Syntheses by Means of 1‐Alkylidene‐ and 1‐(Arylalkylidene)‐3‐pyrazolidone <i>N,N</i>‐Betaines, a New Type of Stable Azomethine Imine

Dorn, Helmut; Otto, Albrecht

doi:10.1002/anie.196802141

Cited by 83 publications

(37 citation statements)

References 8 publications

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“…7 The first example of a catalytic asymmetric intramolecular [3+2] cycloaddition of hydrazones with olefins was performed in the presence of a chiral zirconium catalyst. 24 Different 4-nitrobenzoylhydrazones 17 gave trans-pyrazolidines 18 with high diastereo-and enantioselectivity in the presence of Zr(Oi-Pr) 4 (10 mol%) and the Binol derivative 19 at room temperature in dichloromethane (Scheme 9). Scheme 9 Asymmetric intramolecular 1,3-DC of hydrazones 17 using a chiral Zr-Binol catalyst.…”

Section: From Monosubstituted Hydrazinesmentioning

confidence: 99%

“…The same chiral catalyst formed by Zr(Oi-Pr) 4 and Binol 19 has been used in the intermolecular [3+2] cycloaddition of benzoylhydrazones 20 and electron-rich alkenes like the ketene dimethyl dithioacetal 21. The corresponding 3,5-disubstituted pyrazolidines 22 were obtained in good yields and enantioselectivities (Scheme 10).…”

Section: From Monosubstituted Hydrazinesmentioning

confidence: 99%

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1,3-Dipolar cycloadditions of azomethine imines

2015

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Azomethine imines are considered 1,3-dipoles of the aza-allyl type which are transient intermediates and should be generated in situ but can also be stable and isolable compounds. They react with electron-rich and electron-poor olefins as well as with acetylenic compounds and allenoates mainly by a [3 + 2] cycloaddition but they can also take part in [3 + 3], [4 + 3], [3 + 2 + 2] and [5 + 3] with different dipolarophiles. These 1,3-dipolar cycloadditions (1,3-DC) can be performed not only under thermal or microwave conditions but also using metallo- and organocatalytic systems. In recent years enantiocatalyzed 1,3-dipolar cycloadditions have been extensively considered and applied to the synthesis of a great variety of dinitrogenated heterocycles with biological activity. Acyclic azomethine imines derived from mono and disubstituted hydrazones could be generated by prototropy under heating or by using Lewis or Brønsted acids to give, after [3 + 2] cycloadditions, pyrazolidines and pyrazolines. Cyclic azomethine imines, incorporating a C-N bond in a ring, such as isoquinolinium imides are the most widely used dipoles in normal and inverse-electron demand 1,3-DC allowing the synthesis of tetrahydro-, dihydro- and unsaturated pyrazolo[1,5-a]isoquinolines in racemic and enantioenriched forms with interesting biological activity. Pyridinium and quinolinium imides give the corresponding pyrazolopyridines and indazolo[3,2-a]isoquinolines, respectively. In the case of cyclic azomethine imines with an N-N bond incorporated into a ring, N-alkylidene-3-oxo-pyrazolidinium ylides are the most popular stable and isolated dipoles able to form dinitrogen-fused saturated and unsaturated pyrazolopyrazolones as racemic or enantiomerically enriched compounds present in many pharmaceuticals, agrochemicals and other useful chemicals.

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Section: From Monosubstituted Hydrazinesmentioning

confidence: 99%

Section: From Monosubstituted Hydrazinesmentioning

confidence: 99%

1,3-Dipolar cycloadditions of azomethine imines

2015

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“…6 The first report of an asymmetric reaction between an azomethine imine and an acrylamide was communicated in 2007 by Suga, who described the highly enantioselective and diastereoselective Lewis acid catalysed 1,3-dipolar cycloaddition between azomethine imines (derived from the reaction of pyrazolidin-3-one with an aldehyde) 213 …”

Section: Figure 39mentioning

confidence: 99%

Asymmetric 1,3-dipolar cycloadditions of acrylamides

2010

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This critical review, which is relevant to researchers in synthetic organic chemistry, focuses on asymmetric 1,3-dipolar cycloadditions with acrylamides. The use of chiral acrylamides as dipolarophiles leads to high levels of stereocontrol, due to conformational constraint in the acrylamides. Employment of chiral tertiary acrylamides containing nitrogen heterocycles is particularly effective in controlling the stereoselectivity. Following a general overview of 1,3-dipolar cycloadditions, the main body of the review focuses on asymmetric 1,3-dipolar cycloadditions of acrylamides with nitrile oxides, nitrones, diazoalkanes and azomethine ylides, with particular emphasis on the rationale for the observed stereocontrol (215 references)

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“…Structures 2 are obtained by the condensation of pyrazolidin 3 one 3 with aromatic aldehydes. 8, 9 For the in situ generation of unstable under usual conditions azomethine imines 1 unsubsti tuted in the pyrazolidine ring, thermolysis of 6 aryl 1,5 diazabicyclo[3.1.0]hexanes 4 in the presence of highly re active dipolarophiles, for example, N arylmaleimides 5, is used at 130-140 °C (reflux in xylene). [10][11][12][13][14] In the work 15 of the same authors, it was shown that azomethine imines 1 can also be generated in situ from compounds 4 already at 20 °C using catalysis with Lewis acids (BF 3 •Et 2 O, In(OTf) 3 ) in acetonitrile.…”

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confidence: 99%

Reaction of 1-arylmethylidenepyrazolidin-1-azomethine imines with aryl ketenes

et al. 2010

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A reaction of aryl ketenes with 1 arylmethylidenepyrazolidin 1 azomethine imines, gen erated by the diaziridine ring opening in 6 aryl 1,5 diazabicyclo[3.1.0]hexanes catalyzed with Et 2 O•BF 3 , leads to 1,2 bis(phenylacetyl)pyrazolidine, 2 arylacetyl 1 arylidenepyrazolidin 1 ium chlorides, or a representative of 1,5 diazabicyclo[3.3.0]octan 2 ones, viz., 4 (4 eth oxyphenyl) 3,3 diphenyl 1,5 diazabicyclo[3.3.0]octan 2 one, depending on the reaction con ditions and the structure of the starting compounds. A mechanism suggested earlier for the transformation of 1,5 diazabicyclo[3.1.0]hexanes in the reaction with ketenes was confirmed.

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Syntheses by Means of 1‐Alkylidene‐ and 1‐(Arylalkylidene)‐3‐pyrazolidone N,N‐Betaines, a New Type of Stable Azomethine Imine

Cited by 83 publications

References 8 publications

1,3-Dipolar cycloadditions of azomethine imines

1,3-Dipolar cycloadditions of azomethine imines

Asymmetric 1,3-dipolar cycloadditions of acrylamides

Reaction of 1-arylmethylidenepyrazolidin-1-azomethine imines with aryl ketenes

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