Application of the Perlin Effect to Conformational Analysis

Wedel

Müller

Podlech

et al. 2007

Chemistry A European J

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The 1JC--H coupling constants in conformationally constrained sulfoxides, bissulfoxides, sulfoxide-sulfones, and sulfilimines derived from 2-benzylidene-1,3-dithiane and 2-(2,2-dimethylpropylidene)-1,3-dithiolane were measured by means of HMQC and HSQC NMR experiments and the Perlin effects were calculated. The type and the relative configuration of S==X groups (X= O, NTos) in these compounds have a strong influence on the magnitude of coupling constants for axial and equatorial C--H bonds, respectively. Axial S==O bonds give rise to a stereoelectronic effect on antiperiplanar axial C--H bonds. The resultant weakening of the respective C--H bonds leads to a smaller coupling constant than for a respective equatorial C--H bond. Equatorial S==O groups have an influence on beta-C--H bonds through a homoanomeric effect. Here, the axial C--H bond is weakened and a smaller coupling constant is measured. Sulfilimine groups show similar effects to sulfoxide groups.

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“…Calculations of coupling constants of monocycloalkanes 675 119 which makes axial bonds longer and weaker and, as a result, possessing smaller 1 J(C,H).…”

mentioning

confidence: 99%

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants. Part 8—Monocycloalkanes

Sauer

Krivdin

2004

Magnetic Reson in Chemistry

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Carbon-carbon and carbon-hydrogen spin-spin coupling constants were calculated in the series of the first six monocycloalkanes using SOPPA and SOPPA(CCSD) methods, and very good agreement with the available experimental data was achieved, with the latter method showing slightly better results in most cases, at least in those involving calculations of J(C,C). Benchmark calculations of all possible 21 coupling constants J(C,C), J(C,H) and J(H,H) in chair cyclohexane revealed the importance of using the appropriate level of theory and adequate quality of the basis sets. Many unknown couplings in this series were predicted with high confidence and several interesting structural trends (hybridization effects, multipath coupling transmission mechanisms, hyperconjugative interactions) were elucidated and are discussed based on the present calculations of spin-spin couplings.

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Reversal of .pi.-facial diastereoselection upon electronegative substitution of the substrate and the reagent

Cited by 261 publications

References 4 publications

An AM1 calculational study of the Diels–Alder addition of maleic anhydride to C5-substituted pentamethylcyclopentadienes and 2,5-dimethylthiophene oxide. An attempt to ascertain the factors controlling the π-facial selectivities and relative reactivities

An AM1 calculational study of the Diels–Alder addition of maleic anhydride to C5-substituted pentamethylcyclopentadienes and 2,5-dimethylthiophene oxide. An attempt to ascertain the factors controlling the π-facial selectivities and relative reactivities

Stereoelectronic Effects in Cyclic Sulfoxides, Sulfones, and Sulfilimines: Application of the Perlin Effect to Conformational Analysis

Non‐empirical calculations of NMR indirect carbon–carbon coupling constants. Part 8—Monocycloalkanes

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