Annulation Method Research Articles

An efficient method for cyclopentene annulation onto alpha,beta-unsaturated ketones: W(CO)(5)(L)-catalyzed 5-endo-dig cyclization of 6-siloxy-5-en-1-ynes.

[reaction: see text] A highly efficient method for the cyclopentene annulation onto alpha,beta-unsaturated ketones is described. Indium-mediated 1,4-propargylation onto alpha,beta-unsaturated ketones in the presence of tert-butyldimethylsilyl triflate and dimethyl sulfide gives the 6-siloxy-5-en-1-yne derivatives, which undergo W(CO)(5)(L)-catalyzed 5-endo-dig cyclization to give the corresponding cyclopentene derivatives in good yield.

4 + 2] cycloaromatization of 4-bis(methylthio)-3-buten-2-one with active methylene ketones: a simple and facile phenol annulation.

A new method for beta-phenol annulation involving base-induced [4C + 2C] cycloaromatization of readily available 4-bis(methylthio)-3-buten-2-one with a variety of cyclic and acyclic active methylene ketones has been reported. Appropriate choice of ketones allows synthesis of diverse frameworks such as dihydroindan, tetrahydronaphthalenes, their higher homologues, dihydro/octahydrophenanthrenes, anthracene, and heteroannulated analogue in high yields with regiocontrol of phenolic functionality.

6,8-Dimethylpyrimido[4,5- c]pyridazine-5,7(6 H,8 H)-dione: a novel method of pyrrole-ring annulation to an azine nucleus based on a tandem S NH–S NH process

6,8-Dimethylpyrimido[4,5- c]pyridazine-5,7(6 H,8 H)-dione has been shown to react with some secondary amines in the presence of an oxidant to produce 6,8-dimethylpyrrolo[2′,3′;3,4]pyridazino[6,5- d]pyrimidine-7,9(6 H,8 H)-dione derivatives. The reaction represents a new method of pyrrole-ring annulation to an azine nucleus via a tandem S N H–S N H process.

ChemInform Abstract: A Convenient Method for the Synthesis of Δ1,6‐Bicyclo[4.n.0]alken‐2‐ones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 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.

A new cycloheptenone annulation method: use of the bifunctional reagent (Z )-5-iodo-1-tributylstannylpent-1-ene in organic synthesis

A new seven-membered annulation method that employs (Z)-5-iodo-1-tributylstannylpent-1-ene (1) as a key reagent and that is exemplified by the conversion of compounds 6, 12, 13, 20, 25, and 26 into the annulation products 11, 18, 19, 24, 33, and 34, respectively, is reported.

A convenient method for the synthesis of Δ1,6-bicyclo[4.n.0]alken-2-ones

A convenient annulation method for the synthesis of bicyclic enones from cycloalkanones was developed. In the presence of a Pd(0) catalyst, enol triflates derived from ethyl 2-oxocycloalkanecarboxylates were treated with 3-(ethoxycarbonyl)propylzinc iodide to afford the corresponding diesters via a cross-coupling reaction. The diesters were easily transformed into Δ 1,6-bicyclo[4.n.0]alken-2-ones through Dieckmann condensation followed by decarboxylation. The annulation method was also applicable for the synthesis of the corresponding cycloheptenone derivative.

Synthesis and Regioselective Ribosylation of 6,7-Dichloroimidazo[4,5-b]quinolin-2-one

The polyhalogenated benzimidazole nucleosides 2,5,6-trichloro-1-(β-d-ribofuranosyl)benzimidazole (TCRB) and the 2-bromo analogue (BDCRB) were synthesized in our laboratory and established as potent and selective antiviral agents against human cytomegalovirus (HCMV) with a novel mode of action. In an effort to study the behavior of the key substructure of these analogues in a dimensionally stretched-out manner and probe the spatial limitation of the target enzyme(s), a series of N1- and N3-ribonucleosides of imidazo[4,5-b]quinolines were designed as linear dimensional analogues. The nucleosides 6,7-dichloro-1-(β-d-ribofuranosyl)imidazo[4,5-b]quinolin-2-one and 6,7-dichloro-3-(β-d-ribofuranosyl)imidazo[4,5-b]quinolin-2-one were selected and prepared as the key intermediates in this study. During this study, a novel photoassisted annulation was developed for the synthesis of 6,7-dichloroimidazo[4,5-b]quinolin-2-one, which overcame several problems that were encountered with the literature annulation method. ...

Base-Induced Rearrangement of Perhydronaphthalene-1,4-diol Monosulfonate Esters to 11-Oxatricyclo[5.3.1.0(2,6)]undecanes. Total Synthesis of Furanether B.

It is observed that mesylate 1 on exposure to Li(Ot-Bu)(3)AlH in refluxing toluene rearranges selectively to the 11-oxatricyclo[5.3.1.0(2,6)]undecane derivative 3. A similar rearrangement, leading to a bridged tricyclic ether (14 --> 5), has been used as the key to the total synthesis of furanether B (4), a naturally occurring lactarane sesquiterpene, with the readily available ketone 8 as the starting material. Completion of the synthesis of the natural product is accomplished by an annulation method based on a Pummerer-induced cyclization reaction.

ChemInform Abstract: A New (5 + 2) Annulation Method for the Synthesis of 8‐Oxabicyclo(3.2. 1)octanes from Pyrones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 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.

A simple route to cyclopentane annulation

We have developed a simple method for cyclopentane annulation using inexpensive reagents which is useful for the synthesis of polyquinane systems.

Methylenecyclopentane annulation via formal [3 + 2] cycloaddition reaction

A new method for methylenecyclopentane annulation via formal [3+2] cycloaddition reaction was developed. Under the influence of Lewis acids, enol ethers and vinylsulfides were treated with I-(alkylthio)-2-(trimethylsilylmethyl)allyl esters 1a or 1b to afford methylenecyclopentanes in good yields. The reaction proceeds with almost complete regioselectivity as well as high stereoselectivity.

Asymmetric synthesis of the tremulane skeleton by a tandem cyclopropanation/cope rearrangement

A highly diastereoselective and enantioselective 3 + 4 annulation method for the synthesis of polycyclic systems was achieved in a two step sequence consisting of an asymmetric intramolecular cyclopropanation catalyzed by dirhodium(II) tetrakis((R)-N-(p-(dodecyl)phenylsulfonyl)prolinate) followed by a Cope rearrangement of the resulting divinylcyclopropane intermediate.

A new cyclopentenone annulation method

Alkylation of the substrates 8–12 with ( Z)-3-bromo-1-iodopropene ( 5), followed by n-BuLi-mediated cyclization of the resultant products 15–19, provides the tertiary allylic alcohols 22–26, which, upon oxidation with a Cr(VI) reagent, afford the cyclopentenones 29–33. The α-methylcyclopentenones 34 and 35 are similarly derived from the keto esters 13 and 14.

Total Synthesis of Aegyptinones A and B

This paper describes the first total syntheses of the diterpene quinones aegyptinones A and B via an extremely direct route which should easily accommodate the production of gram quantities of each compound. The key step in the synthetic strategy involves the application of a recently developed «second-generation» photochemical aromatic annulation method for the construction of highly substituted aromatic systems. The synthesis of one of the annulation components, the diazo ketone 6, was achieved using a Diels-Alder-based benzannulation strategy employing cyanoallene and the dienamine 13. Cyanoallene proved to be uniquely effective for this cycloaddition, which either failed or proceeded in poor yield using several substituted acetylenes as dienophiles. The pivotal aromatic annulation reaction was accomplished by irradiating a solution of the diazo ketone 5 and the readily available siloxyalkyne 4 in a Pyrex vessel with a 450-W medium-pressure Hanovia lamp at room temperature for 17-20h. The desired tricyclic phenol 3 was produced in 58-70% yield and was then converted to aegyptinone B (2) by treatment with tetra-n-butylammonium fluoride in the presence of oxygen. Finally, cyclization to generate aegyptinone A was accomplished in high yield by brief exposure of 2 to an ethanolic solution of concentrated sulfuric acid at room temperature. Overall, this strategy provides efficient routes (six and seven steps, respectively) to aegyptinones A and B which should facilitate the systematic investigation of the pharmacological activity of these novel diterpenes

Diastereoselective Synthesis of Actinobolin from D-Glucose by Application of a Novel [3 + 3] Annulation

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDiastereoselective Synthesis of Actinobolin from D-Glucose by Application of a Novel [3 + 3] AnnulationDale E. Ward and Brian F. KallerCite this: J. Org. Chem. 1994, 59, 15, 4230–4238Publication Date (Print):July 1, 1994Publication History Published online1 May 2002Published inissue 1 July 1994https://doi.org/10.1021/jo00094a040RIGHTS & PERMISSIONSArticle Views240Altmetric-Citations15LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

A new annulation method. Total syntheses of the sesquiterpenoids (±)-chiloscyphone and (±)-6-epi-chiloscyphone

The efficacy of a new annulation method, developed for the construction of functionalized bicyclic compounds, is illustrated by conversion of the β-keto esters 18 and 19 into the bicyclo[4.3.0]non-1-enes 33 and 34, respectively, and by transformation of 2-methoxycarbonylcyclopentanone (20) into the bicyclo[4.3.0]non-6-ene 38 and the bicyclo[5.3.0]dec-7-enes 48 and 51. Application of the method to total syntheses of the structurally unusual sesquiterpenoids (±)-chiloscyphone (16) and (±)-6-epi-chiloscyphone (17) is described.

New low-valent titanium reagents for dicarbonyl coupling and their use in a general method of annulation. [Erratum to document cited in CA117(3):25962n

New low-valent titanium reagents for dicarbonyl coupling and their use in a general method of annulation. [Erratum to document cited in CA117(3):25962n

Bifunctional conjunctive reagents: 5-chloro-2-lithio-1-pentene and related substances. A methylenecyclohexane annulation method

The development of a new, synthetically useful methylenecyclohexane annulation method is described. Transmetallation (MeLi, tetrahydrofuran, −78 °C) of 5-chloro-2-trimethylstannyl-1-pentene (8) affords the novel bifunctional reagent 5-chloro-2-lithio-1-pentene (9), which, at temperatures higher than approximately −50 °C, self-destructs to give methylenecyclobutane (14). Reagent 9 can be converted into the Grignard reagent 10 and the organocopper(I) species 15. Conjugate addition of 10 and 15 to a number of cyclic enones (16–22), followed by intramolecular alkylation of the resultant adducts (23–29), produces the corresponding methylenecyclohexane annulation products (30–40).

Synthesis of novel rigid norbornylogous spacers bearing heterocyclic ligands for the investigation of long-range intramolecular electron transfer involving metal centres

The synthesis of some novel 1,4-dimethoxynaphthalene—bridge—heterocycle systems is described. In these systems, the naphthalene and heterocyclic groups are fused to a rigid bridge consisting of linearly fused norbornyl and bicyclo[2.2.0]hexyl groups. Bridges used herein have relays of 2, 4, and 6bonds long. The heterocycle is either 3.6-di(2′-di(2′-pyridyl)-pyridazino, or pyrido and was attached to the bridge by annulation methods. The pyridazino systems, 2( m,n), were synthesized via Diels-Alder reaction of 3,6-di(2′-pyridyl)-1,2,4,5-tetrazine with the alkenes, 13 and 6( m,n), and subsequent aromatization of the adducts with DDQ. Pyridine annulation was successfully carried out using two different methods: (i) Boger pyridine annulation of ketones, 11, 20b, and 21b, (with 1,2,4-triazine and pyrrolidine); (ii) Diels-Alder reaction of alkenes 13 and 6( m,n) with 3-thiomethyl-1,2,4-triazine, followed by Raney nickel reductive desulfurization of the aromatized adducts. The synthesis of Ru(II)(2,2′-bipyridyl) 2 complexes of the pyridazino systems. 9( m,n) and 10, is also described.

ChemInform Abstract: Lewis Acid Catalyzed Michael‐Type Addition. A New Regio‐ and Diastereoselective Annulation Method Using Methyl Vinyl Ketone.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 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.