Decarbonylative radical conjugate addition of aliphatic aldehydes for alkylation of electron-deficient alkenes

A convenient metal-free decarbonylative radical conjugate addition of aliphatic aldehydes to electron-deficient alkenes is developed. With DTBP as an oxidant and radical-initiator, this reaction smoothly converts α-unsubstituted, α-mono-substituted and α-di-substituted aliphatic aldehydes into the corresponding primary, secondary and tertiary alkyl radicals, and subsequently allows for the cascade construction of C(sp³)C(sp³) bond via radical conjugate addition.     

Palladium(II)-catalyzed conjugate addition of arylsiloxanes in water

Palladium-phosphinous acids catalyze the conjugate addition of arylsiloxanes to a wide range of alpha,beta-unsaturated substrates in water. A microwave-assisted procedure is described that uses 5 mol % of POPd1 to afford beta-substituted ketones, aldehydes, esters, nitriles, and nitroalkanes in 83% to 96% yield within 4 h. This method eliminates the need for stoichiometric additives and an excess of arylsiloxane, and does not require an inert atmosphere.     

Effective Au(III)-CuCl2-catalyzed addition of alcohols to alkenes

Alkenes can be activated by Au(III) catalysts, and the effective addition of alcohols to alkenes can be carried out under mild conditions with Au(III), provided that catalytic amounts of CuCl(2) are added, which significantly stabilize the cationic Au(III).     

Efficient copper(II)-catalyzed addition of activated methylene compounds to alkenes

Efficient regioselective addition of beta-diketones to styrenes, norbornene, cyclic enol ether, and diene has been realized by means of copper(II) triflate as the catalyst. The solvent effect is prominent on the reactions, and the desired addition products were obtained in good to excellent yields only in dioxane or ionic liquid [bmim]PF6. The mechanism suggests that copper(II) triflate activates the enolic O-H bond of a beta-diketone substrate to initiate the addition reaction.     

Copper(I)-catalyzed reaction of acylzirconocene chloride: cross-coupling and conjugate addition

For the purpose of exploring a new reaction of acylzirconocene chloride as an acyl anion donor, Cu(I)-catalyzed cross-coupling and conjugate addition reactions of acylzirconocene chloride were studied. The coupling reaction with allylic or propargylic halides efficiently proceeded to yield β,γ-unsaturated ketone or allenyl ketone derivatives, respectively. The conjugated addition reaction to ,β-enones was carried out in the presence of 2 equiv. of BF₃·OEt₂ giving 1,4-diketone compounds.     

Hydroformylation of alkenes employing rhodium(i) complexes and a phosphine oxide ligand

Following the facile synthesis of a novel phosphine oxide compound, (diphenylphosphinoyl)phenylmethanol (1), this compound was employed as a ligand in the rhodium-catalyzed hydroformylation of alkenes, with good conversions and regioselectivities. This ligand was partially resolved using an enzyme, and enantioselective hydroformylation was carried out with the addition of a rhodium(I) complex. The rhodium(I) complex containing ligand 1 was not isolated, although it was subjected to low-temperature NMR studies.     

Synthesis of difluoromethylated benzylborons via rhodium(Ⅰ)-catalyzed fluorine-retainable hydroboration of gem-difluoroalkenes

The synthesis of bo rylated orga nofluorines is of great interest due to their potential values as synthons in modular construction of fluorine-containing molecules.Reported herein is a rhodium-catalyzed hydrobo ration of arylgem-difluoroalkenes leading to a series of α-difluoromethylated benzylborons.The use of cationic rhodium catalyst and a biphosphine ligand with large bite angle was crucial for reactivity by offering good regioselectivity and diminishing the undesired β-F elimination.Preliminary derivatizations of the products were conducted to showcase the utility of this protocol.     

过渡金属催化下的烯烃硼氢化反应

本文综述了在过渡金属尤其是铑络合物催化下烯烃与CB ( 邻苯二酚硼烷 ) 的硼氢化反应在化学、位置和立体选择性的进展, 对它们的机理也进行了讨论。     

Li+-catalyzed radical polymerization of simple terminal alkenes

Solutions of Li+ salts of highly alkylated derivatives of the monocarbadodecaborate anion in 1,2-dichloroethane catalyze the radical polymerization of simple terminal alkenes, dienes, and alkynes under ambient conditions, initiated by azoisobutyronitrile, di-tert-butyl peroxide, or atmospheric air.     

A room-temperature protocol for the rhodium(I)-catalyzed addition of arylboron compounds to sulfinimines

[reaction: see text] The addition of organoboronic acids to chiral sulfinimines proceeds under mild conditions at room temperature, using Rh(I) catalysis in the absence of external phosphine ligands. Clean reaction only occurs in the presence of water as a cosolvent. The sulfinamide adducts are formed with high diastereoselectivities, providing a convenient route to the synthesis of enantiomerically enriched chiral benzylic amines.     

Copper(II)-catalyzed enantioselective conjugate addition of nitro esters to 2-enoyl-pyridine N-oxides

A highly enantioselective Michael addition of nitro esters to 2-enoyl-pyridine N-oxides was developed by using chiral copper catalysts. The Michael addition products can be obtained in high yields and with up to 96% ee.     

Rh(I)-catalyzed conjugate addition of alkenylzirconocene chloride: stereoselective formation of carbocycles through cascade reaction

Stereoselective formation of carbocycles was carried out through [RhCl(cod)]₂-catalyzed reactions of alkenylzirconocene chloride to ω-carbonyl-α,β-ene carbonyls (ketone, ester, and amide) or to bis-enone derivatives. The Rh(I)-catalyzed reaction of alkenylzirconocene chloride with ω-carbonyl-α,β-enoyl amide, which is derived from Oppolzer’s sultam, showed high diastereoselectivity to yield an carbocycle (95% yield, >95% de).     

Indium(III) acetate-catalyzed intermolecular radical addition of organic iodides to electron-deficient alkenes

In the presence of phenylsilane and a catalytic amount of indium(III) acetate, organic iodides added to electron-deficient alkenes in ethanol at room temperature. Both simple and functionalized organic iodides were applicable to this reaction. A plausible reaction mechanism involves the formation of indium hydride species by hydride transfer from silicon to indium and an indium hydride-mediated radical chain process.     

Iridium-catalyzed hydroboration of alkenes with pinacolborane

Hydroboration of terminal and internal alkenes with pinacolborane (1.2 equiv) was carried out at room temperature in the presence of an iridium(I) catalyst (3 mol%). Addition of dppm (2 equiv) to [Ir(cod)Cl]₂ gave the best catalyst for hydroboration of aliphatic terminal and internal alkenes at room temperature, resulting in addition of the boron atom to the terminal carbon of 1-alkenes with more than 99% selectivities. On the other hand, a complex prepared from dppe (2 equiv) and [Ir(cod)Cl]₂ resulted in the best yields for vinylarenes such as styrene. These complexes exhibited higher levels of catalyst activity and selectivity than those of corresponding rhodium complexes.     

Rhodium(i)-catalyzed polymerization of fluorenylacetylenes

The synthesis and characterization of poly(monofluorenylacetylenes) obtained by polymerization of 2-ethynyl-9,9-bis[(S)-3,7-dimethyl-octyl]fluorene and 2-ethynyl-9,9-bis[(S)-2-methylbutyl]fluorene are described. The effect of the structure of the alkyl chain at the C(9) position of fluorene on the properties of the materials was studied by differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction analysis, UV/Vis spectroscopy, photoluminescence, and circular dichroism. Polymerization of chiral 2-ethynylterfluorene functionalized with (S)-2-methylbutylalkyl chains was studied. The resulting polymer exhibits high thermal stability; its emission spectrum occurs in the violet-blue region and shows no significant red shift on passing from a solution to the solid state.Based on the report presented at the International Conference Modern Trends in Organoelement and Polymer Chemistry dedicated to the 50th anniversary of the A. N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences (Moscow, May 30–June 4, 2004).Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1962–1967, September, 2004.     

Palladium(II)-catalyzed intramolecular diamination of unfunctionalized alkenes

Intramolecular diamination reactions are described which yield cyclic ureas as direct products of an oxidative alkene transformation in the presence of palladium acetate and iodosobenzene diacetate as terminal oxidant. The reaction is truly catalytic in metal catalyst and represents the proof of principle for this elusive type of alkene oxidation.