Palladium-catalyzed addition reaction of polyhaloalkanes to olefins

Pd(OAc)₂ combined with phosphines catalyzes homolytic cleavage of the C—Cl bond of CCl₄ and CCl₃CO₂CH₃ leading to facile addition to olefins under mild conditions. BrCCl₃ also reacts with olefins to give 1,1,1-trichloro-3-bromoalkanes. The reaction is accelerated under CO atmosphere, and the presence of bases such as NaOAc or K₂CO₃ is essential to attain high yields of the adducts.     

Concept of polarity of free radicals in reactions of addition to olefins

The concept of polarity (nucleo- and electrophilicity) of free radicals in processes of addition to unsaturated substrates was developed within the framework of the method of qualitative potential energy surfaces on the basis of an analysis of the interaction of diabatic surfaces for reactions of free-radical addition to olefins. A formulation is given for the concept of the polarity (philicity) of the attacking free radical; the theoretical index of philicity and the criterion of polarity of the radicals are proposed; the concept of ambiphilicity of a radical is introduced. The chemical aspects of the philicity of free radicals — the influence of a change in it on the formation and height of the activation barrier of the reaction and the strength of the bond formed — are discussed. A parallel formulation of the concept of polarity of radicals in terms of boundary orbital interactions in the free-radical-unsaturated substrate system is given.Translated from Teoreticheskaya i Éxperimental'naya Khimiya, Vol. 22, No. 5, pp. 562–571, September–October, 1986.     

Determination of absolute rate constants of addition of ethyl radicals to olefins

Theoretical and Experimental Chemistry -     

Samarium diiodide initiated addition reaction of fluoroalkyl iodides to olefins

Samarium diiodide was found to be an effective initiator in the addition reaction of fluoroalkyl iodides to olefins.     

Delocalization model of regioselectivity and reactivity of free radicals in reactions of addition to olefins

On the basis of the concept of polarity (philicity) of free radicals as proposed by the authors, within the framework of methods of qualitative surfaces of potential energy (linear combinations of configurations of fragments) and stabilization energy, an effective model has been developed for the regioselectivity and reactivity of radicals in processes of addition. A critical examination is made of certain key aspects of the change in regiochemistry and reactivity with changes in the electronic structure of the free radical and substrate. The dominant trends in regioselectivity and reactivity in processes of free-radical addition to olefins are controlled by electronic effects and can be predicted by analyzing interactions of diabatic potential energy surfaces or orbital interactions for a system consisting of a free radical and an unsaturated substrate.Presented at 3rd All-Union Symposium Dynamics of Elementary Atomic-Molecular Processes (Chernogolovka, June 1985) and at the 9th All-Union Conference on Quantum Chemistry (Ivanovo, June 1985).Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 2, pp. 135–148, March–April, 1987.The authors are grateful to M. V. Bazilevskii for his constructive discussion of the results obtained in this work.     

Microwave-assisted atom transfer radical addition of polychlorinated compounds to olefins without addition of metal catalysts

A new operationally simple and robust protocol for the metal-free atom transfer radical reaction (ATRA) has been developed. Polychlorinated compounds were effectively reacted with unactivated terminal olefins to generate 1,3-dichlorinated adducts under microwave irradiation in the presence of silicon carbide (SiC) as a heating element. The present microwave-assisted ATRA proceeds under essentially neutral conditions; thus, polar functionalities are well tolerated. In addition, an oxygen or a nitrogen unit was introduced to the internal side of the carbon chain via nucleophilic cyclization of the 1,3-dichlorinated adducts, and single-step formation of the six-membered carbocycle was realized through cyclization of the intermediate radical. The present methodology provides an expeditious way to prepare synthetically useful molecules from simple and unactivated terminal olefins.     

Ultrasound effects on the Mn(III) - promoted addition of amidoalkyl radicals to olefins

Amidoalkyl radicals, generated from amides by Mn(OAc)₃ in acetic acid react with phenyl substituted alkenes to generate five-membered lactones or lactams. Ultrasound at ambient temperature significantly accelerates these single electron transfer reactions even when compared with conventional conditions under reflux or simple mechanical stirring. In some cases sonication leads to unusual products.     

Addition of methoxy radicals to olefins

The addition of methoxy radicals to several olefins has been studied by a competitive method at 127°C in gas phase. The thermal decomposition of dimethyl peroxide was used as methoxy radical source. The rate of addition to the double bond was measured relative to the oxidation of carbon monoxide. For the addition to ethylene it was obtained that This rate constant is similar to the one shown by methyl radicals under similar conditions. From the relative rate of addition to several chlorinated and fluorinated olefins it can be concluded that methoxy radicals show very little “electrophilic” character.     

Copper-homoscorpionate complexes as active catalysts for atom transfer radical addition to olefins

Cu(I) complexes containing trispyrazolylborate ligands efficiently catalyze the atom transfer radical addition (ATRA) of polyhalogenated alkanes to various olefins under mild conditions. The catalytic activity is enhanced when bulky and electron donating Tpx ligands are employed. Kinetic data have allowed the proposal of a mechanistic interpretation that includes a Cu(II) pentacoordinated species that regulates the catalytic cycle.     

Absolute rate constants for the addition of hydroxymethyl radicals to alkenes in methanol solution

Absolute rate constants and their temperature dependencies were determined for the addition of hydroxymethyl radicals (CH₂OH) to 20 mono- or 1,1-disubstituted alkenes (CH₂ = CXY) in methanol by time-resolved electron spin resonance spectroscopy. With the alkene substituents the rate constants at 298 K (k₂₉₈) vary from 180 M^?1s^?1 (ethyl vinylether) to 2.1 middot; 10⁶ M^?1s^?1 (acrolein). The frequency factors obey log A/M^?1s^?1 = 8.1 ± 0.1, whereas the activation energies (E_a) range from 11.6 kJ/mol (methacrylonitrile) to 35.7 kJ/mol (ethyl vinylether). As shown by good correlations with the alkene electron affinities (EA), log k₂₉₈/M^?1s^?1 = 5.57 + 1.53 · EA/eV (R² = 0.820) and E_a = 15.86 ? 7.38 · EA/eV (R² = 0.773), hydroxymethyl is a nucleophilic radical, and its addition rates are strongly influenced by polar effects. No apparent correlation was found between E_a or log k₂₉₈ with the overall reaction enthalpy. © 1995 John Wiley & Sons, Inc.     

Carbocyanation of trisubstituted olefins via Cu-catalyzed atom transfer radical addition

A regioselective Cu(I)-catalyzed carbocyanation of non-polarized trisubstituted olefins 1 has been achieved by employing chlorinated cyanides 2 as starting materials. The present reaction gives the carbocyanated product 3 through radical-based 1,3-transfer of CN. Consequently, two different carbon units, cyano and chlorocyanomethyl groups, are introduced into the highly substituted olefins, generating consecutive quaternary and tertiary carbons. Since both of the attached carbon units can be used as handles for further synthetic elaborations, the present transformation offers a new synthetic methodology for rapid construction of architecturally complex carboskeletons.     

磷化氢与烯烃反应的原位NMR谱研究

本文应用加压原位(in-situ)核磁共振技术, 在反应温度70-75℃, 压力1.0-2.0MPa, 氘代苯为溶剂, 偶氮二异丁腈(AIBN)为引发剂的条件下探索了磷化氢与丙烯腈, 4-乙烯基吡啶, 烯丙基胺, 丙烯酰胺, 氨基吡啉和N-乙烯基咔唑的自由基加成反应, 结果表明除氨基吡啉之外的其它五种含氮化合物均能与磷化氢发生反应, 从而找到合成含氮有机膦的良好路线。     

Halogen atom transfer radical addition of α-polychloroesters to olefins promoted by Fe filings

The Kharasch addition of methyl 2,2-dichlorocarboxylates or trichloro acetic acid derivatives to alkenes, affording the corresponding 1:1 adducts, is promoted by the iron filings/N,N-dimethylformamide system.