Reactions with hydrazonoyl halides XXVIII*: Synthesis of some 2‐thiazolylimino‐2,3‐dihydro‐1,3,4‐thiadiazoles

Hydrazonoyl halides have been caused to react with each of methyl 5‐ethoxycarbonyl‐4‐methylthiazole‐2‐aminothiocarbamate, benzyl 5‐ethoxycarbonyl‐4‐methylthiazole‐2‐aminothiocarbamate, and 5‐ethoxycarbonyl‐4‐methylthiazol‐2‐ylphenylthiourea in the presence of triethylamine to give 2‐imino‐(5‐ethoxycarbonyl‐4‐methyl)thiazolyl‐2,3‐dihydro‐1,3,4‐thiadiazoles in good yields. Structures of the new compounds were elucidated on the basis of elemental analyses, spectral data, and alternative methods of synthesis whenever possible. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:213–217, 2000     

Reaction with hydrazonoyl halides XXIII [1]: Synthesis and reactions of C‐coumarinoyl‐N‐arylformohydrazonoyl bromides

C‐Coumarinoyl‐N‐arylformohydrazonoyl bromides ( 3 ) were synthesized by reaction of N‐nitrosoarylacetamides with an appropriate sulfonium bromide in ethanol at room temperature. The reactions of potassium thiocyanate, potassium selenocyanate, thiourea, methyl phenylthiocarbomate, and methyl phenylhydrazinedithioate with hydrazonoyl bromide 3a were examined. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 355–362, 1999     

Reactions of hydrazonoyl halides 43 : Synthesis of some new 2,3‐dihydro‐1,3,4‐thiadiazoles,pyrazoles, pyrazolo[3,4‐d]‐pyridazines,thieno[2,3‐b]pyridines,pyrimidino[4′,5′:4,5]thieno[2,3‐b]‐pyridines and pyrrolo[3,4‐d]pyrazoles

2,3‐Dihydro‐1,3,4‐thiadiazoles, pyrazoles, pyrazolo[3,4‐d]pyridazines, thieno[2,3‐b]pyridines, pyrim‐idino[4′,5′:4,5]thieno[2,3‐b]pyridines and pyrrolo[3,4‐d]pyrazoles were obtained in a good yields by treatment of hydrazonoyl halides with each of alkyl carbodithioates, 3‐(dimethylamino)‐1‐naphtho[1,2‐d]furan‐2‐ylprop‐2‐en‐1‐one and N‐arylmalemides.     

A single pot synthesis of new dimeric 2‐phenyl‐10,3a‐dihydro‐1,3,4‐oxadiazolino[3,2‐a]quinazolin‐6‐ols

One pot synthesis of new unsymmetrical dimeric 2‐phenyl‐10,3a‐dihydro‐1,3,4‐oxadiazolino[3,2‐a]‐quinazolin‐6‐ols from 2‐amino‐5‐phenyloxadiazole and salicylaldehydes, in solid phase, using Hg (II)‐A1₂O₃ catalyst, is described. The reaction is temperature sensitive, convenient, efficient and environmentally friendly.     

1,3,4‐Thia‐ and ‐selenadiazole and 1,2,4‐triazolo[4,3‐a]pyrimidine derivatives from hydrazonoyl halides

1,2,4‐Triazolo[4,3‐a]pyrimidines, thiadiazolines, selenadiazolines, and unsymmetrical azines were synthesized via reactions of a 4‐isopropylbenzoyl bromide 4‐nitrophenylhydrazone with each of potassium thiocyanate, potassium selenocyanate, ethyl 6‐methyl‐4‐[4‐(methylethyl)phenyl]‐2‐methylthio‐3,4‐dihydropyrimidine‐5‐carboxylate, and alkyl carbodithioate. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:421–426, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10156     

Synthesis and antimicrobial activity of some new N‐(substituted phenyl)‐N′‐[2,3‐dihydro‐2‐oxido‐3‐(4′‐fluorophenyl)‐1H‐(1,3,2)benzoxazaphosphorin 2‐yl]ureas

Substituted benzoxazaphosphorin 2‐yl ureas were synthesized by reacting 2‐(4‐fluoro‐phenylamino)‐methylphenol (4) with different carbamidophosphoric acid dichlorides (3) in the presence of triethylamine in dry toluene at 45‐50 °C and characterized by spectral data. These compounds were found to possess good antimicrobial activity.     

Reaction of N‐(phenyl and methyl)‐C‐arylnitrones with DMAD in ionic liquid: Efficient synthesis of Δ4‐isoxazolines

Facile synthesis of N‐(methyl and phenyl)‐Δ⁴‐isoxazolines via the reaction of (Z)‐N‐(methyl and phenyl)‐C‐arylnitrones with dimethyl acethylenedicarboxylate, DMAD, in ionic liquid is described. (Z)‐N‐methyl‐C‐arylnitrones afforded the high yield of N‐methyl‐Δ⁴‐isoxazolines 4a , 4b , 4c , 4d , 4e in ionic liquid, [bmim]BF₄, at room temperature. However, the reaction of (Z)‐N‐phenyl‐C‐arylnitrones with DMAD afforded the mixtures of cis and trans isomers of related N‐phenyl‐Δ⁴‐isoxazolines ( 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j , 6a , 6b , 6c , 6d , 6e , 6f , 6g , 6h , 6i , 6j ) under these conditions. J. Heterocyclic Chem., (2012).     

8‐tert‐Butyl‐7‐(4‐chlorophenyl)‐10‐phenyl‐5,6‐dihydro‐10H‐benzo[h]pyrazolo[3,4‐b]quinoline

The title compound, C₃₀H₂₆ClN₃, crystallizes with Z′ = 3 in the P space group. The three independent molecules have very similar, although not identical, conformations, with almost perfect screw‐boat forms adopted by the non‐aromatic carbocyclic rings. Four independent C—H...π(arene) hydrogen bonds link the molecules into centrosymmetric six‐component aggregates.     

The Studies of Structure of 2N‐(3‐phenyl‐allyl‐)(5‐phenyl‐[1,3,4] Thiadiazol‐2‐yl) Amine in Solution

2N‐(3‐phenyl‐allyl‐)(5‐phenyl‐[1,3,4] thiadiazol‐2‐yl) amine was studied by means of the ¹H, ¹³C, ¹⁵N NMR spectroscopy and DFT calculations. On the basis of the one‐dimensional ¹H, ¹³C, ¹⁵N‐NMR and two‐dimensional ¹H‐¹³C HMQC, ¹H‐¹³C HMBC, ¹H‐¹⁵N HMQC, ¹H¹H NOESY, ¹H¹H COSY correlation spectra the amine‐type and the imine‐type tautomers have been determined in the solution. Variety of structural forms including: biradical, ionic–biradical, and ionic structures of the amine‐type a and of the imine‐type b , c tautomers exist in the solution. According to the DFT computations the differences in the total energy between a and b , a and c , and b and c tautomers are equal to 1.5 kJ/mol, 1.2 kJ/mol, and 0.3 kJ/mol, respectively.     

Syntheses of New Unsymmetrical 2,5‐Disubstituted‐1,3,4‐oxadiazoles and 1,2,4‐Triazolo[3,4‐b]‐1,3,4‐thiadiazoles Bearing Thieno[2,3‐c]pyrazolo Moiety

New series of (thieno[2,3‐c]pyrazolo‐5‐yl)‐[1,2,4]triazolo[3,4‐b][1,3,4]thiadiazoles 10a , 10b , 10c and (thieno[2,3‐c]pyrazol‐5‐yl)‐1,3,4‐oxadiazol‐3(2H)‐yl)ethanones 6a , 6b , 6c has been synthesized from thieno[2,3‐c]pyrazole‐5‐carbohydrazide 3 by multistep reaction sequence. (5‐Aryl‐1,3,4‐oxadiazol‐2‐yl)‐1H‐thieno[2,3‐c]pyrazoles 4a , 4b , 4c were also synthesized from thieno[2,3‐c]pyrazole‐5‐carbohydrazide 3 by cyclization with various aromatic carboxylic acids. The hydrazide 3 was obtained by reaction of thieno[2,3‐c]pyrazole‐5‐carboxylate 2 with hydrazine hydrate in good yield, and compound 2 was obtained by the reaction of 5‐chloro‐3‐methyl‐1‐phenyl‐1H‐pyrazole‐4‐carbaldehyde 1 and 2‐ethyl thioglycolate in presence of sodium alcoholate in good yield.     

Synthesis and Antimicrobial Activity of Some Novel [4‐(1,2,3‐thiadiazol‐4‐yl)phenoxy]methylene anchored 1,3,4‐triazoles and 1,3,4‐thiadiazoles

A series of novel [4‐(1,2,3‐thiadiazol‐4‐yl)phenoxy]methylene anchored 1,3,4‐triazoles ( 8a , 8b , 8c , 8d , 8e , 8f , 8g , 8h ) and 1,3,4‐thiadiazoles ( 9a , 9b , 9c , 9d , 9e , 9f , 9g , 9h , 9i ) were synthesized from thiosemicarbazide ( 7a , 7b , 7c , 7d , 7e , 7f , 7g , 7h , 7i , 7j ). The structures of these newly synthesized compounds were confirmed on the basis of IR, ¹H‐NMR, mass spectral techniques, and elemental analysis. The in vitro antimicrobial screenings of the synthesized compounds were carried out against four bacterial pathogens, namely Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, Pseudomonas aeruginosa and three fungal pathogens Candida albicans, Aspergillus niger and Aspergillus clavatus, using broth microdilution minimum inhibitory concentration method. The compounds 7d , 7j , 8a , 9a , 9b , and 9i exhibited promising antibacterial activity against the tested strains, whereas some compounds were found to be active against one of the tested bacterial strains.     

2,4‐Dinitroimidazole: Microwave assisted synthesis and use in synthesis of 2,3‐dihydro‐6‐nitroimidazo[2,1‐b]oxazole analogues with antimycobacterial activity

2,4‐Dinitroimidazole (2,4‐DNI), an important starting material for nitroimidazooxazole and nitroimidazooxazine types of antitubercular agents was synthesized by rearrangement of 1,4‐dinitroimidazole (1,4‐DNI) under microwave irradiation. Various new nitroimidazooxazoles analogues were prepared using 2,4‐DNI and were tested preliminarily against Mycobacterium tuberculosis, H₃₇Rv strain. Some were found to be active.     

4‐(2‐Hydroxyphenyl)‐2‐phenyl‐2,3‐dihydro‐1H‐1,5‐benzodiazepine and the 2‐(2,3‐dimethoxyphenyl)‐, 2‐(3,4‐dimethoxyphenyl)‐ and 2‐(2,5‐dimethoxyphenyl)‐substituted derivatives

The 1,5‐benzodiazepine ring system exhibits a puckered boat‐like conformation for all four title compounds [4‐(2‐hydroxyphenyl)‐2‐phenyl‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₁H₁₈N₂O, (I), 2‐(2,3‐dimethoxyphenyl)‐4‐(2‐hydroxyphenyl)‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₃H₂₂N₂O₃, (II), 2‐(3,4‐dimethoxyphenyl)‐4‐(2‐hydroxyphenyl)‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₃H₂₂N₂O₃, (III), and 2‐(2,5‐dimethoxyphenyl)‐4‐(2‐hydroxyphenyl)‐2,3‐dihydro‐1H‐1,5‐benzodiazepine, C₂₃H₂₂N₂O₃, (IV)]. The stereochemical correlation of the two C₆ aromatic groups with respect to the benzodiazepine ring system is pseudo‐equatorial–equatorial for compounds (I) (the phenyl group), (II) (the 2,3‐dimethoxyphenyl group) and (III) (the 3,4‐dimethoxyphenyl group), while for (IV) (the 2,5‐dimethoxyphenyl group) the system is pseudo‐axial–equatorial. An intramolecular hydrogen bond between the hydroxyl OH group and a benzodiazepine N atom is present for all four compounds and defines a six‐membered ring, whose geometry is constant across the series. Although the molecular structures are similar, the supramolecular packing is different; compounds (I) and (IV) form chains, while (II) forms dimeric units and (III) displays a layered structure. The packing seems to depend on at least two factors: (i) the nature of the atoms defining the hydrogen bond and (ii) the number of intermolecular interactions of the types O—H...O, N—H...O, N—H...π(arene) or C—H...π(arene).     

Structural characterization of isomeric 2,3,5‐substituted tetrahydropyrrolo[3,4‐d]isoxazole‐4,6‐diones prepared by cycloaddition of N‐methyl‐C‐arylnitrones to N‐phenyl‐ or N‐methylmaleimide

1,3‐Dipolar cycloaddition reactions of N‐methyl‐C‐arylnitrones with N‐phenyl‐ or N‐methylmaleimide were studied. The reaction of p‐dimethylamino‐, 4‐benzyloxy‐3‐methoxy‐, p‐nitro‐ and p‐chloro‐substituted phenylnitrones with N‐phenylmaleimide gave cis and trans cycloadducts but that of the corresponding phenylnitrones with N‐methylmaleimides only the cis adducts in the case of p‐dimethylamino and 4‐benzyloxy‐3‐methoxy substitution. All cis adducts attain a biased conformation whereas the trans forms are shown (by ¹H NMR at 233 K and ¹³C NMR at 208 K) to be mixtures of two invertomers, namely o‐(N‐lone pair antiperiplanar to 3H; minor) and i‐conformations (3H‐C‐C‐3aH dihedral angle close to 90°; major). PM3 and DFT calculations at the B3LYP/6–31G(d) level of theory prove qualitatively that these two conformers of the trans adduct are of comparable stability and represent energy minima.     

Polycyclic N‐Heterocyclic Compounds. 56 Reaction of N‐(5,6‐Dihydro[1]benzoxepino[5,4‐d]pyrimidin‐4‐yl)amidine or Its Amide Oxime Derivatives with Hydroxylamine Hyrdochloride

The reactions of N‐(5,6‐dihydro[1]benzoxepino[5,4‐ d]pyrimidin‐4‐yl)amidines or its amide oxime derivatives with hydroxylamine hydrochloride gave abnormal cyclization products via a ring cleavage of pyrimidine component accompanied with a ring closure of [1,2,4]oxadiazole.     

Different patterns of supramolecular assembly in constitutionally similar 6‐arylimidazo[2,1‐b][1,3,4]thiadiazoles

Four imidazo[2,1‐b][1,3,4]thiadiazoles containing a simply‐substituted 6‐aryl group have been synthesized by reaction of 2‐amino‐1,3,4‐thiadiazoles with bromoacetylarenes using microwave irradiation and brief reaction times. 6‐(2‐Chlorophenyl)imidazo[2,1‐b][1,3,4]thiadiazole, C₁₀H₆ClN₃S, (I), 6‐(2‐chlorophenyl)‐2‐methylimidazo[2,1‐b][1,3,4]thiadiazole, C₁₁H₈ClN₃S, (II), 6‐(3,4‐dichlorophenyl)imidazo[2,1‐b][1,3,4]thiadiazole, C₁₀H₅Cl₂N₃S, (III), and 6‐(4‐fluoro‐3‐methoxyphenyl)‐2‐methylimidazo[2,1‐b][1,3,4]thiadiazole, C₁₂H₁₀FN₃OS, (IV), crystallize with Z′ values of 2, 1, 1 and 2 respectively. The molecular skeletons are all nearly planar and the dihedral angles between the imidazole and aryl rings are 1.51 (8) and 7.28 (8)° in (I), 9.65 (7)° in (II), 10.44 (8)° in (III), and 1.05 (8) and 7.21 (8)° in (IV). The molecules in (I) are linked by three independent C—H...N hydrogen bonds to form ribbons containing alternating R₂²(8) and R₄⁴(18) rings, and these ribbons are linked into a three‐dimensional array by three independent π‐stacking interactions. Both (II) and (III) contain centrosymmetric dimers formed by π‐stacking interactions but hydrogen bonds are absent, and the molecules of (IV) are linked into centrosymmetric R₂²(8) dimers by C—H...N hydrogen bonds. Comparisons are made with a number of related compounds.     

Synthesis and Antimicrobial Studies of New Bis[4,5‐dihydro‐1‐phenyl‐5‐thienyl‐3‐(phenyl‐4‐alkoxy)‐1H‐pyrazole] Derivatives

Syntheses and antimicrobial behavior of the alkyl linked new bispyrazolines 4a , 4b , 4c , 4d , 4e , 4f , 4g have been investigated. These compounds exhibited better antimicrobial activities as compared with their corresponding bischalcones. The structures of the prepared compounds ( 3a , 3b , 3c , 3d , 3e , 3f , 3g and 4a , 4b , 4c , 4d , 4e , 4f , 4g ) were determined from the rigorous analysis of their IR, ¹H NMR, ¹³C NMR, and mass spectral parameters.     

Racemic and chiral 1‐[N‐(chloro­acetyl)carbamoylamino]‐2,3‐dihydro‐1H‐inden‐2‐yl chloroacetate

In the racemic crystals of (1S,2R)‐ or (1R,2S)‐1‐[N‐(chloro­acetyl)­carbamoyl­amino]‐2,3‐di­hydro‐1H‐inden‐2‐yl chloro­acetate, C₁₄H₁₄Cl₂N₂O₄, (I), the enantiomeric mol­ecules form a dimeric structure via the N—H?O cyclic hydrogen bond of the carbamoyl moieties. In the chiral crystals of (—)‐(1S,2R)‐1‐[N‐(chloro­acetyl)­carbamoyl­amino]‐2,3‐di­hydro‐1H‐inden‐2‐yl chloro­acetate, C₁₄H₁₄Cl₂N₂O₄, (II), the N—­H?O intermolecular hydrogen bond forms a zigzag chain around the twofold screw axis. The melting points and calculated densities of (I) and (II) are 446 and 396 K, and 1.481 and 1.445 Mg m^?3, respectively.     

A mild and highly efficient method for the synthesis of 5‐aryl‐(N‐phenyl‐)6H‐1,3,4‐thiadiazin‐2‐aminium salts using reusable heterogeneous catalysts

5‐Aryl‐6H‐1,3,4‐thiadiazin‐2‐aminium and 5‐aryl‐N‐phenyl‐6H‐1,3,4‐thiadiazin‐2‐aminium salts have efficiently been synthesized from the reaction of thiosemicarbazide and α‐haloketones in acetonitrile at room temperature using i) silica supported sodium hydrogen sulfate and ii) silica sulfuric acid as reusable heterogeneous catalysts. The experimental procedure is simple and the products are obtained in high yields.