A four-component synthesis of novel spiro[pyrazoloquinoline-oxindoles] under solvent-free conditions

A domino reaction for the rapid and diverse synthesis of spiro[1H-pyrazolo[3,4-b]benzo[h]dihydroquinolin-4,3-indolin-2-ones] is reported. The synthesis represents a thermodynamically-favored four-component reaction between phenylhydrazine, isatins, naphthylamines, and 3-ketoesters giving the novel products in excellent yields under solvent-free conditions. Similar applications of anilines in place of naphthylamines have not led to formation of the expected 4-substituted pyrazolo[3,4-b]quinoline derivatives. The difference was ascribed to lower aromatic character of naphthylamines, with respect to anilines, which enables them to act easier as enamines in reaction with the postulated intermediates formed from condensation of isatins and the in situ generated pyrazolones. Surprisingly, 6-aminouracils in despite of their known enamine properties did not participate in reaction with isatins and pyrazolones, the merit of naphthylamines for this synthesis seems to be met by the favorable balance of their N- and C-nucleophilicity.     

Studies in spiroheterocycles. Part XVII. synthesis of novel fluorine containing spiro[indole-pyranobenzopyran] and spiro[indenopyran-indole] derivatives

An elegant one-step synthesis of two novel spiro ring systems viz: spiro[3H-indole-3,4′-(2′-amino-3′-carbonitrile-[4′H]-pyrano[3,2-c]benzopyran)]-2,5′(1H)-dione8 and spiro[(2-amino-3-carbonitrile-indeno[1,2-b]pyran)-4(5H)>3′-[3H]indole]-2′,5(1′H)-diones in 80–85% yields is described. The spiro heterocycles were prepared by the reactions of fluorine containing 3-dicyanomethylene-2H-indol-2-ones with 4-hydroxy-2H-1-benzopyran-2-one and 1H-indene-1,3(2H)-dione respectively. The synthesized compounds have been characterized on the basis of elemental analyses, ir, pmr, ¹⁹F nmr and mass spectral data.     

Grindstone chemistry: one-pot synthesis of spiro[diindenopyridine-indoline]triones and spiro[acenaphthylene-diindenopyridine]triones

A one-pot, pseudo four-component, and simple synthesis of spiro[diindenopyridine-indoline]triones and spiro[acenaphthylene-diindenopyridine]triones via the reaction of 1,3-indandione, aromatic amines and isatins or acenaphthylene-1,2-dione using a ‘Grindstone Chemistry’ method is reported.     

Dzhemilev reaction for the synthesis of spiro[3.3]heptane and spiro[3.4]octanes

For the first time cycloalumination of methylenecyclobutane with the aid of Et₃Al in the presence of Cp₂ZrCl₂ leading to 6-ethyl-6-aluminaspiro[3.4]octane has been realized. The latter, without isolation, was converted into spiro[3.3]heptane, 6-thiaspiro[3.4]octane and also spiro[3.4]octan-6-ol and 6-spiro[3.4]octyl formate with high yields and selectivity.     

Synthesis of novel spiro[2.3]hexane carbocyclic nucleosides via enzymatic resolution

[reaction: see text] Novel R- and S-spiro[2.3]hexane nucleosides have been synthesized. The key step involved the Pseudomonas cepacia lipase catalyzed resolution of racemic compound 2, synthesized in seven steps starting from diethoxyketene and diethyl fumarate, to give (+)-acetate 3 and (-)-alcohol 13. (+)-Acetate 3 and (-)-acetate 14 were converted to R- and S-9-(6-hydroxymethylspiro[2.3]hexane)-4-adenine, respectively.     

A Photochemical Macrocyclization Route to Asymmetric Strained [3.2] Paracyclophanes

The intricate frameworks of paracyclophanes are an important target for synthesis since they are found in various chiral auxiliaries, solar cells, high-performance plastics, pharmaceuticals, and molecular machines. Whereas numerous methods exist for the preparation of symmetric paracyclophanes, protocols for the efficient synthesis of strained asymmetric scaffolds are limited. Here we report a remarkably simple photochemical route to strained [3.2]paracyclophanes starting from readily available educts. By way of NMR and X-ray analyses, we discovered that UV-irradiation of an aromatic carboxylic ester tethered to a toluene moiety leads to the intramolecular formation of a new C−C bond, with loss of an alcohol. A systematic evaluation of the reaction conditions and substituents, as well as radical starter and triplet quenching experiments, point to a reaction mechanism involving an excited triplet state and hydrogen atom transfer. The new method proved to be robust and versatile enabling the synthesis of a range of cyclophanes with different substitutions, including an unusual diastereoisomer with two planar chiral centers, and thus proved to be a valuable addition to the synthetic toolbox.     

Convenient synthesis of spiro[indoline-3,4'-pyrano[2,3-c]pyrazole] and spiro[acenaphthyl-3,4'-pyrano[2,3-c]pyrazoles] via fourcomponent reaction

The base promoted four-component reaction of hydrated hydrazine, dimethyl acetylenedicarboxylate, isatines and malononitrile (ethyl cycanoacetate) in ethanol afforded polysubstituted spiro[indoline-3,4‘-pyrano[2,3-c]pyrazoles] and spiro[acenaphthyl-3,4-pyrano[2,3-c]pyrazoles]     

Synthesis of spiro[indole-3,3′-[1,3,4]thiadiazino[3,2-a]benzimidazoles] and spiro[indole-3,6′-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazines]

A method for annulation of the tetrahydrothiadiazine ring to benzimidazoles and 1,2,4-tri-azoles was developed. A number of earlier unknown [1,3,4]thiadiazino[3,2-a]benzimidazoles and triazolo[3,4-b][1,3,4]thiadiazines were obtained as spiro compounds with the oxindole fragment. According to NMR and X-ray diffraction data, the formation of the tetrahydrothiadiazine ring is a diastereospecific process.     

Synthesis of spiro[benzopyrazolonaphthyridine-indoline]-diones and spiro[chromenopyrazolopyridine-indoline]-diones by one-pot, three-component methods in water

The synthesis of spiro[benzo[h]pyrazolo[3,4-b][1,6]naphthyridine-7,3′-indoline]-2′,6(5H)-diones and spiro[chromeno[4,3-b]pyrazolo[4,3-e]pyridine-7,3′-indoline]-2′,6(6aH,10H)-diones via a one-pot, three-component reaction of 4-hydroxycoumarin or 4-hydroxy-1-methylquinolin-2(1H)-one, isatins and 1H-pyrazol-5-amines in water is reported.     

Convenient construction of spiro[indoline-3,5'-pyrrolo[3,4-c]carbazole] and spiro[indene-2,5'-pyrrolo[3,4-c]carbazole] via acid-catalyzed Diels-Alder reaction

p-TsOH catalyzed Diels-Alder reaction of 3-(indol-3-yl)maleimides with 3-phenacylideneoxindoles in toluene at 80 °C for two hours afforded cis/trans isomers of 3a',4′,6′,10c'-tetrahydrospiro[indoline-3,5′-pyrrolo[3,4-c]carbazoles] in nearly comparable yields, which could be easily converted to the corresponding 4′,6′-dihydrospiro[indoline-3,5′-pyrrolo[3,4-c]carbazole] in high yields and with high diastereoselectivity by further DDQ oxidation. Additionally, the similar reaction of 3-(indol-3-yl)maleimides with 2-arylidene-1,3-indanediones in toluene 80 °C and sequential DDQ oxidation afforded functionalized dihydrospiro[indene-2,5′-pyrrolo[3,4-c]carbazoles] as major products.     

Infrared and Raman spectra of spiro[2.4]hepta-4,6-diene and [1,2-2H4]spiro[2.4]hepta-4,6-diene

The i.r. spectra of spiro[2.4]hepta-4,6-diene and of [1,2-²H₄]spiro[2.4]hepta-4,6-diene have been measured for gas and liquid samples, for carbon disulfide and carbon tetrachloride solutions, and for samples matrix isolated in argon, krypton or nitrogen. The Raman spectra with depolarization ratios were determined for both isotopic molecules. Vibrational assignments for all fundamental modes of both molecules are proposed based upon polarizations of Raman lines, isotopic frequency shifts, and group frequencies in comparison with vibrational assignments of cyclopentadiene, cyclopropane and d₆-cyclopropane.     

A Clean synthesis of spiro[indoline-3,9'-xanthene]trione derivatives

A simple, clean and efficient method for the synthesis of spiro[indoline-3,9'-xanthene]trione derivatives and spiro[acenaphthene-1,9'-xanthene]-1',2,8'(2'H,5'H)-trione by condensation reaction of dimedone and isatins or acenaphthene in aqueous media is reported.     

A novel synthesis of spiro[2.6]nonadienones by the reaction of magnesium cyclopropylidenes with naphtholates and phenolates

The sulfoxide-magnesium exchange reaction of aryl 1-chlorocyclopropyl sulfoxides with i-PrMgCl in THF at low temperature gave magnesium cyclopropylidenes. Treatment of the magnesium cyclopropylidenes with lithium naphtholates or phenolates resulted in the formation of spiro[2.6]nonadienones in up to 82% yield. The structure of the spiro[2.6]nonadienones was found to be dependent on the structure of the naphtholates and phenolates.     

Synthesis of spiro thiopyrano[2,3-d]thiazolidines

Spiro thiazolidine rings 3a,b are obtained in excellent yields by one-pot reaction of 1a,b with Lawesson reagent via [4 + 2] cycloaddition; the X-ray crystallography structure for compound 3a was determined and documented     

Singulett-Sauerstoff-induzierte spaltung von spiro[1,8a]dihydroindolizinen

The ¹O₂-induced degradation of spiro[1,8a]dihydroindolizines $\text{1}$ - a new photochromic system - may involve dioxetanes as intermediates giving fulvenylesters $\text{3}$.