Mass spectra of new heterocycles: X. Fragmentation of the molecular ions of 1-alkyl(cycloalkyl,aryl)-3-alkoxy(aryl)-2-methylsulfanyl-1<Emphasis Type="Italic">H</Emphasis>-pyrroles

The mass spectra of previously unknown 1-alkyl(cycloalkyl, aryl)-3-alkoxy(aryl)-2-methylsulfanyl-1H-pyrroles were studied. Fragmentation of all 3-alkoxy-substituted pyrroles under electron impact (70 eV) follow both ether and sulfide decomposition paths; In particular, 1-R-substituted 3-methoxy-2-methylsulfanyl-1H-pyrroles (R = Me, Et, i-Pr, s-Bu, cyclo-C₅H₉, cyclo-C₆H₁₁, Ph) lose methyl radical group from both methoxy and methylsulfanyl groups. The mass spectra of 1-sec-butyl- and 1-cycloalkylpyrroles also contained a strong peak (10–49%) from odd-electron [M — C _n H_2n ]^+· ion formed via cleavage of the N-R bond with synchronous hydrogen transfer. Cleavage of the O-Alk bond in the fragmentation of 3-alkoxy-1-isopropyl-2-methylsulfanyl-1H-pyrroles (Alk = Et, i-Pr, t-Bu) was accompanied by rearrangement process leading to the corresponding alkene and odd-electron 1-isopropyl-2-methylsulfanyl-1H-pyrrol-3-ol ion. The main fragmentation path of 1-alkyl-2-methylsulfanyl-3-phenyl-1H-pyrroles (Alk = Me, i-Pr) under electron impact involves dissociation of the S-Me bond with formation of rearrangement 1H-[1]benzothieno[2,3-b]pyrrol-8-ium ion.     

Mass spectra of new heterocycles: XII. Main fragmentation pathways of the molecular ions of 5-methylsulfanyl-1-vinyl-1H-pyrrol-2-amines under electron impact and chemical ionization

Fragmentation patterns of 5-methylsulfanyl-1-vinyl-1H-pyrrol-2-amines under electron impact (70 eV) and chemical ionization (methane as reactant gas) were studied for the first time. The electron impact mass spectra of all the examined compounds contained a strong peak of molecular ion which decomposed along four pathways. Two pathways involved cleavage of the C-S bonds with elimination of methyl (major) and MeS radicals (minor), and the two others, decomposition of the pyrrole ring. The chemical ionization mass spectra displayed strong molecular, [M + H]⁺, and odd-electron [M + H ? SMe]⁺ ion peaks. N,N-Dimethyl-5-methylsulfanyl-4-phenyl-1-vinyl-1H-pyrrol-2-amine under chemical ionization with methane as reactant gas characteristically decomposed with formation of [M ? C₄H₉N]⁺ as the only fragment ion.     

Heterocyclizations of 1-(Benzothiazol-2-yl)-4-phenylthiosemicarbazide

1-(Benzothiazol-2-yl)-4-phenylthiosemicarbazide reacted with methyl iodide in the presence of sodium acetate in boiling ethanol to give 2,2′-dithiobis[N-(5-methylsulfanyl-4-phenyl-4H-1,2,4-triazol-3-yl)-benzenamine]. The reaction of the title compound with dimethyl acetylenedicarboxylate in dioxane led to the formation of methyl 3-(benzothiazol-2-yl)-2-(2-methoxy-2-oxoethyl)-2,3-dihydro-1,3,4-thiadiazole-2-carboxylate.     

Mass Spectra of New Functionally Substituted Heterocycles: V. First Example of McLafferty Rearrangement in the Series of 5-(1-Ethoxyethoxy)-2,3-dihydropyridines and 3-(1-Ethoxyethoxy)pyridines Derived from α-Lithiated 1-(1-Ethoxyethoxy)allene and Methoxymethyl Isothiocyanate

Previously unknown 5-(1-ethoxyethoxy)-2-methoxy-6-methylsulfanyl-2,3-dihydropyridine, 3-(1-ethoxyethoxy)-2-methylsulfanylpyridine, and 2-methylsulfanylpyridin-3-ol were synthesized from α-lithiated 1-(1-ethoxyethoxy)allene, methoxymethyl isothiocyanate, and methyl iodide, and their fragmentation under electron impact was studied. At ionizing electron energies of 12 and 60 eV in the temperature range from 50 to 250°C, the molecular ions derived from 5-(1-ethoxyethoxy)-2-methoxy-6-methylsulfanyl-2,3-dihydropyridine and 3-(1-ethoxyethoxy)-2-methylsulfanylpyridine decompose along two main pathways: rupture of the C-O bond in the acetal moiety to give oxonium ions with m/z 73 (in the two cases) and 168 (pyridine derivative) and unexpectedly facile McLafferty rearrangement with elimination of ethoxyethene molecule to produce fragment ions with m/z 173 and 141, respectively. The latter pathway was not observed previously for dihydropyridines and acetals, and it predominates in the fragmentation of 3-(1-ethoxyethoxy)-2-methylsulfanylpyridine. Expulsion of methanol molecule from the molecular ion of 5-(1-ethoxyethoxy)-2-methoxy-6- methylsulfanyl-2,3-dihydropyridine occurred only above 170°C.     

Synthesis and structure elucidation of 3-methoxy-1-methyl-1H-1,2,4,-triazol-5-amine and 5-methoxy-1-methyl-1H-1,2,4,-triazol-3-amine

Previously it was shown that condensation of dimethyl N-cyanodithioimidocarbonate ( 1a ) with methylhydrazine gave predominantly 1-methyl-5-methylthio-1H-,2,4-triazol-3-amine ( 2 ), which was initially identified erroneously as the regioisomer l-methyl-3-methylthio-1H-1,2,4-triazol-5-amine ( 3 ). We have found that reaction of dimethyl N-cyanoimidocarbonate ( 1b ) with methyl hydrazine affords a high yield of 3-methoxy-1-methyl-1H-1,2,4-triazol-5-amine ( 4 ) rather than the regioisomer 5-methoxy-1-methyl-1H-1,2,4-triazol-3-amine ( 5 ). The structure assignment of 4 was confirmed by X-ray crystallographic analysis of the benzenesulfonyl isocyanate adduct 7 . Triazole 5 was obtained after reacting dimethyl N-cyanothioimidocarbonate ( 1c ) with methylhydrazine.     

Synthesis of the stereoisomers of the methylesters of 3-isopropyl-5-methoxy-6-ketoheptanoic acid and of 2-methoxy-4-isopropylhexandioic acid

The four stereoisomers of 3-isopropyl-5-methoxy-6-ketoheptanoic acid methylester and those of 2-methoxy-4-isopropylhexandioic acid methylester were synthesized from R(?)- and S(+)-carvone. The combined data given provide a basis for specific enantiomer assignment to natural product degradation materials.     

Highly stereoselective synthesis of (Z)-3-methoxy-1-methyleneisoindoles via DMAP catalyzed cyclization of methyl 2-alkynylbenzimidates

A DMAP (4-dimethylaminopyridine) catalyzed cyclization of methyl 2-alkynylbenzimidates has been developed, which affords 3-methoxy-1-methyleneisoindoles with excellent Z-stereoselectivity under mild and transition-metal-free conditions. The (Z)-3-methoxy-1-methyleneisoindole products can be converted to corresponding 3-amino-1-methyleneisoindoles, 3-methoxy-isoindoles, 3-methyleneisoindolinones and isoindolinones with high efficiency.     

Synthesis,structure, and antimicrobial activity of methyl (4-alkanoyl-1,5-diaryl-2-hydroxy-3-oxo-2,3-dihydro-1<Emphasis Type="Italic">H</Emphasis>-pyrrol-2-yl)acetates

Reactions of methyl 3,4,6-trioxoalkanoates (3,4-dihydroxy-6-oxo-2,4-alkadienoates) with mixtures of aromatic aldehydes and arylamines or with the corresponding N-(arylmethylidene)anilines afforded methyl (4-alkanoyl-1,5-diaryl-2-hydroxy-3-oxo-2,3-dihydro-1H-pyrrol-2-yl)acetates. The product structure was discussed on the basis of their IR, ¹H NMR, and mass spectra and X-ray diffraction data, and their antimicrobial activity against Staphylococcus aureus P-209 and Escherichia coli M₁₇ was evaluated.     

Novel asymmetric dihetarylethenes derived from N-isopropylindole and thiophene: synthesis and photochromic properties

Novel asymmetric dihetarylethenes, viz., 3-(1-isopropyl-5-methoxy-2-methyl-1H-indol-3-yl)-4-(3-thienyl)furan-2,5-dione and 1-alkyl/aryl-3-(1-isopropyl-5-methoxy-2-methyl-1H-indol-3-yl)-4-(3-thienyl)-1H-pyrrole-2,5-diones, were obtained. These dihetarylethenes exhibit photochromism in solutions. Replacement of the N-methyl group in the indole fragment by the N-isopropyl group imparts photochromic properties to the resulting furan-2,5-dione derivative. The open forms of (N-isopropylindol-3-yl)pyrrole-2,5-diones are characterized by lower quantum yields of fluorescence, and their cyclic forms are thermally more stable.     

Asymmetric synthesis of N-3 substituted phenoxypropyl piperidine benzimidazol-2-one derivatives, potent and selective NOP agonists

The asymmetric synthesis of the potent selective NOP agonist 2-(3-{1-[3-(5-methoxy-2-methyl-phenoxy)-4-methyl-pentyl]-piperidin-4-yl}-2-oxo-2,3-dihydro-benzimidazol-1-yl)-N-methyl-acetamide and analogues was developed. The key step, chiral reduction of methyl isobutyryl acetate, was achieved using a mild Noyori-type asymmetric hydrogenation.     

Transformations of methyl 6-methyl-2-methylsulfanyl-4-oxo-3,4-dihydro-3-pyrimidinylacetate under oxidative conditions

The oxidation of methyl 6-methyl-2-methylsulfanyl-4-oxo-3,4-dihydro-3-pyrimidinylacetate by reagents which oxidized the SMe group to SO₂Me gave the products of the further transformation of the corresponding 2-methylsulfonyl-substituted ester obtained: methyl 5,5-dichloro-6-methoxy-6-methyl-2,4-dioxohexahydro-3-pyrimidinylacetate (using Cl₂ in 70 or 50% MeOH), its mixture (about 1:10) with methyl 6-methyl-2,4-dioxo-1,2,3,4-tetrahydro-3-pyrimidinylacetate (Cl₂ in 30% MeOH) or only to the latter compound (Cl₂ in H₂O, m-ClC₆H₄CO₃H in CHCl₃, H₂O₂ in MeOH). The reaction did not take place with NaOCl in DMF. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 901–905, June, 2006.     

Preparation of single-enantiomer semiochemicals using 2-methoxy-2-(1-naphthyl)propionic acid and 2-methoxy-2-(9-phenanthryl)propionic acid

Enantioresolution of 3-octanol, 6-methyl-5-hepten-2-ol (sulcatol), and 1-octen-3-ol was conducted using (S)-(+)-2-methoxy-2-(1-naphthyl)propionic acid (MαNP acid) and (S)-(+)-2-methoxy-2-(9-phenanthryl)propionic acid (M9PP acid). In each case, the diastereomeric esters obtained were readily separated by HPLC. The stereochemistry of the esters could be assigned from their respective ¹H NMR analyses. Solvolyses of the esters gave enantiopure alcohols and acids. MαNP and M9PP acids displayed almost equivalent properties in ¹H NMR anisotropy. The chiral resolving ability of M9PP acid was slightly superior to that of MαNP acid in HPLC.     

A mild and efficient aza-Diels-Alder reaction of N-benzhydryl imines with trans-1-methoxy-2-methyl-3-trimethylsiloxybuta-1,3-diene catalyzed by Yb(OTf)3

The aza-Diels-Alder reaction of trans-1-methoxy-2-methyl-3-trimethylsiloxybuta-1,3-diene with N-benzhydryl imines in the presence of Yb(OTf)₃ in toluene at room temperature gave the corresponding 2,5-disubstituted 2,3-dihydro-4-pyridones in high yields. This reaction can also be carried out with diene, aldehydes, and amine in a three-component one-pot reaction manner in moderate to high yields under solvent-free conditions. The relationship between Lewis acids and activity, solvents and catalyst loading were studied. Some investigation towards the reaction mechanism was discussed.     

Reaction of 3-methoxy-2-methylphenol with 2-ethoxyvinylphosphonic dichloride

Condensation of 2-ethoxyvinylphosphonic dichloride with 3-methoxy-2-methylphenol in dioxane in the presence of trifluoroacetic acid results in 5,13-dimethoxy-4,14-dimethyl-1-phospha-2,16-dioxatetracyclo[7.7.1.0^3,8.0^10,15]heptadeca-3,5,7,10,12,14-hexaene 1-oxide and 2-hydroxy-7-methoxy-8-methyl-2-oxobenzo[e]-1,2-oxophosphorine.     

Heterocumulenes reactions with organometallic reagents: XX. Quantum-chemical study of concurrent processes of structural reorganization of N-Methyl-2-methoxy- and 2-(methylsulfanyl)buta-2,3-dienimidothioates into pyrroles and/or 2,3-dihydropyridines

Utilizing the MP2/6-31G(d,p) method a quantum-chemical investigation was performed of thermally induced formation of pyrrole and/or 2,3-dihydropyridine structures from methyl N-methyl-2-methoxy- and 2-(methylsulfanyl)buta-2,3-dienimidothioates (1-aza-1,3,4-trienes). According to calculations the pyrrole and dihydropyridine cyclization of a methoxy-substituted 1-aza-1,3,4-triene is both kinetically and thermodynamically virtually equally probable with a little prevalence of the first pathway. The main direction of the structural reorganization of methylsulfanyl-substituted 1-aza-1,3,4-triene is the kinetically controlled formation of the dihydropyridine ring.     

Synthesis of 2-thioxoimidazolines via reaction of 1-unsubstituted 3-aminoquinoline-2,4-diones with isothiocyanates

3-Alkyl/aryl-3-amino-1H,3H-quinoline-2,4-diones react with alkyl/aryl isothiocyanates to give 3a-alkyl/aryl-1,2,3,3a-tetrahydro-9b-hydroxy-2-thioxo-5H-imidazo[4,5-c]quinolin-4(9bH)-ones in high yields. These compounds rearrange in boiling acetic acid or concd hydrochloric acid to give novel 4-(2-aminophenyl)-1H-imidazole-2(3H)-thiones, 1,3-bis(2-(2,3-dihydro-2-thioxo-1H-imidazol-5-yl)phenyl)ureas and minor N-(2-(2,3-dihydro-2-thioxo-1H-imidazol-4-yl)phenyl)acetamides. In the presence of ethanol, the starting compounds rearrange in boiling acetic acid to give ethyl 2-(2,3-dihydro-2-thioxo-1H-imidazol-4-yl)phenylcarbamates. All compounds were characterized by their ¹H, ¹³C, IR and MS spectra and some of them also by ¹⁵N NMR data. The structures of two compounds were supported by single-crystal X-ray diffraction.     

Oxidation of 2-methoxy-6-(1-methylethyl)naphthalene with oxygen

Abstract  

Aerobic oxidation of 2-methoxy-6-(1-methylethyl)naphthalene to hydroperoxide, alcohol, and ketone, is reported. These compounds, particularly 2-acetyl-6-methoxynaphthalene, are important intermediates in naproxen synthesis. N-Hydroxyphthalimide is shown here to be an efficient catalyst for oxidation to the hydroperoxide, 2-methoxy-6-(1-hydroperoxy-1-methylethyl)naphthalene, with a yield of 87%. However, the ketone and alcohol were obtained with lower yields, with a maximum yield of 13% for the ketone and 27% for the alcohol, using N-hydroxyphthalimide and Cu(II) acetylacetonate as a catalyst. The synthesis of the products 2-acetyl-6-methoxynaphthalene and 2-methoxy-6-(1-hydroxy-1-methylethyl)naphthalene via an initial oxidation step to the hydroperoxide followed by a hydroperoxide decomposition step is shown to be more efficient; the ketone and alcohol were obtained from 2-methoxy-6-(1-methylethyl)naphthalene with yields of 40 and 56%, respectively.     

One-step synthesis of diazadihydroacenaphthylene derivatives with an isoxazoline ring, starting from 1-benzylamino-1-methylsulfanyl-2-nitroethenes

At low temperature in trifluoromethanesulfonic acid, 1-benzylamino-1-methylthio-2-nitroethene derivatives form hydroxynitrilium ions (or O-protonated nitrile oxides) observed by NMR. Quenching with water leads to the formation of a reactive nitrile oxide, dipole which undergoes an unexpected INOC reaction leading to new 3-methylsulfanyl-8a,8b-dihydro-5H-1-oxa-2,4-diazaacenaphthylenes.     

Mass spectra of new heterocycles: IX. Main fragmentaion laws of 7-methyl-2-(methylsulfanyl)-3-(1-ethoxyethoxy)-4,5-dihydro-3<Emphasis Type="Italic">H</Emphasis>-azepine and its structural isomers (2,3-dihydropyridine,pyrrole, thiophene) under electron impact

Mass spectra were investigated for the first time of four structural isomers of heterocycles, formerly inavailable 7-methyl-2-(methylsulfanyl)-3-(1-ethoxyethoxy)-4,5-dihydro-3H-azepine, 2,2-dimethyl-6-(methylsulfanyl)-5-(1-ethoxyethoxy)-2,3-dihydropyridine, 1-isopropyl-2-(methylsulfanyl)-3-(1-ethoxyethoxy)pyrrole, and N-isopropyl-N-methyl-3-(1-ethoxyethoxy)-2-thiophenamine prepared from a single linear precursor, adduct of α-lithiated 1-(1-ethoxyethoxy)allene and isopropyl isothiocyanate. All compounds formed a molecular ion (I _rel 1–6%) whose primary fragmentation at the electron impact (70 eV) occurs in two principal directions related to the cleavage of the C-O bonds in the 1-ethoxyethoxy-substituent: with a simple rupture of the bonds C-OEt and C-O(heterocycle) and with the elimination of an ethoxyethene molecule. In the spectra of 4,5-dihydro-3H-azepine and 2,3-dihydropyridine the first fragmentation channel of [M]^+· dominates. The second direction prevailes at the fragmentation of pyrrole and thiophene molecular ions leading to an odd-electrons ion with m/z 171. Further fragmentation of this ion is characteristic of each isomer and resulted in the formation of diagnostic ions providing a possibility of identification of these isomers by mass spectrometry.     

Synthesis,anticancer, and computational studies of 1, 3, 4-oxadiazole-purine derivatives

Theophylline-7-acetic acid (acefylline) ( 3 ) and its derivatives are pharmacologically active compounds and generally recognized as bronchodilators for the treatment of respiratory diseases like acute asthma for over 70 years. In this article, synthesis of 2-((5-((1,3-dimethyl-2,6-dioxo-2,3-dihydro-1H-purin-7(6H)-yl)methyl)-1,3,4-oxadiazol-2-yl)thio)-N-arylacetamides ( 10a-j ) has been reported. All the synthesized derivatives ( 10a-j) were structurally verified by FT-IR, ¹H NMR, ¹³C NMR and evaluated for their anti-cancer (using MTT assay), hemolytic and thrombolytic potential. N-(4-Chlorophenyl)-2-(5-((1,3-dimethyl-2,6-dioxo-2,3-dihydro-1H-purin-7(6H)-yl)methyl)-1,3,4-oxadiazol-2-ylthio)acetamide ( 10g ) was found to be the most active against human liver cancer cell lines (Huh7) having cell viability 53.58 ± 1.28 using 100 μg/mL concentration of compound which was further in-silico modelled to describe the possible mechanistic insights for its anti-proliferative activity. The results of hemolytic and thrombolytic activities indicated that these derivatives were less toxic and hold considerable potential as a drug candidate. 2-(5-((1,3-Dimethyl-2,6-dioxo-2,3-dihydro-1H-purin-7(6H)-yl)methyl)-1,3,4-oxadiazol-2-ylthio)-N-(2-fluorophenyl)acetamide ( 10c ) of the series was found to be least toxic with 0.1% hemolysis relative to ABTS (95.5%) as positive control. 2-(5-((1,3-Dimethyl-2,6-dioxo-2,3-dihydro-1H-purin-7(6H)-yl)methyl)-1,3,4-oxadiazol-2-ylthio)-N-(tetrahydro-2H-pyran-4-yl)acetamide ( 10j ) exhibited potent clot lysis activity (90%) as compared to negative control DMSO (0.57%).