An efficient one-pot synthesis of spiro dihydrofuran oxindole and spiro 2-hydroxytetrahydrofuran oxindole derivatives via (3+2) oxidative cycloaddition mediated by CAN

Spiro dihydrofuran oxindole derivatives were prepared via a (3+2) oxidative cycloaddition of 1,3-dicarbonyl compounds to 3-(phenyl-2-oxoethylidene)-1-methyloxindole and 3-benzylidene-1-methyloxindole derivatives mediated by ceric ammonium nitrate. In the case of the reaction of 3-(phenyl-2-oxoethylidene)-1-methyloxindole derivatives with acyclic 1,3-dicarbonyl compounds, spiro 2-hydroxytetrahydrofuran oxindole derivatives were obtained.     

Facile synthesis of naphthoquinone spiroketals by diastereoselective oxidative [3 + 2] cycloaddition

A highly selective oxidative [3 + 2] cycloaddition of chiral enol ethers and hydroxynaphthoquinone is described. This convergent strategy is amenable to an enantioselective synthesis of beta-rubromycin and related naphthoquinone spiroketals. Several compounds were found to inhibit DNA-polymerase and telomerase in a manner resembling alpha-rubromycin and beta-rubromycin.     

An efficient and novel protocol for the synthesis of spiro[1,3]oxazino[5,6-c]quinoline derivatives by one-pot,three-component reaction

Research on Chemical Intermediates - One-pot, three-component reaction of various aryl glyoxal monohydrates, 5-methylisoxazol-3-amine and 4-hydroxyquinolin-2(1H)-one in the presence of a catalytic...     

Ultrasonic assisted-silica mediated [3+2] cycloaddition of azomethine ylides—a facile multicomponent one-pot synthesis of novel dispiroheterocycles

An efficient synthesis of dispiro-oxindolopyrrolizidine and dispirooxindolothienopyrrole derivatives has been expediently accomplished via a one-pot, three-component 1,3-dipolar cycloaddition reaction. High regioselectivity was achieved on ultrasonication in the presence of silica as a catalyst. X-ray diffraction studies of one of the cycloadducts proved the structure and regiochemistry of the cycloaddition.     

An efficient one-pot synthesis of substituted 2-arylbenzo[b]thiophene derivatives

This communication describes an efficient one-pot procedure for the synthesis of 2-arylbenzo[b]thiophene derivatives via reaction of o-halo or nitro aryl carbonyl compounds with benzyl mercaptans in the presence of an excess of anhydrous K₂CO₃ at elevated temperature.     

Stereoselective synthesis of cycloheptanone derivatives via an intermolecular [5 + 2] cycloaddition reaction

[reaction: see text] A [5 + 2] cycloaddition reaction of a new five-carbon unit was developed on the basis of a dicobalt hexacarbonyl propargyl cation species. Under the influence of EtAlCl(2), [5-benzoyloxy-2-(triisopropylsiloxy)-1-penten-3-yne)]dicobalt hexacarbonyl reacted with enol triisopropylsilyl ethers to yield seven-membered dicobalt acetylene complexes in good yield. The reactions with cyclic enol silyl ethers as well as acyclic enol silyl ethers exhibited remarkably high diastereoselectivity. The cycloadducts can be easily converted into various kinds of cycloheptanone derivatives.     

An efficient one-step regiospecific synthesis of novel isoxazolines and isoxazoles of N-substituted saccharin derivatives through solvent-free microwave-assisted [3+2] cycloaddition

Novel isoxazolines and isoxazoles of N-substituted saccharin derivatives are synthesized in good yields by 1,3-dipolar cycloaddition of N-allyl or propargyl N-substituted saccharin with arylnitrile oxide under solvent-free microwave irradiation. In this process, the yields were significantly improved over conventional heating, without alteration of the selectivity. The regioselectivity as well as the nonthermal specific microwave effect are discussed.     

An efficient one-pot synthesis of tetrahydroquinoline derivatives via an aza Diels-Alder reaction mediated by CAN in an aqueous medium and oxidation to heteroaryl quinolines

Various tetrahydroquinoline derivatives have been synthesized by employing ceric ammonium nitrate in an aqueous medium. Subsequently, the tetrahydroquinolines were oxidized to biheterocycles.     

A three-component, one-pot synthesis of indolizidines and related heterocycles via the [3+2] cycloaddition of nonstabilized azomethine ylides

Nonstabilized azomethine ylides (i.e. those bearing only hydrogens or alkyl groups) can be generated from (2-azaallyl)stannanes and (2-azaallyl)silanes through an intramolecular N-alkylation/demetalation cascade. The resulting ylides undergo [3+2] cycloaddition with electron-poor or electron-rich dipolarophiles yielding indolizidines and related 1-aza[m.3.0]bicycloalkane systems in good yield. An in situ protocol allows for a one-pot, three-component synthesis of indolizidines. The (2-azaallyl)stannanes tolerate enolizable hydrogens in these cycloadditions, while (2-azaallyl)silanes do not. The mechanism of the cycloaddition cascade is clarified by a series of control experiments. The same (2-azaallyl)stannanes may be transmetalated by n-butyllithium to generate 2-azaallyllithiums, which also may undergo a [3+2] cycloaddition/N-alkylation cascade to form indolizidines.     

Asymmetric synthesis of 1,3-dioxolanes by organocatalytic formal [3 + 2] cycloaddition via hemiacetal intermediates

A novel asymmetric formal [3 + 2] cycloaddition reaction for the synthesis of 1,3-dioxolanes using cinchona-alkaloid-thiourea-based bifunctional organocatalysts is reported. The reaction proceeds via the formation of hemiacetal intermediates between γ-hydroxy-α,β-unsaturated ketones and aldehydes.     

Grindstone chemistry: one-pot synthesis of spiro[diindenopyridine-indoline]triones and spiro[acenaphthylene-diindenopyridine]triones

A one-pot, pseudo four-component, and simple synthesis of spiro[diindenopyridine-indoline]triones and spiro[acenaphthylene-diindenopyridine]triones via the reaction of 1,3-indandione, aromatic amines and isatins or acenaphthylene-1,2-dione using a ‘Grindstone Chemistry’ method is reported.     

An expedient approach for the regio- and stereoselective synthesis of novel spiroindolizidines via [3+2] cycloaddition

A new series of spiroindolizidines was synthesized by one-pot, three-component condensation of azomethine ylides, generated from 1,2,3,4-tetrahydroisoquinoline with ninhydrin or isatin derivatives by a 1,5-prototropic shift route, with various derivatives of trans-β-nitrostyrene in a regio- and stereoselective manner. X-ray crystal structure analysis and NMR spectroscopic data confirmed the structure outcome of the cycloaddition reaction.     

Ultrasound-promoted one-pot, three-component synthesis of spiro[indoline-3,1'-pyrazolo[1,2-b]phthalazine] derivatives

A series of 3'-aminospiro[indoline-3,1'-pyrazolo[1,2-b]phthalazine]-2,5',10'-trione derivatives have been synthesized by a one-pot three-component reaction of isatin, malononitrile or ethyl cyanoacetate and phthalhydrazide catalyzed by piperidine under ultrasound irradiation. For comparison the reactions were carried out under both conventional and ultrasonic conditions. In general, improvement in rates and yields were observed when the reactions were carried out under sonication compared with classical conditions.     

Heteropolyacid–silica mediated [3+2] cycloaddition of azomethine ylides—a facile multicomponent one-pot synthesis of novel dispiroheterocycles

An efficient synthesis of dispiroindenoquinoxaline pyrrolizidine derivatives has been expediently accomplished by a one-pot four component 1,3-dipolar cycloaddition reaction. High regioselectivity was achieved using heteropolyacid H₄[Si(W₃O₁₀)₃]–silica as a catalyst. X-ray diffraction studies of one of the cycloadducts proved the structure and regiochemistry of the cycloadduct.     

Enantioselective synthesis of axially chiral hydroxy carboxylic acid derivatives by rhodium-catalyzed [2 + 2 + 2] cycloaddition

Axially chiral hydroxy carboxylic acid derivatives were successfully synthesized with high yields and ee values by the cationic rhodium(I)/axially chiral biaryl bisphosphine complex-catalyzed enantioselective [2 + 2 + 2] cycloaddition. Axially chiral hydroxy and dihydroxy carboxylic acid derivatives, bearing the aryl group at the ortho-position of the alkoxycarbonyl group, were also synthesized with high regio- and enantioselectivity.     

Formal synthesis of aspidosperma alkaloids via the intramolecular [3 + 2] cycloaddition of 2-azapentdienyllithiums

[reaction: see text] A formal synthesis of the Aspidosperma alkaloids aspidospermidine, aspidospermine, and quebrachamine is reported through an efficient preparation of Stork's penultimate intermediate. The key step of the sequence involved an intramolecular [3 + 2] cycloaddition of the 2-azapentadienyllithium 21 formed in situ from the corresponding imine 1, which after N-alkylation of the resulting cycloadduct provided 2 in excellent yield. The synthesis represents a new disconnection of the classical tricyclic ketone used for appendage of the requisite indole.