Rhodium-Catalyzed Ring Opening Research Articles

Rhodium-Catalyzed Ring-Opening Hydroacylation of Alkylidenecyclopropanes with Chelating Aldehydes for the Synthesis of γ,δ-Unsaturated Ketones.

The first intermolecular ring-opening hydroacylation of alkylidenecyclopropanes with chelating aldehydes through a rhodium-catalyzed acrylamide-promoted protocol is reported. This highly efficient catalytic system enables the direct synthesis of a diverse range of linear γ,δ-unsaturated ketones. Good functional group compatibility is demonstrated for the completely atom-economical and remarkably selective proximal C-C bond cleavage process. Mechanistic studies reveal that the bidentate coordination of N,N-dimethylmethacrylamide (L1) to the acylrhodium intermediates might facilitate the cyclopropane ring fragmentation and isomerization.

Ruthenium- and Rhodium-Catalyzed Ring-Opening Coupling Reactions of Cyclopropenones with Alkenes or Alkynes

Ru3(CO)12-catalyzed divergent ring-opening coupling reactions of a cyclopropenone with methyl acrylate (an electron-deficient alkene) are developed. Under an argon atmosphere, a decarbonylative linear codimer is obtained, while cyclopentenones are obtained under carbon monoxide (20 atm) without decarbonylation. While ruthenium complexes show no catalytic activity for the ring-opening cocyclization of cyclopropenones with ethylene (20 atm) or bicyclo[2.2.1]hept-2-ene (2-norbornene), rhodium complexes, especially [RhCl(η4-1,5-cod)]2, show high catalytic activity for the desired cocyclization reactions to give the corresponding cyclopentenones in high yields and selectivities. In addition, [RhCl(η4-1,5-cod)]2 realizes the catalytic ring-opening co­cyclization of cyclopropenones with internal alkynes to give the corresponding cyclopentadienones. In all these reactions, ruthena- or rhodacyclobutenones are considered to be key intermediates, generated by strain-driven oxidative addition of a cyclopropenone C–C bond to an ­active ruthenium or rhodium species.

Rhodium-Catalyzed Ring Opening of Stereodefined Vinyl Aziridines

Rhodium-Catalyzed Ring Opening of Stereodefined Vinyl Aziridines

ChemInform Abstract: Tunable Chiral Monophosphines as Ligands in Enantioselective Rhodium‐Catalyzed Ring‐Opening of Oxabenzonorbornadienes with Amines.

Abstract A new tunable chiral monophosphine was used as a ligand for asymmetric rhodium-catalyzed ring-opening of oxabenzonorbornadiene with amines, providing a series of chiral ring-opened products in high yields (up to 97%) and with high enantioselectivities (>99%).The reaction can be performed at rt to obtain the desired product with high enantioselectivity.

Tunable chiral monophosphines as ligands in enantioselective rhodium-catalyzed ring-opening of oxabenzonorbornadienes with amines

A new tunable chiral monophosphine was used as a ligand for asymmetric rhodium-catalyzed ring-opening of oxabenzonorbornadiene with amines, providing a series of chiral ring-opened products in high yields (up to 97%) and with high enantioselectivities (>99%).The reaction can be performed at rt to obtain the desired product with high enantioselectivity.

Rhodium-catalyzed regioselective opening of vinyl epoxides with Et3N·3HF reagent – formation of allylic fluorohydrins

A highly regioselective rhodium-catalyzed ring-opening of vinyl epoxides with Et3N·3HF reagent to form branched allylic fluorohydrins is described. The reaction occurs at room temperature under ambient air and relies on RhCOD2BF4 as an effective catalyst, providing the desired 1,2-addition allylic fluorohydrins in moderate to good yields with excellent levels of regioselectivity. Mechanistic studies demonstrate that the regioselective ring-opening of enantiopure vinyl epoxide occurs with inversion of stereochemistry.

Rhodium-Catalyzed Ring Opening of Benzocyclobutenols with Site-Selectivity Complementary to Thermal Ring Opening

A rhodium catalyst induced ring opening of benzocyclobutenols with selective cleavage of the C(sp(2))-C(sp(3)) bond adjacent to the hydroxyl group. The site-selectivity markedly contrasted with that of their thermal ring-opening reaction. The rhodium-catalyzed ring opening led to the development of a new alkyne insertion reaction constructing a dihydronaphthalene framework.

ChemInform Abstract: Rhodium-Catalyzed Ring-Opening Reaction of Cyclopropenes. Control of Regioselectivity by the Oxidation State of the Metal.

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Rhodium-Catalyzed Ring-Opening Reactions of a 3-Aza-2-oxabicyclo[2.2.1]hept-5-ene with Arylboronic Acids

Rhodium-catalyzed ring-opening reactions of a 3-aza-2-oxabicyclo[2.2.1]hept-5-ene with arylboronic acids were investigated. The use of [RhCl(COD)](2), (+/-)-BINAP, and NaHCO(3) in MeOH at 60 degrees C was found to be the optimized conditions for the ring-opening reactions to give the 1,2-ring-opened products. Various arylboronic acids were examined, and low to moderate yields were obtained and stereoselectivities (trans/cis) from 50:50 to 100:0 were observed.

Synthesis of µ-Opioid Selective Ligands

The Lautens rhodium-catalyzed ring opening of oxa- and aza-benzonorbornadienes A and H was used to synthesize libraries of 1-aminotetralin scaffolds which were screened against human opioid receptors. Compound G was a high-affinity selective µ-opioid receptor ligand.

Stereoselective Transformations of meso Bicyclic Hydrazines: Versatile Access to Functionalized Aminocyclopentanes

Bicyclic hydrazines, prepared by cycloaddition of cyclopentadieneand diazo compounds, have great synthetic potential. Numerous asymmetrictransformations of these building blocks have been developed, involvingthe electrophilicity of their strained double bond, ring-openingreactions or skeletal rearrangements. All these transformationsare fully diastereoselective, and, in some cases-, enantioselective,enabling the preparation of a wide range of useful synthetic intermediatesfrom a single precursor in a few synthetic steps. 1 Introduction 2 Preparation and Conformational Properties of Bicyclic [nl]Hydrazines 3 Synthetic Transformations without Ring Fragmentation 3.1 Hydroboration 3.2 Hydroformylation and Halocarbomethoxylation 3.3 Dihydroxylation and Aminohydroxylation 3.4 Hydroarylation 3.5 Sequential Arylation-Alkynylation 3.6 Arylative Cyclization 3.7 Cyclopropanation 3.8 Pauson-Khand Reaction 3.9 Cycloaddition Reactions 4 Synthetic Transformations with Ring Fragmentation 4.1 Palladium-Catalyzed Ring-Opening Reactions 4.2 Copper-Catalyzed Ring-Opening Reactions 4.3 Rhodium-Catalyzed Ring-Opening Reactions 4.4 Ruthenium-Catalyzed Ring-Opening-Metathesis Reactions andOxidative Cleavage 5 Rearrangements 5.1 Rearrangements Involving Allylic Cations 5.2 Rearrangements Involving Aziridiniums 6 Synthetic Applications 7 Conclusion

Rhodium-Catalyzed Ring-Opening Reactions of N-Boc-azabenzonor­bornadiene with Chiral Amine Nucleophiles Derived from Amino Acids

The rhodium-catalyzed ring-opening of azabenzonorbornadienes with chiral amino nucleophiles derived from amino acids such as (S)-proline and (R)-phenylglycine is reported. The desired products were obtained as a mixture of diastereomers, which ] could be easily separated in high yield. Enantiomerically pure ring-fused nitrogen heterocycles and 1,2-diamines were also obtained by further transformation of the ring-opened products.

Studies of rhodium-catalyzed ring opening of vinyl epoxides

The stereoselective 6-endo mode cyclization of vinyl epoxides has been achieved by the use of a catalytic amount of [Rh(CO)2Cl]2 affording six-membered heterocycle systems, such as piperidines and tetrahydropyrans. The scope and limitations of the reaction are discussed.

ChemInform Abstract: Rhodium-Catalyzed Ring Opening of Vinyl Epoxides with Alcohols and Aromatic Amines.

[Rh(CO)2Cl]2 is an effective catalyst for the ring opening of vinyl epoxides with alcohols and aromatic amines under neutral conditions at room temperature. The reaction occurs with excellent diastereo- and regioselectivity (>20:1) giving the trans-1,2-amino alcohols or alkoxy alcohols for a wide range of substrates. The regio- and stereochemistry of these reactions is complementary to that typically obtained with palladium-catalyzed ring openings of vinyl epoxides.

Rhodium-catalyzed ring opening of vinyl epoxides with alcohols and aromatic amines

[Rh(CO)(2)Cl](2) is an effective catalyst for the ring opening of vinyl epoxides with alcohols and aromatic amines under neutral conditions at room temperature. The reaction occurs with excellent diastereo- and regioselectivity (>20:1) giving the trans-1,2-amino alcohols or alkoxy alcohols for a wide range of substrates. The regio- and stereochemistry of these reactions is complementary to that typically obtained with palladium-catalyzed ring openings of vinyl epoxides.