Regioselective synthesis of pentacyclic polyheterocycles: Sequential [3,3] sigmatropic rearrangement of 4‐(4′‐aryloxybut‐2′‐ynyloxy)‐1‐phenyl‐1,8‐naphthyridin‐2(1H)‐ones

A number of 4‐aryloxymethyl‐6‐phenyl‐2H‐pyrano[3,2‐c][1,8]naphthyridin‐5(6H)‐ones ( 4a‐f ) are regioselectively synthesized in 72‐78% yield by the Claisen rearrangement of 4‐(4′‐aryloxybut‐2′‐ynyloxy)‐1‐phenyl‐1,8‐naphthyridin‐2(1H)‐ones ( 3a‐f ) in refluxing chlorobenzene for 4‐6 h. These products are then subjected to a second Claisen rearrangement catalyzed by anhydrous AlCl₃ at room temperature for 2 h to give hitherto unreported pentacyclic heterocycles ( 5a‐f ) in 78‐85% yield.     

Regioselective epoxidation of 3‐(3‐Oxo‐3‐arylpropenyl)chromen‐4‐ones by dimethyldioxirane

Regioselective epoxidation of 3‐(3‐oxo‐3‐arylpropenyl)chromen‐4‐ones 1a‐h by isolated dimethyldioxirane provided epoxides 2a‐h as sole detectable and isolable products in good (75–86%) yields.     

A new efficient synthesis of 3‐(hydroxymethyl)‐4H‐chromen‐4‐ones

An efficient and versatile synthesis of variously substituted 3‐(hydroxymethyl)‐4H‐chromen‐4‐ones is reported. The compounds are prepared by hydroxymethylation of the precursor 2‐hydroxy‐4‐chromanones followed by acid dehydration.     

Regioselective Synthesis of 4‐(Arylsulfanyl)‐2‐hydroxyhomophthalates by [4+2] Cycloaddition of 3‐(Arylsulfanyl)‐1‐(trimethylsilyloxy)buta‐1,3‐dienes with Dimethyl Penta‐2,3‐dienedioate

The [4+2] cycloaddition of 3‐(arylsulfanyl)‐1‐(trimethylsilyloxy)buta‐1,3‐dienes with dimethyl penta‐2,3‐dienedioate provides a convenient and regioselective approach to a variety of 4‐(arylsulfanyl)‐2‐hydroxyhomophthalates.     

An efficient protocol for the one‐pot synthesis of 4‐(2‐(4‐bromophenyl)‐1,2,3‐triazol‐4‐yl)‐3,4‐dihydropyrimidin‐2(1H)‐ones/thiones catalyzed by Mg(NO3)2

A series of novel 4‐(2‐(4‐bromophenyl)‐1,2,3‐triazol‐4‐yl)‐3,4‐dihydropyrimidin‐2(1H)‐ones/thiones were prepared by condensing 2‐(4‐bromophenyl)‐4‐formyl‐1,2,3‐triazole with 1,3‐dicarbonyl compound and urea or thiourea using Mg(NO₃)₂ as an efficient and cheap catalyst. The satisfactory results were obtained with excellent yields and short reaction time. J. Heterocyclic Chem., (2010).     

A convenient synthesis of 5‐(O,O‐dialkylphosphoryl)‐4‐aryl‐3,4‐dihydropyrimidin‐2(1H)‐ones

A general and convenient route for the synthesis of dihydropyrimidines bearing the phosphoryl moiety by a one‐pot cyclocondensation involving aldehydes, urea, and O,O‐dialkyl‐2‐oxo‐propanephosphonates, using ytterbium triflate as catalyst, is reported. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:13–17, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10058     

Synthesis of 5‐(Arylselanyl)‐2‐(arylsulfanyl)benzoates by [3+3] Cyclocondensation of 3‐(Arylsulfanyl)‐1‐(silyloxy)buta‐1,3‐dienes with 2‐(Arylselanyl)‐3‐(silyloxy)alk‐2‐en‐1‐ones

Functionalized 5‐(arylselanyl)‐2‐(arylsulfanyl)benzoates were prepared by [3+3] cyclocondensation of 3‐(arylsulfanyl)‐1‐(silyloxy)buta‐1,3‐dienes with 2‐(arylselanyl)‐3‐(silyloxy)‐alk‐2‐en‐1‐ones.     

The synthesis of 3,3‐dimethyl‐2‐(1‐aryl‐1h‐pyrazol‐4‐yl)‐3h‐indoles

2,3,3‐Trimethylindolenine and 5‐chloro‐2,3,3‐trimethylindolenine were converted into β‐diformyl compounds by the action of the Vilsmeier reagent at 50°C. The dialdehydes reacted with various arylhydrazines and 2‐pyridylhydrazine to produce mono‐hydrazones as mixtures of cis and trans isomers. Heating the hydrazones in refluxing ethanol produced 3,3‐dimethyl‐2‐(1‐aryl‐1H‐pyrazol‐4‐yl)‐3H‐indoles in excellent yields. Reaction of the β‐diformyl compounds with hydrazine itself led directly to 3,3‐dimethyl‐2‐(pyrazol‐4‐yl)‐3H‐indoles.     

Synthesis of 1‐substituted 5‐aryl‐3‐(3‐coumarinyl)‐2‐pyrazolines by the reaction of 3‐aryl‐1‐(3‐coumarinyl)propen‐1‐ones with hydrazines

1‐Acetyl‐ and 1‐propionyl‐2‐pyrazolines 11‐27 have been synthesized by the reaction of (3‐coumarinyl)chalcones 1‐10 with hydrazine in hot acetic acid or propionic acid. While 5‐aryl‐3‐(3‐coumarinyl)‐1‐phenyl‐2‐pyrazolines 28‐35 have been prepared by the reaction of (3‐coumarinyl)chalcones 1,3,5‐10 with phenylhydrazine in hot pyridine. Structures of all new compounds have been elucidated by microanalyses, ¹H and ¹³C nmr spectroscopies.     

Synthesis,Antimicrobial, and Brine Shrimps Lethality Assays of 3,3‐Diaryl‐4‐(1‐methyl‐1H‐indol‐3‐yl)azetidin‐2‐ones

The paper describes the synthesis, characterization data, and biological activity (antibacterial, antifungal, and brine shrimps lethality) of new azetidin‐2‐ones. The compounds have been synthesized by the reaction of diarylketenes, generated in situ from thermal decomposition of the 2‐diazo‐1,2‐diarylethanones, with N‐(1‐methyl‐1H‐indol‐3‐yl)methyleneamines. The compounds have been characterized by elemental analysis and spectral (IR, ¹H and ¹³C NMR, and MS) data. The paper also reports the results of antibacterial, antifungal, and brine shrimps lethality assays of these compounds. Some of the compounds exhibited significant biological activity.     

Synthesis of 3‐aminoalkyl‐2‐arylaminoquiazolin‐4(3H)‐ones and 3,3′‐disubstituted bis‐2‐arylaminoquinazolin‐4(3H)‐ones via reactions of 1‐aryl‐3‐(2‐ethoxycarbonylphenyl)carbodiimides with diamines

1‐Aryl‐3‐(2‐ethoxycarbonylphenyl)carbodiimides 2 , obtained from aza‐Wittig reactions of iminophosphorane 1 with aryl isocyanates, reacted with primary diamines in 1:1 and 2:1 molar ratio under mild conditions to give selectively the regioisomers 3‐aminoalkyl‐2‐arylaminoquinazolin‐4(3H)‐ones 3 and 3,3′‐disubstituted bis‐2‐arylaminoquinazolin‐4(3H)‐ones 4 in good yields, respectively. To fully characterize the regioselectivity of aza‐Wittig reactions of 1‐aryl‐3‐(2‐ethoxycarbonylphenyl)carbo‐diimides with primary diamines, crystals of 4e were obtained, and its structure was determined by X‐ray crystallography.     

2‐(3,4‐Dichlorophenylimino)‐5‐((3‐(p‐substitutedphenyl)‐1‐phenyl‐1H‐pyrazol‐4‐yl)methylene)thiazolidin‐4‐one as an Antibacterial,Antifungal and Antimycobacterial Agent

2‐(3,4‐Dichlorophenylimino)‐5‐((3‐(p‐substitutedphenyl)‐1‐phenyl‐1H‐pyrazol‐4‐yl)methylene) thiazolidin‐4‐one has been selected as a target bio‐active molecules. Newly synthesized compounds were screened with Eschericha coli (MTCC 443), Pseudomonas aeruginosa (MTCC 1688), Staphylococcus aureus (MTCC 96), Streptococcus pyogenes (MTCC 442) for antibacterial, Candida albicans (MTCC 227), Aspergillus niger (MTCC 282), Aspergillus clavatus (MTCC 1323) for antifungal activity and H ₃₇ Rv for antimycobacterial activity. Compounds 3a , 3c , 3d , 3e , and 3h are potentially active against Staphylococcus aureus , while 3h is active against C. albicans . Compounds 3d and 3f are active against H ₃₇Rv for mycobacterium tuberculosis. Other possesses moderate to good activity. The structures of synthesized compounds were firmly established by well‐defined elemental analyses (C, H, N, S/O) and spectral analysis technique likes, IR, ¹H NMR and GC–MS.     

Two isomorphous azastilbene derivatives: 1‐(2‐chlorobenzyl)‐4‐[(E)‐2‐(4‐hydroxyphenyl)ethenyl]pyridinium chloride and 1‐(2‐bromobenzyl)‐4‐[(E)‐2‐(4‐hydroxyphenyl)ethenyl]pyridinium bromide

The crystal structures of the two title (E)‐stilbazolium halogenates, C₂₀H₁₇ClNO⁺·Cl⁻ and C₂₀H₁₇BrNO⁺·Br⁻, are isomorphous, with an isostructurality index of 0.985. The azastyryl fragments are almost planar, with dihedral angles between the benzene and pyridine rings of ca 4.5°. The rings of the benzyl groups are, in turn, almost perpendicular to the azastyryl planes, with dihedral angles larger than 80°. The cations and anions are connected by O—H...X⁻ (X = halogen) hydrogen bonds. The halide anions are `sandwiched' between the charged pyridinium rings of neighbouring molecules, and weak C—H...O hydrogen bonds and C—H...X and C—H...π interactions also contribute to the crystal structures.     

Regioselective Lactonization of α‐(2→8)‐Trisialic Acid

A simple and selective method has been developed to obtain both monolactones of the title compound, a model compound for biologically important polyneuraminic acid derivatives: acidic lactonization and alkaline hydrolysis of dilactone 1 . The two monolactonized trimers can be separated by capillary electrophoresis, and then distinguished by enzymatic hydrolysis with neuraminidase; only the 2‐monolactone undergoes reaction.     

Efficient microwave‐assisted synthesis and antioxidant activity of 4‐arylidene‐2‐phenyl‐1H‐imidazol‐5(4H)‐ones

The efficient synthesis of 4‐arylidene‐2‐phenyl‐1H‐imidazol‐5(4H)‐ones was achieved via microwave‐assisted reactions of 4‐arylmethylene‐2‐phenyloxazol‐5(4H)‐ones with urea in glycol. This approach provides a facile shortcut for the synthesis of this type of compounds with short reaction time, high yields, broad substrate scope and easy operation. Besides, the synthesized compounds were subject to the test of antioxidant activity, which is represented by their capacities for scavenging 1,1‐diphenyl‐2‐picrylhydrazyl, hydroxyl and superoxide anion free radicals. Bioassay of these compounds resulted in the finding of several 4‐arylidene‐2‐phenyl‐1H‐imidazol‐5(4H)‐ones with significant antioxidant activity. J. Heterocyclic Chem., (2012).