Amine Cocatalyst Research Articles

InCl3/CyNH2Cocatalyzed Carbocyclization Reaction: An Entry to α-Disubstitutedexo-Methylene Cyclopentanes

An efficient and cheap synthetic approach to functionalized exo-methylene cyclopentanes has been developed from α-disubstituted formyl-alkynes by merging amine catalysis with the indium activation of alkynes. We uncovered the crucial role of the amine cocatalyst and the development of a new cooperative catalytic system allowed the cyclization of a broad range of substrates. A mechanistic study was realized in order to rationalize the determining influence of the amine cocatalyst.

Highly Active and Removable Ruthenium Catalysts for Transition‐Metal‐Catalyzed Living Radical Polymerization: Design of Ligands and Cocatalysts

The systematic search and design of phosphine ligands (PR(3)) and amine cocatalysts resulted in obtaining pentamethyl-cyclopentadienyl (Cp*) ruthenium(II) phosphine complexes [RuCp*Cl(PR(3))(2)], which are highly active and removable catalysts, for transition-metal-catalyzed living radical polymerization of methyl methacrylate (MMA). The catalysts are conveniently prepared in situ from a tetrameric precursor [RuCp*(mu(3)-Cl)](4) and a selected phosphine (PR(3)). The combination of the meta-tolyl phosphine [P(m-Tol)(3)] ligand and a primary diamine cocatalyst [NH(2)(CH(2))(6)NH(2)] provides a highly active catalytic system with precision control of the molecular weight of the polymer. The high activity enables a low catalyst dose and a high turn-over frequency without deteriorating the controllability. A hydrophilic amine cocatalyst (amino alcohol) in place of the diamine, further forms an active and removable catalyst; simple treatment with acidic water gave colorless polymers visually free from metal residues (>97 % removal; <64 ppm).

Role of chiral amine cocatalysts in the helix-sense-selective polymerization of a phenylacetylene using a catalytic system

We have examined the role of the chiral amine cocatalyst in the recently discovered helix-sense-selective polymerization of a phenylacetylene using a catalytic system consisting of an achiral rhodium complex ([Rh(norbornadiene)Cl] 2) as the catalyst and a chiral amine as the cocatalyst. Several chiral amines were effective for the polymerization reaction and their effectiveness depended on their bulkiness and coordination ability to rhodium. The sense selectivity of the polymerization increased with the concentration of the chiral amines. To discuss the structure of the true active species in the catalytic system, we have synthesized a new chiral rhodium complex having two chiral amines as ligands ([Rh(norbornadiene)(chiral amine) 2] +BF 4 −). The isolated chiral complex also catalyzed the helix-sense-selective polymerization. These findings suggest that a chiral rhodium complex having two chiral amines may be the true active species when using the catalytic system consisting of [Rh(norbornadiene)Cl] 2 and a chiral amine.

Progress in the Palladium‐Catalyzed Cyanation of Aryl Chlorides.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Progress in the palladium-catalyzed cyanation of aryl chlorides.

The development of new palladium catalysts for the cyanation of various aryl and heteroaryl chlorides is described. The combination of amine co-catalysts with chelating phosphine ligands, for example, 1,4-bis(diphenylphosphino)butane (dppb) or 1,5-bis(diphenylphosphino)pentane (dpppe), allows an efficient cyanation of chloroarenes with simple potassium cyanide. General palladium-catalyzed cyanation of nonactivated and deactivated chloroarenes is possible for the first time. Studies of the oxidative addition of aryl halides to palladium triphenylphosphine complexes in the presence and absence of amines suggest that the co-catalyst is capable of preventing catalyst deactivation caused by the presence of excess cyanide ions in solution.

Alternating copolymerization of propylene oxide with carbon monoxide catalyzed by Co complex and Co/Ru complexes

AbstractCo2(CO)8 catalyzes the ring‐opening copolymerization of propylene oxide with CO to afford the polyester in the presence of various amine cocatalysts. The 1H and 13C{1H} NMR spectra of the polyester, obtained by the Co2(CO)8–3‐hydroxypyridine catalyst, show the following structure [CH2CH(CH3)OCO]n. The Co2(CO)8–phenol catalyst gives the polyester, which contains the partial structural unit formed through the ring‐opening copolymerization of tetrahydrofuran with CO. The bidentate amines, such as bipyridine and N,N,N′,N′‐tetramethylethylenediamine, enhance the Co complex‐catalyzed copolymerization, which produces the polyester with a regulated structure. Acylcobalt complexes, (RCO)Co(CO)n (R = Me or CH2Ph), prepared in situ, do not catalyze the copolymerization even in the presence of pyridine. This suggests that the chain growth involves the intermolecular nucleophilic addition of the OH group of the intermediate complex to the acyl–cobalt bond, forming an ester bond rather than the insertion of propylene oxide into the acyl–cobalt bond. Co2(CO)8Ru3(CO)12 mixtures also bring about the copolymerization of propylene oxide with CO. The molar ratio of Ru to Co affects the yield, molecular weight, and structure of the produced copolymer. The catalysis is ascribed to the RuCo mixed‐metal cluster formed in the reaction mixture. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4530–4537, 2002

Development of a catalytic enantioselective conjugate addition of 1,3-dicarbonyl compounds to nitroalkenes for the synthesis of endothelin-A antagonist ABT-546. Scope, mechanism, and further application to the synthesis of the antidepressant rolipram.

The enantioselective synthesis of endothelin-A antagonist ABT-546 has been accomplished via the discovery and development of a highly selective catalytic asymmetric conjugate addition of ketoesters to nitroolefins. Employing just 4 mol % bis(oxazoline)-Mg(OTf)(2) complex with an amine cocatalyst, we obtained the product nitroketone with 88% selectivity at the aryl-bearing stereocenter and in good yield on scales ranging to 13 mol. The effects of ligand structure, metal salt, and solvent on the reaction are described. Particularly important to the reaction is the water content. While water is necessary during the generation of the catalyst, the water must be then removed to maximize stereoselectivity and reactivity. The reaction has been extended to other dicarbonyl substrates, and a variety of substitution patterns are tolerated on the nitroolefin partner. The reaction has also been employed in the synthesis of the antidepressant rolipram. Investigations relating to the mechanism of the reaction are also described.