On the mechanism of stereospecific S(3P) and O(3P) additions to olefins

Leppin, Eberhard; Gollnick, Klaus

doi:10.1016/s0040-4039(01)88522-1

Cited by 10 publications

(4 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Unfortunately, very few data of triplet carbenic addition reactions have been reported for the heavy atom effect, but the few available results are in agreement with this prediction. Some supporting evidence comes from the fact that ground sulfur atom (in the 3 P state), whose valence shell is isoelectronic with methylene, adds largely stereospecifically to cis -2-butene. − On the other hand, it was found that triplet nitrene (NH) and triplet oxygen atom (in the 3 P state), which are isoelectronic to the carbene (CH 2 ), always added in a nonstereospecific manner. The reason for this is presumably because the heavy atom effect is relatively unimportant in the first low elements.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Role of Spin−Orbit Coupling and Symmetry in Triplet Carbenic Addition Chemistry

1996

J. Phys. Chem.

View full text Add to dashboard Cite

The spin-orbit coupling parts in the effective one-electron Hamiltonian operator, with the inclusion of symmetry, have been used to formulate mechanisms based on the Shaik and Epiotis theory in triplet reactions for the radiationless decay of triplet complexes to singlet ground state products. This has been applied to investigate the stereochemical behavior of additions of triplet carbenes to olefins. It is shown that triplet carbene-olefin complexes can be classified according to the number and the direction of the atomic orbital rotations required to maximize spin-orbit coupling and simultaneously maintain the intermolecular binding, from which it may produce different stereoisomers. It is suggested that six spin-inversion reaction mechanisms produce geometric isomers. It is found that, as a direct of the different symmetries of the three sublevels of the triplet state (T x , T y , T z ) and their comparable spin-orbit coupling expressions, the triplet carbene could add to olefins nonstereospecifically. Nevertheless, it is also suggested that, because of its larger spin-orbit coupling expression as well as the less conformational change, the cycloaddition of a triplet carbene to a double bond will lead to the stereospecific cyclopropane with retention of geometry in a concerted pathway. The solvent polarity, substituent effect, and heavy atom effect must all play an important role in determining the stereoconformations of adducts. The results obtained are in agreement with the available experimental results and allow a number of predictions to be made. It is found that the approach proposed in this study is proved to be a good alternative to the traditionally accepted explanation, the Skell-Woodworth mechanism.

show abstract

Section: Resultsmentioning

confidence: 99%

“…(b) For a similar explanation based on orbital correlation diagrams and ab initio SCF study refer to refs and , respectively.…”

Section: Referencesmentioning

confidence: 99%

Role of Spin−Orbit Coupling and Symmetry in Triplet Carbenic Addition Chemistry

1996

J. Phys. Chem.

View full text Add to dashboard Cite

show abstract

“…This radical-type atomic sulfur adds to Z-butene to form a diradical, which on cyclization and intersystem crossing affords the thiirane; insertion into a C-H bond to form mercaptans was not observed. 13 Due to the fast intersystem crossing (heavy atom effect of sulfur), 18 the episulfidation with S( 3 P) occurs under retention of the alkene configuration. 19 Since the trapping of S( 3 P) by a CC double-bond substrate is very efficient, triplet atomic sulfur is also a good candidate for the stereoselective episulfidation of allenes 20 (Scheme 2).…”

Section: Atomic Sulfurmentioning

confidence: 99%

Synthesis of Thiiranes by Direct Sulfur Transfer: The Challenge of Developing Effective Sulfur Donors and Metal Catalysts

Adam

Bargon

2003

Chem. Rev.

View full text Add to dashboard Cite

“…These mechanisms have been criticized (4) and an alternate, symmetric path for the triplet cycloaddition reaction proposed on several theoretical grounds (18)(19)(20). The existence of an open-ring triplet diradical in the cycloaddition reactions has been proposed (12) to account for the loss of stereospecificity, to provide paths to the other reaction products observed, and as an explanation for the observed increased production of addition at the expense of fragmentation products for larger substituted olefins (9,13).…”

Section: Introductionmentioning

confidence: 99%

Theoretical studies of the chemistry of singlet and triplet species. II. Cycloaddition reaction

Bader¹,

Stephens²,

Gangi³

1977

Can. J. Chem.

View full text Add to dashboard Cite

. GANGI. Can. J. Chem. 55,2755 (1977.Ab initio SCF potential energy surfaces for the cycloaddition reactions C2H4(tAlg) + O(ID, 3P) are reported. The lowest energy singlet path corresponds to the symmetric, concerted addition reaction yielding ethylene oxide. The lowest energy triplet path corresponds to an asymmetric approach of the reactants to form an open ring adduct (LCCO = 105"). The spatial distribution of the spin density in this adduct conforms to that expected for a diradical. The barrier to internal rotation of the terminal methylene is calculated to be N 5 kcal mol-'. The lowest intersystem crossing from the triplet to the singlet surface, as required for ring closure to yield ground state product, is found to occur ~3 6 kcal mol-I above the energy of the triplet reactants.The differences in singlet and triplet charge distributions and energies for similar approach geometries may be rationalized in terms of the additional restraints imposed on the course of the triplet reaction by the Pauli principle, restraints which are made evident by the spatial distribution of the spin density. Two principal mechanisms of spin polarization, spin unpairing and spin decoupling, are found to provide a rationale for the observed differences of singlet and triplet reactants in abstraction, insertion and addition reactions. The favoured course of a triplet reaction is found to be governed by the axiom that localized distributions of spin density are to be maximally separated in space. pour former un adduit a cycle ouvert (LCCO = 105'). La distribution spatiale des densitts de spin dans cet adduit est en conformite avec celle attendue pour un diradical. On a calcul6 que la barriere a la rotation interne du methylene terminal est d'environ 5 kcal mol-I. La conversion intersystkme la plus basse entre la surface triplet et la surface singulet, telle que requise pour la fermeture du cycle conduisant a un produit dans 1'Btat fondamental, se produirait environ 36 kcal mol-' au dessus de 1'6nergie des reactifs triplets.On peut rationaliser les differences dans les distributions de charge des etats singulet et triplet et les energies pour les geometries d'approches similaires en termes de contraintes additionnelles imposQs sur I'evolution de la reaction triplet par le principe de Pauli, restrictions qui sont rendues evidentes par la distribution spatiale des densites de spin. On a trouve que deux mecanismes principaux de polarisation de spin, de depairage de spin et de dtcouplage de spin peuvent fournir une explication rationnelle pour les differences observees dans les reactions d'enlevement d'insertion et d'addition des reactifs singulet et triplet. On a trouve que le chemin favoris6 pour une reaction a 1'6tat triplet est gouverne par I'axiome voulant que les distributions localisees de densite de spin doivent &re separees au maximum dans I'espace.[Traduit par le journal] Introduction bond. Ab initio SCF potential surfaces are reThis paper presents a theoretical study and ported for the cycloaddition reactions of o('D, compa...

show abstract

On the mechanism of stereospecific S(3P) and O(3P) additions to olefins

Cited by 10 publications

References 8 publications

Role of Spin−Orbit Coupling and Symmetry in Triplet Carbenic Addition Chemistry

Role of Spin−Orbit Coupling and Symmetry in Triplet Carbenic Addition Chemistry

Synthesis of Thiiranes by Direct Sulfur Transfer: The Challenge of Developing Effective Sulfur Donors and Metal Catalysts

Theoretical studies of the chemistry of singlet and triplet species. II. Cycloaddition reaction

Contact Info

Product

Resources

About