A facile synthesis of glyco 3-nitrochromane hybrid pyrrolidinyl spiro heterocycles via [3+2] cycloaddition of azomethine ylides

Synthesis of pyrrolidin-2-ylidenes and pyrrol-2-ylidenes via 1,3-dipolar cycloaddition of H-bond-assisted azomethine ylides to nitrostyrenes

Hydrogen-bond-assisted azomethine ylides, generated from 2-(benzylamino)-2-(1,3-dioxo-1,3-dihydro-2H-inden-2-ylidene)acetonitriles, undergo a formal Huisgen 1,3-dipolar cycloaddition with β-bromo-β-nitrostyrenes to afford a diastereoselective synthesis of highly substituted pyrrolidin-2-ylidene derivatives. When β-nitrostyrenes were used as the alkene component, 2-(4,5-diaryl-1,5-dihydro-2H-pyrrol-2-ylidene)-1H-indene-1,3(2H)-diones were obtained. Efficient conversion of pyrrolidene-2-ylidenes to the corresponding pyrrol-2-ylidenes takes place in refluxing 1-propanol in the presence of excess Et₃N. Also, the structure of the pyrrolidene-2-ylidene derivative was determined by X-ray crystallography.

Azomethine Ylides-Versatile Synthons for Pyrrolidinyl-Heterocyclic Compounds

Azomethine ylides are nitrogen-based three-atom components commonly used in [3+2]-cycloaddition reactions with various unsaturated 2π-electron components. These reactions are highly regio- and stereoselective and have attracted the attention of organic chemists with respect to the construction of diverse heterocycles potentially bearing four new contiguous stereogenic centers. This review article complies the most important [3+2]-cycloaddition reactions of azomethine ylides with various olefinic, unsaturated 2π-electron components (acyclic, alicyclic, heterocyclic, and exocyclic ones) reported over the past two decades.

Recent advancement in the synthesis of diverse spiro-indeno[1,2-b]quinoxalines: a review

The nitrogen-containing indeno[1,2-b]quinoxaline ring is a privileged structurally fused active system and has notable applications in various fields of chemistry.

Highly regio- and diastereoselective [3 + 2]-cycloadditions involving indolediones and α,β-disubstituted nitroethylenes

A highly diastereoselective [3 + 2]-cycloaddition strategy involving multiple oxindoles and several α,β-disubstituted nitroethylenes is developed to access tetra-substituted α-spiropyrrolidine frameworks. A variety of α-amino acids were employed for the first time in order to generate azomethine ylides under thermal conditions, affording regioisomers 13 and 14 merely by changing the α-substituents (R = H and substituted carbons) of the α-amino acids. The reaction tolerates various sterically demanding, electron-rich and electron-deficient aryl and nitrogen substituents on glycines, oxindoles and nitroethylenes. The operational simplicity, such as the use of a metal-free and non-inert environment, the utilization of non-halogenated solvents and the ease of isolation, adhering to the principles of green chemistry, makes this process attractive for scale-up opportunities. The reaction delivers good yields (80-94%) and diastereoselectivities (up to 98 : 2) in favor of (cis,cis)-spirooxindoles, with opposite regioselectivity compared to β-nitrostyrenes under identical conditions. Two spiropyrrolidine cycloadducts with unprotected amides exhibited significant activity against Gram-positive MRSA.

A regio- and stereocontrolled approach to the synthesis of 4-CF3-substituted spiro[chromeno[3,4-c]pyrrolidine-oxindoles]viareversible [3+2] cycloaddition of azomethine ylides generated from isatins and sarcosine to 3-nitro-2-(trifluoromethyl)-2H-chromenes

The first example of regio- and stereocontrolled synthesis of 4-CF₃-spiro[chromeno[3,4-c]pyrrolidine-oxindoles] with anticancer activity.

Synthesis of pyrrolizidines and indolizidines by multicomponent 1,3-dipolar cycloaddition of azomethine ylides

Different multicomponent 1,3-dipolar cycloadditions (1,3-DC) of cyclic α-amino acid derivatives with aldehydes and dipolarophiles have been described as efficient and simple methodologies for the synthesis of the pyrrolidine unit of pyrrolizidines and indolizidines. When free cyclic α-amino acids are used, a thermal promoted decarboxylative process generates in situ the corresponding non-stabilized azomethine ylides, which afforded the corresponding pyrrolizidines and indolizidines with a hydrogen in the bicyclic units. This methodology has been employed to the synthesis of complex systems including spiro derivatives when ketones are used as carbonyl component. In addition, working with cyclic α-amino acid derived esters, the three-component 1,3-DC takes place under milder reaction conditions giving the corresponding pyrrolizidines and indolizidines with an alkoxycarbonyl group in the bridge adjacent carbon to the nitrogen. This methodology can be carried out by a double consecutive or stepwise 1,3-DC to provide pyrrolizidines via the precursor prolinates. The conformation of the azomethine ylide controls the endo/exo diastereoselectivity of the 1,3-DC.

Diastereoselective synthesis of benzo[d]chromeno[3′,4′:3,4]pyrrolo[2,1-b]thiazoles via cycloaddition reaction of benzothiazolium salts with 3-nitrochromenes

Diastereospecific synthesis of benzo[d]chromeno[3′,4′:3,4]pyrrolo[2,1-b]thiazoles via cycloaddition reaction of benzothiazolium salts with 3-nitrochromenes.

Synthesis and Antibacterial Activity of New Spiro[thiadiazoline-(pyrazolo[3,4-d]pyrimidine)] Derivatives

New heterocyclic compounds spiroderivatives of allopurinol of biological interest were prepared from allopurinol via thionation and 1,3-dipolar cycloaddition and were produced in high to excellent yields. These compounds were characterized on the basis of spectral and spectroscopic data (1H NMR,13C, IR, and MS). The antibacterial activity of the synthesized products was studied using bacterial strains:Staphylococcus aureus,Enterococcus faecalis,Escherichia coli, andPseudomonas aeruginosa. Compounds having an ethyl group showed the best activity with MIC value of 31.25 µg/mL againstStaphylococcus aureusandStreptococcus fasciens.