Chemoselective SN2′ reaction of nitroalkanes to dialkyl 2-(bromomethyl)fumarates under cetyltrimethylammonium hydroxide (CTAOH) catalysis

The chemoselective S_N2′ reaction of a variety of primary nitroalkanes to dialkyl 2-(bromomethyl)fumarates can be efficiently performed under cetyltrimethylammonium hydroxide (CTAOH) catalysis. The α,β-unsaturated esters were obtained in satisfactory to good yields with the complete retention of the nitro group.     

Use of heterogeneous catalyst KG-60-NEt2 in Michael and Henry reactions involving nitroalkanes

The N,N-diethylpropylamine supported on amorphous silica (KG-60-NEt₂) catalyses the formation of carboncarbon bonds by nitroalkanes through both the nitroaldol (Henry) and Michael reactions. The catalyst shows general utility with a variety of electrophilic acceptors. Moreover, the catalyst can be reused for two further cycles without loss of the activity.     

A palladacyclic azobenzene derivative as a catalyst for carbon-carbon bond formation reactions

A bis-chelated palladacycle in which the Pd atom is [(C, N)(C, N)]-tetracoordinated to two azobenzene ligands proved to be a moderately active catalyst for the Suzuki and Heck reactions. A voltammetric study revealed that the two-electron oxidation of this complex is accounted for by the irreversible Pd^II/Pd^IV transition.     

Enantioselective total synthesis of (−)-strychnine: development of a highly practical catalytic asymmetric carbon-carbon bond formation and domino cyclization

An enantioselective total synthesis of (−)-strychnine was accomplished through the use of the highly practical catalytic asymmetric Michael reaction (0.1 mol% of (R)-ALB, greater than kilogram scale, without chromatography, 91% yield and >99% ee), and a domino cyclization that simultaneously constructed the B- and D- rings of strychnine (>77% yield). Newly-developed reaction conditions for thionium ion cyclization, NaBH₃CN reduction of the imine moiety in the presence of a Lewis acid to prevent the ring-opening reaction, and chemoselective reduction of the thioether (desulfurization) in the presence of exocyclic olefin were pivotal to complete the synthesis. The described chemistry paves the way for the synthesis of more advanced Strychnos alkaloids.     

Stereospecific carbon-carbon bond formation by the reaction of a chiral episelenonium ion with aromatic compounds

The stereospecific exchange of a hydroxyl group of chiral alcohols bearing a pyridylseleno group on the adjacent carbon atom with aromatic compounds occurred smoothly in the presence of Lewis acid.     

Sn-Beta zeolite as diastereoselective water-resistant heterogeneous Lewis-acid catalyst for carbon-carbon bond formation in the intramolecular carbonyl-ene reaction

The water-tolerant Lewis acid Sn-Beta isomerises citronellal to isopulegol with high diastereoselectivity working in batch or in fixed bed reactors with very high turnover numbers.     

A facile method for synthesis of polysubstituted naphthalene derivatives through pyrrolidine catalyzed domino reaction

A novel synthetic method for polysubstituted naphthalene derivatives via a pyrrolidine-mediated cascade Michael/Henry reaction was developed, in which easily prepared 2-(2-oxoethyl)benzaldehydes and nitroalkenes were employed as the starting materials. The reaction consists of four consecutive reactions that include a cascade Michael/Henry reaction, a dehydration reaction, and an aromatization reaction in one pot to afford synthetically important naphthalene derivatives with moderate yields.     

A new kind of organophosphorus compounds as an efficient catalyst for asymmetric C-C bond formation reactions

A new class of chiral pyrrolidine-phosphite organocatalysts, available from commercially starting materials, has been synthesized and shown to be good catalytic activity for asymmetric Michael and Aldol reactions. The reactions proceeded to give the products in good yield and in a highly selective manner. Ionic liquid [Bmim][BF₄] as an efficient green solvent has been employed in the Michael addition.     

Colloidal gold nanoparticles as catalyst for carbon-carbon bond formation: application to aerobic homocoupling of phenylboronic acid in water

Gold nanoparticles (<2 nm) stabilized by poly(N-vinyl-2-pyrrolidone) (Au:PVP NPs) were prepared by reduction of AuCl4- with NaBH4 in the presence of PVP and characterized via an array of methods including optical absorption spectroscopy, transmission electron microscopy, X-ray diffraction, X-ray absorption near-edge structure, extended X-ray absorption fine structure, and X-ray photoelectron spectroscopy. We demonstrate for the first time that the Au:PVP NPs act as catalyst toward homocoupling of phenylboronic acid in water under aerobic conditions. Suppression of biphenyl formation under anaerobic conditions indicates that molecular oxygen dissolved in water is intimately involved in the coupling reactions. A mechanism of the aerobic homocoupling catalyzed by the Au:PVP NPs is proposed on the basis of a crucial role of dissolved oxygen, steric effects on the product yields, and the well-established mechanism for the Pd(II)-based catalysts.     

Regioselective, nucleophilic carbon-carbon bond formation at the C4-position of indoles initiated by the aromatic Pummerer-type reaction

The treatment of the 5-(phenylsulfinyl)indoles with trifluoroacetic anhydride in the presence of carbon nucleophiles achieved the title reactions with complete regioselectivity.     

Unprecedented carbon-carbon bond formation induced by photoactivation of a platinum(IV)-diazido complex

UVA-induced photodecomposition of a Pt(IV)-diazido complex involves not only reduction to Pt(II) and N(2) release, but also O(2) evolution and formation of nitrene intermediates, whose trapping with (CH(3))(2)S gives rise to an unusual N,N'-bis(ethyl)sulfurousdiamide ligand in an apparently unprecedented process involving C-C bond formation.     

Reconstructed hydrotalcite as a highly active heterogeneous base catalyst for carbon-carbon bond formations in the presence of water

The aldol reaction of carbonyl compounds is efficiently catalyzed by reconstructed hydrotalcites, obtained by treating the Mg-Al mixed oxide with water, as solid base catalysts in the presence of water. The catalysis of the reconstructed hydrotalcites is attributable to the surface base sites, created during the organization of the layered structure, with uniformly distributed strength. Furthermore, the reconstructed hydrotalcites provide a unique acid-base bifunctional surface capable of promoting the Knoevenagel and Michael reactions of nitriles with carbonyl compounds.     

Periodic mesoporous silica-immobilized palladium(II) complex as an effective and reusable catalyst for water-medium carbon-carbon coupling reactions

Ethyl-bridged periodic mesoporous organosilicas (PMOs) functionalized with diphenylphosphino (PPh₂) ligands were synthesized by one-step evaporation-induced self-assembly (EISA), which were used as a support to immobilize Pd(II) organometallic catalyst by coordination reaction. The as-prepared Pd(II)-PPh₂-PMO(Et) exhibited high activity in water-medium C-C coupling reactions and could be used repetitively. The high activity could be attributed to the high dispersion of Pd(II) active sites and ordered mesopore channels which effectively diminished the steric hindrance and thus, diffusion limit. Meanwhile, the ethyl-fragments and the PPh₂-ligands in the support wall could synergic enhance surface hydrophobicity, which promoted the adsorption for organic reactant molecules.     

Stimulation on the addition reactivity of fluorinated vinyl monomers—Facile carbon-carbon bond formation by the aid of fluorine substituents

The high addition reactivity of fluorinated vinyl compounds toward radical and anionic species was demonstrated to afford facile methods for the carbon-carbon bond formation by the aid of fluorinated substituents of vinyl groups. Some of the reactions are proved to be applicable to the preparation of polymers by radical or anionic polyaddition reaction mechanism. The investigation on the anionic reactivity order of fluorinated acrylates and methacrylates may contribute to the development in the field of the estimation by the computer chemistry to determine which effect of the fluorine-substitution would control the reactions.     

Palladium(0) nanoparticles: an efficient catalyst for the one-pot synthesis of polyhydroquinolines

A mild, concise, and efficient protocol for the synthesis of polyhydroquinoline via four component reaction of aromatic aldehydes, dimedone, ethyl acetoacetate or ethyl cyanoacetate, and ammonium acetate using Pd-nanoparticles is described. The same phenomenon was observed in the case of arylmethylene bis(3-hydroxy-2-cyclohexene-1-ones), ethyl acetoacetate, ammonium acetate, and Pd-nanoparticles in one-pot. The present method also allows us to synthesize highly functionalized title compounds from simple and readily available inputs.     

Functionalization of the pyridine ring. 1. Reactions with carbon-carbon bond formation (review)

A review is presented for advances in the direct introduction of alkyl, alkenyl, alkynyl, aryl, and hetaryl substituents into the pyridine ring over the past IS years.