Synthesis of substituted 3‐(5‐amino‐[1,3,4]thiadiazol‐2‐yl)‐2H‐pyrano[2,3‐c]pyridin‐2‐ones

An efficient two‐step synthesis of novel 3‐(5‐amino‐[1,3,4]thiadiazol‐2‐yl)‐2H‐pyrano[2,3‐c]pyridine‐2‐ones was developed. In the first step, a new 2H‐pyrano[2,3‐c]pyridine‐3‐carboxamide 5 was prepared by Knoevenagel condensation of pyridoxal hydrochloride with cyanoacetamide. In the second step, the reaction of carboxamide 5 with a series of N⁴‐substituted thiosemicarbazides yielded a library of 35 dis crete compounds 8 {1–35} in high yields. The intermolecular recyclization mechanism leading to these products is discussed.     

Polymorphism of 3‐(5‐phenyl‐1,3,4‐oxadiazol‐2‐yl)‐ and 3‐[5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazol‐2‐yl]‐2H‐chromen‐2‐ones

This study of 3‐(5‐phenyl‐1,3,4‐oxadiazol‐2‐yl)‐2H‐chromen‐2‐one, C₁₇H₁₀N₂O₃, 1 , and 3‐[5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazol‐2‐yl]‐2H‐chromen‐2‐one, C₁₆H₉N₃O₃, 2 , was performed on the assumption of the potential anticancer activity of the compounds. Three polymorphic structures for 1 and two polymorphic structures for 2 have been studied thoroughly. The strongest intermolecular interaction is stacking of the `head‐to‐head' type in all the studied crystals. The polymorphic structures of 1 differ with respect to the intermolecular interactions between stacked columns. Two of the polymorphs have a columnar or double columnar type of crystal organization, while the third polymorphic structure can be classified as columnar‐layered. The difference between the two structures of 2 is less pronounced. Both crystals can be considered as having very similar arrangements of neighbouring columns. The formation of polymorphic modifications is caused by a subtle balance of very weak intermolecular interactions and packing differences can be identified only using an analysis based on a study of the pairwise interaction energies.     

Synthesis of Novel 3‐(3‐(5‐Methylisoxazol‐3‐yl)‐7H‐[1,2,4]Triazolo [3,4‐b][1,3,4]Thiadiazin‐6‐yl)‐2H‐Chromen‐2‐Ones

A novel series of coumarin substituted triazolo‐thiadiazine derivatives were designed and synthesized by using 5‐methyl isoxazole‐3‐carboxylic acid ( 1 ), thiocarbohydrazide ( 2 ), and various substituted 3‐(2‐bromo acetyl) coumarins ( 4a , 4b , 4c , 4e , 4d , 4f , 4g , 4h , 4i , 4j ). Fusion of 5‐methyl isoxazole‐3‐carboxylic acid with thiocarbohydrazide resulted in the formation of the intermediate 4‐amino‐5‐(5‐methylisoxazol‐3‐yl)‐4H‐1,2,4‐triazole‐3‐thiol ( 3 ). This intermediate on further reaction with substituted 3‐(2‐bromo acetyl) coumarins under simple reaction conditions formed the title products 3‐(3‐(5‐methylisoxazol‐3‐yl)‐7H‐[1,2,4]triazolo[3,4‐b][1,3,4]thiadiazin‐6‐yl‐2H‐chromen‐2‐ones ( 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j ) in good to excellent yields. All the synthesized compounds were well characterized by physical, analytical, and spectroscopic techniques.     

Synthesis,characterization, antibacterial and antifungal activity of 2‐(aryl)‐3‐(3‐((8‐hydroxyquinolin‐5‐yl)diazenyl)phenyl)thiazolidin‐4‐ones

5‐((3‐Aminophenyl)diazenyl)quinolin‐8‐ol ( 1 ) was synthesized by diazotization reaction and coupled with 8‐hydroxyquinoline moiety. This amine on facile condensation with aromatic aldehydes in presence of glacial acetic acid and ethanol affords anils ( 2 ). These anils on cyclocondensation reaction with thioglycolic acid (i.e., mercaptoacetic acid) yield the titled compound ( 3 ). The structure of the newly synthesized anils ( 2 ) and thiazolidinones ( 3 ) has been confirmed by elemental analysis and spectral analysis. The titled compounds have been screened against different bacterial and fungal strains. J. Heterocyclic Chem., (2011).     

Novel Rearrangement of 3‐Acylaminofuro[2,3‐b]pyridines into 3‐(oxazol‐4‐yl)pyridin‐2‐ones

3‐Acylaminofuro[2,3‐b]pyridine derivatives have been synthesized, and their behavior under acidic and basic conditions was studied. A new base‐catalyzed rearrangement of 3‐acylaminofuro[2,3‐b]pyridine derivatives into 3‐(oxazol‐4‐yl)pyridine‐2‐ones has been founded.     

2‐[2‐(Pyrrolidin‐2‐yl)propan‐2‐yl]‐1H‐pyrrole and its amide derivative 1‐{2‐[2‐(1H‐pyrrol‐2‐yl)propan‐2‐yl]pyrrolidin‐1‐yl}ethanone

In the title compounds, C₁₁H₁₈N₂, (II), and C₁₃H₂₀N₂O, (III), the pyrrolidine rings have twist conformations. Compound (II) crystallizes with two independent molecules (A and B) in the asymmetric unit. The mean planes of the pyrrole and pyrrolidine rings are inclined to one another by 89.99 (11) and 89.35 (10)° in molecules A and B, respectively. In (III), the amide derivative of (II), the same dihedral angle is much smaller, at only 13.42 (10)°. In the crystal structure of (II), the individual molecules are linked via N—H...N hydrogen bonds to form inversion dimers, each with an R²₂(12) graph‐set motif. In the crystal structure of (III), the molecules are linked via N—H...O hydrogen bonds to form inversion dimers with an R²₂(16) graph‐set motif.     

Synthesis of Macrocyclic Lactones via Ring Transformation of 4‐(ω‐Hydroxyalkyl)‐1,3‐oxazol‐5(4H)‐ones

The synthesis of α‐benzamido‐α‐benzyl lactones 23 of various ring size was achieved either via ‘direct amide cyclization’ by treatment of 2‐benzamido‐2‐benzyl‐ω‐hydroxy‐N,N‐dimethylalkanamides 21 in toluene at 90 – 110° with HCl gas or by ‘ring transformation’ of 4‐benzyl‐4‐(ω‐hydroxyalkyl)‐2‐phenyl‐1,3‐oxazol‐5(4H)‐ones under the same conditions. The precursors were obtained by C‐alkylations of 4‐benzyl‐2‐phenyl‐1,3‐oxazol‐5(4H)‐one ( 15 ) with THP‐ or TBDMS‐protected ω‐hydroxyalkyl iodides. Ring opening of the THP‐protected oxazolones by treatment with Me₂NH followed by deprotection of the OH group gave the diamides 21 , whereas deprotection of the TBDMS series of oxazolones 25 with TBAF followed by treatment with HCl gas led to the corresponding lactones 23 in a one‐pot reaction.     

Utility of 2‐[4‐(3‐oxobenzo[f]‐2H‐chromen‐2‐yl)‐1,3‐thiazol‐2‐yl]ethanenitrile in heterocyclic synthesis

Pyrazolo[4,3‐d]pyrimidines, pyrazolo[4,3‐d]triazolino[4,3‐a]pyrimidines, 3‐(2‐thiazolyl)thiophenes, thiazolo[3,2‐a]pyridine and pyrazolo[1,5‐a]pyrimidines were synthesized from 2‐[4‐(3‐oxobenzo[f]‐2H‐chromen‐2‐yl)‐1,3‐thiazol‐2‐yl]ethanenitrile. The newly synthesized compounds were elucidated by elemental analysis, spectral data, chemical transformation and alternative synthesis route whenever possible.     

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.     

Design,synthesis and biological evaluation of novel 6,7,8,9‐tetrahydro‐2‐(2‐aryloxypyrimidin‐4‐yl)‐2H‐[1,2,4]triazolo[4,3‐a]azepin‐3(5H)‐ones

A series of novel 6,7,8,9‐tetrahydro‐2‐(2‐aryloxypyrimidin‐4‐yl)‐2H‐[1,2,4]triazolo[4,3‐a]azepin‐3(5H)‐ones were designed and efficiently synthesized. Their structures were determined by IR, ¹³C and ¹H NMR, mass spectroscopy, and elemental analysis. These compounds were screened for herbicidal activities against rape and barnyard grass. Compounds 5a‐5f and 5m exhibited moderate herbicidal activity against rape. In addition, the synthesis of the intermediate 1‐(azepan‐2‐ylidene)‐2‐(2‐chloropyrimidin‐4‐yl)‐hydrazine ( 3 ) was studied and the reason for the low yield in the initial procedure is discussed as well.     

Synthesis and herbicidal activity of 2‐(3‐(trifluoromethyl)‐5‐(alkoxy)‐1H‐pyrazol‐1‐yl)‐4‐aryloxypyrimidine derivatives

A series of 2‐(3‐(trifluoromethyl)‐5‐(alkoxy)‐1H‐pyrazol‐1‐yl)‐4‐aryloxypyrimidine derivatives were designed and synthesized. The structures of all the title compounds were confirmed by ¹H NMR and elementary analysis. These compounds were screened for herbicidal activity against rape and barnyard grass. Compound B13 exhibited moderate herbicidal activity.     

An Efficient Synthesis of 3‐(1H‐Tetrazol‐5‐yl)coumarins (=3‐(1H‐Tetrazol‐5‐yl)‐2H‐1‐benzopyran‐2‐ones) via Domino Knoevenagel Condensation,Pinner Reaction,and 1,3‐Dipolar Cycloaddition in Water

A novel straightforward synthesis of 3‐(1H‐tetrazol‐5‐yl)coumarins (=3‐(1H‐tetrazol‐5‐yl)‐2H‐1‐benzopyran‐2‐ones) 6 via domino Knoevenagel condensation, Pinner reaction, and 1,3‐dipolar cycloaddition of substituted salicylaldehydes (=2‐hydroxybenzaldehydes), malononitrile (propanedinitrile), and sodium azide in H₂O is reported (Scheme 1 and Table 2). This general protocol provides a wide variety of 3‐(1H‐tetrazol‐5‐yl)coumarins in good yields under mild reaction conditions.     

Synthesis of 5‐[2‐(guanin‐9‐yl)‐ and 5‐[2‐(2‐aminopurin‐9‐yl)ethyl]‐2‐D‐ribo‐(1,2′,3′,4′‐tetrahydroxybutyl)‐1,3‐dioxane

Stereoselective synthesis of 5‐[2‐(guanin‐9‐yl)‐ and 5‐[2‐(2‐aminopurin‐9‐yl)ethyl]‐2‐D‐ribo‐(1′,2′,3′,4′‐tetrahydroxybutyl)‐1,3‐dioxane, 2‐5, as potential prodrugs of penciclovir, has been accomplished in six steps from readily available 2,3,4,5‐tetra‐O‐acetyl‐aldehydo‐D‐ribose ( 6 ) and the 1,3‐diol 7 . It has been demonstrated that the use of boron trifluoride diethyl etherate (BF₃·Et₂O) in dichloromethane along with excess anhydrous copper(II) sulfate was crucial for the efficient formation of cyclic acetal 8 . In addition, the chromatographic separation of cis and trans isomers of the cyclic acetal at the bromide stage 10 was feasible, which was requisite for the successful stereoselective synthesis of the ribosyl derivatives 2–5 .     

3‐[5‐(4‐Chlorophenyl)‐1‐(4‐methoxyphenyl)‐1H‐pyrazol‐3‐yl]propionic acid and the corresponding methyl ester

The synthesis of 3‐[5‐(4‐chlorophenyl)‐1‐(4‐methoxyphenyl)‐1H‐pyrazol‐3‐yl]propionic acid, C₁₉H₁₇ClN₂O₃, (I), and its corresponding methyl ester, methyl 3‐[5‐(4‐chlorophenyl)‐1‐(4‐methoxyphenyl)‐1H‐pyrazol‐3‐yl]propionate, C₂₀H₁₉ClN₂O₃, (II), is regiospecific. However, correct identification of the regioisomer formed by spectroscopic techniques is not trivial and single‐crystal X‐ray analysis provided the only means of unambiguous structure determination. Compound (I) crystallizes with Z′ = 2. The propionic acid groups of the two crystallographically unique molecules form a hydrogen‐bonded dimer, as is typical of carboxylic acid groups in the solid state. Conformational differences between the methoxybenzene and pyrazole rings give rise to two unique molecules. The structure of (II) features just one molecule in the asymmetric unit and the crystal packing makes greater use than (I) of weak C—H...A interactions, despite the lack of any functional groups for classical hydrogen bonding.     

2‐(1,3‐Dithian‐2‐yl)benzaldehyde and N‐{2‐[2‐(1,3‐dioxan‐2‐yl)phenoxy]­ethyl}phthalimide

The crystal structures of two elaborated‐porphyrin precursors have been determined. In the crystalline state, 2‐(1,3‐di­thian‐2‐yl)­benz­aldehyde, C₁₁H₁₂OS₂, has its di­thiane ring in a slightly distorted chair conformation. The mol­ecules pack in anti‐parallel chains. N‐{2‐[2‐(1,3‐Dioxan‐2‐yl)­phenoxy]­ethyl}­phthal­imide, C₂₀H₁₉NO₅, is in a folded conformation. The dihedral angle between the phthal­imide and phenyl planes is 80.07 (3)°. In the crystalline states, mol­ecules stack on top of one another.     

A convenient one‐pot synthesis of new 3‐(4‐aryl‐5‐oxo‐5,6,7,8‐tetrahydro‐4H‐chromen‐2‐yl)‐2H‐chromen‐2‐ones

Anhydrous zinc bromide catalysed reactions of arylidine‐3‐acetyl coumarins ( 1a‐c ) and 5,6‐benzoanalogs of arylidine 3‐acetyl coumarins ( 4a,4b ) with 1,3‐cyclohexanedione gives ‐(4‐aryl‐5‐oxo‐5,6,7,8‐tetrahydro‐4H‐chromen‐2yl)‐2H‐chromen‐2‐ones ( 3a, 3c ) and 5,6‐benzoanalogs of 3‐(4‐aryl‐5‐oxo‐5,6,7,8‐tetrahydro‐4H‐chromen‐2yl)‐2H‐chromen‐2‐one ( 5a,5b ). Under similar conditions arylidine‐3‐acetylcoumarins ( 1a, 1b,1d, 1e, 1f ) and 5,6‐benzoanalog of arylidine 3‐acetyl coumarin ( 4b ) react with 5,5‐dimethyl‐1,3‐cyclohexanedione (dimedone) yielding 3‐(4‐aryl‐7,7‐dimethyl‐5‐oxo‐5,6,7,8‐tetrahydro‐4H‐chromen‐2‐yl)‐2H‐chromen‐2‐ones ( 3d‐3h ) and the 5,6‐benzoanalog of 3.(4‐aryl‐7,7‐dimethyl‐5‐oxo‐5,6,7,8‐tetrahydro‐4H‐chromen‐2‐yl)‐2H‐chromen‐2‐one ( 5c ).     

Synthesis and antibacterial activity of novel series of 2‐(p‐tolyloxy)‐3‐(5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazol‐2‐yl)quinoline

A new series of 2‐(p‐tolyloxy)‐3‐(5‐(pyridin‐4‐yl)‐1,3,4‐oxadiazol‐2‐yl)quinoline were synthesized from oxidative cyclization of N′‐((2‐(p‐tolyloxy)quinoline‐3‐yl)methylene)isonicotinohydrazide in DMSO/I₂ at reflux condition for 3–4 h. The structures of the new compounds were confirmed by elemental analyses as well as IR, ¹H‐NMR, and mass spectral data. All the synthesized compounds were screened for their antibacterial activities against various bacterial strains. Several of these compounds showed potential antibacterial activity. J. Heterocyclic Chem., (2011).     

Synthesis and antifungal activity of novel 5‐substituted 4‐(1,3,4‐thiadiazol‐2‐yl)benzene‐1,3‐diols

5‐Substituted (amine, alkyl, aryl, heterocyclic) 4‐(1,3,4‐thiadiazol‐2‐yl)benzene‐1,3‐ diols were synthesized, and their antifungal properties were examined. The compounds were obtained by the one‐pot reaction of sulfinylbis((2,4‐dihydroxyphenyl)methanethione) with hydrazides or thiosemicarbazides. Their structures were identified from elemental, IR, ¹H NMR, and MS spectra analyses. The activities of the derivatives against five phytopathogenic fungi in vitro were measured. Moderate fungicidal effect of the compounds under consideration was found. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:533–540, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20645     

(Z)‐5‐[4‐(Dimethylamino)benzylidene]‐2‐(piperidin‐1‐yl)‐1,3‐thiazolidin‐4(5H)‐one

The molecules of the title compound, C₁₇H₂₁N₃OS, are characterized by a wide C—C—C angle at the methine C atom linking the aryl and thiazolidine rings, associated with a short repulsive intramolecular S...H contact between atoms in these two rings. A single piperidine–arene C—H...π hydrogen bond links pairs of molecules into centrosymmetric dimers.     

Isomeric 3‐ and 4‐chloro‐N‐[1‐(1H‐pyrrol‐2‐yl)ethylidene]aniline

The title isomers, namely 3‐chloro‐N‐[1‐(1H‐pyrrol‐2‐yl)ethylidene]aniline, (I), and 4‐chloro‐N‐[1‐(1H‐pyrrol‐2‐yl)ethylidene]aniline, (II), both C₁₂H₁₁ClN₂, differ in the position of the chlorine substitution. Both compounds have the basic iminopyrrole structure, which shows a planar backbone with similar features. The dihedral angle formed by the planes of the pyrrole and benzene rings is 75.65 (7)° for (I) and 86.56 (8)° for (II). The H atom bound to the pyrrole N atom is positionally disordered and partial protonation occurs at the imino N atom in (I), while this phenomenon is absent from the structure of (II). Packing interactions for both compounds include intermolecular N—H...N hydrogen bonds and C—H...π interactions, forming centrosymmetric dimers for both (I) and (II).