1595-11-5

Here, we describe a photoredox-assisted catalytic system for the direct reductive coupling of two carbon electrophiles. Recent advances have shown that nickel catalysts are active toward the coupling of sp3-carbon electrophiles and that well-controlled, light-driven coupling systems are possible. Our system, composed of a nickel catalyst, an iridium photosensitizer, and an amine electron donor, is capable of coupling halocarbons with high yields. Spectroscopic studies support a mechanism where under visible light irradiation the Ir photosensitizer in conjunction with triethanolamine are capable of reducing a nickel catalyst and activating the catalyst toward cross-coupling of carbon electrophiles. The synthetic methodology developed here operates at low 1 mol % catalyst and photosensitizer loadings. The catalytic system also operates without reaction additives such as inorganic salts or bases. A general and effective sp2-sp3 cross-coupling scheme has been achieved that exhibits tolerance to a wide array of functional groups.

Bis(pyrazole)-palladium(II) and nickel(II) halide complexes, [(pz)2PdCl2] (1), [(3,5-Me2pz)2PdCl2] (2), [(3,5-tBu2pz)2PdCl2] (3), [(3,5-Ph2pz)2PdCl2] (4), [(3-CF3,5-Phpz)2PdCl2] (5),[(pz)4NiBr2] (6), [(3,5-Me2pz)2NiBr2] (7), [(3,5-tBu2pz)2NiBr2] (8), [(3,5-Ph2pz)2NiBr2] (9) and [(3-CF3,5-Phpz)2NiBr2] (10), were investigated as catalysts for ethylene oligomerization using four alkylaluminium compounds as co-catalysts in toluene, benzene and chlorobenzene. The palladium complexes with ethylaluminium dichloride (EtAlCl2) in toluene selectively produced ethyl- and butyl- toluenes via a Friedel-Crafts alkylation of toluene from the ethylene and butenes formed from the dimerization of ethylene. On the other hand, the nickel complexes produced a mixture of butenes and their Friedel-Crafts toluene alkylation products, but very little ethyltoluene. Changing the solvent to benzene produced similar alkyl-aromatics but in chlorobenzene the reaction produced butenes and a yellow oil, with a molecular weight between 501 to 509 g mol-1; representing C18-C20 carbon-containing compounds. Similarly changing the co-catalyst to methylaluminoxane (MAO), modified methylaluminoxane (MMAO), diethylaluminium chloride (Et2AlCl) and ethylaluminiumsesquichloride (Et3Al2Cl3) also selectively produced butenes and little or no alkylaromatics.

(Figure Presented) Cross-Si-ing the Jordan: Cross-coupling reactions of 2-(2-hydroxyprop-2-yl)phenylsubstituted alkylsilanes with a variety of aryl halides proceed in the presence of palladium and copper catalysts. The use of K3PO4 base allows for highly chemoselective alkyl coupling with both primary and secondary alkyl groups (Alk).

Several N-functionalized bis(phosphanyl)amine ligands respectively containing benzyl, furfuryl, thiophene-2-methyl, thiophene-2-ethyl, and 2-picolyl groups (la-e) were synthesized and characterized. The ligands reacted with (DME)NiBr2 in CH2Cl2 to give their corresponding nickel complexes [Ph2PN(R)PPh2NiBr 2] [R = CH2C6H5 (2a), CH 2C4H3O (2b), CH2C4H 3S (2c), CH2C5H4N (2d), and CH 2CH2C4H3S (2e)], The structures of these complexes were established by single-crystal X-ray crystallography, All these nickel complexes were highly active towards ethylene oligomerization in the presence of methylaluminoxane or Et2AlCl, producing a high content of butene (C4), Especially for 2e, which contains a thiophene-2-ethyl pendant group, the oligomerization products obtained at -40 °C contained 95.9 mol-% C4 fraction with 100 mol-% 1-butene. Over 50 °C, however, these nickel complexes underwent: Friedel-Crafts alkylation of toluene with ethylene and the olefin oligomers.

A combination of nickel(II) acetylacetonate and (Z)-3,3-dimethyl-1,2- bis(diphenylphosphino)but-1-ene catalyzes cross-coupling reactions of alkyl aryl sulfides and alkenyl alkyl sulfides with alkyl Grignard reagents. Not only primary but also secondary alkyl Grignard reagents can be employed. Georg Thieme Verlag Stuttgart.

A method of producing an o-disubstituted aromatic compound, containing: continuously conducting at least the following steps (a) to (d): (a) a step of mono-lithiating one halogen atom of an o-dihaloaromatic compound, using a first microreactor; (b) a step of making the thus-obtained monolithiated product to react with an electrophilic compound, using a second microreactor, to obtain a monosubstituted-monohaloaromatic compound; (c) a step of lithiating the other halogen atom of the o-dihaloaromatic compound, using a third microreactor; and (d) a step of making the thus-obtained lithiated product successively to react with an electrophilic compound, using a forth microreactor.

Mechanistic studies of the Ni-catalyzed cross-coupling reaction of Grignard reagents through analysis of kinetic isotope effects and theoretical calculations indicated that the product-to-substrate ligand exchange process is the first irreversible step and affects the turnover efficiency and selectivity of the reaction. On the other hand, the oxidative addition step is the first irreversible step in Pd catalysis. This finding has useful implications for the development of efficient Ni catalysis and also illustrates the importance of the catalyst turnover step that has so far received less attention than subsequent catalytic steps. Copyright

A new tetraphosphine, all-cis-3-(2-diphenylphosphinoethyl)-1,2,4-tris(diphenylphosphinomethyl)cyclopentane (Ditricyp), has been synthesised in seven steps from commercially available dicyclopentadiene. The ozonolysis of dicyclopentadiene occurred first on the double bond of the bicycloheptene moiety. A very high chemoselective ozonolysis was observed at -60 °C leading to the diol after reductive treatment. From this diol, cis,cis,cis-3-(2-hydroxyethyl)-1,2,4-tri(hydroxymethyl)cyclopentane was obtained after a second ozonolysis. Mesylation and substitution with Ph2PLi led to the title tetradiphenylphosphine Ditricyp. The efficiency of this new tetraphosphine ligand for palladium-catalysed coupling reactions has been studied. Satisfactory results in terms of substrate/catalyst ratio have been obtained for Suzuki, Negishi and Sonogashira couplings and also for Heck vinylation reaction. After chromatographic separation, one enantiomer of this ligand associated to palladium was able to induce enantioselective allylic alkylation with modest enantiomeric excess.

Reductive alkylation of benzonitrile, ortho-, meta-, para-tolunitriles, and 1-naphthonitrile by sequential action of alkali metal and alkyl bromide in liquid ammonia results in corresponding alkylarenes and 1-alkyl-1- cyanocyclohexa-2,5-dienes. The experimental conditions for target synthesis of the specified products are found. A method of synthesis of 1-(ω- bromoalkyl)-1-cyanocyclohexa-2,5-dienes based on the interaction of two-electronic reduction products of aromatic nitriles with α,ω- dibromoalkanes Br(CH2)nBr (n = 3-5) is developed.

The present invention is directed to a transition metal catalyst, comprising a Group 8 metal and a ligand having the structure wherein R, R′ and R″ are organic groups having 1-15 carbon atoms, n=1-5, and m=0-4. The present invention is also directed to a method of forming a compound having an aromatic or vinylic carbon-oxygen, carbon-nitrogen, or carbon-carbon bond using the above catalyst. The catalyst and the method of using the catalyst are advantageous in preparation of compounds under mild conditions of approximately room temperature and pressure.

Pentaphenylferrocenyl di-tert-butylphosphine has been prepared in high yield from a two-step synthetic procedure, and the scope of various cross-coupling processes catalyzed by complexes bearing this ligand has been investigated. This ligand creates a remarkably general palladium catalyst for aryl halide amination and for Suzuki coupling. Turnovers of roughly 1000 were observed for aminations with unactivated aryl bromides or chlorides. In addition, complexes of this ligand catalyzed the formation of selected aryl ethers under mild conditions. The reactions encompassed electron-rich and electron-poor aryl bromides and chlorides. In the presence of catalysts containing this ligand, these aryl halides coupled with acyclic or cyclic secondary alkyl- and arylamines, with primary alkyl- and arylamines, and with aryl- and primary alkylboronic acids. These last couplings provide the first general procedure for reaction of terminal alkylboronic acids with aryl halides without toxic or expensive bases. The ligand not only generates highly active palladium catalysts, but it is air stable in solution and in the solid state. Palladium(0) complexes of this ligand are also air stable as a solid and react only slowly with oxygen in solution.

With a single protocol, commercially available Pd(P(t-Bu)3)2 can effect the Negishi cross-coupling of a wide range of aryl and vinyl chlorides with aryl- and alkylzinc reagents. The process tolerates nitro groups, and it efficiently generates sterically hindered biaryls. In addition, a high turnover number (>3000) can be achieved.

The Cp2ZrCl2-catalyzed reaction of arylolefins (styrene, o-and p-methylstyrenes, trans-stilbene, 1,4-diphenyl-1,3-butadiene) with AlEt3 resulting in mono-and disubstituted alumacyclopentanes and substituted alumacyclopropa

A three-component coupling of p-iodobenzyl derivatives, trialkylzincates, and electrophiles is described. Lithium trialkylzincates (R3ZnLi) react with p-iodobenzyl methanesulfonate to give benzylzinc reagents p-RC6H4CH2Zn(L). The reaction proceeds through a mechanism involving initial iodine/zinc exchange and the 1,2-migration of the resulting arylzincates. The benzylzinc reagents, thus prepared, are subsequently used in coupling reaction with electrophiles such as aldehydes, ketones, acyl chlorides, tosyl cyanide, and chlorosilanes to give a variety of functionalized p-substituted benzenes. Reactions under Barbier conditions in which the corresponding benzylzinc reagents are generated in the presence of electrophiles work well for Me3ZnLi and for magnesium zincates R3ZnMgBr derived from Grignard reagents. Generation of secondary benzylzinc reagents starting from diethyl 1-(p-iodophenyl)ethyl phosphate and their reaction with electrophiles are also achieved under Barbier conditions. Ketones, allyl bromides, and chlorosilanes are successfully used as electrophiles under these conditions.

The application discloses certain stilbene compounds, pharmaceutical compositions thereof, method of treating thereof, method of diagnosis therewith, and method for the preparation thereof. The compounds and compositions are useful for diagnosis of leukemia types, the treatment of dermatological disorders, and as differentiation-inducing agents for neoplastic cells.

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Several phosphine-palladium and -nickel complexes were examined for their catalytic activity in the reaction of sec-butylmagnesium chloride with bromobenzene, (E)-β-bromostyrene, 4-bromoanisole, and 2-bromotoluene.Dichloropalladium(II) was found to be by far the most active and selective catalyst to give the corresponding sec-butyl derivatives in high yields with no byproducts.The palladium-dppf complex was also found highly effective in catalyzing the reaction of n-butylmagnesium chloride and sec- and n- butylzinc chloride with organic bromides to give the corresponding cross-coupling products in high yields.The structure of PdCl2(dppf) has been determined by an X-ray diffraction study.It is proposed that the high efficiency of PdCl2(dppf) catalyst can be ascribed to its large P-Pd-P angle and small Cl-Pd-Cl angle.

Aryl oxazolines have been converted to their corresponding benzaldehydes and toluenes by several routes by passing through the intermediate amino alcohols.The transformations proceeded under mild conditions and were shown to be generally applicable to a variety of substitutions on the aromatic nucleus.