Cooperative Catalytic Reactions Research Articles

Cobalt Carbonyls Stabilized by N,P-Ligands: Synthesis, Structure, and Catalytic Property for Ethylene Oxide Hydroalkoxycarbonylation.

Reactions of N,P-Ligands as Ph2 P(o-NMe2 C6 H4 ) (1 L), 2,6-iPr2 C6 H3 NHC(Ph)=NC6 H4 (o-PPh2 ) (2 L), and Ph2 PN(R)PPh2 (R=iPr (3 L), cyclo-C6 H11 (4 L), tBu (5 L), CH2 C4 H7 O (6 L)) each with dicobalt octacarbonyl produced complexes [1 LCo(CO)3 ]2 (1), [2 LCo(CO)(μ-CO)2 Co(CO)3 ] (2), [3 LCo(CO)3 ]+ [Co(CO)4 ]- (3), [3 LCo(CO)2 ]2 (4), [4 LCo(CO)2 ]2 (5), [5 LCo(CO)2 ]+ [Co(CO)4 ]- (6), and [6 LCo(CO)2 ]+ [Co(CO)4 ]- (7). Complexes 1-7 have all been structurally characterized by X-ray crystallography, IR and NMR spectroscopies, and elemental analysis. Catalytic tests on transformation of ethylene oxide (EO), CO and MeOH into methyl 3-hydroxypropionate (3-HMP) indicate that complexes 1-7 are active, where ion-pair complexes 3 and 6-7 behave more excellently (by achieving 88.4-93.6% 3-HMP yields) than the neutral species 1-2 and 4-5 (35.0-46.5% 3-HMP yields) when the reactions are all operated at 2 MPa CO pressure and 50 °C in MeOH solvent. Density functional theory (DFT) study by selecting 3 as a model suggests a cooperative catalytic reaction mechanism by [Co(CO)4 ]- and its counter cation [3 LCo(CO)3 ]+ . The cobalt-homonuclear ion-pair catalyzed hydroalkoxycarbonylation of EO is present herein.

Dinuclear zinc cooperative catalytic three-component reactions for highly enantioselective synthesis of 3,3'-dihydrofuran spirooxindoles.

A new dinuclear zinc cooperative catalytic enantioselective three-component reaction via a domino Knoevenagel /Michael/cyclization sequence has been developed. A series of chiral 3,3'-dihydrofuran spirooxindoles are obtained in excellent yields (up to 99%) and enantioselectivities (up to 99% ee). In addition, the reaction is carried out smoothly on a gram scale under mild conditions.

Lewis Base/Copper Cooperatively Catalyzed Asymmetric α-Amination of Esters with Diaziridinone.

An enantioselective α-amination of esters by a Lewis base/copper(I) cooperative catalysis strategy has been developed. The transient chiral C1-ammonium enolate generated from pentafluorophenyl ester and nucleophilic Lewis base is nicely compatible with the copper intermediate formed from N, N-di- t-butyldiaziridinone and Cu(I) to allow for high levels of stereochemical control. The cooperative catalytic reaction leads to a diverse set of highly enantioenriched hydantoins in good yields with excellent enantioselectivities (90-99% ee).

Carbene and Acid Cooperative Catalytic Reactions of Aldehydes and o-Hydroxybenzhydryl Amines for Highly Enantioselective Access to Dihydrocoumarins.

A highly enantioselective method for quick access to dihydrocoumarins is reported. The reaction involves a cooperative catalytic process with carbene and in situ generated Brønsted acid as the catalysts. α-Chloro aldehyde and readily available and stable o-hydroxybenzhydryl amine substrates were used to generate reactive azolium ester enolate and ortho-quinone methide (o-QM) intermediates, respectively, to form dihydrocoumarins with exceptionally high diastereo- and enantioselectivities. The catalytic reaction products can be easily transformed to valuable pharmaceuticals and bioactive molecules.

Asymmetric Cooperative Catalysis in a Three-Component Reaction: Mechanism and Origin of Enantio- and Diastereoselectivities.

Mechanistic insights gained through density functional theory (DFT M06 and B3LYP) computations on a three-component cooperative asymmetric catalytic reaction between a diazo ester, a carbamate, and an imine, catalyzed by dirhodium acetate and chiral phosphoric acid (Brønsted acid), are presented. The addition of the dirhodium-bound enol to the imine yielding an α,β-diamino ester is energetically more preferred over a potentially competitive protonation of the same enol leading to an α-amino ester.

ChemInform Abstract: Enantioselective Cooperative Catalysis

AbstractReview: [102 refs.

Enantioselective cooperative catalysis.

In recent years, enantioselective cooperative catalytic reactions, wherein two catalysts work simultaneously to form products which cannot be obtained by the use of a single catalyst alone, have attracted considerable attention. This review focuses on this emerging field, with particular emphasis on mechanistic aspects, which will help readers to understand the role of each catalyst.

Mechanism of Palladium/Amine Cocatalyzed Carbocyclization of Aldehydes with Alkynes and Its Merging with “Pd Oxidase Catalysis”

The reaction mechanism for the palladium and amine cocatalyzed carbocyclization of aldehydes with alkynes has been investigated by means of density functional theory calculations and experiments. The Pd/amine cocatalyzed transformation is a carbocyclization of in situ generated enaminynes where the C–C bond-forming step is most likely promoted by a Pd(II) species. Notably, the latent Pd(0)/Pd(II) catalytic redox cycle of this metal/organo cooperative catalytic reaction can be merged with catalytic direct aerobic alcohol oxidation (Pd oxidase catalysis).

Importance of ligand exchanges in Pd(II)-Brønsted acid cooperative catalytic approach to spirocyclic rings.

Increasing number of reports in the most recent literature convey the use of palladium and Brønsted acids as cooperative catalytic partners. However, the mechanistic understanding of several such cooperative catalytic reactions and the origin of cooperativity continue to remain limited. In transition metal catalysis, it is typically assumed that the native ligands, such as the acetates in palladium acetate, are retained throughout the catalytic cycle. Herein, we convey the significance of invoking ligand exchanges in transition metal catalysis by using the mechanism of a representative cooperative dual-catalytic reaction. Density functional theory (M06 and B3LYP) computations have been employed to decipher the mechanism of Pd(II)-Brønsted acid catalyzed migratory ring expansion reaction of an indenyl cyclobutanol to a spirocyclic indene bearing a quaternary carbon. The molecular role of water, benzoquinone and phosphoric acid has been probed by computing the energetics using several combinations of all these as ligands on palladium. Of the two key mechanistic possibilities examined, a Wacker-type pathway (involving a semipinacol ring expansion of cyclobutanol followed by a reductive elimination) is found to be energetically more preferred over an allylic pathway wherein the ring expansion in a Pd-π-allyl intermediate occurs subsequent to the initial allylic C-H activation. The Gibbs free energies of the transition states with the native palladium acetate are much higher than a Pd-bis-phosphate species generated through ligand exchanges.

Asymmetric organocatalysis combined with metal catalysis: concept, proof of concept, and beyond.

Asymmetric catalysis has been considered to be the most intriguing means for building collections of functionalized optically active compounds. In particular, metal and organocatalysis have been well established to allow many fundamentally different reactions. Metal catalysis has enabled the participation of a much broader scope of chemical bonds in organic transformations than are allowed by organocatalysis, while organocatalysis permits a broader scope of functional groups to undergo a diverse range of enantioselective transformations, individually, simultaneously, or sequentially. Theoretically, the combination of organocatalysts and metal complexes could probably render new transformations through the simultaneous or sequential activation and reorganization of multiple chemical bonds if the superior features of both the catalysts are adopted. In 2001, both our research group and Takemoto's group separately described an asymmetric allylation of glycine imino esters with allyl acetate catalyzed by palladium complexes and chiral ammonium salts. In these cases, the oxidative addition of palladium complexes to allyl acetate formed the π-allylic fragments, while the chiral ammonium salts were actually responsible for controlling the stereoselectivity. These reactions in fact marked the beginning of asymmetric organo/metal combined catalysis. Since then, asymmetric organocatalysis combined with metal catalysis, including cooperative catalysis, relay catalysis, and sequential catalysis, has been a versatile concept for the creation of unknown organic transformations. Sequential catalysis describes a one-pot reaction involving two or more incompatible catalytic cycles. Alternatively, cooperative and relay catalyses require high compatibility of principally distinct catalysts and will be the focus of this Account. The catalysts in cooperative catalytic reactions must be able to simultaneously and individually activate both substrates to drive a bond-forming reaction, while relay catalysis is basically defined as a cascade process in which two or more sequential bond-forming transformations are independently catalyzed by distinct catalysts. In the past decade, we have discovered a variety of binary catalytic systems consisting of metals, including Rh(II), Pd(0), Au(I), and Mg(II), and chiral organocatalysts, including chiral phosphoric acids and quinine-based bifunctional molecules, for cooperative catalysis and relay catalysis, allowing the accomplishment of many unprecedented asymmetric transformations. In this Account, these achievements will be summarized, particularly focusing on the description of the concept and proof of the concept, to demonstrate the robustness of combined organo/metal catalysis in the creation of efficient enantioselective transformations. In addition, elegant studies from other laboratories using chiral phosphoric acid/Au(I) for the establishment of asymmetric cascade reactions involving the carbon-carbon triple bond functionality and typical combined organo/metal catalytic systems, very recently disclosed, will also be highlighted.

Synthesis of Nitroalkenes Involving a Cooperative Catalytic Action of Iron(III) and Piperidine: A One‐Pot Synthetic Strategy to 3‐Alkylindoles, 2H‐Chromenes and N‐Arylpyrrole

AbstractAn efficient and simple strategy has been developed to synthesize various substituted nitroalkenes involving a cooperative catalytic system of FeCl3 and piperidine. This dual catalytic protocol simultaneously activates both electrophile and nucleophile and works under mild reaction conditions so that many sensitive functional groups were tolerated. Moreover, this cooperative catalytic reaction is also suitable for various one‐pot reactions involving nitroalkenes such as, 2H‐chromenes, N‐arylpyrrole and Michael reaction with indole. Notably, this method is low‐cost, efficient and environmentally friendly.

ChemInform Abstract: Cooperative Catalytic Reactions Using Distinct Transition‐Metal Catalysts: Ruthenium‐ and Copper‐Catalyzed Enantioselective Propargylic Alkylation.

AbstractA Ru—Cu co‐catalyzed reaction of β‐ketoesters with propargylic alcohols is described, which provides the products (III) in high yields and enantioselectivities (up to 93% e.e.).

Cooperative Catalytic Reactions Using Organocatalysts and Transition Metal Catalysts: Propargylic Allylation of Propargylic Alcohols with α,β-Unsaturated Aldehydes

Propargylic allylation of propargylic alcohols with α,β-unsaturated aldehydes in the presence of a thiolate-bridged diruthenium complex and a secondary amine as cocatalysts has been found to give t...

ChemInform Abstract: Cooperative Catalytic Reactions Using Lewis Acids and Organocatalysts: Enantioselective Propargylic Alkylation of Propargylic Alcohols Bearing an Internal Alkyne with Aldehydes.

AbstractAn optically active secondary amine is used as co‐catalyst in the title reaction affording the corresponding propargylic alkylated products in high yields as a mixture of two diastereoisomers with high enantioselectivity.

ChemInform Abstract: Cooperative Catalytic Reactions Using Organocatalysts and Transition Metal Catalysts: Enantioselective Propargylic Alkylation of Propargylic Esters with Aldehydes.

AbstractIn the presence of CuOTf, BINAP, and the prolinol (PRO) propargylic esters are found to undergo highly enantioselective reaction with aldehydes to afford alcohols like (III), (IV), (VI), and (VII).

Cooperative Catalytic Reactions Using Lewis Acids and Organocatalysts: Enantioselective Propargylic Alkylation of Propargylic Alcohols Bearing an Internal Alkyne with Aldehydes (Eur. J. Org. Chem. 12/2011)

AbstractThe cover picture shows that both wings are necessary for a butterfly to fly. Likewise, both a Lewis acid and an organocatalyst contribute cooperatively to the catalytic enantioselective propargylic alkylation of proparglylic alcohols bearing an internal alkyne moiety with aldehydes. Details are discussed in the article by Y. Nishibayashi et al. on p. 2239 ff.

Cooperative Catalytic Reactions Using Lewis Acids and Organocatalysts: Enantioselective Propargylic Alkylation of Propargylic Alcohols Bearing an Internal Alkyne with Aldehydes

AbstractThe enantioselective propargylic alkylation of propargylic alcohols bearing an internal alkyne moiety with aldehydes in the presence of a metal salt as the Lewis acid and an optically active secondary amine as the co‐catalyst has been found to give the corresponding propargylic alkylated products in high yields as a mixture of two diastereoisomers with high enantioselectivity.

ChemInform Abstract: Cooperative Catalytic Reactions Using Organocatalysts and Transition‐Metal Catalysts: Enantioselective Propargylic Alkylation of Propargylic Alcohols with Aldehydes.

AbstractA thiolate‐bridged diruthenium complex and a prolinol‐derived secondary amine are used as catalysts.

Cooperative Catalytic Reactions Using Organocatalysts and Transition Metal Catalysts: Enantioselective Propargylic Alkylation of Propargylic Esters with Aldehydes

The enantioselective propargylic alkylation of propargylic esters with aldehydes in the presence of a copper complex and an optically active secondary amine as cocatalysts has been found to give the corresponding propargylic alkylated products in good yields as a mixture of two diastereoisomers with a high enantioselectivity.

ChemInform Abstract: Cooperative and Enantioselective NbCl5/Primary Amine Catalyzed Biginelli Reaction.

A series of chiral organocatalysts and Lewis acids have been evaluated in the Lewis acid/organocatalysts-based cooperative catalytic Biginelli reaction, which resulted in the determination of a novel cooperative Lewis acid/primary amine catalyst system, NbCl5/QN-NH2. The synergistic effect of NbCl5 and the quinine-derived primary amine is pronounced and gave dihydropyrimidiones (DHPMs) in moderate to good enantioselectivities (up to 84 % ee) and good to excellent yields (up to 99 % yield) under mild conditions.