Stereoselective cycloadditions of (1Z,4R∗,5R∗)-1-arylmethylidene-4-benzoylamino-5-phenylpyrazolidin-3-on-1-azomethine imines to maleimides

Pezdirc, Lidija; Cerkovnik, Janez; Pirc, Samo; Stanovnik, B.; Svete, Jurij

doi:10.1016/j.tet.2006.11.012

Cited by 29 publications

(19 citation statements)

References 34 publications

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“…[40][41][42]44,47,[72][73][74][75][76][77] The 1 H-NMR spectroscopic data of the pyrazolidinones 4 and 25-33 and azomethine imines 24 revealed some interesting structural features of these compounds. In solution, these pyrazolidinone derivatives can equilibrate between two envelope conformers A and C via the planar conformer B (Scheme 21).…”

Section: Structural Features Of 3-pyrazolidinonesmentioning

confidence: 99%

“…In the last decade, our studies on [3+2] cycloadditions of (1Z,4R*,5R*)-1-arylmethylidene-4-benzoylamino-3-oxo-5-phenyltetrahydropyrazol-1-ium-2-ides 41 to various dipolarophiles has revealed the general reactivity and selectivity of these cycloadditions, 9 as well as their applicability in high-throughput synthesis. 72,73 Stereocontrol can be illustrated by cycloadditions of 41 to methyl methacrylate (Scheme 10). The stereoselectivity of the cycloadditions of dipoles 41a-e to methyl methacrylate was in agreement with the stereochemistry observed by related cycloadditions 9,72,73,75 and could be explained in the following way: an ortho-unsubstituted 1′-aryl group in dipoles 41a-c can rotate around the C(1′)-Ar bond, thus shielding equally both faces of the dipole 41′a-c. Consequently, the phenyl ring at position 5 is the stereodirecting group, which hinders the (1′Si)-face of the (Z)-dipole 41′.…”

Section: Pyrazolo[12-a]pyrazolesmentioning

confidence: 99%

“…72,73 Stereocontrol can be illustrated by cycloadditions of 41 to methyl methacrylate (Scheme 10). The stereoselectivity of the cycloadditions of dipoles 41a-e to methyl methacrylate was in agreement with the stereochemistry observed by related cycloadditions 9,72,73,75 and could be explained in the following way: an ortho-unsubstituted 1′-aryl group in dipoles 41a-c can rotate around the C(1′)-Ar bond, thus shielding equally both faces of the dipole 41′a-c. Consequently, the phenyl ring at position 5 is the stereodirecting group, which hinders the (1′Si)-face of the (Z)-dipole 41′. Formation of the major (1R*,3R*,5R*,6R*)-isomers 42a-c is explainable by preferential endo-attack of methyl methacrylate from the less hindered (1′Re)-face of dipole 41′a-c via the proposed transition state TS1.…”

Section: Pyrazolo[12-a]pyrazolesmentioning

confidence: 99%

“…74 Selectivity of these cycloadditions was somewhat lower than expected on the basis of results with analogous reactions. 9,38,[72][73][74][75] Nevertheless, isolation of multiple isomers may also be advantageous, providing more stereochemical diversity of the 6-amino-7-oxotetrahydropyrazolo[1,2-a]-pyrazole-1(or 2)-carboxylic acid scaffold (c.f. .…”

Section: Page 189mentioning

confidence: 99%

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Recent advances in the synthesis of polysubstituted 3-pyrazolidinones

Grošelj¹,

Svete²

2015

Arkivoc

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An account of recent developments in the field of 3-pyrazolidinone chemistry is given with special focus on the synthesis and transformations of 5-substituted 4-benzyloxycarbonylamino-3-pyrazolidinones, pyrazolo[1,2-a]pyrazole-based peptide analogues, and tetrahydropyrazolo-[1,5-c]pyrimidine-2,7-diones. In terms of practical application, polyfunctionalized 3-pyrazolidinones as 'aza-deoxa' analogues of cycloserine, peptide mimetics based on 3-amino-2-oxo-1,5-diazabicyclo[3.3.0]octane-7-carboxylic acid, and 1,6-disubstituted tetrahydropyrazolo[1,5-c]-pyrimidine-2,7-diones as the first representatives of a novel saturated heterocyclic system were prepared by these newly developed synthetic methods.

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Section: Structural Features Of 3-pyrazolidinonesmentioning

confidence: 99%

Section: Pyrazolo[12-a]pyrazolesmentioning

confidence: 99%

Section: Pyrazolo[12-a]pyrazolesmentioning

confidence: 99%

Section: Page 189mentioning

confidence: 99%

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Recent advances in the synthesis of polysubstituted 3-pyrazolidinones

Grošelj¹,

Svete²

2015

Arkivoc

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“…Under analogous conditions (toluene, 110°C, 6 h), the conversion of (Z)-1-(2,6-dichlorobenzylidene)-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ide in the reaction with N-(4-methoxyphenyl)maleimide was insignificant since in this case both exo and endo approaches of the dipolarophile were hindered for steric reasons. On the other hand, there are published data according to which the cycloaddition of structurally related pyrazolidinone-based azomethine imines can be accomplished by heating in boiling anisole [9]. The relative configuration of adducts 3a and 4a was determined by analyzing spin-spin coupling constants for the 9-H and 9a-H protons.…”

mentioning

confidence: 99%

Steric hindrances to the cycloaddition of (Z)-1-arylmethylidene-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ides to N-arylmaleimides

et al. 2015

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Sterically hindered cycloaddition of (Z)-1-arylmethylidene-5,5-dimethyl-3-oxopyrazolidin-1-ium-2ides to 4-mono-and 2,6-disubstituted N-arylmaleimides requires prolonged heating (40-60 h) at ~150-155°C and yields mixtures of diastereoisomeric cycloadducts. The observed diastereoselectivity is determined by both electronic and steric interactions, depending on the nature and position of substituents in the azomethine imine and maleimide. The reactions of (Z)-1-(2,6-dichlorobenzylidene)-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ide with 4-substituted N-arylmaleimides give mainly the corresponding cis adducts as a result of preferential exo attack by the dipolarophile, whereas trans adducts predominate in the cycloaddition of (Z)-1-(4-X-benzylidene)-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ide and (Z)-1-(2,6-dichlorobenzylidene)-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ide to 2,6-disubstituted N-arylmaleimides.By carrying out the reaction under more severe conditions, in boiling anisole at ~150-155°C (40-60 h), we succeeded in attaining the complete conversion of azomethine imines 1a-1c and obtain the corresponding adducts with N-arylmaleimides 2a-2i. When azomethine imine 1a was heated for ~40 h with parasubstituted N-arylmaleimides 2a-2f, the products were diastereoisomer mixtures 3/4 (yield 52-74%), the cis

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[3 + 2] Cycloadditions of Azomethine Imines

Grošelj

Svete

2020

Organic Reactions

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In spite of their late discovery in the middle of 20 th century, the importance of azomethine imines and their [3+2] cycloaddition reactions has grown constantly throughout the decades. Today, [3+2] cycloadditions of azomethine imines have become indispensable in the preparation of pyrazole derivatives with all degrees of saturation. The structural diversity of azomethine imines is wide and comprises acyclic, C , N ‐cyclic, N , N ‐cyclic, and C , N , N ‐cyclic 1,3‐dipoles. Although electron‐deficient dipolarophiles are preferred, electron‐rich dipolarophiles, such as enol ethers and enamines, are also commonly used in these reactions. Compared to cyclocondensation methods and [3+2] cycloadditions with diazoalkanes and nitrile imines, [3+2] cycloadditions with azomethine imines provide access to a greater diversity of pyrazole derivatives with all degrees of saturation. As with other 1,3‐dipolar cycloadditions, a concerted and nearly synchronous mechanism has been proposed for most [3+2] cycloadditions of azomethine imines, although a stepwise mechanism may be viable in some cases. Several examples of asymmetric [3+2] cycloadditions of azomethine imines that afford non‐racemic cycloadducts with high enantioselectivity have been reported. These asymmetric cycloadditions are performed with various types of transition metal catalysts and organocatalysts, and indicate their potential for the asymmetric synthesis of saturated pyrazole derivatives. Finally, many examples of copper‐catalyzed and thermal, strain‐promoted [3+2] cycloadditions of azomethine imines (in particular sydnones) clearly indicate wide applicability of these reactions in bioconjugation, fluorescent labelling, materials functionalization, and other applications outside the realm of pure organic synthesis.

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Stereoselective cycloadditions of (1Z,4R∗,5R∗)-1-arylmethylidene-4-benzoylamino-5-phenylpyrazolidin-3-on-1-azomethine imines to maleimides

Cited by 29 publications

References 34 publications

Recent advances in the synthesis of polysubstituted 3-pyrazolidinones

Recent advances in the synthesis of polysubstituted 3-pyrazolidinones

Steric hindrances to the cycloaddition of (Z)-1-arylmethylidene-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ides to N-arylmaleimides

[3 + 2] Cycloadditions of Azomethine Imines

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