An expedient diastereoselective synthesis of pyrrolidinyl spirooxindoles fused to sugar lactone via [3+2] cycloaddition of azomethine ylides

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.

An experimental and mechanism study on the regioselective click reaction toward the synthesis of thiazolidinone-triazole

An efficient procedure for the synthesis of novel thiazolidinone triazoles through 32 cycloaddition reactions in the presence of copper(I) species was described, and the molecular mechanism of this 32CA was investigated computationally. Different possible pathways for CA process have been studied to achieve this goal, including one-step pathways for both regioisomers 1,4- and 1,5-triazoles (uncatalyzed, mono-copper, di-copper) and also mono- and di-copper stepwise pathways for 1,4-disubstituted triazole. It was exhibited that the most convenient route in terms of energy barriers includes two copper ions. Based on the calculation, the reaction follows a di-copper stepwise mechanism involving the formation of a six-membered ring and then undergoes a ring contraction to a five-membered ring. The regiochemistry of the reaction was investigated based on local and global reactivity indices of reactants, the transition state stabilities calculation. The electron reorganization along the uncatalyzed one-step mechanism has been investigated by the ELF topological analysis of the bonding changes along with the CA reaction.

Highly stereoselective dearomative [3 + 2] cycloadditon of cyclic pyridinium ylides to access spiro-indolizidine scaffolds

A novel type of pyridinium salt bearing a EWG on the pyridine was developed as an efficient pyridinium ylide precursor in the [3 + 2] cycloaddition with nitroolefins to construct various spiro-indolizidine scaffolds via a dearomative pathway.

Stereoselective synthesis of dispiro heterocycles by [3 + 2] cycloaddition of azomethine ylides with a thiazolo[3,2-a]indole derivative

A green one pot three component [3 + 2] cycloaddition of a thiazolo[3,2-a]indole derivative (generated by the reaction of thieno[2,3-b]indole-2,3-dione and dimethyl acetylenedicarboxylate) with isatin derived azomethine ylides is reported here. An eco-friendly acetyl choline iodide-ethylene glycol (ACI/EG)-mediated deep eutectic solvent system was adopted for the reaction. Spiropyrrolidine oxindoles incorporating multiple stereocenters were obtained in a highly diastereoselective manner in excellent yields.

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.

Ultrasound-assisted one-pot multicomponent 1,3-dipolar cycloaddition strategy: combinatorial synthesis of spiro-acenaphthylene-S,S-acetal and 2H-pyranone derivatives

The stereo/regio/chemoselective syntheses of a library of novel spiro[acenaphthylene-1,3′-pyrrolizin]-2-one and spiro[acenaphthylene-1,5′-pyrrolo[1,2-c]thiazol]-2-one have been achieved through 1,3-dipolar cycloaddition.

Construction of Spirooxindole Skeleton Through Intramolecular Dieckmann Cyclization

A highly efficient and direct approach was developed to construct the structurally diverse spirooxindole skeleton, which is an important basic motif in natural products. Both the 3,3'-pyrrolidonyl spirooxindoles and spiroindolin-2-one δ-lactones were smoothly obtained by the intramolecular Dieckmann cyclization of oxindoles in excellent yield under mild conditions.

Molecular Hybridization-Guided One-Pot Multicomponent Synthesis of Turmerone Motif-Fused 3,3'-Pyrrolidinyl-dispirooxindoles via a 1,3-Dipolar Cycloaddition Reaction

Described herein is the development of a facile and efficient methodology for the synthesis of novel turmerone motif-fused 3,3′-pyrrolidinyl-dispirooxindoles 3–5 via a multicomponent 1,3-dipolar cycloaddition of dienones 2 with azomethine ylides (thermally generated in situfrom isatins and proline or thioproline or sarcosine). Products bearing four or three consecutive stereocenters consist of two oxindole moieties and a pyrrolidinyl core, including vicinal spiroquaternary stereocenters fused in one ring structure were smoothly obtained in high yields (up to 93% yield) with good diastereoselectivity (up to >20:1). Another valuable application of this method was for the design of new hybrid architectures for biological screening through the adequate fusion of these sub-units of turmerone and 3,3′-pyrrolidinyl-dispirooxindole, generating drug-like molecules.

Multicomponent synthesis of spiropyrrolidine analogues derived from vinylindole/indazole by a 1,3-dipolar cycloaddition reaction

A new series of spiropyrrolidine compounds containing indole/indazole moieties as side chains have been accomplished via a one-pot multicomponent synthesis. The method uses the 1,3-dipolar cycloaddition reaction between N-alkylvinylindole/indazole and azomethine ylides, prepared in situ from cyclic/acyclic amino acids. The 1,3-dipolar cycloaddition proceeds efficiently under thermal conditions to afford the regio- and stereospecific cyclic adducts.

Potent Synergy between Spirocyclic Pyrrolidinoindolinones and Fluconazole against Candida albicans

A spiroindolinone, (1S,3R,3aR,6aS)-1-benzyl-6'-chloro-5-(4-fluorophenyl)-7'-methylspiro[1,2,3a,6a-tetrahydropyrrolo[3,4-c]pyrrole-3,3'-1H-indole]-2',4,6-trione, was previously reported to enhance the antifungal effect of fluconazole against Candida albicans. A diastereomer of this compound was synthesized, along with various analogues. Many of the compounds were shown to enhance the antifungal effect of fluconazole against C. albicans, some with exquisite potency. One spirocyclic piperazine derivative, which we have named synazo-1, was found to enhance the effect of fluconazole with an EC50 value of 300 pM against a susceptible strain of C. albicans and going as low as 2 nM against some resistant strains. Synazo-1 exhibits true synergy with fluconazole, with an FIC index below 0.5 in the strains tested. Synazo-1 exhibited low toxicity in mammalian cells relative to the concentrations required for antifungal synergy.

Molecular diversity of spirooxindoles. Synthesis and biological activity

Spirooxindoles are important synthetic targets possessing extended biological activity and drug discovery applications. This review focuses on the various strategies for the enantioselective synthesis of spirocyclic oxindoles relying on reports over the past decade and from earlier work. The spirooxindoles in this review are separated into three structural classes, and then further categorized into the method type from which the spirocycle is generated.

Recent advances in multicomponent reactions involving carbohydrates

Being an attractive class of naturally occurring molecules with fascinating properties, sugars and their derivatives have wide applications in different fields especially in drug discovery.

One-pot chemo/regio/stereoselective generation of a library of functionalized spiro-oxindoles/pyrrolizines/pyrrolidines from α-aroylidineketene dithioacetals

An efficient chemo/regio/stereoselective synthesis of novel and functionalized spiro-oxindole/pyrrolizine/pyrrolidine scaffolds has been achieved.

Combinatorial synthesis of functionalized spirooxindole-pyrrolidine/pyrrolizidine/pyrrolothiazole derivatives via three-component 1,3-dipolar cycloaddition reactions

A series of diverse polycyclic heterocycles containing spirooxindole, pyridine/thiophene, and pyrrolidine/pyrrolizidine/pyrrolothiazole rings have been synthesized through the 1,3-dipolar cycloaddition of azomethine ylides generated in situ by the condensation of dicarbonyl compounds (isatin or acenaphthenequinone) and secondary amino acids with dipolarophiles. The method is simple and provides diverse and biologically interesting products with excellent yields.

Highly Efficient and Stereoselective Construction of Bispirooxindole Derivatives via a Three-Component 1,3-Dipolar Cycloaddition Reaction

A highly regio- and stereoselective synthesis of bispirooxindoles by 1,3-dipolar cycloaddition of in situ generated azomethine ylides from isatin and proline to different electron-deficient alkenes has been developed. The synthesis affords the desired bispiro scaffold compounds in excellent yields with high regioselectivity under mild conditions. The stereochemistry was determined by single-crystal X-ray analysis.

The regioselective synthesis of spirooxindolo pyrrolidines and pyrrolizidines via three-component reactions of acrylamides and aroylacrylic acids with isatins and α-amino acids

The regioselective three-component condensation of azomethine ylides derived from isatins and α-amino acids with acrylamides or aroylacrylic acids as dipolarophiles has been realized through a one-pot 1,3-dipolar cycloaddition protocol. Decarboxylation of 2'-aroyl-2-oxo-1,1',2,2',5',6',7',7a'-octahydrospiro[indole-3,3'-pyrrolizine]-1'-carboxylic acids is accompanied by cyclative rearrangement with formation of dihydropyrrolizinyl indolones.

Efficient Synthesis of Dispiropyrrolidines Linked to Sugars

An expedient method for the synthesis of glyco-dispiropyrrolidines is reported through 1,3-dipolar cycloaddition reaction (1,3 DC reaction). The novel glycosyl dipolarophiles derived from D-glucose underwent neat [3+2] cycloaddition reaction with the azomethine ylides generated from 1,2-diketones and sarcosine to give the corresponding glycosidic heterocycles in good yields.

Regioselective Synthesis of Dispiro Pyrrolizidines as Potent Antimicrobial Agents for Human Pathogens

Synthesis of a series of novel dispiro pyrrolizidines has been accomplished by 1,3-dipolar cycloaddition reaction of azomethine ylide generated from secondary amino acids and diketones with bischalcones. These compounds were evaluated for their antibacterial activity. Most of the synthetic compounds exhibited good antibacterial activity against microorganisms.