scholarly journals Ring-closing-metathesis-based synthesis of annellated coumarins from 8-allylcoumarins

2018 ◽  
Vol 14 ◽  
pp. 2991-2998 ◽  
Author(s):  
Christiane Schultze ◽  
Bernd Schmidt
Keyword(s):  
Double Bond ◽  
Olefin Metathesis ◽  
Claisen Rearrangement ◽  
Allylic Oxidation ◽  
Allyl Ether ◽  
Ring Closing Metathesis ◽  
Wittig Olefination

8-Allylcoumarins are conveniently accessible through a microwave-promoted tandem Claisen rearrangement/Wittig olefination/cyclization sequence. They serve as a versatile platform for the annellation of five- to seven-membered rings using ring-closing olefin metathesis (RCM). Furano-, pyrano-, oxepino- and azepinocoumarins were synthesized from the same set of precursors using Ru-catalyzed double bond isomerizations and RCM in a defined order. One class of products, pyrano[2,3-f]chromene-2,8-diones, were inaccessible through direct RCM of an acrylate, but became available from the analogous allyl ether via an assisted tandem catalytic RCM/allylic oxidation sequence.

scholarly journals Synthesis of Dihydropyrano[3,2-c]pyrazoles via Double Bond Migration and Ring-Closing Metathesis

Molecules ◽  
2019 ◽  
Vol 24 (2) ◽  
pp. 296 ◽  
Author(s):  
Yoshihide Usami ◽  
Kodai Sumimoto ◽  
Azusa Kishima ◽  
Yuya Tatsui ◽  
Hiroki Yoneyama ◽  
...  
Keyword(s):  
Double Bond ◽  
Claisen Rearrangement ◽  
Ring Closing Metathesis ◽  
Double Bond Migration ◽  
Ruthenium Hydride

Three types of pyrazole-fused heterobicycles, i.e., 1,5-, 1,7-, and 2,5-dihydropyrano[3,2-c]pyrazoles, were synthesized from 4-allyloxy-1H-pyrazoles. A sequence of the Claisen rearrangement of 4-allyloxy-1H-pyrazoles, ruthenium-hydride-catalyzed double bond migration, O-allylation, and ring-closing metathesis was employed in this study.

Sequential olefin metathesis — Intramolecular asymmetric Heck reactions in the synthesis of polycycles

2004 ◽  
Vol 82 (2) ◽  
pp. 399-407 ◽  
Author(s):  
Mark Lautens ◽  
Valentin Zunic
Keyword(s):  
Double Bond ◽  
Heck Reaction ◽  
Olefin Metathesis ◽  
Heck Reactions ◽  
Ring Closing Metathesis ◽  
Double Bond Migration ◽  
Double Ring ◽  
Asymmetric Heck Reaction

Application of the intramolecular asymmetric Heck reaction in the desymmetrization of a novel class of symmetrical bicyclodienes, synthesized through a diastereoselective double ring-closing metathesis (DSRCM) reaction, was achieved with good yields (approximately 80%) and excellent enantioselectivities (up to 99% ee). Three contiguous stereocenters are established in a single desymmetrization reaction. The use of thallium carbonate as base in the asymmetric Heck reaction favours double bond migration in 13. Cationic conditions delivered products with good to excellent enantioselectivities, surpassing the results under neutral conditions.Key words: asymmetric, Heck, polycycles, metathesis, stereoselective, desymmetrization.

scholarly journals Transformations of terpenes and terpenoids via carbon–carbon double bond metathesis

2018 ◽  
Vol 8 (16) ◽  
pp. 3989-4004 ◽  
Author(s):  
Christian Bruneau ◽  
Cédric Fischmeister ◽  
Dalmo Mandelli ◽  
Wagner A. Carvalho ◽  
Eduardo N. dos Santos ◽  
...  
Keyword(s):  
Double Bond ◽  
Olefin Metathesis ◽  
Ring Opening ◽  
Ring Closing Metathesis ◽  
Cross Metathesis ◽  
Carbon Double Bond ◽  
Review Reports

The review reports on transformations of unsaturated terpenes and terpenoids via olefin metathesis processes including ring closing metathesis of dienes, cross metathesis with functional olefins and ethenolysis, and ring opening metathesis as well as ring opening/cross metathesis.

Connecting catalytic cycles by organometallic transformations in situ: Novel perspectives in the olefin metathesis field

2006 ◽  
Vol 78 (2) ◽  
pp. 469-476 ◽  
Author(s):  
Bernd Schmidt
Keyword(s):  
Double Bond ◽  
Olefin Metathesis ◽  
Metathesis Reaction ◽  
Ring Closing Metathesis ◽  
Double Bond Isomerization ◽  
Metathesis Catalyst ◽  
Organometallic Transformations ◽  
Catalytic Cycles

Tandem sequences consisting of an olefin metathesis step and a subsequent non-metathesis reaction become accessible by organometallic transformations of the Ru-carbene species in situ. This contribution highlights some tandem sequences that rely on the conversion of the metathesis catalyst to Ru-hydrides, with special emphasis on the tandem ring-closing metathesis (RCM)-double-bond isomerization sequence.

New pseudohalide ligands in Ru-catalyzed olefin metathesis — A robust, air-activated iminopyrrolato catalyst

2005 ◽  
Vol 83 (6-7) ◽  
pp. 748-754 ◽  
Author(s):  
Samantha D Drouin ◽  
Heather M Foucault ◽  
Glenn PA Yap ◽  
Deryn E Fogg
Keyword(s):  
Key Words ◽  
Olefin Metathesis ◽  
High Reactivity ◽  
Ring Closing Metathesis ◽  
Grubbs Catalyst ◽  
X Ray ◽  
X Ray Crystallography

Reaction of the Grubbs catalyst RuCl2(PCy3)2(CHPh) (1) with lithium 2-[(2,6-diisopropylphenyl)imino]pyrrolide·Et2O (LiNN′·Et2O) gives alkylidene complex 5, containing a chelating, σ-bound iminopyrrolato unit. The structure of 5 is confirmed by X-ray crystallography. Treatment of 5 with pyridine generates RuCl(NN′)(py)2(CHPh) (6) via displacement of PCy3. Complex 5 effects ring-closing metathesis in air, displaying high reactivity relative to 6.Key words: ruthenium, alkylidene, metathesis, pyrrolimine, iminopyrrolato.

scholarly journals Axially chiral racemic half-sandwich nickel(ii) complexes by ring-closing metathesis

2017 ◽  
Vol 46 (12) ◽  
pp. 3805-3808 ◽  
Author(s):  
Włodzimierz Buchowicz ◽  
Łukasz Banach ◽  
Radosław Kamiński ◽  
Piotr Buchalski
Keyword(s):  
Coordination Sphere ◽  
Olefin Metathesis ◽  
Ring Closing Metathesis ◽  
Axially Chiral ◽  
Half Sandwich

A remarkable helical complex with a chelating Cp-NHC ligand has been synthesised via olefin metathesis in the Ni(ii) coordination sphere.

Synthesis of a Simplified Analogue of Eleutherobin via a Claisen Rearrangement and Ring Closing Metathesis Strategy.

ChemInform ◽  
2005 ◽  
Vol 36 (35) ◽  
Author(s):  
Gary C. H. Chiang ◽  
Andrew D. Bond ◽  
Andrew Ayscough ◽  
Gilles Pain ◽  
Sylvie Ducki ◽  
...  
Keyword(s):  
Claisen Rearrangement ◽  
Ring Closing Metathesis

A Concise Total Synthesis of (±)-Mesembrine

Synlett ◽  
2018 ◽  
Vol 29 (09) ◽  
pp. 1203-1206 ◽  
Author(s):  
Hyoungsu Kim ◽  
Hosam Choi ◽  
Kiyoun Lee
Keyword(s):  
Total Synthesis ◽  
Claisen Rearrangement ◽  
Addition Reaction ◽  
Conjugate Addition ◽  
Allylic Oxidation ◽  
Quaternary Stereocenter

A concise total synthesis of (±)-mesembrine has been successfully accomplished in seven steps and 24% overall yield from commercially available 3-ethoxy-2-cyclohexen-1-one. Central to the assembly of the skeleton of mesembrine are a Johnson–Claisen rearrangement for the formation of the benzylic quaternary stereocenter and direct allylic oxidation to generate the substrate for the amidation/transannular aza-conjugate addition reaction.

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