Mechanism Of Ene Reaction Research Articles

Understanding the polar mechanism of the ene reaction. A DFT study.

The molecular mechanism of ene reactions has been characterised by DFT methods at the MPWB1K/6-311G(d,p) level of theory. Most reactions take place along a two-stage one-step mechanism in which the C-C bond formation takes place before the hydrogen transfer process. A very good correlation between the polar character of the reaction measured by the global electron density transfer at the transition state and the activation energy has been found. This behaviour allows establishing a useful classification of ene reactions in N-ene having a very high activation energy, P-ene reactions having activation energies between 35 and 20 kcal mol(-1), and H-ene reactions having activation energies below 20 kcal mol(-1). ELF topological analysis allows the characterisation of the two-stage one-step mechanism associated with a two-centre nucleophilic/electrophilic interaction. Formation of the C-C single bond is achieved by the C-to-C coupling of two pseudoradical centres formed at the two interacting carbon atoms in the first stage of the reaction. This topological analysis establishes that bonding changes are non-concerted. Finally, a DFT reactivity analysis makes it possible to characterise the electrophilic/nucleophilic behaviour of the reagents involved in ene reactions, and consequently, to predict the feasibility of ene reactions.

Driving force of metallo (Mg–H and Mg–Cl)-ene reaction mechanisms

The potential-energy surfaces of the metallo-ene reactions of allyl-MgH and allyl-MgCl with ethylene were studied using ab initio molecular-orbital (MO) methods. The concerted path and the stepwise path of the metallo-ene reactions of allyl-MgH and allyl-MgCl with ethylene were identified and it was determined that the energy barriers on concerted paths of the metallo-ene reactions of allyl-MgH and allyl-MgCl with ethylene are lower than those on the stepwise paths. Furthermore, the concerted path of the metallo-ene reaction of allyl-MgCl with ethylene is more favorable than that of the allyl-MgH reaction system. The reaction mechanisms were analyzed using a CiLC method on the basis of CASSCF MOs. The driving force for the concerted path reactions arises from the migration process of the metal. The difference between the reactivity of allyl-MgH and allyl-MgCl can be explained with the reaction mechanism on the basis of the driving force.

金属（Li，Na)ーエン反応機構の理論的研究。協奏機構か段階機構かあるいは金属触媒機構？

金属（Li，Na)ーエン反応機構の理論的研究。協奏機構か段階機構かあるいは金属触媒機構？

Theoretical Studies of Metallo (Li and Na)−Ene Reaction Mechanisms

The reaction mechanisms of allyl-lithium and allyl-sodium with ethylene were studied by ab initio molecular orbital (MO) methods. The reaction mechanisms were analyzed by a CiLC-IRC method on the basis of ab initio CASSCF MOs. The ene reaction pathways of allyl-Li and allyl-Na with ethylene were located. The complex between allyl-metal and ethylene for both systems is found in the first step of the reaction, and then the metal migration and new C-C bond formation occur synchronously through the transition state. The complexation energies are -13.2 and -9.6 kcal/mol for Li and Na systems, respectively. The activation energy barriers from the reactants are 3.5 kcal/mol for the Li system and 2.0 kcal/mol for the Na system at the MRMP2 calculation level. These barriers are significantly lower than that of the ene reaction of propene with ethylene as the parent reaction. The CiLC-IRC analysis shows that the reaction of allyl-metal with ethylene is a concerted ene reaction mechanism, not a metal catalysis and/or a stepwise reaction.

Theoretical Studies on the Ene Reaction Mechanisms of Propene and Cyclopropene with Ethylene and Cyclopropene: Concerted or Stepwise

The potential energy surfaces of the ene reactions of propene and cyclopropene with ethylene and cyclopropene were studied by ab initio molecular orbital (MO) methods. The reaction mechanisms were analyzed by CiLC method on the basis of CASSCF MOs. The concerted and stepwise reaction pathways of the ene reaction of propene with ethylene as the parent reaction were located. The energy barrier of the stepwise process is about 4 kcal/mol lower than that of the concerted one. The other reactions can be found only the stepwise mechanism. Although the endo-type reaction of propene with cyclopropene, where cyclopropene is the enophile, probably occurs through a one-step process, the mechanism is divided into the CC bond formations and the hydrogen migration as a stepwise reaction. The CiLC-IRC analysis of the concerted process of propene with ethylene shows the different patterns of the electronic state variation for the CC bond formation/breaking and the hydrogen migration.

Mechanism of ene reactions of singlet oxygen. A two-step no-intermediate mechanism.

The mechanism of the ene reaction of singlet ((1)delta(g)) oxygen with simple alkenes is investigated by a combination of experimental isotope effects and several levels of theoretical calculations. For the reaction of 2,4-dimethyl-3-isopropyl-2-pentene, the olefinic carbons exhibit small and nearly equal (13)C isotope effects of 1.005-1.007, while the reacting methyl groups exhibit (13)C isotope effects near unity. In a novel experiment, the (13)C composition of the product is analyzed to determine the intramolecular (13)C isotope effects in the ene reaction of tetramethylethylene. The new (13)C and literature (2)H isotope effects are then used to evaluate the accuracy of theoretical calculations. RHF, CASSCF(10e, 8o), and restricted and unrestricted B3LYP calculations are each applied to the ene reaction with tetramethylethylene. Each predicts a different mechanism, but none leads to reasonable predictions of the experimental isotope effects. It is concluded that none of these calculations accurately describe the reaction. A more successful approach was to use high-level, up to CCSD(T), single-point energy calculations on a grid of B3LYP geometries. The resulting energy surface is supported by its accurate predictions of the intermolecular (13)C and (2)H isotope effects and a very good prediction of the reaction barrier. This CCSD(T)//B3LYP surface features two adjacent transition states without an intervening intermediate. This is the first experimentally supported example of such a surface and the first example of a valley-ridge inflection with significant chemical consequences.

ChemInform Abstract: Ene Reaction Mechanisms. Part 3. Intermolecular and Intramolecular Kinetic Isotope Effects (KIE) for Some Ene Reactions of Hetero Enophiles.

Chemischer InformationsdienstVolume 17, Issue 25 Preparative Organic Chemistry ChemInform Abstract: Ene Reaction Mechanisms. Part 3. Intermolecular and Intramolecular Kinetic Isotope Effects (KIE) for Some Ene Reactions of Hetero Enophiles. W. STARFLINGER, W. STARFLINGERSearch for more papers by this authorG. KRESZE, G. KRESZESearch for more papers by this authorK. HUSS, K. HUSSSearch for more papers by this author W. STARFLINGER, W. STARFLINGERSearch for more papers by this authorG. KRESZE, G. KRESZESearch for more papers by this authorK. HUSS, K. HUSSSearch for more papers by this author First published: June 24, 1986 https://doi.org/10.1002/chin.198625093AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume17, Issue25June 24, 1986 RelatedInformation

Ene reaction mechanisms. 3. Intermolecular and intramolecular kinetic isotope effects (KIE) for some ene reactions of hetero enophiles

Ene reaction mechanisms. 3. Intermolecular and intramolecular kinetic isotope effects (KIE) for some ene reactions of hetero enophiles

Ene reaction mechanisms. 1. Chirality transfer to the enophile 4-methyl-N-sulfinylbenzenesulfonamide

Ene reaction mechanisms. 1. Chirality transfer to the enophile 4-methyl-N-sulfinylbenzenesulfonamide

Ene reaction mechanisms. 2. Regioselectivity with N-aryl-N'-p-tosylsulfur diimides as enophiles. Crystal structure of N-(pentafluorophenyl)-N'-p-tosylsulfur diimide

Etude des reactions des sulfodiimides TosNSNAr (Ar=CH 5 , NO 2 - 4 C 6 H 4 et C 6 F 5 ) avec le methyl-2 butene-2

Changes in ene reaction mechanisms with Lewis acid catalysis

Changes in ene reaction mechanisms with Lewis acid catalysis

On the mechanism of ene reaction of electron-rich olefins with singlet oxygen. Ab-initio MO calculations

The ab-initio MO (STO-3G) calculations were performed for the reaction of 2-aminopropene with singlet oxygen.