Palladium complexes of P,P and P,S type bidentate ligands: Implication in Suzuki–Miyaura cross-coupling reaction

New palladium complexes of the type [PdCl₂(η²–P∩P)] (1a,1b) and [PdCl₂(η²–P∩S)] (1c,1d) have been synthesised by the reaction of PdCl₂ with P,P and P,S type bidentate ligands in 1:1 mol ratio, where, P∩P = 9,9–dimethyl-4,5-bis(diphenylphosphanyl) xanthene {Xantphos}(a) or bis(2-diphenylphosphanylphenyl)ether{DPEphos}(b); P∩S = 9,9-dimethyl-4,5-bis(diphenyl -phosphanyl) xanthenemonosulfide {Xantphos(S)}(c) or bis(2-diphenylphosphanyl phenyl) ether monosulfide {DPEphos(S)}(d). The complexes are characterized by elemental analyses, mass spectrometry, ¹H, ¹³C and ³¹P NMR spectroscopy together with the single crystal X-ray structure determination of 1a and 1d. The palladium atom in all the complexes occupies the centre of a slightly distorted square planar environment formed by a P atom, a P/S atom and two Cl atoms. The catalytic activities of 1a–1d investigated for Suzuki–Miyaura cross-coupling reactions at room temperature exhibit higher yield of the coupling products than catalysed by PdCl₂ itself. Among 1a–1d, the palladium complexes of bidentate phosphine (1a, 1b) show higher efficacy than their monosulfide analogues (1c, 1d). However, the recycling experiments with the catalysts for a selected coupling reaction between 4-bromobenzonitrile and phenylboronic acid exhibit that 1c and 1d are more efficient than 1a and 1b, which may be due to the donor effect of the P,S ligands during catalytic reaction.     

Palladium complexes of P,P and P,S type bidentate ligands: Implication in Suzuki–Miyaura cross-coupling reaction

New palladium complexes of the type [PdCl₂(η²–P∩P)] (1a,1b) and [PdCl₂(η²–P∩S)] (1c,1d) have been synthesised by the reaction of PdCl₂ with P,P and P,S type bidentate ligands in 1:1 mol ratio, where, P∩P = 9,9–dimethyl-4,5-bis(diphenylphosphanyl) xanthene {Xantphos}(a) or bis(2-diphenylphosphanylphenyl)ether{DPEphos}(b); P∩S = 9,9-dimethyl-4,5-bis(diphenyl -phosphanyl) xanthenemonosulfide {Xantphos(S)}(c) or bis(2-diphenylphosphanyl phenyl) ether monosulfide {DPEphos(S)}(d). The complexes are characterized by elemental analyses, mass spectrometry, ¹H, ¹³C and ³¹P NMR spectroscopy together with the single crystal X-ray structure determination of 1a and 1d. The palladium atom in all the complexes occupies the centre of a slightly distorted square planar environment formed by a P atom, a P/S atom and two Cl atoms. The catalytic activities of 1a–1d investigated for Suzuki–Miyaura cross-coupling reactions at room temperature exhibit higher yield of the coupling products than catalysed by PdCl₂ itself. Among 1a–1d, the palladium complexes of bidentate phosphine (1a, 1b) show higher efficacy than their monosulfide analogues (1c, 1d). However, the recycling experiments with the catalysts for a selected coupling reaction between 4-bromobenzonitrile and phenylboronic acid exhibit that 1c and 1d are more efficient than 1a and 1b, which may be due to the donor effect of the P,S ligands during catalytic reaction.     

Simple and condensed β-lactams-I : The application of diketene in β-lactam synthesis. The synthesis and functional group manipulations of diethyl 3-acetyl-4-oxoazetidine-2,2-dicarboxylates

Acylation of the N-substituted diethyl aminomalonates 3a–3d with diketene furnished the ring tautomers 6a–6d of the expected acetoacetyl derivatives 5. By treatment with iodine and sodium ethoxide compounds 6a–6d are smoothly converted into the β-lactam derivatives 2a–2d. Deethoxycarbonylation of the ethylene ketals 7a–7d of the latter furnishes mixtures of the corresponding diastereomeric monoesters 8 and10. The ethoxycarbonyl groups of the trans esters 8 are more reactive than those of the cis isomers 10. This permits, under appropriate conditions, selective alkaline hydrolysis and NaBH₄ reduction of the trans esters 8 in the presence of the cis esters 10. Reduction of the cis ester 10c under more forceful conditions furnishes the trans hydroxymethyl derivative 11c.     

Oxide der 1,2,3-thiadiazole—III : Darstellung und eigenschaften der cycloalkeno-1,2,3-thiadiazole und ihrer mono- und trioxide

Cycloalkeno-1,2,3-thiadiazoles (3a–d) can be prepared from cycloalkanone-tosylhydrazones (2a–d) by treatment with SOCl₂. Oxidation of 3a–d with peracetic acid yields 1,2,3-thiadiazole-2-oxides (4a–d) and 1,2,3-thiadiazole-1,1,2-trioxides (5a–c). A characterisation of these three classes of compounds is performed by discussion of their UV, IR, NMR and mass spectra.     

Synthesis and evaluation of in vitro antibacterial activity of novel 2,5-disubstituted-1,3,4-thiadiazoles from fatty acids

A series of new 1-（alkenoyl/hydroxyalkenoyl）-4-benzoyl-thiosemicarbazides 2a-d and 2-benzamide-5-alkenyl/hydroxyalk- enyl-1,3,4-thiadiazoles 3a-d were synthesized from fatty acid hydrazides. Structure of all these compounds was confirmed by IR, IH NMR, Sac NMR, mass spectra and elemental analysis. The bioassay results indicate that some compounds 2e, 2d, 3e and 3d have good antibacterial activity.     

An efficient synthesis of enantiomerically pure 2-[(2R)-arylmorpholin-2-yl]ethanols,key intermediates of tachykinin receptor antagonist

We report herein an efficient and practical synthetic method for the preparation of enantiomerically pure 2-[(2R)-arylmorpholin-2-yl]ethanols 1a–d, key intermediates of tachykinin receptor antagonist. Sharpless catalytic asymmetric dihydroxylation of 4a–d was employed to introduce the required absolute stereochemistry, and cyclization of 7a–d was accomplished by the Mitsunobu reaction.     

Stereoselective intramolecular cycloadditions of homochiral N-alkenoyl aryl azides

Starting from the commercially available (S)-1-phenylethylamine and l-alanine benzylester, we synthesised the homochiral N-alkenoyl aryl azides 2a–2d. The intramolecular cycloaddition of unsubstituted 2a and 2b gave enantiopure 3,3a-dihydro-1,2,3-triazolo[1,5-a][1,4]benzodiazepine-4(6H)-ones 3a, 3b, 4a and 4b, while phenyl-substituted 2c and 2d gave enantiopure 1,1a-dihydro-2H-azirino[2,1-c][1,4]benzodiazepine-4(6H)-ones 5c, 5d, 6c and 6d.     

Application of pig liver esterase catalyzed transesterification in organic media to the kinetic resolution of glycerol derivatives

The PLE/MPEG catalyzed transesterification of the glycerol ketals rac-1a and rac-1d–f with vinyl propionate in toluene proceeded with good selectivities (E=24–34) and gave the enantiomerically enriched S-alcohols 1a and 1d–f, and the S-esters 2a and 2d–f. High selectivities (E=99 and E≥200) were observed in the transesterification of the glycerol ether rac-3 and its desoxy analog rac-5, both having a secondary hydroxy group, with PLE/MPEG. In transesterifications in organic media PLE exhibited a much higher enantioselectivity than in hydrolysis in water.     

Simple Synthesis of Modafinil Derivatives and Their Anti-inflammatory Activity

Simple synthesis of modafinil derivatives and their biological activity are described. The key synthetic strategies involve substitution and coupling reactions. We determined the anti-inflammatory effects of modafinil derivatives in cultured BV2 cells by measuring the inhibition of nitrite production and expression of iNOS and COX-2 after LPS stimulation. It was found that for sulfide analogues introduction of aliphatic groups on the amide part (compounds 11a-d) resulted in lower anti-inflammatory activity compared with cyclic or aromatic moieties (compounds 11e-k). However, for the sulfoxide analogues, introduction of aliphatic moieties (compounds 12a-d) showed higher anti-inflammatory activity than cyclic or aromatic fragments (compounds 12e-k) in BV-2 microglia cells.     

Oxidative cyclization of 2-pyrrolidinyl-acetamide and 2-pyrrolidinyl-propionamide local anaesthetics

2 - Pyrrolidinyl - acetamide and -propionamide local anaesthetics (1a–d) on oxidation with mercuric acetate, potassium hexacyanoferrate(III) and potassium permanganate underwent oxidative cyclization to give new bicyclic compounds, hexahydro - 1H - pyrrolo[1,2 - a]imidazolin - 2 - ones (2a–d). The propionamides (1c–d) yielded mixtures of the two possible diastereoisomers of 2c and 2d. These were separated; in solution and above their melting points they epimerized via ring opening and reclosure between the 7a-carbon and 1-nitrogen atoms.     

Highly diastereoselective alkylation,acylation and aldol condensation of cis- and trans-(N-acyloyl)hexahydrobenzoxazolidin-2-ones

The potential of hexahydrobenzoxazolidinones 1a–d as chiral auxiliaries was explored. N-Acylation of 1a–d, 2a–d and 3a–d was followed by methylation and benzylation via the corresponding sodium enolates generated by treatment with NaHMDS. Diastereoselectivities of 98% or higher were observed. The absolute configuration of the newly created stereogenic center was established by chemical correlation with 2-benzyl-1-propanol. The stereochemical results are congruent with addition to the electrophile from the less hindered face of a (Z)-configured enolate, the sodium cation being coordinated by both carbonyl oxygens of the substrate. cis- and trans-N-Propionyl derivatives 2a–d were treated with Bu₂BOTf/Et₃N to give dialkylboron enolates 6a–d, which were then reacted with acetaldehyde and benzaldehyde. ¹H and ¹³C NMR analyses showed the formation of a single diastereomeric aldol addition product, whose relative configuration was ascertained as syn from the measurement of the ³J_{H(2′)/H(3′)} coupling constants, and whose absolute configuration was determined by X-ray crystallographic analysis. The results are rationalized in terms of a Zimmerman–Traxler transition state, with a (Z)-configured enolate where boron is coordinated to the aldehyde carbonyl rather than the oxazolidinone carbonyl. Substrate 2a was also reacted with acyl chlorides via the sodium enolate (NaHMDS). The effect of reaction conditions on O- versus C-acylation, as well as the influence of solvent and additives on diastereoselectivity, are discussed.     

Kinetic resolution of 1-(benzofuran-2-yl)ethanols by lipase-catalyzed enantiomer selective reactions

Kinetic resolution of racemic 1-(benzofuran-2-yl)ethanols rac-1a–d was performed by lipase-catalyzed enantiomer selective acylation (E≫100) yielding (1R)-1-acetoxy-1-(benzofuran-2-yl)ethanes (R)-2a–d and (1S)-1-(benzofuran-2-yl)ethanols (S)-1a–d in highly enantiopure form. The degree of enantiomer selectivity for enzymatic alcoholysis/hydrolysis processes starting from racemic 1-acetoxy-1-(benzofuran-2-yl)ethane rac-2 was also tested under various conditions including supercritical CO₂ medium. Racemization-free lipase-catalyzed ethanolysis of the (1R)-1-acetoxy-1-(benzofuran-2-yl)ethanes (R)-2a–d yielded almost quantitatively the enantiopure (1R)-1-(benzofuran-2-yl)ethanols (R)-1a–d.     

New benzimidazole derivatives: Design,synthesis, docking,and biological evaluation

The aim of this study was to synthesize novel enaminonitrile derivatives starting from 2-aminobenzimidazole and utilize this derivative for the preparation of novel heterocyclic compounds and assess their function for biological activity screening. The key precursor N-(1H-benzo[d]imidazol-2-yl)carbonohydrazonoyl dicyanide (2) was prepared in pyridine by coupling of diazotized 2-aminobenzimidazole (1) with malononitrile. Compound 2 was subjected to react with various secondary amines such as piperidine, morpholine, piperazine, diphenylamine, N-methylglucamine, and diethanolamine in boiling ethanol to give the acrylonitriles (2Z)-2-((1H-benzo[d]imidazol-2-yl)diazenyl)-3-amino-3-(piperidin-1-yl)acrylonitrile (3), (2Z)-2-((1H-benzo[d]imidazol-2-yl)diazenyl)-3-amino-3-morpholinoacrylonitrile (4), (2Z)-2-((1H-benzo[d]imidazol-2-yl)diazenyl)-3-amino-3-(piperazin-1-yl)acrylonitrile (5), (2Z)-2-((1H-benzo[d]imidazol-2-yl)diazenyl)-3-amino-3-(diphenylamino)acrylonitrile (6), (2Z)-2-((1H-benzo[d]imidazol-2-yl)diazenyl)-3-amino-3-(methyl((2S,3R,4R,5R)-2,3,4,5,6-pentahydroxyhexyl)amino)acrylonitrile (7), and (2Z)-2-((1H-benzo[d]imidazol-2-yl)diazenyl)-3-amino-3-(bis(2-hydroxyethyl)amino)acrylonitrile (8), respectively. It has been found that the behaviour of nitrile derivative 2 towards hydrazine hydrate to the creation of 4-((1H-benzo[d]imidazol-2-yl)diazenyl)-1H-pyrazole-3,5-diamine (9). The reaction of malononitrile with compound 2 in an ethanolic solution catalyzed with sodium ethoxide afforded 4-amino-1-(1H-benzo[d]imidazol-2-yl)-6-imino-1,6-dihydropyridazine-3,5-dicarbonitrile (11). Moreover, malononitrile reacted with 7 in a boiling ethanolic sodium ethoxide solution to give 2-(5-((1H-benzo[d]imidazol-2-yl)diazenyl)-4-amino-6-(methyl((2S,3R,4R,5R)-2,3,4,5,6-pentahydroxyhexyl)amino)pyrimidin-2-yl)acetonitrile (14). Heating 7 in boiling acetic anhydride and pyridine afforded (2R,3R,4R,5S)-6-(((1E)-2-((1-acetyl-1H-benzo[d]imidazol-2-yl)diazenyl)-1-(N-acetylacetamido)-2-cyanovinyl)(methyl)amino)hexane-1,2,3,4,5-pentayl pentaacetate (15). When compound 15 is heated for a long time in refluxing DMF including a catalytic of TEA, cyclization occurs to give the corresponding (2R,3R,4R,5S)-6-((1-acetyl-3-((1-acetyl-1H-benzo[d]imidazol-2-yl)diazenyl)-4-amino-6-oxo-1,6-dihydropyridin-2-yl)(methyl)amino)hexane-1,2,3,4,5-pentayl pentaacetate (16). In addition, triethyl orthoformate was reacted with compound 7 in the presence of acetic anhydride to afford the corresponding ethoxymethyleneamino derivative (2R,3R,4R,5S)-6-(((1E)-2-((1-acetyl-1H-benzo[d]imidazol-2-yl)diazenyl)-2-cyano-1-(((E) ethoxymethylene)amino)vinyl)(methyl)amino)hexane-1,2,3,4,5-pentayl pentaacetate (17). Also, it has been found that heating a mixture of 7 with DMF/DMA in anhydrous xylene yielded compound (1E)-N'-((1E)-2-((1H-benzo[d]imidazol-2-yl)diazenyl)-2-cyano-1-(methyl((2S,3R,4R,5R)-2,3,4,5,6-pentahydroxyhexyl)amino)vinyl)-N,N-dimethylformimidamide (18). In addition, compound 7, when reacted with several acid anhydrides, allowed the matching phthalimide derivatives 19–26. The results showed that compound 14 has significantly higher ABTS and antitumor activities than the other compounds. Molecular modelling was also studied for compounds 22 and 24. The viability of four many cell lines—the African green monkey kidney epithelial cells (VERO), human breast adenocarcinoma cell line (MCF-7), human lung fibroblast cell line (WI-38), and human hepatocellular liver carcinoma cell line (HepG2) was examined to determine the antitumor activities of the newly synthesized compounds. Also, it was found that compounds 9, 11, 15, 16, 22, 23, 24 and 25 are strong against HepG2 cell lines, while 16, 22, and 25 are strong against WI-38 cell lines. Moreover, it was also found that compounds 16 and 22 are strong against VERO cell lines. On the other hand, compounds 7, 14, 15, 16, and 22 are strong while the rest of the other compounds are moderate against the MCF-7 cell line. The result of docking showed that compound 24 got stabilized inside the pocket with a very promising binding score of ? 8.12 through hydrogen bonds with Arg184 and Lys179, respectively.     

Vicinal phenyl group shift in the lead tetraacetate and related oxidations of 5,5,5-triphenyl-1-pentanol

In the lead tetraacetate and heavy metal-bromine oxidations of 5,5,5-triphenyl-1-pentanol 1d, the major cyclization product obtained was the rearranged 2,2,3-triphenyltetrahydro-2H-pyran 11d, resulting from homolytic and heterolytic 1,2-phenyl group shift (the latter only in the lead tetraacetate reaction) in the respective intermediate species with electron deficient δ-carbon 4d and 6d.     

Cycloadditionsreaktionen des tetrachlor-o-benzochinons mit fulvenen

Tetrahloro-o-benzoquinone (1) reacts with 6,6-diphenyl- and 6,6-bis (p-methoxyphenyl)fulvene resp. (2a, b) forming [π4 + π2]-cycloadducts of the dihydrobenzodioxin type (4a, b); besides 6,6-dimethyl- and 6,6-pentamethylenefulvene (2c, d) yield dimeric 1:1-adducts (7c, d; 8c, d), which originated from primarily formed [π4 + π6]-cycloadducts of the dihydrobenzo [b]cyclopenta [e] [1·4]dioxepin type (6c, d) through a Diels-Alder reaction. The structures of 7c, d and 8c have been clarified through X-ray crystallography. Some investigations concerning the mechanism are reported.     

Vapor phase phototransposition of pyrazine deuterium labeling studies

2,5-Dideuteriopyrazine (1-2,5-d₂) and 2,6-dideuteriopyrazine (1-2,6-d₂) phototranspose in the vapor phase to mixtures of 4,6-dideuteriopyrimidine (2-4,6-d₂) and 2,5-dideuteriopyrimidine (2-2,5-d₂) or 4,5-dideuteropyrimidine (2-4,5-d₂) and 2,4-dideuteriopyrimidine (2-2,4-d₂), respectively. In each case, a trace quantity of a dideuteriopyridazine (7-d₂) photoproduct was also observed. These products are consistent with a diazaprefulvene mechanism involving, 2,6-bonding, one or two nitrogen migrations, and rearomatization.     

Palladium catalyzed insertion of carbon monoxide into benzyl-tetrahydroisoquinolines : A new synthesis of berbine alkaloids

A new total synthesis of the berbine alkaloid ring system has been achieved. Palladium catalyzed insertion of carbon monoxide into the 1 - (2 - bromobenzyl) - substituted - 1,2,3,4 - tetrahydroisoquinolines (1a–1d) by the use of catalytic amounts of palladium diacetate and triphenylphosphine in the presence of tri-n-butylamine afforded the berbin-8-ones (2a–2d) which, on reduction with lithium aluminium hydride gave the berbines (±)-berbine 3a, (±)2,3-dimethoxyberbine 3b, (±)-xylopinine 3c and (±)-pseudoepitetrahydroberbine 3d.     

Aluminum and zinc complexes supported by functionalized phenolate ligands: Synthesis, characterization and catalysis in the ring-opening polymerization of ε-caprolactone and rac-lactide

A series of aluminum and zinc complexes supported by functionalized phenolate ligands were synthesized and characterized. Reaction of 2-(3,5-R₂C₃N₂)C₆H₄NH₂ (R = Me, Ph) with salicylaldehyde or 3,5-di-tert-butylsalicylaldehyde afforded 2-((2-(1H-pyrazol-1-yl)phenylimino)methyl)phenol derivatives 2a-2d. Treatment of 2a-2d with an equiv. of AlR²₃ (R² = Me, Et) gave corresponding aluminum aryloxides 3a-3e, while reaction with an equiv. of ZnEt₂ afforded zinc aryloxides 4a-4d. Treatment of 2c with 0.5 equiv. of ZnEt₂ formed diphenolato zinc complex 5. All new compounds were characterized by ¹H and ¹³C NMR spectroscopy and elemental analyses. The structures of complexes 3a, 4a and 5 were further characterized by single crystal X-ray diffraction techniques. The catalytic activity of complexes 3-5 toward the ring-opening polymerization of ε-caprolactone was studied. The zinc complexes (4a-4d) exhibited higher catalytic activity than the aluminum complexes (3a-3e). The diphenolato zinc complex 5 showed lower catalytic activity than the ethylzinc complexes 4a-4d. The aluminum complex (3b) is inactive to initiate the ROP of rac-lactide, while the zinc complex (4d) is active initiator for the ROP of rac-lactide, giving atactic polylactide.     

Utilization of 2-ylidene-4-thiazolidinones in the synthesis of heterocyclic compounds. Part I: Synthesis of pyrazoles

2-Ylidene and 2,5-diylidene-4-thiazolidinones 2a–d were synthesized and converted into pyrazole derivatives 4a–d by reaction with hydrazine hydrate. A mechanism of this novel conversion is suggested.     

Triterpenoid constituents of thai medicinal plants—II : Isomeric aglaitriols and aglaiondiol

Three new tetracyclic triterpenes, aglaiondiol and two isomers of aglaitriol, were isolated from the light petroleum extracts of leaves of Aglaia odorata. The isomers of aglaitriol (2) were separated by fractional crystallisation of the triacetates which on hydrolysis gave the epimers 2c and 2d. The structures of 2c, 2d and aglaiondiol (3) have been established by interconversion with aglaiol (1).