Ruthenium-catalyzed Ring-closing Metathesis Research Articles

New tandem catalysis: preparation of cyclic enol ethers through a ruthenium-catalyzed ring-closing metathesis-olefin isomerization sequence.

Tandem reactions that proceed with a single metal catalyst precursor offer novel opportunities for developing efficient new reaction sequences. In this regard, reaction conditions have been identified that allows for a tandem ring-closing metathesis-olefin isomerization sequence catalyzed by a common ruthenium precursor. Specifically, the tandem process generates cyclic enol ethers from a variety of readily available acyclic dienes in a single reaction vessel using Grubbs' ruthenium alkylidene.

ALKENE METATHESIS IN IONIC LIQUIDS

RUTHENIUM-CATALYZED RING-closing metathesis is a powerful method for synthesizing heterocyclic compounds and complex natural products from acyclic dienes. But recovering and recycling the catalyst has proven to be a problem for the reaction. Two groups in Europe have now shown that environmentally friendly room-temperature ionic liquids that are recyclable and nonvolatile, such as l-butyl-3-methylimidazolium hexafluorophosphate ([bmim]{PF 6 }), maybe used to overcome the problem. In the Netherlands, chemists at the pharmaceutical company Organon, based in Oss, demonstrated that {bmim}{PF 6 } and related ionic liquids are effective media for ring-closing metathesis of dienes using neutral ruthenium carbene catalysts [ Org. Lett ., 3, 3785 (2001)]. And in a separate development in France, chemistry professor Pierre H. Dixneuf and coworkers at the University of Rennes and senior ...

Synthesis of cyclic dienamide using ruthenium-catalyzed ring-closing metathesis of ene-ynamide.

[reaction: see text] Ring-closing metathesis of ene-ynamide using the second-generation Grubbs' catalyst produced nitrogen-containing heterocycles, which have dienamide moieties, in high yields. Diels-Alder reaction of the cyclized product and dienophile proceeded smoothly to afford a bi- or tricyclic compound.

A short and concise synthetic route to (−)-coniceine

(−)-Coniceine, the simplest framework of indolizidine alkaloids, has been successfully accessed using a route in which ruthenium-catalyzed ring-closing olefin metathesis (RCM) was the key reaction to establish the unsaturated bicyclic lactam system.

Enantioselective ruthenium-catalyzed ring-closing metathesis.

[reaction: see text] The first enantioselective ruthenium olefin metathesis catalysts have been prepared, and high enantiomeric excesses (up to 90%) are observed in the desymmetrization of achiral trienes. A model consistent with the stereochemical outcome of the reactions is described and suggests side-on olefin binding and reorganization of the halide ligands.

A divergent synthesis of d- and l-carbocyclic 4′-fluoro-2′,3′-dideoxynucleosides as potential antiviral agents

d- and l-Carbocyclic 4′-fluoro-2′,3′-dideoxynucleosides have been synthesized from 2, which can be conveniently prepared from 1,2:5,6-di-O-isopropylidene-d-mannitol 1 in eight steps. Ruthenium-catalyzed ring-closing metathesis has been employed in the synthesis of d-nucleosides, whereas the l-series have been obtained through an intramolecular nucleophilic substitution reaction. The Mitsunobu condensation was used as a general tool for the synthesis of both purine and pyrimidine nucleosides.

Macrocycle Formation by Ring-Closing Metathesis. Application to the Syntheses of Novel Macrocyclic Taxoids

A series of novel macrocyclic taxoids 6 and 6‘ bearing 16-, 17-, and 18-membered rings connecting the substituents at the C-2 and C-3‘ positions were designed and synthesized. The syntheses of these macrocycles 6 and 6‘ were accomplished using the highly efficient ruthenium-catalyzed ring-closing metathesis (RCM) of taxoid-ω,ω‘-dienes 7 in the key step. Taxoid-ω,ω‘-dienes 7 were obtained through the ring-opening coupling of 4-alkenyl-β-lactams 9 with 2-alkenoylbaccatins 8 in good to high yields. Although various novel pentacyclic macrocycles 6 and 6‘ were successfully synthesized, there were cases in which the desired RCM did not proceed. The scope and limitation of RCM in its application to highly functionalized complex substrates are discussed. All macrocyclic taxoids 6 and 6‘ were found to be cytotoxic, with some of them exhibiting submicromolar IC50 values against a human breast cancer cell line.

Asymmetric synthesis of the balanol heterocycle via a palladium-mediated epimerization and olefin metathesis.

[formula: see text] The enantioselective formal synthesis of balanol, a potent protein kinase C inhibitor, was accomplished from D-serine utilizing a Pd-catalyzed equilibration of diastereomeric 5-vinyloxazolines to set the stereochemistry of the vicinal amino and hydroxyl groups. A ruthenium-catalyzed ring-closing metathesis was employed to form the seven-membered nitrogen heterocyle.

Synthesis of N,N-Disubstituted (1R,2R)-1,2-Diaminocyclohex-4-enes by a Ruthenium-Catalyzed Ring-Closing Metathesis Reaction

Synthesis of N,N-Disubstituted (1R,2R)-1,2-Diaminocyclohex-4-enes by a Ruthenium-Catalyzed Ring-Closing Metathesis Reaction

Synthesis ofN,N′-Disubstituted (1R,2R)-1,2-Diaminocyclohex-4-enes by a Ruthenium-Catalyzed Ring-Closing Metathesis Reaction

Enantiopure (1R,2R)-1,2-diaminocyclohex-4-ene derivatives have been synthesized by the ruthenium-catalyzed ring-closing metathesis reaction of (4R,5R)-N,N′-bis[(S)-1-phenylethyl]-4,5-diamino-1,7-octadiene dihydrochloride.

Total synthesis of (−)- and (±)-frontalin via ring-closing metathesis

Racemic and enantiopure targets containing the 6,8-dioxabicyclo [3.2.1]octane skeleton, can be conveniently synthesized from monocyclic diene precursors using an intramolecular ruthenium-catalyzed ring-closing metathesis reaction as the key step.

Combining the [2,3] sigmatropic rearrangement and ring-closing metathesis strategies for the synthesis of spirocyclic alkaloids. A short and efficient route to (±)-perhydrohistrionicotoxin

This paper describes the use of selenium-based [2,3] sigmatropic rearrangement in combination with ruthenium-catalyzed ring-closing metathesis (RCM) for the synthesis of azaspiro ring systems, as exemplified by the reactions of model substrates 5 and 6. The methodology has been applied to a short and efficient formal total synthesis of the alkaloid (±)-perhydrohistrionicotoxin ( 2). Thus, (±)-depentylperhydrohistrionicotoxin, 1, a known key intermediate for the synthesis of 2, was synthesised from 2,3-epoxycyclohexan-1-one in 10 laboratory operations and ca. 20% overall yield. The synthetic route is potentially enantioselective, and key steps were the [2,3] sigmatropic rearrangement of 11 to 12 via the corresponding allylic selenide (86% yield) and ruthenium-catalyzed RCM of 13 to 14 (80%).

Lithium templated synthesis of catenanes: efficient synthesis of doubly interlocked [2]-catenanes

Li+ (3 equiv.) is used as an assembling centre to generate a double-stranded helical complex from two linear coordinating fragments, each containing three 1,10-phenanthroline units and bearing terminal olefins at their ends; ruthenium-catalyzed ring-closing metathesis on the helical precursor leads to a 4-crossing [2]-catenane in 30% yield, making the procedure reasonably preparative.