Relay Catalysis Research Articles

ChemInform Abstract: Direct Access to Enantioenriched Spiroacetals Through Asymmetric Relay Catalytic Three‐Component Reaction.

The gold(I)/chiral Bronsted acid relay catalysis enabled a highly stereoselective three-component reaction of salicylaldehydes, anilines, and alkynols to give aromatic spiroacetals in high yields and stereoselectivities.

Relay Catalysis by a Multifunctional Cu Catalyst in a Tandem Dehydro-/Dehalogenation Sequence along with N-Arylation

A Cu-catalyzed tandem dehydrogenation/dehalogenation sequential reaction along with N-arylation has been developed for the synthesis of pyridazinone derivatives in an aerobic and aqueous environment. To achieve the transformation of three chemical bonds in a one-pot reaction, a multifunctional copper catalyst was used which afforded excellent activity, high selectivity, and recyclability. The catalytic system consists of a water-soluble Cusalen complex and Na2CO3 in neat water and an air atmosphere.

Gold/Brønsted Acid Relay Catalysis for Enantioselective Construction of Spirocyclic Diketones

Gold/Brønsted Acid Relay Catalysis for Enantioselective Construction of Spirocyclic Diketones

Relay Catalysis: Enantioselective Synthesis of Cyclic Benzo‐Fused Homoallylic Alcohols by Chiral Brønsted Acid‐Catalyzed Allylboration/Ring Closing Metathesis

AbstractSix‐ and seven‐membered benzo‐fused cyclic homoallylic alcohols can be readily synthesized by a tandem chiral Brønsted acid‐catalyzed allyl (crotyl)boration/ring closing metathesis sequence performed under orthogonal relay catalysis conditions. Excellent enantio‐ and diastereoselectivities are obtained in most of the cases. In addition, the parent crotylboration/RCM process is also described. The required substrates, ortho‐vinylbenzaldehydes, are readily available in one step from commercially available starting materials. Both catalysts and reactants are also available from commercial suppliers. The reaction shows broad functional group compatibility and is also suitable for heteroaromatic substrates. Substitution at any position of the aromatic ring is tolerated; however, substitution at position 6 results in a substantial drop in enantioselectivity.

Enantioselective Relay Catalytic Cascade Intramolecular Hydrosiloxylation and Mukaiyama Aldol Reaction

Cascading chemistry! The first practical relay catalytic cascade intramolecular hydrosiloxylation of arylacetylene and asymmetric Mukaiyama aldol reaction has been established to give synthetically useful products in high yields and with excellent ee (see scheme).

Cascade Hydroamination/Redox Reaction for the Synthesis of Cyclic Aminals Catalyzed by a Combined Gold Complex and Brønsted Acid

Relay catalysis: An unprecedented protocol for the synthesis of cyclic aminals has been realized under the relay catalysis of a gold(I)/Brønsted acid binary system to generate cyclic aminals in excellent yields of up to 99 % with moderate to high diastereoselectivity (see scheme; up to 95:5 d.r.).

Relay Catalysis by a Ruthenium Complex-Chiral Brønsted Acid Binary Sytem for Ternary Reaction Sequence Involving Enantioselective Pictet-Spengler-Type Cyclization as the Key Step

Relay catalysis for a ternary reaction sequence composed of double-bond isomerization, protonation of the double bond, and enantioselective Pictet–Spengler-type cyclization was accomplished using a binary catalytic system consisting of a ruthenium hydride complex and a chiral phosphoric acid as the chiral Brønsted acid catalyst.

From Cyclopropenes to Tetrasubstituted Furans: Tandem Isomerization/Alkenylation Sequence with Cu/Pd Relay Catalysis

Pon de relay: A convenient and efficient synthesis of alkene-functionalized furans from cyclopropenes, which proceeds through an isomerization/olefination cascade sequence under copper–palladium relay catalysis, has been developed (see scheme). As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Relay catalysis at a boron centre

A boron complex catalyses the addition of allyl groups — hydrocarbon motifs — to 'activated imines' in a relay-like process, generating synthetically useful compounds as single mirror-image isomers. See Letter p.216 A team from the chemistry department of Boston College in Chestnut Hill, Massachusetts, has designed and synthesized a series of related small organic molecules capable of catalysing enantioselective transformations. Specifically, the molecules — derived from the abundant amino acid valine in a simple four-step process that uses inexpensive reagents — catalyse reactions of unsaturated organoboron reagents with imines and carbonyls. The products of the reactions are enantiomerically pure amines and alcohols that can be used to synthesize more complex, biologically active molecules for applications in chemistry, biology and medicine.

Relay Catalytic Branching Cascade: A Technique to Access Diverse Molecular Scaffolds

Skeletal diversity: The reactions of alkynoic acids (A, common type of substrates) with various scaffold-building agents (B) under gold catalysis produce a series of multifunctional polyheterocyclic structures (see scheme). The approach enables the preparation of compound libraries with high skeletal diversity.

Relay Catalytic Branching Cascade: A Technique to Access Diverse Molecular Scaffolds

Gerüstvielfalt: Die Gold-katalysierten Reaktionen von Alkinsäuren (A) mit verschiedenen gerüstgebenden Substraten (B) führen zur Bildung einer großen Zahl multifunktioneller polyheterocyclischer Strukturen (siehe Schema). Dieser Ansatz ermöglicht die Herstellung von Substanzbibliotheken mit hoher Gerüstdiversität.

Direct Access to Enantioenriched Spiroacetals through Asymmetric Relay Catalytic Three-Component Reaction

The gold(I)/chiral Brønsted acid relay catalysis enabled a highly stereoselective three-component reaction of salicylaldehydes, anilines, and alkynols to give aromatic spiroacetals in high yields and stereoselectivities.

Asymmetric Relay Catalysis Reaction Consisting of Metal Complex and Chiral Phosphoric Acids

Metal complex and organo combined catalysis is a new and exciting research area and has attracted close atten- tion. Relay catalysis (or sequential catalysis), in which both the organocatalyst and the metal catalyst perform two distinct catalytic cycles for the consecutive reactions, enables the assembling readily available starting materials into structurally complex molecules. Besides, relay catalysis can also accomplish unprecedented reactions, which are not accessible through the use of either of the catalytic systems alone. More essentially, it avoids the purification of unstable intermediate and im- proves process economy and atom economy. Chiral phosphoric acids become the hottest kind of organocatalysts in recent decades. Chiral phosphoric acid has been applied to asymmetric transfer hydrogenation of imines, enantioselective Friedel-Crafts reaction, Mannich reaction, hydrophosphonylation reaction, Strecker reaction, aza-Diels-Alder reaction, alky- lation of diazoester reaction and so on. Chiral phosphoric acid can act as both proton donor and proton acceptor simultane- ously, and the system of which combining with metal has attracted intensive study. Transition metal catalysis was dominated in catalytic organic synthesis. Owing to the explosive development of organocatalysis in recent years, the combination of transition metal catalysts and organocatalysts has displayed as a new and powerful strategy for developing new and useful reactions, and has attracted increasing attention. In this review, we summarize recent progress in the field of metal com- plex/phosphoric acids relay catalysis. And in our opinion, the study of new catalysis systems will continue to be an exciting research area, the inquiry of the applications in the total synthesis of natural products is worthy of further investigation and the exploration of appropriate catalysis systems applied in industrial production represents the future research direction.

A cascade approach to fused indolizinones through Lewis acid–copper(i) relay catalysis

A relay catalytic cascade process involving Lewis acid triggered ring-opening of cyclopropyl ketones with nitriles, the copper(I)-catalyzed Ritter process, and acid-promoted N-acyliminium ion cyclization is described, which efficiently provides thieno-, furano-, and benzo-indolizinones in moderate to good yields.

Modular synthesis of all-substituted furans through oxidative carbonylation of cyclopropenes with tandem metal relay catalysis

A modular synthesis of tetrasubstituted furan carboxylates using a tandem cycloisomerization/oxidative carbonylation sequence of cyclopropenes has been successfully developed. The Tandem Metal Relay Catalysis (TMRC) pathway accounted for the high efficiency of this transformation.

Dimerization of cyclopropenes to bifurans using tandem metal relay catalysis

An efficient synthesis of bifurans via dimerization of cyclopropenes has been successfully developed using a copper-promoted cycloisomerization and palladium-catalyzed dimerization cascade. These novel bifuran structures possess interesting optoelectronic properties.

A Concise Assembly of Electron‐Deficient 2,4‐Dienes and 2,4‐Dienals: Regio‐ and Stereoselective exo‐Diels–Alder and Redox Reactions through Sequential Amine and Carbene Catalysis

Ideal relay catalysis: A γ,δ-regioselective anomalous exo-Diels–Alder reaction with electron-deficient β-substituted 2,4-dienes and 2,4-dienals has been developed by using trienamine activation. The resulting multifunctional cycloadducts contain perfectly positioned functional groups, thereby facilitating a 1,5-hydride transfer from the C–H group of an aldehyde to an activated alkene under sequential catalysis of a carbene (see scheme).

Relay Catalysis Enables Hydrogen Gas to Participate in Asymmetric Organocatalytic Hydrogenation

Teamwork: Through relay catalysis by a RuII complex and a chiral phosphoric acid ((S)-BPA in the scheme) recently developed by Zhou's group, hydrogen gas can act as the terminal reductant in the catalytic asymmetric hydrogenation of heterocycles. This is a completely new concept in the area of asymmetric hydrogenation.

ChemInform Abstract: The Combination of Relay and Cooperative Catalysis with a Gold/Palladium/Broensted Acid Ternary System for the Cascade Hydroamination/Allylic Alkylation Reaction.

ChemInform Abstract: The Combination of Relay and Cooperative Catalysis with a Gold/Palladium/Broensted Acid Ternary System for the Cascade Hydroamination/Allylic Alkylation Reaction.

ChemInform Abstract: Relay Catalysis: Combined Metal Catalyzed Oxidation and Asymmetric Iminium Catalysis for the Synthesis of Bi‐ and Tricyclic Chromenes.

AbstractA catalytic asymmetric oxidative iminium—allenamine cascade reaction of propargyl alcohols provides access to chiral bicyclic 4H‐chromenes under mild conditions in good yields and with high enantioselectivities.