Cyclopentene Annulation Research Articles

Total Synthesis of Hypersampsone M.

We report the first total synthesis of hypersampsone M, an archetypal member of the homoadamantane polycyclic polyprenylated acylphloroglucinols (PPAPs). Commencing from cyclohexenone, a key cyclopentene annulation followed by ring-expansion results in an elusive hydrazulene that undergoes a series of unexpected late-stage transformations, ultimately enabling completion of the synthesis. The route detailed herein represents a potentially general strategy for the synthesis of related homoadamantane PPAPs.

Synthetic study on the angular triquinanes

The synthesis of an angular triquinane, which could serve as a suitable platform for the synthesis of several natural products (panaginsene, silphinene, senoxydene) is described. The synthesis is based on two consecutive cyclopentene annulations, where alkenes were used as latent carbonyl functionalities (via Wacker reaction), and cyclopentenone annulation was effected by aldol condensation.

Modular Approaches to Cyclopentanoids and their Heteroanalogs

AbstractCyclopentanoids and their derivatives are interesting targets in synthetic organic chemistry due to their extensive applications in various branches of chemical sciences like pharmaceuticals, natural and non-natural products. In view of these applications, several synthetic strategies have been developed in the past three to four decades. In this article, we describe our work towards the synthesis of cyclopentanoids and their heteroanalogs involving diverse synthetic strategies during the past two decades. Among these, photo-thermal olefin metathesis, ring-closing metathesis, ring-rearrangement metathesis, cyclopentane annulation, [2+2+2] cycloaddition and Diels–Alder reactions have been used to assemble cyclopentane rings of diverse architecture. 1 Introduction 2 Synthesis of Spiro[4.4]nonane (A1) Derivatives 3 Synthesis of Octahydropentalene (A2) Derivatives 4 Synthesis of Linear Triquinanes (A3) 5 Synthesis Spiro Triquinanes (A4) 6 Synthesis of Angular Triquinane (A5) Systems 7 Synthesis of Hexahydro-2′H-spiro[cyclopentane-1,1′-pentalene] (A6) Ring System 8 Synthesis of Dispiro[4.1.47.25]tridecane (A7) Ring System 9 Synthesis of Hexahydro-1H-3a,7a-propanoindene Ring System10 Synthesis of Linear Tetraquinanes (A11 and A12)11 Synthesis of Tetrahydro-1′H,3′H-dispiro[cyclopentane-1,2′-pentalene-5′,1′′-cyclopentane] (A13) Ring System12 Synthesis of Decahydro-1H,8H-dicyclopenta[a,h]pentalene (A14) Ring System13 Synthesis of Dodecahydro-1H-dicyclopenta[a,d]pentalene (A15) Ring System14 Synthesis of Octahydro-1′H-spiro[cyclopentane-1,2′-cyclopenta[c]pentalene] (A16) Ring System15 Synthesis of Decahydrospiro[cyclopentane-1,7′-cyclopenta-[a]pentalene] (A17) Ring System16 Synthesis of Compact Tetraquinane (A18)17 Synthesis of Higher Polyquinanes18 Conclusions19 Acronyms

Cyclopentene Annulations of Alkene Radical Cations with Vinyl Diazo Species Using Photocatalysis.

A direct (3+2) cycloaddition between alkenes and vinyl diazo reagents using either Cr or Ru photocatalysis is described. The intermediacy of a radical cation species enables a nucleophilic interception by vinyl diazo compounds, a departure from their traditional electrophilic behavior. A variety of cyclopentenes are synthesized using this method, and experimental insights implicate a direct cycloaddition instead of a cyclopropanation/rearrangement process.

Cyclopentene Annulations of Alkene Radical Cations with Vinyl Diazo Species Using Photocatalysis

AbstractA direct (3+2) cycloaddition between alkenes and vinyl diazo reagents using either Cr or Ru photocatalysis is described. The intermediacy of a radical cation species enables a nucleophilic interception by vinyl diazo compounds, a departure from their traditional electrophilic behavior. A variety of cyclopentenes are synthesized using this method, and experimental insights implicate a direct cycloaddition instead of a cyclopropanation/rearrangement process.

Stereoselective synthesis of the right-hand segment of tubiferal A

Tubiferal A, a triterpenoid isolated from myxomycete Tubifera dimorphotheca, exhibits a reversal effect of vincristine (VCR) resistance against VCR-resistant KB cell lines. The compound possesses a complex structure involving the 6-7-6-5 polycyclic carbon framework with various functional groups. The stereoselective synthesis of the right-hand segment of tubiferal A was achieved on the basis of the cyclopentene annulation method and the semi-pinacol rearrangement reaction of an epoxy alcohol for constructing the trans-fused 6-5 bicyclic skeleton possessing two quaternary carbon atoms at the angular positions.

ChemInform Abstract: Ring-Enlarging Cyclopentene Annulations.

Abstract Ethynylation of 2-[(2,2-dialkoxy)ethyl]cycloalkanones followed by Lewis acid-promoted rearrangement occasions cyclopentene annulation with concomitant one-carbon ring expansion of the starting cycloalkanone.

Asymmetric Total Synthesis of Glycinoeclepin A: Generation of a Novel Bridgehead Anion Species

Abstract The asymmetric total synthesis of glycinoeclepin A, a hatch-stimulating agent of the soybean cyst nematode, was accomplished on the basis of a cyclopentene annulation for constructing the CD ring moiety having contiguous quaternary carbon atoms. Introduction of the A ring moiety was achieved by an alkylation reaction using a 7-oxabicyclo[2.2.1]hex-1-yl anion species.

ChemInform Abstract: Synthesis of s‐Indacene Derivatives by Double Robinson‐Type Cyclopentene Annulation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Enantioselective Synthesis of the Hydroazulene Core of 3α‐Hydroxy‐15‐rippertene

AbstractAs part of a project directed toward the total synthesis of the tetracyclic diterpene 3α‐hydroxy‐15‐rippertene, a constituent of the defense secretion of higher termites, a fast access to two advanced hydroazulene key intermediates has been achieved by starting from (–)‐isopulegol. A regio‐ and diastereoselective formal hydromethallylation and a regioselective ring expansion served as the key steps in the formation of the seven‐membered ring. Completion of the bicyclic title compounds was then achieved by cyclopentene annulation through diastereoselective conjugate addition of organocuprates and subsequent intramolecular aldol condensations.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Synthesis of s-Indacene Derivatives by Double Robinson-Type Cyclopentene Annulation

Michael reactions of 2,5-dioxocyclohexane-1,4-dicarboxylates with methyl vinyl ketone yield bis-adducts that can be further cyclized in a Robinson-type annulation to give s-indacene derivatives as single diastereomers. The carboxylate functions of this scaffold can be deprotected and subsequently decarboxylated to yield tricyclic products with a central aromatic ring.

Synthesis of s‐Indacene Derivatives by Robinson‐Type Cyclopentene Annulation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

A Novel Cyclopentene Annulation Method Based on Conjugate Addition Reactions of α‐Cyano Carbanion Species.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

A Novel Cyclopentene Annulation Method Based on Conjugate Addition Reactions of α‐Cyano Carbanion Species

AbstractA new cyclopentene annulation method based on a conjugate addition reaction with 4‐methoxybut‐3‐enenitrile was developed. Treatment of a cyclic enone with the potassium carbanion of the nitrile followed by acetic anhydride afforded an enol acetate, which underwent an HCl‐mediated intramolecular cyclization reaction to yield a bicyclo[n.3.0]alkenone derivative in good yield. A lipase‐mediated optical resolution of the annulation product provided a new chiral building block for steroids and other natural compounds.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Synthesis ofs-Indacene Derivatives by Robinson-Type Cyclopentene Annulation

s-Indacene derivatives are obtained as single diastereo­isomers by a Robinson-type annulation of 2,5-cyclohexandione-1,4-dicarboxylates with methyl vinyl ketone. Hydrogenative debenzylation and subsequent decarboxylation yields tricyclic products with a central aromatic ring.

Tandem Michael Addition—Carbene Insertion Reaction of 1‐Alkynyl(aryl)(tetrafluoroborato)‐λ3‐bromanes: 1‐(Phenylsulfonyl)‐ and 1‐(Trifluoromethylsulfonyl)cyclopentene Annulation.

AbstractFor Abstract see ChemInform Abstract in Full Text.

An iterative approach to higher polyquinanes

A simple cyclopentane annulation strategy has been developed using inexpensive reagents. Starting from the readily available bicyclo(3.3.0)octane system several polyquinanes were prepared by iterative annulation procedure and herein we report a short and a convenient route to a new C20-hexaquinane system.

Tandem Michael addition–carbene insertion reaction of 1-alkynyl(aryl)(tetrafluoroborato)-λ3-bromanes: 1-(phenylsulfonyl)- and 1-(trifluoromethylsulfonyl)cyclopentene annulation

Exposure of 1-alkynyl[p-(trifluoromethyl)phenyl](tetrafluoroborato)-lambda(3)-bromanes to sodium benzenesulfinate or sodium trifluoromethanesulfinate in dichloromethane at 0 degree C under argon resulted in tandem Michael-carbene insertion reactions to produce 1-sulfonylcyclopentenes selectively, with concomitant formation of a small amount of rearranged 1-alkynyl sulfones.

W(CO)5(L)‐Catalyzed Endo‐Selective Cyclization of Allenyl Silyl Enol Ethers: An Efficient Method for the Cyclopentene Annulation onto α,β‐Unsaturated Ketones.

AbstractFor Abstract see ChemInform Abstract in Full Text.

An Efficient Method for Cyclopentene Annulation onto α,β‐Unsaturated Ketones: W(CO)5(L)‐Catalyzed 5‐endo‐dig Cyclization of 6‐Siloxy‐5‐en‐1‐ynes.

AbstractFor Abstract see ChemInform Abstract in Full Text.