Synthesis of Diacetals of 2,2-bis(Hydroxymethyl)-1,3-Propanediol Under Microwave Irradiation

Nine diacetals (3a-i) of 2,2-bis(hydroxymethyl)-1,3-propanediol (2) were prepared by condensation of aldehydes with 2 under microwave irradiation in the presence of TsOH without solvent.     

Zur Reaktivität des neuen Codimeren aus Malonitril und Cyanessigester bzw. dimeren Cyanessigester gegenüber Benzilen

Condensation of benzils with 3-amino-2,4-dicyano-crotonic-ester (2a, b) and dimer cyanoacetate (2c, d) resp. leads to 4,5-diaryl-3-pyrroline-2-ylidenecyanoacetates3a-m. It can be shown by¹³C-spectroscopy that in the monosubstituted benzil1c the carbonyl function adjacent to the unsubstituted phenyl reacts with the methylene group of2a orb. With aqueous alkaline the pyrrolines3 rearrange to pyrrolidinones4a-i.¹H-NMR-CIDNP experiments support the assumption of a partial radical character of this rearrangement.

     

Gould-Jacobs reaction of 6-amino-2,3-diphenylquinoxaline

Summary Catalytic hydrogenation of 2,3-diphenyl-6-nitroquinoxaline led to the corresponding amine1 which in turn afforded products3a-i on reaction with alkoxymethylene derivatives2a-i. Thermal cyclization of3b and3f yielded substituted pyrazinoquinolones5b and5f, respectively. Optimal conditions for the successful hydrolysis of ester5b were found. The structures of all products were deduced from their IR, UV,¹H, and¹³C NMR spectroscopic data.Dedicated to Prof.F. Sauter on the occasion of his 65th birthday     

3-Aminopyrazolo[4,3-c]pyridine-4,6-dione as a precursor for novel pyrazolo[4,5,1-ij][1,6]naphthyridines and pyrido[4’,3’:3,4]pyrazolo[1,5-a]pyrimidines

The versatile, 3-aminopyrazolo[4,3-c]pyridine-4,6-dione (2) was synthesized and allowed to react with aldehydes, aryldiazonium chlorides, chalcones and enaminones to afford regioselectively the novel pyrazolo[4,3-c]pyridine derivatives 4a-c, pyrazolo[4,5,1-ij][1,6] naphthyridines 9a-d and pyrido[4’,3':3,4]pyrazlo[1,5-a]pyrimidines 19a-i. The structure of all the newly synthesized compounds was assigned from elemental analysis and spectral data. Also, the mechanistic aspects for the formation of the newly synthesized compounds is discussed.     

Synthesis of adamantane derivatives—43: 1,3-Dipolar cycloaddition reactivity of methyleneadamantane derivatives with substituted benzonitrile oxides

The 1,3-dipolar cycloaddition reactivity and regioselectivity of methyleneadamantane 1, ethyl adamantylideneacetate 7a, adamantylideneacetonitrile 7b and ω-methoxymethyleneadamantane 7c with substituted benzonitrile oxides 3a-i were calculated by CNDO/2 method using the perturbation equation derived by Klopman and Salem. The calculation predicted an exclusive formation of adamantan - 2 - spiro - 5' - 3' - aryl - Δ²' - isooxazoline 4a-i in the reactions of 1, 7a and 7b with 3a-i, and a formation of 67–69:33-31 mixture of 4a-i and isomeric 5a-i in the reaction of 7c with 3a-i. The predicted exclusive formation of 4a-i were experimentally observed in the reactions of 1,7a and 7b with 3a-i generated from 2a-i with Et₃N or thermally, but the reaction of 7c with 3a did not afford the corresponding adducts. A considerably higher reactivity of CN triple bond than CC double bond was observed in the reaction of 7b with 3a and 1,2,4-oxadiazole derivative 11 was obtained as the major product.     

A Simple and Eco-Compatible One-Pot Synthesis of New Symmetrical Dithiocarbamate Podands and Their Dynamic NMR Studies

Abstract

A simple and eco-compatible synthesis of podands as 4_a-i is performed using amines (3_a-c ), CS₂, and dichlordiamides (DCDs) (2_{a, c} ) in the absence of a catalyst in water. Three reacting DCDs (2_a-c ) were obtained in the reaction of aromatic diamines (1_{a, c} ) with chloroacetyl chloride. Dynamic NMR spectroscopic data of three series of podands (4_a-c , 4_d-f , and 4_g-i ) are discussed and their free energies of activations are calculated (ΔG ^≠ _c s) at coalescence temperatures. The ΔG ^≠ _c of these podands were attributed to conformational isomerization in the range of 14.7–17 kcal/mol due to rotation and resonance effects about the thioamide C?N bond.

[Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional figures.]     

A Facile Synthesis of Ethyl-2-Methyl-5h-Chromeno[3,4-c]Pyridine-1-Carboxylates

4-Chloro-2H-3-chromene carbaldehydes (2a-i) on reaction with ethyl-3-aminocrotonate 3 gives ethyl-2-methyl-5H-chromeno[3,4-c]pyridine- 1- carboxylates 4a-i in good yields.     

New Biologically Active N-(Tetrahydrobenzothienopyrimidin-4-YL)-Amino Acids,Thiourethane, Sulfonamides and Related Compounds

Abstract

Some derivatives of thieno[2,3-d]pyrimidine containing amino acids 3a-i, imidazoles 4a-f, isothiocyanate 5, thiourethane 6, triazine 8, pyrimidine 10, sulphonamides 13a-d, 14, pyrazole 16 and pyrazolone 17 were synthesized. The structural assignments of the new compounds were based on analytical, spectroscopic measurements and chemical reactions. Some of the obtained compounds showed interesting antimicrobial activities.     

New soluble aromatic polyamides containing ether linkages and laterally attached p-terphenyls

Two series of new polyamides containing flexible ether linkages and laterally attached side rods (3a-i and 4a-i) were synthesized from 2^′,5^′-bis(4-aminophenoxy)-[1,1^′;4^′,1^″]terphenyl (1a) and 2^′,5^′-bis(4-amino-2-trifluoromethylphenoxy)-[1,1^′;4^′,1^″]terphenyl (1b), respectively, with various aromatic dicarboxylic acids by the direct phosphorylation polycondensation. The polymers were produced with high yields and moderate to high inherent viscosities (0.41-0.97 dl/g) that corresponded to weight-average molecular weights (by size exclusion chromatography) of 47,000-65,000. Except for some polyamides that derived from rigid diacids, the obtained polyamides were readily soluble in aprotic polar solvents, such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc), and could afford flexible and tough films via solvent casting. The polymer films cast from DMAc solutions possessed tensile strengths of 85-106 MPa and initial moduli of 1.82-2.96 GPa. These polyamides showed glass-transition temperatures (T_g) in the range of 206-263 °C (by DSC) and softening temperatures (T_s) in the range of 211-253 °C (by TMA). Decomposition temperatures (T_d) for 10% weight loss all occurred above 400 °C (by TGA) in both nitrogen and air atmospheres. The polyamides 4a-i derived from trifluoromethyl-substituted diamine 1b generally showed a higher solubility, T_g and T_s but lower thermal stability as compared to the analogous polyamides 3a-i based on diamine 1a.     

Phenylselenium Trichloride,Preparation and Use as a Vinylic Chlorination Reagent

Phenylselenium trichloride (1) is prepared from benzeneseleninic acid (2) and thionyl chloride and used to effect vinylic chlorination, viz. the conversion of 3-chloro-2-chloromethyl-1-propene (4) into 2-chloromethyl-1,3-dichloro-propene (3).     

Dihaloheptasilanes X2Si[SiMe(SiMe3)2]2 as potential precursors for silylenes, disilenes and cyclotrisilanes

The synthesis of new dihaloheptasilanes X₂Si[SiMe(SiMe₃)₂]₂ (X=Cl: 2, Br: 3, I: 4) was performed by treating dihydridoheptasilane 1 (X=H) with CCl₄, HCBr₃ or HCI₃. Difluoroheptasilane 6 (X=F) was prepared from either diphenylheptasilane 5 (X=Ph), triflic acid (HOTf), and LiF with concomitant isolation of heptasilanes 7 (X₂=Ph and OTf), 8 (X₂=F and Ph), and 9 (X₂=F and OTf), or by halogen exchange from 2 using ZnF₂. Crystal structures of 2, 3, 4, and 5 are reported. The reduction of 2 with Li, Na or KC₈ resulted in the instantaneous formation of various cyclotrisilanes, while the reduction of 3 gave exclusively the unsymmetrical cyclotrisilane (E)-1-methyl-2,3,3-tris[methylbis(trimethylsilyl)silyl]-1,2-bis(trimethylsilyl)cyclotrisilane 10, which was characterized by X-ray crystallography. A mechanism for the formation of cyclotrisilanes via a silylsilylene-to-disilene rearrangement is proposed. Attempts to prepare the tetradekasilane [(Me₃Si)₂MeSi]₂SiH–SiH[SiMe(SiMe₃)₂]₂ (by reductive dehalogenation of either HClSi[SiMe(SiMe₃)₂]₂ 13 or HISi[SiMe(SiMe₃)₂]₂ 18), or the tetradekasilane [(Me₃Si)₂MeSi]₂SiPh–SiPh[SiMe(SiMe₃)₂]₂ (by reductive dehalogenation of either PhClSi[SiMe(SiMe₃)₂]₂ 14 or PhISi[SiMe(SiMe₃)₂]₂ 19) as precursors for the disilene [(Me₃Si)₂MeSi]₂Si=Si[SiMe(SiMe₃)₂]₂ failed. 14 was characterized by X-ray crystallography. All compounds described were also characterized by multinuclear NMR spectroscopy and elemental analysis.     

Design,synthesis, and biological evaluation of novel substituted imidazo[2,1-a]isoindole derivatives as antibacterial agents

An efficient protocol has been developed for the synthesis of fused imidazo[2,1-a]isoindol-5-ones (2a–d) from 2-iodo benzoic acids and N,N-carbonyldiimidazole (CDI) using one-pot Pd-catalyzed C?C bond coupling. The reaction of imidazo[2,1-a]isoindol-5-one (2a–d) with substituted α-bromo ketones in toluene afforded corresponding imidazo[2,1-a]isoindolium derivatives (3a–i) in good yields. The structures of the title compounds were well established on the basis of infrared (IR), ¹H NMR, carbon-13 nuclear magnetic resonance (¹³C NMR), mass spectral data, and elemental analysis (C, H, and N). In vitro antibacterial results revealed that, the compounds 3b and 3i were found to possess an excellent broad spectrum of inhibiting potency against all the tested bacterial strains with minimum inhibitory concentration values ranging from 3.125 to 25?µg mL^?1.     

Synthesis,Characterization, and Thermal and Antibacterial Studies of Diorganotin(Iv) Derivatives of Amino Acids

Abstract

Six diorganotin(IV) derivatives of α-aminoacids with general formulae [(CH₃)₂ SnAACl]₂ and [(CH₃CH₂CH₂CH₂)₂SnAACl]₂, where AA = L-alaninate, L-phenylalaninate, and L-isoleucinate, have been synthesized by reacting dimethyltin(IV) dichloride (M) and dibutyltin(IV) dichloride (B) with L-alanine (A) or L-phenylalanine (PA) or L-isoleucine (I) using acetonitrile as the solvent and designated as MA, MPA, MI, BA, BPA, and BI. These complexes have been characterized by elemental analysis, infrared (IR), ¹H NMR, ¹³C NMR, and ¹¹⁹Sn NMR spectroscopy. Thermal studies of all of the synthesized complexes were also carried out using thermogravimetric (TG) and differential scanning calorimetry (DSC) techniques. The thermal decomposition mechanisms were similar for MA, BA, MI, and BI and occurred in one step, while in compounds MPA and BPA, it occurred in two consecutive steps. The TG curves of MPA and BPA suggest the loss of the ligand (AA) in the first step, with probable formation of a tin oxide R₂SnO as an intermediate, and in the second step, free tin is obtained, similar to MA, BA, MI, and BI, in accordance with the stoichiometry of the related derivatives. The diorganotin(IV) complexes have also been screened for their antibacterial activity against Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa. The minimum inhibitory concentration values of these complexes show enhanced activity.     

Condensed thiazoles,I: Synthesis of 5,7-disubstituted thiazolo[4,5-d]pyrimidines as possible anti-HIV,anticancer, and antimicrobial agents

Summary A convenient and simple synthesis of 5-mercapto-3-phenyl-2-thioxo-2,3-dihydrothiazolo-[4,5-d]pyrimidin-7(6H-one(2) and its 5,7-dichloro (3), 5,7-diazido (4), 5,7-diamino (5), 5,7-dimerapto (6), 5,7-dimethylthio (7), and 6-methyl-5-methylthio (8) derivatives is described. The prepared compounds were screened for theirin vitro anti-HIV, anticancer, antibacterial and antifungal activities.

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Kondensierte Thiazole, 1. Mitt.: Synthese von 5,7-disubstituierten Thiazolo[4,5-d]pyrimidinen als potentielle anti-HIV, anticancerogene und antimikrobielle Verbindungen

Zusammenfassung Die Synthese von 5-Mercapto-3-phenyl-2-thioxo-2,3-dihydrothiazolo[4,5-d-pyrimidin-7(6H)-on (2) und seiner 5,7-dichloro-(3), 5,7-diazido-(4), 5,7-dimanio-(5), 5,7-dimercapto-(6), 5,7-dimethylthio- (7) und 6-methyl-5-methylthio-Derivaten (8) wird beschrieben. Die hergestellten Verbindungen wurden auf ihrein vitro anti-HIV, anticancerogenen, antibakteriellen und antimykotischen Aktivitäten geprüft.

     

A highly efficient,simple, and ecofriendly microwave-induced synthesis of indolyl chalcones and pyrazolines

Abstract

One-pot synthesis of indolyl chalcones (3a–c) employing indole-3-carboxaldehyde (1) and heteroaryl active methyl compounds (2a–c) under microwave irradiation is described. The indolyl chalcones (3a–c) are transformed into medicinally important pyrazolines (5a–f) using different hydrazines. Application of microwave irradiation leads to many remarkable advantages, such as solvent- and catalyst-free reaction conditions, simple work up procedure, shorter reaction time, in addition to ecofriendly ‘green chemistry’ economical and environmental impacts.     

Water-mediated,green, and efficient synthesis of bisquinolones under catalyst-free conditions

Water-mediated, green, and efficient synthesis involving condensation of 4-hydroxy-1-methylquinoline-2(1H)-one (3) with different aromatic and heterocyclic aldehydes (4a–n) leading to 3,3′-(arylmethylene)-bis-(4-hydroxy-1-methylquinolin-2(1H)-one) 5(a–n) under catalyst-free conditions is described. This reaction has an easy workup without using column chromatography and provides excellent yields of the products in shorter reaction times. It does not require any catalyst and uses water as the medium which is the greenest solvent. 3 required in this work was itself obtained by condensation of N-methylaniline (1) with malonic acid (2) in the presence of POCl₃ using a previously reported procedure.     

Benzimidazole condensed ring systems,VI: Organic azides in heterocyclic synthesis,X: Synthesis of some substituted pyrimido[1,6-a]-benzimidazoles as potential antimicrobial agents

Summary The syntheses of 3-chloro derivatives of 2-alkyl-pyrimido[1,6-a]benzimidazol-1(2H)-ones2a, b as well as of 4,4-dichloro and 4,4-dibromo derivatives of 2-alkylpyrimido[1,6-a]benzimidazole-1,3(2H,4H)-diones3 a, b and4 are reported. Methods for converting some of the chloro compounds to azido (5, 6), amino (8), morpholino (9 a,10,11), piperidino (9 b), cyano (12), and methoxy (13) derivatives of the adopted tricyclic system are also described.

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Kondensierte Ringsysteme des Benzimidazols, 6. Mitt.: Organische Azide in der Heterocyclen-Synthese, 10. Mitt.: Synthese von substituierten Pyrimido[1,6-a]benzimidazolen als mögliche antimikrobielle Wirkstoffe

Zusammenfassung Die Synthese von 3-Chlor-2-alkyl-pyrimido[1,6-a]benzimidazol-1(2H)-onen (2 a, b) und von 4,4-Dichlor- und 4,4-dibrom-pyrimido[1,6-a]benzimidazol-1,3(2H,4H)-dionen (3 a, b, 4) wird beschrieben. Diese Verbindungen lassen sich zu den entsprechenden Azido- (5, 6), Amino- (8), Morpholino- (9 a, 10, 11), Piperidino- (9 b), Cyano- (12) und Methoxy- (13) Derivaten umwandeln.

     

Stereoselective synthesis of the lichen metabolite, (+) montagnetol and its congeners as antimicrobial agents

Abstract

In view of structural diversity, (+) montagnetol, the major metabolite of the fruticose lichen, Roccella montagnei was synthesized along with three of its congeners by employing highly efficient protocols. (+) Montagnetol (2?R, 3S; 11) and (-) montagnetol (2S, 3R; 5) were synthesized in 7 and 9 steps, respectively, from L-ascorbic acid. The two new congeners 3 (2?R, 3R) and 6 (2S, 3S), which differ in configuration at C-2 and C-3 positions of the (+) montagnetol, were synthesized from (?) diethyl D-tartrate and (+) diethyl L-tartrate, respectively. The synthesized compounds were evaluated in vitro for antimicrobial activity against two Gram-positive (S. aureus and E. coli) and two Gram-negative (S. typhi and P. aeruginosa) bacteria and one fungal strain Candida albicans. Interestingly, the congener 3 showed promising anti-bacterial activity (MIC: 0.062?µg/ml) against P. aeruginosa, whereas the congener 6 displayed potent anti-fungal activity (MIC: 0.062?µg/ml) against C. Albicans.     

Synthesis,characterization, antioxidant properties and DFT calculation of some new pyrimidine derivatives

Abstract

In this study, 5-benzoyl-4-(4-(methylthio)phenyl)-6-phenyl-1,2,3,4-tetrahydro-2-thioxo (1), oxo (2) and imino (3) pyrimidine derivatives were prepared via Multicomponent Cyclocondensation Reactions (MCRs). The compounds thiazolo[3,2-a]pyrimidin-3(5H)-one (4) and thiazin-4(6H)-one (5) were obtained via the reaction of compound 1 with bromoacetic acid and 3-bromopropionic acid, respectively. Structures were determined by using FT-IR, ¹H/¹³C NMR and elemental analyses. Also the compounds 4 and 5 were analyzed by X-ray single crystal analysis. All compounds were investigated as corrosion inhibitors using density functional theory (DFT) at the level of B3LYP/6-31G (d, p). According to the calculations, the compound 3 appears to be a good inhibitor for corrosion. On the other hand, total antioxidant properties were measured in vitro by DPPH^?, ABTS^?+ test, hemolysis of phenylhydrazine erythrocytes and metal chelating effect. The results were compared with standard antioxidants such as trolox and α-tocopherol. These data revealed that compounds 1, 2 and 5 are more active with respect to 3 and 4 in scavenging the radicals.