Two approaches toward the regio- and stereoselective synthesis of N-unsubstituted 3-aryl-4-(trifluoromethyl)-4H-spiro-[chromeno[3,4-c]pyrrolidine-1,3'-oxindoles]

Synthesis of xanthenone fused spiro pyrrolidine oxindoles via multicomponent [3 + 2] cycloaddition reactions

Xanthenone fused spiro-pyrrolidine oxindoles were conveniently synthesized in good yields with high regio- and diastereoselectivity from a multicomponent synthesis involving tetrahydroxanthenones, α-amino acids, and isatins via an azomethine ylide based [3 + 2] cycloaddition process. We utilized tetrahydroxanthenone as a dipolarophile for the first time in the [3 + 2] cycloaddition of decarboxylated azomethine ylide. The relative configuration of the spirocycloadduct was determined by single-crystal X-ray diffraction analysis.

1-Styryl-1,3-diketones in the synthesis of spiro[oxindole-3,2'-pyrrolidines] with notable anticancer activity

A regio- and stereoselective method for the synthesis of spiro[indolin-3,2'-pyrrolidine]-2-ones based on the [3 + 2] cycloaddition of azomethine ylides, generated in situ from isatins and proteinogenic α-amino acids, and (E)-5-arylpent-4-ene-1,3-diones under reflux in methanol within 12 h in 28-91% yields has been developed. A number of representative examples of spiro[indolin-3,2'-pyrrolidine]-2-ones have been studied for cytotoxic activity against HeLa cervical cancer cell line and human dermal fibroblasts (HDF) by the MTT assay. Every investigated compound has shown cytotoxic activity against HeLa cells (IC50 0.24-38.43 μM), while some of them have also shown low cytotoxicity against HDF cells (IC50 100.08-7821.27 μM). A preliminary structure-activity relationship (SAR) correlations have been made.

Different Behavior of 2-Substituted 3-Nitro-2H-chromenes in the Reaction with Stabilized Azomethine Ylides Generated from α-Iminoesters

The AgOAc-catalysed reaction of 3-nitro-2-phenyl-2H-chromenes with stabilized azomethine ylides generated from the imines based on methyl glycinate and arylaldehydes leads to a mixture of endo and endo' isomers of the corresponding chromeno[3,4-c]pyrrolidines in a ratio of 2.0-2.3:1 in 85-93% total yields as a result of a Michael addition/Mannich reaction sequence. In a similar reaction involving 2-trifluoromethyl-3-nitro-2H-chromenes, only endo chromeno[3,4-c]pyrrolidines are formed in 85-94% yields. 3-Nitro-2-(trichloromethyl)-2H-chromenes under the same conditions react with these azomethine ylides to give the corresponding Michael adducts as individual anti-isomers with the cis,trans-configuration of the chromane ring in 40-67% yields. Some 4-CF₃-substituted chromano[3,4-c]pyrrolidines exhibited high cytotoxic activity against HeLa human cervical carcinoma cells.

Synthesis, Structure and Stereochemistry of Dispirocompounds Based on Imidazothiazolotriazine and Pyrrolidineoxindole

Methods for the synthesis of two types of isomeric dispirocompounds based on imidazothiazolotriazine and pyrrolidineoxindole, differing in the structure of imidazothiazolotriazine fragment, namely, linear dispiro[imidazo[4,5-e]thiazolo[3,2-b][1,2,4]triazine-6,3'-pyrrolidine- 4',3″-indolines] and angular dispiro[imidazo[4,5-e]thiazolo[2,3-c][1,2,4]triazine-7,3'-pyrrolidine-4',3″-indolines] were proposed. The first method relies on a 1,3-dipolar cycloaddition of azomethine ylides generated in situ from paraformaldehyde and N-alkylglycine derivatives to the corresponding oxindolylidene derivatives of imidazothiazolotriazine. The cycloaddition leads to a mixture of two diastereomers resulted from anti- and syn-approaches of azomethine ylide in approximately a 1:1 ratio, which were separated by column chromatography. Another method consists in rearrangement of linear dispiro[imidazo[4,5-e]thiazolo[3,2-b][1,2,4]triazine-6,3'-pyrrolidine-4',3″-indolines] into hitherto unavailable angular dispiro[imidazo[4,5-e]thiazolo[2,3-c]-[1,2,4]triazine-7,3'-pyrrolidine-4',3″-indolines] upon treatment with KOH. It was found that the anti-diastereomer of linear type underwent rearrangement into the isomeric angular syn-diastereomer, while the rearrangement of the linear syn-diastereomer gave the angular anti-diastereomer.

Highly diastereoselective annulation of 2-substituted 3-nitro-2H-chromenes with hemicurcuminoids and curcuminoids via a double and triple Michael reaction cascade

The K2CO3-catalysed double Michael addition of (E)-1,5-diaryl- and 1-alkyl-5-arylpent-4-ene-1,3-diones to 2-trifluoromethyl- and 2-phenyl-substituted 3-nitro-2H-chromenes in dichloromethane at room temperature for 48 h results in 10-aroyl(acyl)-7-aryl-6a-nitro-6,6a,7,8,10,10a-hexahydro-9H-benzo[c]chromen-9-ones in 75-98% yields as individual...