Ring-closing metathesis in the synthesis of fused sultones

Synthesis of seven-membered sultones fused with different carbo- and heterocycles have been developed using ring closing metathesis as the key operation. The required substrates have been easily synthesized from their commercially available corresponding phenols.     

Claisen rearrangement/Baylis-Hillman reaction/ring-closing metathesis as bases for the construction of substituted cyanonaphthalenes

The present paper described how to establish a novel approach for various alkoxycyanonaphthalenes. It was started from isovanillin, and based on the Claisen rearrangement, O-alkylation, the Baylis-Hillman reaction, and ring-closing metathesis in sequence to produce the title compounds in good yield.     

Ring-closing metathesis as a tool for the efficient preparation of chiral spirocyclic ethers from homoallylic alcohols

The preparation of chiral spirocyclic ethers via allylic etherification/olefin metathesis of homoallylic alcohols is investigated. This reaction sequence transforms the enantiopure substrate alcohols, synthesized by a one-pot asymmetric rhodium-catalyzed conjugate addition/metal-mediated allylation procedure, into the desired spiro ethers with full conversions and in excellent isolated yields. The synthetic sequence provides an efficient means for a rapid construction of functionalized spiro ethers in a stereoselective manner.     

A cross metathesis strategy for the synthesis of highly functionalized conjugated cyanodienes: synthesis of the C3-C17 framework of (−)-borrelidin

A cross metathesis strategy for the synthesis of highly functionalized conjugated cyanodienes was developed and was successfully applied in the synthesis of the C3-C17 framework of (−)-borrelidin.     

Tandem Claisen rearrangement and ruthenium catalyzed enyne bond reorganization as a route to the synthesis of tricyclic 1,8-naphthyridinones

A novel procedure for the synthesis of substituted 1,8-naphthyridinones via tandem Claisen rearrangement and ring-closing enyne metathesis is reported.     

Ring-closing olefin metathesis in the aqueous phase of amphiphilic conetworks consisting of fluorophilic and hydrophilic compartments

A Grubbs-Hoveyda-Type metathesis catalyst bearing a tris(perfluoroalkyl)silyl tag was immobilized in the fluorophilic phase of amphiphilic conetworks (APCNs). This catalytic system was applied to ring-closing metathesis (RCM) reactions in aqueous media. Different substrates were evaluated and with 10 mol% of catalyst at 60 °C good conversions were observed. Reuse of the catalytic system was possible, but resulted generally in lower conversions.     

Design of new synthetic strategies to cyclophanes via ring-closing metathesis

A simple synthetic methodology to cyclophanes containing hydroxyl groups has been reported. The key steps involved here are: Grignard reaction, double Claisen rearrangement, and ring-closing metathesis. The strategy reported here is protecting group-free synthesis.     

Ring-closing metathesis for the synthesis of heteroaromatics: evaluating routes to pyridines and pyridazines

Ring-closing olefin metathesis (RCM) has been applied to the efficient synthesis of densely and diversely substituted pyridine and pyridazine frameworks. Routes to suitable metathesis precursors have been investigated and the scope of the metathesis step has been probed. The metathesis products function as precursors to the target heteroaromatic structures via elimination of a suitable leaving group, which also facilitates earlier steps by serving as a protecting group at nitrogen. Further functionalisation of the metathesis products is possible both prior to and after aromatisation. The net result is a powerful strategy for the de novo synthesis of highly substituted heteroaromatic scaffolds.     

Design and synthesis of novel propellanes by using claisen rearrangement and ring-closing metathesis as the key steps

Novel hexacyclic caged compounds are prepared by a combination of Claisen rearrangement and ring-closing metathesis (RCM). Additionally, a Grignard reaction in conjugation with RCM produced intricate hexacyclic caged molecules.     

Ring-closing metathesis toward the synthesis of 2,5-dihydrofuran and 2,5-dihydropyrrole skeletons from Baylis-Hillman adducts

We have developed an efficient method for the synthesis of 2,5-dihydrofuran and 2,5-dihydropyrrole skeletons from the simply modified Baylis-Hillman adducts via RCM reaction.     

Synthesis of oxepine-, oxocine- and azepine-annulated carbazole derivatives by combined Claisen rearrangement and diene/enyne metathesis

A new route to various medium ring heterocycle-annulated tetra-, penta- and hexacyclic carbazole derivatives has been developed using successive applications of three atom economic processes, viz. Claisen rearrangement, olefin metathesis and Diels-Alder reactions.     

Preparation of some angularly substituted and highly functionalized quinolizidines as building blocks for the synthesis of various alkaloids and related scaffolds of medicinal interest

The epimeric forms of the angularly substituted quinolizidine 6, representing potentially useful building blocks for the synthesis of various alkaloids, have been prepared via a pathway involving two consecutive ring-closing metathesis reactions. Variously hydroxy-protected derivatives (21, 22, and 26-29) of these compounds have also been generated.     

C-Glycosides of dodecanoic acid: new capping/reducing agents for glyconanoparticle synthesis

A concise synthesis of 12-C-glycosylated dodecanoic acids employing an olefin cross-metathesis reaction is developed. Examination of these acids as capping agents for the synthesis of metal nanoparticles reveals that they do not cap the Co-metal nanoparticles synthesized in aqueous phase, but that two of them can reduce and cap the Ag nanoparticles in water without any aggregation.     

An isomerization-ring-closing metathesis strategy for the synthesis of substituted benzofurans

Twelve substituted benzofurans were synthesized from their corresponding substituted 1-allyl-2-allyloxybenzenes using ruthenium-mediated C- and O-allyl isomerization followed by ring-closing metathesis.     

A ring-closing metathesis approach to a synthesis of the B ring of eleutherobin

A short and efficient RCM route is reported for the construction of the key nine-membered B ring of eleutherobin starting from the readily available 1,2,5,6-diisopropylidene-d-glucose.     

Ring-closing metathesis for the synthesis of 2H- and 4H-chromenes

Six 4H-chromenes were synthesized from substituted phenols using vinylstannylation and ring-closing metathesis (RCM) as key steps. In addition, a different approach involving amongst other steps, an aryl allyl isomerization and RCM afforded a set of seven 2H-chromenes from phenolic precursors.     

Synthesis of phosphorus containing medium ring heterocycles by sequential Claisen rearrangement and ring closing metathesis

An efficient method for the synthesis of novel medium ring phosphorus containing heterocycles starting from phenol derivatives by ruthenium catalyzed ring closing metathesis is described. This work deals with a sequential aromatic Claisen-rearrangement, coupling of an allyl/vinyl phosphonate, and ring closing metathesis reaction. All of these reactions were carried out at ambient temperature to afford the medium-sized phosphorus heterocycles in excellent yields.     

Ring-closing metathesis as a basis for the construction of aromatic compounds

The use of metathesis, especially in the context of ring-closing metathesis (RCM) to form five- and six-membered rings, is widespread in organic chemistry today. However, there are surprisingly few examples of the reaction being used to form aromatic compounds. The central place of aromatic compounds in both medicinal chemistry and natural products synthesis, coupled with the efficiency and functional group tolerance of RCM catalysts, means that there is now an interesting opportunity to use RCM for the synthesis of arenes. Although the formation of an aromatic compound was viewed in many early examples as an undesirable degradation product, several rationally designed methods towards the preparation of aromatic compounds by RCM have recently been developed.     

Microwave-assisted ring-closing metathesis of diallylamines: a rapid synthesis of pyrrole and pyrroline derivatives

The ring-closing metathesis (RCM) reactions of diallylamines occurred under controlled microwave irradiation. In addition to the high reaction rate, the key features of the reaction are that it can be carried out without deactivation of the substrates and without the use of Lewis acids.     

Stereoselective synthesis of the phytotoxic nonenolide herbarumin-I from l-ascorbic acid

A stereoselective synthesis of herbarumin-I in 22% overall yield, starting from l-ascorbic acid derived (S)-2,3-O-isopropylidine glyceraldehyde as a chiral template is reported. Stereoselective allylation and vinylation to control the required stereogenic centres and macrolactonisation followed by a ring-closing metathesis (RCM) are the key steps.