Diversity-oriented approach to biologically relevant molecular frameworks starting with beta-naphthol and using the Claisen rearrangement and olefin metathesis as key steps

A diversity-oriented approach for the synthesis of various structurally different molecular frameworks from readily accessible and common precursors is described. A Claisen rearrangement followed by ring-closing metathesis or ethylene-promoted ring-closing enyne metathesis has been utilized as the key synthetic transformation to generate naphthoxepine derivatives. The ring-closing metathesis approach has also been used to generate spirocyclic compounds and the pleiadene framework.     

Enantioselective synthesis of condensed and transannular ring skeletons containing pyrrolidine moiety

A new approach toward condensed and transannular ring structures containing pyrrolidine unit has been developed, based on diastereoselective nucleophilic addition of lithium enolate of α-diazoacetoacetate to chiral N-sulfinyl imine and ring-closing metathesis.     

Total synthesis of (+/-)-asteriscanolide.

The total synthesis of asteriscanolide (1) has been achieved by taking advantage on an intermolecular Pauson-Khand cycloaddition and a ring-closing metathesis as key bond-forming transformations. The approach incorporates the cyclooctane stereogenic center prior to ring formation. Interestingly, the ring-closing metathesis generates a new eight-membered ring with an "in-out" intrabridgehead relationship.     

Asymmetric synthesis of all the stereoisomers of tarchonanthuslactone

We describe herein an efficient synthesis of all the four stereoisomers of tarchonanthuslactone from (R)-3-hydroxy butanoate, easily prepared from l-threonine. The approach involves the use of a β,γ-unsaturated δ-lactone as an intermediate, obtained via a Kulinkovich reaction followed by a ring-closing metathesis strategy.     

The synthesis of 12-membered macrocycles containing a C1–C8 alkene unit via ring-closing metathesis

Model cross and ring-closing metathesis strategies toward the C1–C8-linear carbon skeleton are presented. The introduction of a four-atom tether enables the formation of 12-membered rings in good-to-excellent yields and stereoselectivity. Furthermore, the study revealed that the cross-metathesis approach and the formation of medium ring sizes via ring-closing metathesis are much less favorable.     

Combining α-amidoalkylation reactions of N-acyliminium ions with ring-closing metathesis: access to versatile novel isoindolones spirocyclic compounds

A novel approach to diversely spirocyclic isoindoles has been developed by using N-acyliminium/ring-closing metathesis strategy. Spirocyclization precursors, diolefinic, and enyne spiro-fused-isoindole derivatives have been obtained by a regioselective reduction of the spiro-imide compounds, followed by the allylation of the N-acyliminium intermediates (generated from the acetoxylactam compounds). Ruthenium catalyzed ring-closing metathesis of the above unsaturated derivatives provided novel spiroisoindoles.     

Tandem cyclopropanation/ring-closing metathesis of dienynes

Certain dienynes give cyclorearrangement by tandem cyclopropanation/ring-closing alkene metathesis, triggered by either a ruthenium carbene or noncarbene ruthenium(II) precatalyst. The process represents a variation of enyne metathesis where presumed cyclopropyl carbene intermediates undergo a consecutive ring-closing metathesis. A mechanistic proposal is offered, and sequential use of catalysts provided a tandem ring-closing enyne/alkene metathesis product.     

Convergent synthesis of the FGHI ring segment of yessotoxin

A convergent synthesis of the FGHI ring segment of yessotoxin was achieved via the intramolecular allylation of an α-chloroacetoxy ether and subsequent ring-closing metathesis.     

Efficient synthesis of RGD-containing cyclic peptide-porphyrin conjugates by ring-closing metathesis on solid support

We report the efficient solid-phase synthesis of a new family of peptidic porphyrins containing a constrained RGD moiety obtained by ring-closing metathesis.     

A convergent approach to the formal total synthesis of hemibrevetoxin B

A convergent synthesis of the key synthetic intermediate of hemibrevetoxin B was achieved via the intramolecular allylation of an α-chloroacetoxy ether and subsequent ring-closing metathesis.     

Convergent synthesis of the A-F ring segment of yessotoxin and adriatoxin

A convergent synthesis of the A-F ring segment of yessotoxin and adriatoxin was achieved via the intramolecular allylation of an α-chloroacetoxy ether and subsequent ring-closing metathesis.     

Convergent synthesis of the F-K ring segment of brevetoxin B

A convergent synthesis of the F-K ring segment of brevetoxin B has been achieved via the intramolecular allylation of an α-chloroacetoxy ether and subsequent ring-closing metathesis.     

Toward the synthesis of the antibiotic branimycin: novel approaches to highly substituted cis-decalin systems

A variety of highly functionalized cis-decalin systems have been prepared by means of the stereoselective transannular Diels-Alder (TADA) reaction of a (Z,E,Z,Z)-tetraene macrolide, and by means of intramolecular nitrile oxide olefin (INOC) or ring-closing metathesis (RCM) annulations to quinic acid derivatives.     

Synthesis of 2,6-dioxabicyclo[3.3.0]octenes by tandem ring-rearrangement/cross metathesis

A facile synthesis of stereodefined 2,6-dioxabicyclo[3.3.0]octene derivatives from the vinyl ether of endo-7-oxanorbornen-2-ol via tandem ring-opening/ring-closing(ring-rearrangement)/cross metathesis is reported.     

Diastereoselective ring-closing metathesis in the synthesis of dihydropyrans

An investigation into the factors influencing the diastereochemical outcome of the ring-closing metathesis based synthesis of dihydropyrans is presented in this paper. Divinyl carbinols derived from alpha-hydroxy carboxylic acid esters are elaborated to trienes with two diastereotopic vinyl moieties. Depending on the steric demand of the oxo substituent of the divinyl carbinol moiety (either unprotected OH, TBDMS, or benzyl ether) different diastereomers are preferrably formed upon ring-closing metathesis. An extension to diastereoselective double ring-closing metathesis in the formation of spirocycles has also been investigated.     

AuCl3-Catalyzed Ring-Closing Carbonyl–Olefin Metathesis

Compared with the ripeness of olefin metathesis, exploration of the construction of carbon–carbon double bonds through the catalytic carbonyl–olefin metathesis reaction remains stagnant and has received scant attention. Herein, a highly efficient AuCl₃-catalyzed intramolecular ring-closing carbonyl–olefin metathesis reaction is described. This method features easily accessible starting materials, simple operation, good functional-group tolerance and short reaction times, and provides the target cyclopentenes, polycycles, benzocarbocycles, and N-heterocycle derivatives in good to excellent yields.     

Efficient microwave-assisted formation of functionalized 2,5-dihydropyrroles using ruthenium-catalyzed ring-closing metathesis

A rapid method for the formation of functionalized 2,5-dihydropyrroles using ruthenium-catalyzed ring-closing metathesis under microwave irradiation is presented. The diene substrates were efficiently prepared from aza-Baylis-Hillman adducts.     

Studies on synthesis of spirolactone annulated bicyclo[2.2.2]octanes: tricyclic core of yaoshanenolides

A stereoselective approach to tricyclic core of yaoshanenolides from simple aromatic precursor is described. Cycloaddition of highly reactive spiroepoxycyclohexa-2,4-dienone, stereoselective Grignard reaction, alkylation, and ring-closing metathesis reaction are the key features of our approach.     

Pyrrole synthesis using a tandem Grubbs’ carbene-RuCl3 catalytic system

A straightforward pyrrole synthesis from diallylamines is developed by using a tandem catalyst system leading to ring-closing metathesis with the second generation Grubbs’ catalyst (10%) followed by dehydrogenation in the presence of RuCl₃ × H₂O (2%).     

Stereoselective construction of the tetracyclic core of Cryptotrione

An efficient stereoselective approach to the tetracyclic core of Cryptotrione, involving an asymmetric Michael addition, ring-closing metathesis, and subsequent cyclopropanation, is described.