5-Endo-trigonal reactions: a disfavoured ring closure

Baldwin, Jack E.; Cutting, J. D.; Dupont, William; Kruse, Lawrence I.; Silberman, Lee; Thomas, Richard

doi:10.1039/c39760000736

Cited by 444 publications

(150 citation statements)

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“…Reaction I is also very similar to the reaction given by Baldwin et al (3) as an example of a 6-endo-trig process (Scheme 2(b)). Both of these intramolecular cyclizations reacted experimentally without difficulty.…”

Section: Introductionsupporting

confidence: 59%

Comparison of an intramolecular Michael-type addition with its intermolecular counterpart: an abinitio theoretical study

Bayly¹,

Grein²

1989

Can. J. Chem.

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C. I. F. GREIN. Can. J. Chem. 67, 2173 (1989). Ab initio theoretical calculations were carried out on the intramolecular addition of 3-ketopent-4-en-I-olate 1 to form 1-oxacyclohex-3-en-4-olate 2 (reaction I; Scheme 1) and the corresponding intermolecular Michael addition of methanolate to butenone forming 4-methoxybut-2-en-2-olate 4 (reaction LI; Scheme 1). The calculations were carried out at the RHF level using an augmented 4-3 1G basis set; single point energies were then taken using the 6-31 +G* basis set. The overall energy change of the reaction in going from reactants to products is very similar for both reactions, with products being about 8.3 kcallmol more stable than reactants; the major difference energetically between the two reactions is at the level of the transition state: the transition state energy for reaction I (intramolecular) is 6 kcallmol higher than that for reaction I1 (intermolecular). The transition state geometry of reaction I1 conforms quite closely to the stereoelectronic requirements for a Michael addition, but that of reaction I is very distorted, reflecting significant compromises in the stereoelectronic requirements.

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Section: Introductionsupporting

confidence: 59%

Comparison of an intramolecular Michael-type addition with its intermolecular counterpart: an abinitio theoretical study

Bayly¹,

Grein²

1989

Can. J. Chem.

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“…It therefore appears reasonable to assert that the preferred crystal conformation of the molecule may be due to such an interaction. Furthermore, the geometry at C(2), in particular the O(2)-C(2)-C(3) angle, is very similar to that predicted by the empirical rules proposed by Baldwin (1976) and Baldwin, Cutting, Dupont, Kruse, Silberman & Thomas (1976) for the transition state of nucleophilic 1,4-addition reactions to a,fl-unsaturated ketones, and one may therefore postulate that the interaction 0(2)..…”

mentioning

confidence: 69%

cis,trans-Tetrahydromitchelladione

Lewis¹,

Massy-Westropp²,

Snow³

1979

Acta Crystallogr Sect B

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Abstract. C3oH4402, M r : 436.68, orthorhombic, P21212 ~, a = 18.723(9), b = 12.334(6), c = 11.300(6) A,Z= 4, Dm= 1.100 (2), Dx = 1.112 Mg m -a. The structure was solved by direct methods with diffractometer data. Refinement of the structure gave a final value of R = 0.073 on F for 1325 non-zero reflections. The sesquiterpene dimer from the wood oil of Eremophila mitchelli exhibits a conformation in which the centres of the two halves of the molecule are as close as possible, most probably due to a dipolar interaction between them.

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“…The role of stereoelectronic factors in controlling organic ring-forming and ring-breaking reaction pathways is a subject of current experimental (1)(2)(3)(4)(5)(6)(7)(8) and theoretical (9)(10)(11) interest. In the case of smaller rings (less than eight atoms) where entropy considerations are not dominant, the formation of rings is governed largely by two interrelated factors.…”

Section: Introductionmentioning

confidence: 99%

“…As stated in the Introduction, neither the forward nor the reverse transformation takes place in basic medium in the case of 4 (G = H) or 4 (G = OCH,) or similar compounds (3). The failure to react has been shown to be due to a high barrier to interconversion rather than to an unfavourable equilibrium (3).…”

mentioning

confidence: 99%

The mechanism of an intramolecular Michael addition: a MNDO study

Ellis¹,

Tavares²,

Rauk³

1985

Can. J. Chem.

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The 5-endo-trig cyclization reactions of a'-hydroxy a,P-unsaturated carbonyl compounds to form the 3-furanone ring system has been investigated by means of MNDO calculations. In acid medium, the activation energy for ring formation is reduced by protonation of the carbonyl oxygen and by electron-releasing P-substituents, both of which facilitate torsion about the a,P-CC bond. Rotation about the a,P-CC bond is essentially complete when the transition structure is achieved. In reverse ring opening, heterolytic rupture of the C-0 bond is aided by prior enolization since induced polarization of the en01 7~ system acts to stabilize the developing cationic centre at the P-carbon. In basic medium, ring closure is hindered by the combined effects of the intrinsic barrier to cyclization and solvation of the intermediate alkoxide. Ring opening in basic medium is prevented by prohibitively high intrinsic barriers except when a strongly electron-releasing group such as p-0(-)-phenyl is at the P-carbon. GRAHAM W. L. ELLIS, DONALD F. TAVARES et ARVI RAUK. Can. J. Chem. 63, 3510 (1985). Faisant appel ti des calculs MNDO, on a CtudiC les reactions de cyclisation du type endo-5 trig des composts carboxyles a$-insaturCs, portant un groupement d'hydroxy en position a ' , qui conduisent au systkme cyclique de la furanone-3. En milieu acide, la protonation de l'oxygbne du carboxyle ainsi que la presence de substituants Clectrodonneurs en position P, qui toutes deux facilitent la rotation autour de la liaison carbone-carbone, rCduisent I'Cnergie d'activation de la rkaction. La rotation autour de la liaison carbone-carbone en a , P est totale au moment de la transition de structure. Contrairement ii l'ouverture de cycle, I'Cnolisation prkalable facilite la scission hCtCrolytique de la liaison C-0 puisque la polarisation induite des systbmes Cnoliques 7~ agit de f a~o n a stabiliser le centre cationique en voie de formation au niveau du carbone en position P. En milieu basique, les effets combines de la barribre intrinsbque ii la cyclisation et la solvatation de l'alcoolate intermediaire empkchent la cyclisation. La haute barribre intrinsbque inhibe I'ouverture de cycle en milieu basique mais la presence de groupements fortement Clectrodonneurs tels le p-0(-)-phCnyl au niveau du carbone en position P annule cet effet. [Traduit par le journal] IntroductionThe role of stereoelectronic factors in controlling organic ring-forming and ring-breaking reaction pathways is a subject of current experimental (1-8) and theoretical (9-11) interest. In the case of smaller rings (less than eight atoms) where entropy considerations are not dominant, the formation of rings is governed largely by two interrelated factors. First, the atoms to be bonded must be able to approach each other sufficiently closely to initiate bond formation. Secondly, the approach path must be more or less compatible with the electronic requirements of the nucleophilic and electrophilic functionalities. The first factor includes angular and torsional strain that must be overco...

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5-Endo-trigonal reactions: a disfavoured ring closure

Cited by 444 publications

References 0 publications

Comparison of an intramolecular Michael-type addition with its intermolecular counterpart: an abinitio theoretical study

Comparison of an intramolecular Michael-type addition with its intermolecular counterpart: an abinitio theoretical study

cis,trans-Tetrahydromitchelladione

The mechanism of an intramolecular Michael addition: a MNDO study

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