1,3-Dipolar cycloaddition reactions of alkenylalkoxycarbene chromium complexes

New spiropyrazoline derivatives from the 1,3-dipolar cycloaddition of diazomethane to alkenylalkoxycarbene complexes are isolated and fully characterized as Cr(CO) ₅ complexes. Me₃SiCHN₂ reacts selectively with the CC double bond to give new pentacarbonylchromium carbene complexes.     

1,3-Dipolar cycloaddition reactions of vinylcephalosporins with diazoalkanes

The vinylcephalosporin ( 1 ) undergoes a regio- and stereoselective 1, 3 -dipolar cycloaddition with diazomethane to give novel cephalosporins, a 3 -pyrazolinocephem ( 4 ) and a double adduct ( 5 ). The vinylcephalosporin sulphoxide ( 2 ) gives only the pyrazolinocephem ( 7 ). In the reaction with diphenyldiazomethane upon heating the initially formed pyrazolines decompose and cyclopropylcephalosporin ( 9 ) formation takes place. The determination of the structures and stereochemistry of these compounds is also described.     

1,3-Dipolar cycloaddition reactions of 4,6-diazaphenanthrene 6-phenacylide

Summary The 1,3-dipolar cycloaddition reactions of 4,6-diazaphenanthrene 6-phenacylide formed in situ from the appropriate quaternary bromide in basic medium were investigated; as dipolarophiles acrylonitrile, ethyl acrylate,n-butyl acrylate and diethyl maleate were used.

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1,3-Dipolare Cycloadditionsreaktionen von 4,6-Diazaphenanthren-6-phenacylid

Zusammenfassung Es wurden die 1,3-dipolaren Cycloadditionen von 4,6-Diazaphenanthren-6-phenacylid untersucht, welches in situ aus dem entsprechenden quaternären Bromid in Gegenwart von Alkali dargestellt wurde. Als Dipolarophile wurden Acrylnitril, Ethylacrylat,n-Buthylacrylat und Diethylmaleat eingesetzt.

     

1,3-Dipolar cycloaddition reactions of 1,4-benzoquinones with nitrilimines

The cycloaddition reactions of some aryl conjugated p-benzoquinones with nitrilimines were studied. Depending upon the reaction conditions mono- and/or bis- adducts were isolated only from carbon-carbon double bond. The structure determination was unequivocally established by an X-ray analysis carried out on a bis-adduct. The observed regio-, as well as site-selectivity, was qualitatively correlated with frontier molecular orbitals of the reacting species.     

1,3-Dipolar cycloaddition reactions of cyclooctyne with pyridinium dicynomethylides

Cyclooctyne smoothly underwent 1,3-dipolar cycloaddition with pyridinium dicyanomethylides to afford the corresponding indolizines (8-cyario-7-azatricyclo[7.6.0.0^2,7]pentadeca-1,3,5,8-tetraenes) in excellent yields.     

1,3-Dipolar cycloaddition reactions of azomethine ylides and alkynes

Chemistry of Heterocyclic Compounds - In this review, we consider 1,3-dipolar cycloaddition reactions between azomethine ylides and alkynes, resulting in the formation of pyrroles, as well as their...     

1,3-Dipolar cycloaddition reactions of cyclooctyne with azomethine ylides

Cyclooctyne smoothly underwent 1,3-dipolar cycloaddition with aziridines and pyridinium ylides to afford the corresponding pyrroles and indolizines in moderate to good yields.     

1,3-Dipolar cycloaddition reactions of 3-acylimino-1-methylbenzimidazolium betaines

3-Acylimino-1-methylbenzimidazolium betaines undergo 1,3-dipolar cycloaddition reactions with activated alkenes (methyl acrylate, acrylonitrile, and fumaronitrile) and methyl propiolate to produce 2-substituted 1-methylbenzimidazoles. The transformation involves the initial formation of a 1,3-dipolar cycloadduct followed by the N? N bond cleavage. The primary adducts can be isolated from the reaction with methyl acrylate and acrylonitrile.     

1,3-Dipolar cycloaddition reactions of ylides formed from pyridines and dichlorocarbene

Pyridinium dichloromethylides, generated from substituted pyridines and dichlorocarbene, react endo-stereoselectively with dimethyl maleate to give substituted 3,3-dichloro-1,2,3,8a-tetrahydroindolizine-1,2-dicarboxylic acid dimethyl esters; the latter compounds are readily dehydrochlorinated and dehydrogenated to give the corresponding indolizine derivatives. Reaction of 3-substituted pyridines with dichlorocarbene and dimethyl maleate leads predominantly to the formation of 8-substituted indolizines. Cycloaddition of 4-picolinium dichloromethylide to unsymmetrical dipolarophiles occurs regioselectively. The observed selectivity in these reactions is consistent with predictions made on the basis of PMO theory.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 355–362, March, 1990.     

1,3-Dipolar cycloaddition reactions of benzo[h]naphthyridinium N-phenacylides

The 1,3-dipolar cycloaddition reactions of 1,5- and 1,6-benzo[h]naphthyridinium N-phenacylides, formedin situ from the appropriate quaternary bromides in basic medium, with acrylonitrile, ethyl acrylate and dimethyl acetylenedicarboxylate were investigated.

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1,3-Dipolare Cycloadditionsreaktionen von Benzo[h]naphthyridinium-N-phenacyliden

Zusammenfassung Es wurden die 1,3-dipolaren Cycloadditionsreaktionen von 1,5- und 1,6-Benzo[h]naphthyridinium-N-phenacyliden untersucht, diein situ aus den entsprechenden quaternären Bromiden in Gegenwart von Alkali dargestellt wurden. Als Dipolarophile wurden Acrylnitril, Ethylacrylat und Acetylendicarbonsäuredimethylester eingesetzt.

     

1,3-Dipolar cycloaddition reactions of 1-methyl- and 1,3-dimethylindol-2-yl nitrile oxides

Reactions of the in situ prepared 1-methylindol-2-yl nitrile oxide ( 2a ) with dipolarophiles lead to isoxazolines 5 and isoxazoles 8 and to their chloro-derivatives 6 and 9 in good yields. Analogous reactions of the 1,3-dimethylindol-2-yl nitrile oxide ( 2b ) give the isoxazolines 10 and the isoxazoles 12 as main products as well as their oxidation products 11 and 13 in low yields. The mechanism of the reactions and the spectral elucidation of the cycloadducts are discussed.     

1,3-Dipolar cycloaddition reactions of 1,3,4-oxadiazin-6-ones with nitrile oxides

2,5-Diaryl-1,3,4-oxadiazin-6-ones 1 gave with nitrile oxides 2 1,2,4-oxadiazole derivatives 4 . When mesitonitrile oxide 2a was used, bis-adducts 3 were also formed. The cycloadditions showed a remarkable site selectivity towards one carbon nitrogen double bond. The structure of both adducts was fully characterized by X-ray analysis.     

1,3-Dipolar cycloaddition reactions. Regioselective synthesis of heterocycles and theoretical studies

We report a 1,3-dipolar cycloaddition reaction between a oxazolium 5-oxide derivative with chloroacrylonitrile or ethyl propiolate as dipolarophiles, in order to obtain substituted pyrrolizidines. Experimentally we found that the reaction is regiospecific with chloroacrylonitrile and regioselective with ethyl propiolate. The secondary attractive orbital interactions from the Frontier Molecular Orbital Theory, the differences in stability of the possible biradical intermediaries postulated for the reaction and some hindrance effects, explain the regioselectivity observed experimentally.     

1,3-Dipolar cycloaddition of diazomethane to β-arylacrylyloxiranes

Diastereomeric 4-aryl-3-epoxypropionyl-2-pyrazolines were obtained by cycloaddition of diazomethane to -arylacrylyloxiranes. It was established that, in addition to the formation of pyrazolines, competitive addition of diazomethane to the carbonyl group to give oxadiazolines occurs when electron-donor substituents are present in the aromatic ring in the 2 or 4 position. Some chemical properties of 4-aryl-3-epoxypropionyl-2-pyrazolines were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 679–683, May, 1982.     

1,3-Dipolar cycloaddition reactions of nitrile oxides and nitrile imines with 2-methoxyvinyl phenyl ketone

Nitrile oxides react regioselectively with 2-methoxyvinyl phenyl ketone 1 to give 4-benzoylisoxazoles 4 via elimination of methanol from the primary cycloadducts 3 . After heating with an excess of nitrile oxide bis-cycloadducts 5 were also formed. Reactions of nitrile imines with 1 are less regioselective yielding both 4-benzoylpyrazoles 9 and 5-benzoytpyrazoles 10 , whereas no bis-cycloadducts were isolated.     

1,3-Dipolar cycloaddition of 2-benzylideneindan-1,3-dione α-oxide to olefins

A carbonyl ylid, which reacts with maleic anhydride, N-phenylmaleinimide, and -nitrostyrene to form adducts resulting from 1,3-dipolar cycloaddition, is formed reversibly when 2-benzylideneindan-1,3-dione -oxide is heated (80C). The reaction proceeds regio- and stereospecifically.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1463–1466, November, 1987.     

1,3-Dipolar cycloaddition of organic azides to alkynes by a dicopper-substituted silicotungstate

The dicopper-substituted gamma-Keggin silicotungstate TBA 4[gamma-H2SiW10O36Cu2(mu-1,1-N3)2] (I, TBA = tetra- n-butylammonium) could act as an efficient precatalyst for the regioselective 1,3-dipolar cycloaddition of organic azides to alkynes. Various combinations of substrates (four azides and eight alkynes) were efficiently converted to the corresponding 1,2,3-triazole derivatives in excellent yields without any additives. The present system was applicable to a larger-scale cycloaddition of benzyl azide to phenylacetylene under solvent-free conditions (100 mmol scale) in which 21.5 g of the analytically pure corresponding triazole could be isolated. In this case, the turnover frequency and the turnover number reached up to 14,800 h(-1) and 91,500, respectively, and these values were the highest among those reported for the copper-mediated systems so far. In addition, I could be applied to the one-pot synthesis of 1-benzyl-4-phenyl-1H-1,2,3-triazole from benzyl chloride, sodium azide, and phenylacetylene. The catalyst effect, kinetic, mechanistic, and computational studies show that the reduced dicopper core plays an important role in the present 1,3-dipolar cycloaddition.     

1,3-Dipolar cycloaddition reactions of 4-arylidene-2-phenyl-1,4-dihydroimidazol-5-ones with nitrile oxides

Stable nitrile oxides add regioselectively to the carbon-carbon double bond of 4-arylidene-2-phenyl-1,4-dihydroimidazol-5-ones to afford spiro isoxazolines 3 . Compounds 3 are further hydrolysed to isoxazole derivatives.     

1,3-Dipolar cycloaddition in the synthesis of pyrazolyl-substituted nitronyl nitroxides

A new approach to the synthesis of polyfunctional pyrazolyl-substituted nitronyl nitroxides was developed based on the presynthesized pyrazole derivatives prepared by 1,3-dipolar cycloaddition. The structures of the resulting mono-and biradicals were confirmed by X-ray diffraction. Dedicated to Academician A. L. Buchachenko on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2105–2116, September, 2005.