Preparation of fluorinated esters of abietic acid

The reaction of abietic acid chloride with sodium salts of 1H,1H-dihydrotrifluoroethanol, 1H,1H,3H-trihydrotetrafluoropropanol, 1H,1H,5H-trihydrooctafluoropentanol, and pentafluorophenol was studied. The main reaction products are the corresponding fluorinated alkyl (aryl) abietates.     

Site-selective Suzuki-Miyaura reactions of 2,3-dibromo-1H-inden-1-one

The first transition metal-catalyzed cross-coupling reactions of 2,3-dibromo-1H-inden-1-one are reported. The Suzuki-Miyaura reaction of 2,3-dibromo-1H-inden-1-one with 2 equiv of arylboronic acid gave 2,3-diaryl-1H-inden-1-ones. The reaction with 1 equiv of arylboronic acid gave 2-bromo-3-aryl-1H-inden-1-ones with very good site-selectivity. The one-pot reaction of 2,3-dibromo-1H-inden-1-one with two different arylboronic acids afforded 2,3-diaryl-1H-inden-1-ones containing two different terminal aryl groups.     

Reductive coupling of hydantoins with benzophenones by low-valent titanium: Synthesis of 4-substituted 1H-imidazol-2(3H)-ones and unusual two-to-two coupled products

The reductive coupling of 1,3-dimethyhydantoin with benzophenones by TiCl₄-Zn in THF gave 4-diarylmethyl-1H-imidazol-2(3H)-ones as four-electron reduced one-to-one coupled products and their dimers as two-to-two coupled products predominantly by controlling the reaction conditions. The reductive coupling of 5-alkyl-1,3-dimethyhydantoins with benzophenones produced 5-alkyl-4-diarylmethyl-1H-imidazol-2(3H)-ones as the sole products irrespective to the reaction conditions. On the other hand, the reductive coupling of 1,3-dimethyhydantoin with cyclic benzophenones selectively 4-arylhydroxymethyl-1H-imidazol-2(3H)-ones as two-electron reduced one-to-one coupled products and they were further reduced to 4-diarylmethyl-1H-imidazol-2(3H)-ones.     

CAN-promoted, diastereoselective synthesis of fused 2,3-dihydrofurans and their transformation into tetrahydroindoles

The reaction between 1,3-cyclohexanediones and chalcones (or their vinilogs) in the presence of 2.5 equiv of cerium(IV) ammonium nitrate afforded trans-2-arylcarbonyl-3-aryl (or styryl)-2,3,6,7-tetrahydrobenzofuran-4(5H)-ones in good to excellent yields and in high diastereoselectivities. The method was also extended to the preparation of derivatives of the 5,6-dihydro-2H-cyclopenta[b]furan-4(3H)-one system. The fused 2,3-dihydrofuran derivatives were transformed into 1-alkyl-2-acyl-3-aryl-6,7-dihydroindole-4(5H)-ones by 2,3-dehydrogenation followed by reaction with primary amines. The direct reaction of the tetrahydrobenzofuran-4(5H)-one compounds derived from dimedone with amines gave 1-alkyl-2-alkylimino-3-aryl-6,7-dihydroindole-4(5H)-ones, while starting materials derived from 1,3-cyclohexanedione underwent an unprecedented 2-deacylation reaction and gave 1-alkyl-3-aryl-6,7-dihydroindole-4(5H)-ones.     

Synthesis and structure of the products of the reactions of 3-chloro-5-methoxy-4-[(4-methylphenyl)sulfanyl]-2(5H)-furanone with N,N-binucleophilic agents

Reactions of 3-chloro-5-methoxy-4-[(4-methylphenyl)sulfanyl]-2(5H)-furanone with different nitrogen-containing binucleophilic agents were studied. The reaction with hydrazine monohydrate resulted in the formation of 1,5-dihydro-2H-pyrrol-2-one and pyridazin-3(2H)-one derivatives, whereas the reaction with phenylhydrazine led exclusively to 1-phenylamino-1,5-dihydro-2H-pyrrol-2-one. The reaction with ethylenediamine resulted in the isolation of 1,2-bis[2-oxo-1,5-dihydro-2H-pyrrol-1-yl]ethane: the enantiomeric dl-pair and two poly-morphic modifications of meso-form, which were characterized by X-ray crystallography.     

Reaction of 3-chloroquinoline-2,4-diones with ethanolamine and rearrangement of the reaction products

The reaction of tertiary α-chloroketones with ethanolamine has not been hitherto described in the literature. Herein, we describe the reaction of tertiary 3-chloroquinoline-2,4-diones with ethanolamine to give novel 3-(2-hydroxyethylamino)quinoline-2,4-diones. These compounds provide 3-(2-oxooxazolidin-3-yl)quinoline-2,4(1H,3H)-diones and new compounds with dimeric character after reaction with triphosgene. Molecular rearrangement proceeds during the reaction of 3-(2-hydroxyethylamino)quinoline-2,4-diones with isocyanic acid. Three types of reaction products arise: 2-(2-hydroxyethyl)imidazo[1,5-c]quinazoline-3,5-diones, 3-(2-hydroxyethyl)-3,3a-dihydro-2H-imidazo[4,5-]quinoline-4(5H)diones and primarily 5-hydroxy-1-(hydroxyethyl)-1′H-spiro[imidazolidine-5,3′-indole]-2,2′-diones. The reaction mechanism and product stereochemistry are discussed. The ¹H, ¹³C and ¹⁵N NMR spectra of the prepared compounds were measured, and all resonances were assigned from appropriate two-dimensional experiments.     

Synthesis of 5H-pyridazino[4,5-b]indoles and their benzofurane analogues utilizing an intramolecular Heck-type reaction

The title ring systems were prepared from pyridazin-3(2H)-one precursors in novel, efficient pathways. 2-Methylbenzo[b]furo[2,3-d]pyridazin-1(2H)-one was synthesized via a regioselective nucleophilic substitution reaction of a 2-methyl-4,5-dihalopyridazin-3(2H)-one with phenol followed by an intramolecular Heck-type reaction. The same molecule and its 6-phenyl analogue were also prepared via reaction of 2-methyl-5-iodopyridazin-3(2H)-one or 2-methyl-5-chloro-6-phenylpyridazin-3(2H)-one, respectively, with 2-bromophenol or 2-iodophenol followed by Pd-catalyzed cyclodehydrohalogenation. Moreover, a new approach for the synthesis of 2-methyl-2,5-dihydro-1H-pyridazino[4,5-b]indol-1-ones was also elaborated utilizing a Heck-type ring closure reaction on 5-[(2-bromophenyl)amino]-2-methylpyridazin-3(2H)-ones which were obtained via Buchwald-Hartwig amination of 2-methyl-5-halopyridazin-3(2H)-ones with 2-bromoaniline.     

Synthesis of 6-substituted 7-aryl-5,6-dihydropyrido[2,3-d]pyrimidine(1H,3H)-2,4-diones using the Vilsmeier reaction

The reaction of 6-amino-1,3-dimethyluracil with equimolar amounts of arylalkanone Mannich bases under optimized reaction conditions leads to 7-aryl-5,6-dihydropyrido[2,3-d]pyrimidines in a yield of 50-80%. Functionalization of these dihydropyridopyrimidine(1H,3H)-2,4-diones with the Vilsmeier reagent affords, depending on the reaction conditions, either 6-dimethylaminomethylidene substituted 5H-pyrido[2,3-d]pyrimidine(1H,3H)-2,4-diones or the corresponding pyridopyrimidine(1H,3H)-2,4-diones bearing a carboxaldehyde function in position 6 of the heterocycle. Some further transformations of the aldehyde function demonstrate the synthetic potential of the synthesized structures, introducing pharmacologically relevant basic substituents into the side chain of these pyrido[2,3-d]pyrimidine derivatives.     

Synthesis of (Z)-1-benzylidene-3-(1H-indol-1-yl)-1H-indene-2,2(3H)-dicarbonitriles via three-component reaction of 2-alkynylbenzaldehyde, malononitrile, and indole

Three-component reaction of 2-alkynylbenzaldehyde, malononitrile, and indole under mild conditions is described, which generates the desired (Z)-1-benzylidene-3-(1H-indol-1-yl)-1H-indene-2,2(3H)-dicarbonitriles in moderate to good yields. This reaction proceeds smoothly with high selectivity. The tandem condensation, nucleophilic addition, and 5-exo-cyclization may be involved in the process.     

On the preparation of azepinones

We report here a simple and efficient preparation of 1H-azepin-5(2H)-ones and their unexpectedly facile isomerization to 1H-azepin-5(4H)-ones under mildly basic reaction conditions.     

Synthesis of zwitterionic 4-hydroxy-2(1H)-quinolinone derivatives

Zwitterionic 4-hydroxy-2(1H)-quinolinone derivatives were synthesized through a unique reaction of 4-hydroxy-2(1H)-quinolinone with p-benzoquinone and N-heterocyclic aromatics. The zwitterions possessed astropisomeric nature. A possible mechanism of the reaction was presented.     

Regioselectivity in the reactions of <Emphasis Type="Italic">N</Emphasis>-(polychloroethylidene)-sulfonamides with 1<Emphasis Type="Italic">H</Emphasis>-pyrrole and 1-methyl-1<Emphasis Type="Italic">H</Emphasis>-pyrrole

N-(2,2,2-Trichloroethylidene)arenesulfonamides react with 1H-pyrrole and 1-methyl-1H-pyrrole to give the corresponding N-[2,2,2-trichloro-1-(1H-pyrrol-2-yl)ethyl]arenesulfonamides. The reaction of N-(2,2,2-trichloroethylidene)trifluoromethanesulfonamide with pyrrole leads to a mixture of 2-mono-and 2,5-disubstituted pyrroles, whereas in the reaction with 1-methyl-1H-pyrrole only the 2-substituted compound is formed. N-(2,2-Dichloro-2-phenylethylidene)-4-methylbenzenesulfonamide reacts with 1H-pyrrole to form N-[2,2-dichloro-2-phenyl-1-(1H-pyrrol-2-yl)ethyl]-4-methylbenzenesulfonamide, and its reaction with 1-methyl-1H-pyrrole gives a mixture of 2-and 3-monosubstituted derivatives. The results of quantum-chemical calculations of the initial reactants and products indicate that the process is orbital-controlled. A good agreement is observed between the experimental data and theoretical conclusions concerning the dependence of the reaction regioselectivity on the nature of substituents in the electrophile molecule.     

Benzazoles: II. Synthesis and arenesulfonylation of 1-methyl-1H-benzimidazol-2-amine

The reaction of 1-methyl-1H-benzimidazol-2-amine with arenesulfonyl chlorides in the presence of triethylamine afforded 1-arenesulfonyl-3-methyl-2,3-dihydro-1H-benzimidazol-2-imines instead of expected N-(1-methyl-1H-benzimidazol 2-yl)arenesulfonamides.     

Chan-Lam cross-coupling reaction based on the Cu2S/TMEDA system

A catalyst based on the readily available Cu₂S/TMEDA system using a stable copper(I) source was developed for the Chan-Lam cross-coupling reaction. The capability of the catalyst was demonstrated with 1H-benzo[d]imidazol-2(3H)-one, 1H-benzo[d]imidazole, and 1H-imidazole together with electron-deficient, electron-rich, and sterically demanding boronic acids at room temperature in the presence of atmospheric oxygen to give the cross-coupling products in moderate to excellent yields. In addition, the coupling reaction of 1H-benzo[d]imidazole with several pinacol or neopentylglycol boronates indicated further potential of the catalyst. The reaction conditions tolerate the hydroxyl and bromo functional groups. The catalytic system also enables to synthesize the mono-N-substituted anilines from primary aliphatic amines. However, the two model compounds for the secondary and aromatic amines, piperidine and aniline, do not react. Two sterically demanding products with the restricted CN bond rotation, synthesized by the N-arylation of 1H-benzo[d]imidazol-2(3H)-one with o-tolylboronic acid, enabled to confirm the atropisomers prepared by the Chan-Lam cross-coupling reaction. Furthermore, an example of one-pot Chan-Lam and Suzuki-Miyaura reaction has been reported.     

Flash vacuum pyrolysis of 2,2-dioxo-1H,3H-pyrrolo[1,2-c]thiazoles and 2-vinyl-1H-pyrroles

The flash vacuum pyrolysis of new 1,1-dimethyl- and 1-methyl-1H,3H-pyrrolo[1,2-c]thiazole-2,2-dioxides gave penta-substituted 2-vinyl-1H-pyrroles via sigmatropic [1,8]-H shift of the corresponding azafulvenium methide intermediates. In some cases these 1H-pyrroles underwent rearrangement to 2-allyl-1H-pyrroles. Di-substituted 2-vinylpyrroles have also been prepared and their reactivity studied. Under FVP N-benzyl-pyrrol-2-ylpropenoates were converted into 3H-pyrrolizin-3-ones. On the other hand, microwave-assisted reaction of 1-benzyl-2-vinyl-1H-pyrrole gave a 4,5,6,7-tetrahydro-1H-indole derivative.     

Reactions of 5,6,7,8-Tetrafluoro-4-hydroxy-2H-chromen-2-ones with methylamine

5,6,7,8-Tetrafluoro-4-hydroxy-2H-chromen-2-one reacts with methylamine to give methylammonium 5,6,7,8-tetrafluoro-2-oxo-2H-chromen-4-olate, regardless of the solvent. The reaction of 3-acetyl-5,6,7,8-tetrafluoro-4-hydroxy-2H-chromen-2-one with the same amine in ethanol or acetonitrile leads to the formation of methylammonium 3-acetyl-5,6,7,8-tetrafluoro-2-oxo-2H-chromen-4-olate, while in dimethyl sulfoxide 5,6,8-trifluoro-7-methylamino-3-(1-methylaminoethylidene)-3,4-dihydro-2H-chromene-2,4-dione is formed. The latter is also formed in the reaction of 5,6,7,8-tetrafluoro-4-hydroxy-3-(1-iminoethyl)-2H-chromen-2-one with methylamine in DMSO, whereas in ethanol and acetonitrile 5,6,7,8-tetrafluoro-3-(1-methylaminoethylidene)-3,4-dihydro-2H-chromene-2,4-dione is obtained. 5,6,7,8-Tetrafluoro-3-(1-methylaminoethylidene)-3,4-dihydro-2H-chromene-2,4-dione reacts with methylamine, yielding 7-mono-or 5,7-bis(methylamino)-substituted derivatives.     

Reaction between isocyanides and dialkyl acetylenedicarboxylates in the presence of 2,4-dihydro-3H-pyrazol-3-ones. One-pot synthesis of highly functionalized 7-oxo-1H,7H-pyrazolo[1,2-a]pyrazoles

The reactive 1:1 intermediate produced in the reaction between isocyanides and dialkyl acetylenedicarboxylates was trapped by 2,4-dihydro-3H-pyrazol-3-ones to yield highly functionalized 7-oxo-1H,7H-pyrazolo[1,2-a]pyrazoles in fairly good yields.     

Reaction of functionalized azomethine ylides with acetylenic dipolarophiles: the facile synthesis of functionalized 2H- and 1H-pyrroles

The reaction of functionalized azomethine ylides as C-unsubstituted nitrile ylide equivalents with acetylenic dipolarophiles is mentioned. Therein, the initially formed cycloadducts, 2,5-dihydropyrroles, by the reaction of the azomethine ylides with substituted acetylenes, undergo a fission reaction to afford 2H-pyrroles and the parent heterocyclic system. Some 2H-pyrroles isomerized to 1H-pyrroles under both thermal and acidic conditions.     

The reactions of 3-ethoxycarbonylmethylene-3,4-dihydroquinoxalin-2(1H)-one and its derivatives in the synthesis of benzodiazepines and benzimidazoles: reinvestigation,structural reassignment,and new insight

The reaction of 3-ethoxycarbonylmethylene-3,4-dihydroquinoxalin-2(1H)-one with the Vilsmeier reagent, the treatment of 3-(3,4-dihydroquinoxalin-2(1H)-on-3-yl)-1,2-dihydro-1,5-benzodiazepin-2(1H)-one hydrochloride with 10% sodium hydroxide and 3-benzimidazoylquinoxalin-2(1H)-one with both 1,2-phenylenediamine dihydrochloride, and the reactions of 1,2-phenylenediamine have been reinvestigated and the structures of these reaction products have been revised. It has been shown that in all the three cases other regioisomers of products have been formed as distinct from the literature data. The mechanisms to explain the formation of the products are suggested.     

Superelectrophilic activation of N-aryl amides of 3-arylpropynoic acids: synthesis of quinolin-2(1H)-one derivatives

The superelectrophilic activation of N-aryl amides of 3-arylpropynoic acids by Bronsted superacids (CF₃SO₃H, HSO₃F) or strong Lewis acids AlX₃ (X=Cl, Br) results in the formation of 4-aryl quinolin-2(1H)-ones in quantitative yields. The vinyl triflates or vinyl chlorides may be formed as additional reaction products. The investigated amides in reactions with benzene give 4,4-diaryl 3,4-dihydroquinolin-2-(1H)-ones under the superelectrophilic activation. 4-Aryl quinolin-2(1H)-ones in POCl₃ are converted into 4-aryl 2-chloroquinolines. 4-Fluorophenyl-4-phenyl 3,4-dihydroquinolin-2-(1H)-one give N-formylation products in a yield of 79% under the Vilsmeier–Haack reaction conditions.