Molecular diversity of cycloaddition reactions of the functionalized pyridinium salts with 3-phenacylideneoxindoles

Solvent-Controlled Divergent Cyclization of 3-Ylideneoxindoles with Ethyl 2-Diazoacetate: Access to Spirocyclopropyl and Spiropyrazolines Oxindoles

Herein a catalyst-free solvent-controlled method for the divergent synthesis of spirocyclopropyl and spiropyrazoline oxindoles from 3-ylideneoxindoles and ethyl diazoacetate was developed. With ClCH2CH2Cl as the solvent, spirocyclopropyl oxindoles were obtained in moderate to excellent yields, whereas the use of MeOH as solvent afforded spiropyrazoline oxindoles in moderate to good yields. The readily available substrates, simple operation and various product transformations further highlighted the utility of this method.

DNA-Conjugated Cyclopropane Derivatives Constructed from Sulfonium Ylides with α,β-Unsaturated Ketones

Here, we report a DNA-compatible reaction for the generation of cyclopropane derivatives using thiolides with α,β-unsaturated ketones in the absence of transition metal and N2 protection, which is convenient for DNA encoded library (DEL) construction. This approach allows the rapid and efficient production of a series of DEL libraries of potentially biologically active cyclopropanes and spirocyclopropyl oxindole derivatives.

Highly Diastereoselective Multicomponent Synthesis of Spirocyclopropyl Oxindoles Enabled by Rare-Earth Metal Salts

The synthesis of polysubstituted spirocyclopropyl oxindoles using a series of rare-earth metal (REM) salts is reported. REMs, in particular Sc(OTf)₃, allowed access to the target compounds by a multicomponent reaction with high diastereoselectivity (≤94:6:0:0). Density functional theory calculations on the model reaction are consistent with the observed selectivity and revealed that the special coordinating capabilities and the oxophilicity of the metal are key factors in inducing the formation of one main diastereoisomer.

Sulphur ylide-mediated cyclopropanation and subsequent spirocyclopropane rearrangement reactions

The efficient construction of cyclopropyl spiroindoline skeletons and the exploration of related follow-up synthetic transformations have elicited considerable interest amongst members of the chemistry community. Here, we describe a formal (2 + 1) annulation and three-component (1 + 1 + 1) cascade cyclisation via sulphur ylide cyclopropanation under mild conditions. The spiro-cyclopropyl iminoindoline moiety can be readily transformed into another medicinally interesting pyrrolo[3,4-c]quinoline framework through a novel rearrangement process.

Diastereoselective trans Cyclopropanation of 3-Alkylidene Oxindoles with In Situ Generated α-Diazo Carbonyls or α,β-Unsaturated Diazo Compounds

An efficient diastereoselective trans cyclopropanation of 3-alkylidene oxindoles with in situ generated α-diazo carbonyl compounds or α,β-unsaturated diazo compounds under metal-free conditions has been developed to synthesize 3-spirocyclopropyl-2-oxindole derivatives. The procedure is based on the 1,3-dipolar character of the corresponding diazo compounds under base-catalyzed conditions. The method has a wide substrate scope and uses easily available starting materials.

Assembly of functionalized π-extended indolizine polycycles through dearomative [3+2] cycloaddition/oxidative decarbonylation

Reported herein is an unexpected construction of functionalized π-extended indolizine polycycles through a one-pot two-step cascade process comprising the base-promoted dearomative [3+2] cycloaddition of quinilinium salts and 3-alkenyl oxindoles, followed by a DDQ-mediated oxidative decarbonylation. Moreover, we could achieve the substrate-controlled diverse synthesis of structurally strained cyclopropane spirooxindole by using pyridinium salts as starting materials.

Synthesis of novel pyridinium 1,5-zwitterions and their reactivity with isatin-based α-(trifluoromethyl)imines: a sulfur-controlled domino reaction

A new stable pyridinium 1,5-zwitterion, generated from azadiene and 4-dimethylaminopyridine, was isolated. The reaction of pyridinium 1,5-zwitterion and isatin-derived α-(trifluoromethyl)imine was regulated by temperature.

Microwave-Assisted Synthesis of Fluorescent Pyrido[2,3-b]indolizines from Alkylpyridinium Salts and Enaminones

Pyridinium ylides are well recognized as dipoles for cycloaddition reactions. In its turn, the microwave-assisted interaction of N-(cyanomethyl)-2-alkylpyridinium salts with enaminones unexpectedly proceeds as a domino sequence of cycloisomerization and cyclocondensation reactions, instead of a 1,3-dipolar cycloaddition. The reaction takes place in the presence of sodium acetate as base and employs benign solvents. The optical properties of the resulting pyrido[2,3-b]indolizines were studied, showing green light emission with high fluorescence quantum yields.

[4 + 1] annulation reaction of cyclic pyridinium ylides with in situ generated azoalkenes for the construction of spirocyclic skeletons

Two new types of cyclic pyridinium ylides were designed and further used in reactions with azoalkenes to access structurally diverse spirocyclic compounds. A range of spiropyrazoline oxindoles could be smoothly obtained in up to 99% yield via a [4 + 1] annulation process with oxindole 3-pyridinium ylides as C1 synthons. Similarly, a series of spiropyrazoline indanones could be prepared with indanone 2-pyridinium ylides as C1 synthons. This work represents the first example of cyclic pyridinium ylides as C1 synthons for the efficient construction of spirocyclic compounds.

Diastereoselective Sonochemical Synthesis of Spirocyclopropaneoxindoles and Evaluation of Their Antioxidant and Cytotoxic Activities

An efficient diastereoselective synthesis of spirocyclopropaneoxindoles is reported using three-component reactions of various phenacylidenetriphenylphosphorane, isatins and phenacyl bromide under ultrasonic irradiation. The structures of synthesized spirocyclopropaneoxindoles were characterized by their spectral data. The antioxidant activities of the synthesized compounds were evaluated by 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay. Among the products, those with NH group in their structure exhibited higher antioxidant activities than other derivatives. Also, in vitro cytotoxicity of compounds 4b, 4e, 4j, 4k were examined against heLa cancer cell lines using MTT assay. The results revealed that compound 4j with chlorine substituent on phenyl group displayed higher cytotoxicity activity (IC₅₀ =4.50±0.30 μg/mL) after 48 h.

Solvent-Controlled, Tunable Domino Reaction of 3-Ylideneoxindoles with in Situ-Generated α-Aryldiazomethanes: A Facile Access to 3-Spirocyclopropyl-2-oxindole and Pyrazoloquinazolinone Scaffolds

A mild and efficient solvent-controlled, metal-free switchable 1,3-dipolar cycloaddition/ring contraction or ring expansion domino reaction of 3-ylideneoxindoles with in situ-generated α-aryldiazomethanes has been developed. This domino reaction provided a series of aryl-substituted 3-spirocyclopropyl-2-oxindoles and pyrazoloquinazolinones with excellent regio- and diastereoselectivity from common substrates under varying solvent conditions.

Cyclodimerization of 3-phenacylideneoxindolines with amino esters for the synthesis of dispiro[indoline-3,1′-cyclopentane-3′,3″-indolines]

Triethylamine-promoted domino cyclodimerization reaction of 3-phenacylideneoxindolines with amino ester hydrochlorides in acetonitrile afforded substituted dispiro[indoline-3,1′-cyclopentane-3′,3″-indolines] in good yields. The relative configuration of the major diastereoisomers was determined by the X-ray diffraction analysis of three single crystal structures.

Formation of diverse polycyclic spirooxindoles via three-component reaction of isoquinolinium salts, isatins and malononitrile

The triethylamine promoted three-component reaction of N-(4-nitrobenzyl), N-ethoxycarbonylmethylisoquinolinium bromide, isatins and malononitrile in ethanol afforded spiro[indoline-3,2′-pyrrolo[2,1-a]isoquinolines] in good yields and with high diastereoselectivity. The similar reaction of N-cyanomethylisoquinolinium chloride mainly gave complex indolo[2″,3″:2′,3′]pyrrolo[3′,4′:4,5]pyrrolo[2,1-a]isoquinoline derivatives. However, the three-component reaction of N-cyanomethylisoquinolinium chloride, isatins and ethyl cyanoacetate mainly resulted in functionalized spiro[indoline-3,8′-pyrido[2′,3′:4,5]pyrrolo[2,1-a]isoquinolines].

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.

A [3 + 2]–[4 + 2]–[3 + 2] cycloaddition sequence of isoquinolinium ylide

A unique [3 + 2]–[4 + 2]–[3 + 2] cycloaddition sequence of isoquinolinium ylide is investigated to afford polycyclic compounds with ten stereogenic centers.

Lanthanide amide-catalyzed one-pot functionalization of isatins: synthesis of spiro[cyclopropan-1,3′-oxindoles] and 2-oxoindolin-3-yl phosphates

A lanthanide-catalyzed one-pot reaction using readily accessible substrates was developed affording spiro[cyclopropan-1,3′-oxindoles] in good yields and with high stereoselectivity.

Convenient synthesis of functionalized pyrrolo[3,4-b]pyridines and pyrrolo[3,4-b]quinolines via three-component reactions

A simple protocol for convenient construction of pyrrolo[3,4-b]pyridine skeleton was successfully developed by base promoted three-component reaction of β-enamino imide, aromatic aldehydes and malononitrile as well as its ester and amide derivatives.

Diastereoselective synthesis of spiro[benzo[d]pyrrolo[2,1-b]thiazole-3,3'-indolines] via cycloaddition reaction of N-phenacylbenzothiazolium bromides and 3-methyleneoxindoles

The domino cycloaddition reactions of N-phenacylbenzothiazolium bromides with 3-phenacylideneoxindoles or ethyl 2-(2-oxoindolin-3-ylidene)acetates in ethanol at room temperature in the presence of triethylamine as a base afforded functionalized spiro[benzo[d]pyrrolo[2,1-b]thiazole-3,3'-indolines] in good yields and with high diastereoselectivity. The similar reactions of N-phenacylthiazolium bromides with 3-phenacylideneoxindoles resulted in the corresponding functionalized spiro[indoline-3,7'-pyrrolo[2,1-b]thiazoles] in satisfactory yields and also with high diastereoselectivity.

Construction of dispirocyclohexyl-3,3′-bisoxindole and dispirocyclopentyl-3,3′-bisoxindole via domino cycloaddition reactions of N-benzylbenzimidazolium salts with 2-(2-oxoindolin-3-ylidene)acetates

Two kinds of spirocyclic oxindoles were selectively synthesized from cycloaddition of N-benzyl-N-phenacylbenzimidazolium salts with two molecules of 2-(2-oxoindolin-3-ylidene)acetates.

Diastereoselective synthesis of spiro[cyclopropane-1,3′-indolin]-2′-ones through metal-free cyclopropanation using tosylhydrazone salts

Anticancer spiro[cyclopropane-1,3′-indolin]-2′-ones are accessible through a transition metal-free diastereoselective cyclopropanation using in situ generated diazo-compounds.