Ring-opening Cyclization Research Articles

Efficient One-Pot Synthesis of Highly Substituted Pyridin-2(1H)-ones via the Vilsmeier−Haack Reaction of 1-Acetyl,1-Carbamoyl Cyclopropanes

A facile and efficient one-pot synthesis of highly substituted pyridin-2(1H)-ones is developed via the Vilsmeier-Haack reaction of readily available 1-acetyl,1-carbamoyl cyclopropanes, and a mechanism involving sequential ring-opening, haloformylation, and intramolecular nucleophilic cyclization reactions is proposed.

Effect of ethanol on the synthesis of large-ring cyclodextrins by cyclodextrin glucanotransferases

Cyclodextrin glucanotransferase (EC 2.4.1.19, CGTase) synthesizes cyclodextrins (CD) composed of 6 to more than hundred glucose units from amylose by an intramolecular transglycosylation reaction. The addition of ethanol to the reaction medium resulted in an increase of the yield of large-ring CD obtained with a CGTase from Bacillus sp. BT3-2 and Bacillus macerans. The presence of 15% ethanol in the reaction mixture with the CGTase from Bacillus sp. BT3-2 resulted in a 30% increase of the amounts of CD10–CD13 synthesized after 5 h of reaction. The addition of 20% ethanol increased the yield of CD14–CD21 up to 1000%. The hydrolysis of the large-ring CD by the CGTases was suppressed in the presence of ethanol. The ring-opening coupling cyclization reactions of the CGTase were effected differently by the organic solvent which may contribute to the observed increase of the yield and size of the CD obtained in the synthesis reactions.

Generation of ketyl radical anions by photoinduced electron transfer (PET) between ketones and amines. Synthetic applications

Abstract Photoreduction of ketones in the presence of amines led to ketyl radicals through photoinduced electron transfer (PET). Tertiary amines, such as triethylamine (Et 3 N) have frequently been used in these reactions. Different reactions can occur from ketyl radicals such as photoreduction, coupling reactions, additions on activated double bonds, cyclizations, bond cleavage of strained rings, tandem reactions such as cyclization–ring opening or ring opening–cyclization.

One-Pot Syntheses of 5-Amino-1-aryltetrazole Derivatives

A novel facile route for the introduction of 5-amino and 5-alkylamino substituents into 1-aryltetrazoles has been developed. A range of 5-amino-1-aryltetrazoles was obtained directly from the corresponding 1-aryltetrazoles in one pot by consecutive ring-opening, azidation and intramolecular cyclization. 5-Alkylamino-1-aryltetrazoles were formed by a similar mechanism from 1,4-disubstituted tetrazolium salts. An influence of the nature of aryl substituents and reaction conditions on the regioselectivity of the intramolecular cyclization of intermediate guanyl azides is revealed.

A New Synthesis of Tetrahydrofuran Fragment of Amphidinolides X and Y

A new synthesis of the tetrasubstituted tetrahydrofuran fragment of the marine secondary metabolites amphidinolides X and Y is described. The oxygenated chiral quaternary carbon was assembled by asymmetric dihydroxylation in high enantioselec­tivity and the tetrahydrofuran ring was constructed by an acid-catalyzed 5-endo ring-opening cyclization of the epoxide possessing a vinyl moiety.

Scandium triflate catalyzed cycloaddition of imines with 1,1-cyclopropanediesters: efficient and diastereoselective synthesis of multisubstituted pyrrolidines

A tandem ring-opening-cyclization reaction of cyclopropanes with imines in the presence of 5 mol% of scandium triflate was developed for the highly diastereoselective synthesis of multi-substituted pyrrolidines.

Synthesis of highly substituted pyrrolidines via palladium catalysed formal [2+3] cycloaddition of 5-vinyloxazolidin-2-ones to activated alkenes

Glycine-derived N-tosyl-5,5-divinyloxazolidin-2-one 10 undergoes a palladium catalysed decarboxylative ring-opening cyclization with strongly electron deficient alkylidenemalonate derivatives to give highly substituted pyrrolidines 14 containing two contiguous quaternary centres.

Practical Synthesis of 1‐Aryl‐6‐(hydroxymethyl)‐2‐ketopiperazines via a 6‐exo Amide—Epoxide Cyclization.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Practical Synthesis of 1-Aryl-6-(hydroxymethyl)-2-ketopiperazines via a 6-exo Amide−Epoxide Cyclization

[reaction: see text] Chiral 1-aryl-6-(hydroxymethyl)-2-ketopiperazines can be prepared via an operationally simple, 6-exo epoxide ring-opening cyclization to form the ketopiperazine C6-N1 bond in high yields and with excellent enantiomeric purity.

CeCl3‐Promoted Asymmetric Cycloaddition of Isocyanates with 2‐Vinylaziridines.

Abstract The enantioselective ring-opening cyclization of 2-vinylaziridines with various isocyanates, using Pd 2 (dba) 3 ·CHCl 3 , ( S )-BINAP and CeCl 3 as the catalytic system, afforded chiral imidazolidinones in 58–89% yield and in up to 83% ee.

CeCl 3 promoted asymmetric cycloaddition of isocyanates with 2-vinylaziridines

The enantioselective ring-opening cyclization of 2-vinylaziridines with various isocyanates, using Pd 2(dba) 3·CHCl 3, ( S)-BINAP and CeCl 3 as the catalytic system, afforded chiral imidazolidinones in 58–89% yield and in up to 83% ee.

ChemInform Abstract: The Synthesis of Mono- and Bicyclic Ethers via Acid-Catalyzed Ring-Opening Cyclization of Tetrahydropyranyl Ether Derivatives.

ChemInform Abstract: The Synthesis of Mono- and Bicyclic Ethers via Acid-Catalyzed Ring-Opening Cyclization of Tetrahydropyranyl Ether Derivatives.

Room temperature ring-opening cyclization reactions of 2-vinylaziridines with isocyanates, carbodiimides, and isothiocyanates catalyzed by

2-Vinylaziridines undergo cycloaddition reactions with various heterocumulenes, in the presence of [Pd(OAc)(2)] and PPh(3), at room temperature and 1 atm pressure, regioselectively affording five-membered ring products in moderate to high yields. The mixture of stereoisomers obtained by reactions employing cis-1-butyl-2-vinyl-3-methylaziridine as the reactant provides evidence for a mechanism involving a eta(3)-eta(1)-eta(3) interconversion of a (pi-allyl)palladium intermediate.

Signaling and Expression of Electronic Effects by Dihydroazulene-Vinylheptafulvene Photochromism

Dihydroazulene(DHA)/vinylheptafulvene(VHF) equilibration is based on photochemical ring opening and thermal cyclization. Optical and non-linear optical properties of DHA/VHF are reported. Multimode switching, comprising both photo-redox and off/on-fluorescence switching, are investigated. DHA covalently attached to cellulose shows multifold switching. A concept for cyclic multistate switching is proposed based on biphotochromic compounds.

Synthesis of cyclopropylamine with phase transfer catalysis

Cyclopropylamine is synthesized with γ-butyrolactone and isopropanol by five steps of ring-opening esterification, cyclization, hydrolysis, acylation and Hofmann degradation. Cyclization and hydrolysis are key steps in the process, and Phase Transfer Catalysis (PTC) is used in the two steps respectively. In the cyclization reaction, because solid-liquid PTC, sodium hydroxide is applied instead of expensive sodium alcoholate, the reaction can be carried out in mild conditions. The optimum reaction conditions are as follows: 0.03:1:1.5 mole ratio of BTEAC to ester to sodium hydroxide, reacting at 50 °C for 2 h with yield of 92%. Hydrolysis of isopropyl cyclopropanecarboxylate is accelerated by liquid-liquid PTC, and the order of catalytic activity is BTEC > BTMAC > CTMAB > TBAB. The results show that the new synthesis method is superior to those from literature and feasible for production with simple routes, mild reaction conditions, cheap materials and total yield of 52.6%.

ChemInform Abstract: Pyrrolidines from Olefins via Radical Cyclization.

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.

Pyrrolidines from olefins via radical cyclization

2,4-Disubstituted N-tosylpyrrolidines were prepared from olefins via N-tosylaziridination, benseneselenolate ring-opening and reductive radical cyclization. Azidoselenation of olefins, followed by ...

Rearrangement studies on 3,3-bis(methylthio)-1-(arylcyclopropyl) -2-propen-1-ols: Synthesis of functionalized cyclopentenes and polyene esters

The cyclopropyl carbinols 8 and 9 obtained by either borohydride reduction (or Grignard addition) of the cyclopropyl ketones 1 are shown to undergo acid induced ring opening and intramolecular cyclization (5-exo or 6-endo) or deprotonation to afford either cyclopentene, biphenyl or conjugated polyene derivatives depending on the nature of Lewis acid, reaction conditions and the structuralfeatures present in the cyclopropyl carbinol. A probable mechanism for the formation of various products has been suggested.