Direct Synthesis of Trichloro‐thiazolo[3,2‐a]pyrimidine and Thiazolo[2,3‐b]quinazoline Derivatives

An efficient one‐pot method for synthesis of new biologically active thiazolo[3,2‐a ]pyrimidine and thiazolo[2,3‐b ]quinazoline derivatives is described via reaction of pentachloropyridine with fused pyrimidine‐2(5H )‐thiones or quinazoline‐2(1H )‐thiones. These reactions were carried out in the presence of potassium carbonate as a base in acetonitrile as a solvent to produce products 3a – n in good‐to‐excellent yield. Pentachloropyridine is doubly electrophilic building blocks for the formation of ring annulated thiazolo[3,2‐a ]pyrimidine and thiazolo[2,3‐b ]quinazoline products.     

Synthesis of Some New 1,2,3,4‐Tetrahydropyrimidine‐2‐thione and Their Thiazolo[3,2‐a]pyrimidine,Thiazino and Benzothiazepine Derivatives

The starting N‐(2‐pyridyl)‐6‐methyl‐4‐phenyl‐2‐thioxo‐1,2,3,4‐tetrahydropyrimidine‐5‐carboxamide ( 4 ) was used as a key intermediate for the synthesis of new 1,2,3,4‐tetrahydropyrimidine‐2‐thione and their thiazolo[3,2‐a]pyrimidine, thiazino and benzothiazipen derivatives. The reaction of 4 with haloketones in ethanol catalyzed by base afforded the corresponding thiophenopyrimidine and pyrimidothiazipine derivatives 5 , 6 , 7 , 8 , 9 , 10 . Methylation and formylation of 4 led to the pyrimidine derivatives 15 and 16 , respectively. The preventative compounds were established on the basis of elemental and spectral data.     

Chemical Reactivity of 4,9‐Dimethoxy‐5‐oxo‐5H‐furo[3,2‐g]chromene‐6‐Carboxaldehyde Toward Some Nucleophilic Reagents

The chemical reactivity of 4,9‐dimethoxy‐5‐oxo‐5H‐furo[3,2‐g ]chromene‐6‐carboxaldehyde (6‐formylkhellin) ( 1 ) was studied toward a diversity of nitrogen nucleophilic reagents. Reaction of carboxaldehyde 1 with some primary amines and heterocyclic amines afforded the corresponding Schiff bases. Also, the reactivity of carboxaldehyde 1 was studied toward some hydrazine derivatives, namely 7‐chloro‐4‐hydrazinoquinoline, 3‐hydrazino‐5,6‐diphenyl‐1,2,4‐triazine, N⁴‐phenylthiosemicarbazide, and S‐benzyldithiocarbazate. 6‐Formylkhellin ( 1 ) underwent ring transformation upon treatment with hydroxylamine hydrochloride producing 5‐hydroxy‐4,9‐dimethoxy‐7‐oxo‐7H‐furo[3,2‐g ]chromene‐6‐carbonitrile ( 22 ). Some pyrimidine, [1,2,4]triazolo[4,3‐a ]pyrimidine, tetrazolo[1,5‐a ]pyrimidine, and diazepine derivatives linked benzofuran were efficiently synthesized. Reaction of carboxaldehyde 1 with a variety of 1,4‐binucleophiles produced furochromone‐fused benzodiazepine, pyridotriazepine, benzoxazepine, and benzothiazepine derivatives. Some unsymmetrical thiocarbohydrazones were also synthesized. Structures of the new synthesized products were deduced on the basis of their analytical and spectral data.     

Researches on thiazolobenzodiazepines: Behavior of tetrahydro‐1,5‐benzodiazepinethiones with aromatic α‐haloketones

A number of 1‐substituted 4H,5H,6H‐[1,3]thiazolo[3,2‐a][1,5]benzodiazepinium‐11‐bromides and S‐(2‐oxo‐2‐phenyl‐X‐(p)‐ethyl)‐3‐(2‐methyl‐1H‐benzimidazol‐1‐yl) propane (or butane) thioate hydrobromides were obtained by direct reaction of the 5‐acetyl(or formyl, or anilinocarbonyl)‐substituted tetrahydro‐1,5‐benzodiazepine‐2‐thiones with aromatic α‐bromoketones. 2‐[(1‐Acetyl‐2(or 3)‐methyl‐2,3‐dihydro‐1H‐1,5‐benzodiazepin‐4‐yl) sulfanyl]‐1‐phenylethanones as intermediates of the formation of thiazolo [3,2‐a][1,5]benzodiazepine and N‐substituted 2‐methyl‐1H‐benzimidazole derivatives have been synthesized. Semiempirical AM1 calculations of a mechanism and energetic parameters for the heptatomic nucleus rearrangement to benzimidazole ring are presented. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:72–81, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20414     

Synthesis and Antibacterial Activity of Novel (4‐Fluorophenyl)(4‐(naphthalen‐2‐yl)‐6‐aryl‐2‐thioxo‐2,3‐dihydropyrimidin‐1(6H)‐yl)methanone Derivatives

A novel series of (4‐fluorophenyl)(4‐(naphthalen‐2‐yl)‐6‐aryl‐2‐thioxo‐2,3‐dihydropyrimidin‐1(6H)‐yl)methanone derivatives were synthesized from reaction of 6‐(naphthalen‐2‐yl)‐4‐aryl‐3,4‐dihydropyrimidine‐2(1H)‐thiones with 4‐fluorobenzoylchloride in dichloromethane in the presence of triethylamine. The synthesized compounds were screened for antibacterial activity against Gram positive bacteria, namely, Staphylococcus aureus ATCC25923 and Listeria monocytogenes MTCC657, and Gram negative bacteria, namely, Escherichia coli ATCC25922 and Klebsiella pneumoniae ATCC700603, respectively. Some of the tested compounds showed significant antimicrobial activity.     

Synthesis of 3‐substituted pyrido[4′,3′:4,5]thieno[2,3‐d]pyrimidines and related fused thiazolo derivatives

Convenient syntheses of 3‐substituted ethyl 4‐oxo‐2‐thioxo‐1,2,3,4,5,6,7,8‐octahydropyrid[4′,3′:4,5]thieno[2,3‐d]pyrimidine‐7‐carboxylates 3a, b, 6, 11–13 , ethyl 3‐methyl‐5‐oxo‐2,3,6,9‐tetrahydro‐5 H‐pyrido[4′,3′:4,5]thieno[2,3‐d][1,3]thiazolo[3,2‐a]pyrimidine‐8‐7H‐carboxylate ( 4 ), and ethyl 2‐methyl‐5‐oxo‐2,3,6,9‐tetrahydro‐5H‐pyrido[4′,3′:4,5]thieno[2, 3‐d][1,3]thiazolo[3,2‐a]pyrimidine‐8[7H]carboxylate ( 8 ) from diethyl 2‐isothiocyanato‐4,5,6,7‐tetrahythieno[2,3‐c]pyridine‐3,6‐dicarboxylate ( 1 ) are reported. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:201–207, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10131     

Synthesis of Acetyl and Iodo Derivatives of 4‐Hydroxy‐6‐phenyl‐6H‐pyrano[3,2‐c]pyridine‐2,5‐diones and 4‐Hydroxy‐1‐phenylpyridin‐2(1H)‐ones

A simple and efficient method has been described for the synthesis of acetyl and iodo derivatives of 4‐hydroxy‐6‐phenyl‐6H‐pyrano[3,2‐c ]pyridine‐2,5‐diones 1 and 4‐hydroxy‐1‐phenylpyridin‐2(1H )‐ones 5 . Compounds 1 with phenyl and alkyl substituent at C(7) and C(8), respectively, can be easily acetylated by refluxing in a mixture of acetic acid and polyphosphoric acid to give 3‐acetyl‐4‐hydroxy‐6‐phenyl‐6H‐pyrano[3,2‐c ]pyridine‐2,5‐diones 2 in excellent yields. Compounds 1 and 5 can be iodinated with iodine and anhydrous sodium carbonate in boiling dioxane to give 4‐hydroxy‐3‐iodo‐6‐phenyl‐6H‐pyrano[3,2‐c ]pyridine‐2,5‐diones 3 and 4‐hydroxy‐3‐iodo‐1‐phenylpyridin‐2(1H )‐ones 6 , respectively, in good yields. The structures were confirmed using infrared, nuclear magnetic resonance , and elemental analysis.     

Synthesis of Novel Fused Thiazolo[3,2‐a]pyrimidin‐3‐ols and Evaluation for their Antibacterial Activity

A series of novel fused thiazolo[3,2‐a]pyrimidin‐3‐ol derivatives have been synthesized by reaction of fused pyrimidine‐thiones with 4‐substituted phenacyl bromide/3(2‐bromoacetyl)coumarin in refluxing acetic acid with good yields. All the synthesized compounds were confirmed by spectral studies and screened for their in vitro antibacterial activity against Staphylococcus aureus, Bacillus thuringiensis (Gram positive), Escherichia coli, and Klebsiella pneumoniae (Gram negative) bacterial strains. Activity results revealed that all the compounds were weak to good active against the tested bacterial strains on comparing with the standard drug gentamicin.     

Synthesis of Some New Heterocycles Derived from Ethyl 7‐Amino‐3‐(3‐methyl‐5‐oxo‐1‐phenyl‐2‐pyrazolin‐4‐yl)‐5‐aryl‐5H‐thiazolo[3,2‐a]pyrimidine‐6‐carboxylate of Biological Importance

Ethyl 7‐amino‐3‐(3‐methyl‐5‐oxo‐1‐phenyl‐2‐pyrazolin‐4‐yl)‐5‐aryl‐5H‐thiazolo[3,2‐a]pyrimidine‐6‐carboxylate was synthesized by the reaction of 4‐(2‐aminothiazol‐4‐yl)‐3‐methyl‐5‐oxo‐1‐phenyl‐2‐pyrazoline with arylidene ethyl cyanoacetate and it transformed to related fused heterocyclic systems via reaction with various reagents. The biological activities of these compounds were evaluated.     

New Substituted 1‐Aryl‐4,4,6‐Trimethyl‐3,4‐Dihydropyrimidine‐2‐(1H)Thiones; A Metal‐Free and Solvent‐Free Synthesis,Characterization, and Lymphoid Tyrosine Phosphatase Inhibition Studies

A series of fourteen 3,4‐dihydropyrimidine‐2‐thiones ( 3a–n ) were synthesized by a green protocol, and their structures were characterized by spectroanalytical data. The compounds were obtained in high yields by efficient annulation of mesityl oxide (4‐methylpent‐3‐en‐2‐one) with anilines in the presence of potassium thiocyanate. The reaction is essentially metal‐catalyst‐ and solvent‐free, as mesityl oxide itself is the solvent as well as the reactant. The compounds were tested for their ability to inhibit the lymphoid tyrosine phosphatase PTPN22, and 5 of the 14 compounds exhibited IC₅₀ values in the mid‐micromolar range, with the most potent hit being the compound 3d , having a methoxy substituent at the 2‐position of the phenyl ring with an IC₅₀ = 18 ± 1 μM, and second most potent compound ( 3c ) with an IC₅₀ value of 45 ± 3 μM, having methyl substituents at both 2‐ and 4‐position of the phenyl ring.     

Synthesis,crystal structure and activity evaluation of novel 3,4‐dihydro‐1‐benzoxepin‐5(2H)‐one derivatives as protein–tyrosine kinase (PTK) inhibitors

Four new 3,4‐dihydro‐1‐benzoxepin‐5(2H )‐one derivatives, namely (E )‐4‐(5‐bromo‐2‐hydroxybenzylidene)‐6,8‐dimethoxy‐3,4‐dihydrobenzo[b ]oxepin‐5(2H )‐one, ( 7 ), (E )‐4‐[(E )‐3‐(5‐bromo‐2‐hydroxyphenyl)allylidene]‐6,8‐dimethoxy‐3,4‐dihydrobenzo[b ]oxepin‐5(2H )‐one, ( 8 ), (E )‐4‐(5‐bromo‐2‐hydroxybenzylidene)‐6‐hydroxy‐8‐methoxy‐3,4‐dihydrobenzo[b ]oxepin‐5(2H )‐one, C₁₈H₁₅BrO₅, ( 9 ), and (E )‐4‐[(E )‐3‐(5‐bromo‐2‐hydroxyphenyl)allylidene]‐6‐hydroxy‐8‐methoxy‐3,4‐dihydrobenzo[b ]oxepin‐5(2H )‐one, ( 10 ), have been synthesized and characterized by FT–IR, NMR and MS. The structure of ( 9 ) was confirmed by single‐crystal X‐ray diffraction. Crystal structure analysis shows that molecules of ( 9 ) are connected into a one‐dimensional chain in the [010] direction through classical hydrogen bonds and these chains are further extended into a three‐dimensional network via C—H…O interactions. The inhibitory activities of these compounds against protein–tyrosine kinases (PTKs) show that 6‐hydroxy‐substituted compounds ( 9 ) and ( 10 ) are more effective for inhibiting ErbB1 and ErbB2 than are 6‐methoxy‐substituted compounds ( 7 ) and ( 8 ). This may be because ( 9 ) and ( 10 ) could effectively bind to the active pockets of the protein through intermolecular interactions.     

Two regioisomers of condensed thioheterocyclic triazine synthesized from 6‐phenyl‐3‐thioxo‐2,3,4,5‐tetrahydro‐1,2,4‐triazin‐5‐one

In the crystal structure of 6‐phenyl‐3‐thioxo‐2,3,4,5‐tetrahydro‐1,2,4‐triazin‐5‐one, C₉H₇N₃OS, (I), the 1,2,4‐triazine moieties are connected by face‐to‐face contacts through two kinds of double hydrogen bonds (N—H...O and N—H...S), which form planar ribbons along the a axis. The ribbons are crosslinked through C—H...π interactions between the phenyl rings. The molecular structures of two regioisomeric compounds, namely 6‐phenyl‐2,3‐dihydro‐7H‐1,3‐thiazolo[3,2‐b][1,2,4]triazin‐7‐one, C₁₁H₉N₃OS, (II), and 3‐phenyl‐6,7‐dihydro‐4H‐1,3‐thiazolo[2,3‐c][1,2,4]triazin‐4‐one, C₁₁H₉N₃OS, (III), which were prepared by the condensation reaction of (I) with 1,2‐dibromoethane, have been characterized by X‐ray crystallography and spectroscopic studies. The crystal structures of (II) and (III) both show two crystallographically independent molecules. While the two compounds are isomers, the unit‐cell parameters and crystal packing are quite different and (II) has a chiral crystal structure.     

Three‐Component Reaction for Construction of Spiro[indoline‐3,7′‐thiazolo[3,2‐a]pyridines] and Spiro[benzo[4,5]thiazolo[3,2‐a]pyridine‐3,3′‐indolines]

The three‐component reaction of thiazole (benzothiazole), dialkyl but‐2‐ynedioate, and isatinylidene malononitriles in toluene at 110–120°C in a sealed tube afforded a mixture of cis/trans‐isomers of functionalized diastereoisomeric spiro[indoline‐3,7′‐thiazolo[3,2‐a]pyridines] and spiro[benzo[4,5]thiazolo[3,2‐a]pyridine‐3,3′‐indolines] in good yields. Both cis‐isomers and trans‐isomers were successfully separated out and fully characterized with spectroscopy and single crystal determination. Under similar conditions, the three‐component reaction containing 2‐(1,3‐dioxo‐1H‐inden‐2(3H)‐ylidene)malononitrile resulted in spiro[indene‐2,7′‐thiazolo[3,2‐a]pyridine] derivatives.     

Synthesis of some new pyrido[2,3‐d]pyrimidines and their ribofuranosides as possible antimicrobial agents

The ribofuranosides, namely, 4‐amino‐5,7‐disubstituted‐1‐[2′,3′,5′‐tri‐O‐benzoyl‐α‐d ‐ribofuranosyl]pyrido‐[2,3‐d] pyrimidine‐2(1H)‐thiones, have been synthesized by the condensation of trimethylsilyl derivatives of 5,7‐disubstituted pyrido[2,3‐d]pyrimidine‐2(1H)‐thiones with β‐d ‐ribofuranose‐1‐acetate‐2,3,5‐tribenzoate in the presence of SnCl₄. The heterocyclic bases, namely, 4‐amino‐5,7‐disubstituted pyrido[2,3‐d]pyrimidine‐2(1H)‐thiones, were synthesized by the treatment of 2‐amino‐3‐cyano‐4,6‐disubstituted pyridines with thiourea. The structures of all the synthesized ribofuranosides and their precursors have been established by elemental analysis, IR, and ¹H NMR spectral data. The ¹³C NMR data of ribofuranosides has also been presented. All the synthesized heterocyclic bases and their ribofuranosides have been screened for their antibacterial and antifungal activities. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:52–56, 2001     

Synthesis of 1‐Acyl‐3,4‐dihydroquinazoline‐2(1H)‐thiones by Cyclization of N‐[2‐(Isothiocyanatomethyl)phenyl] Amides Generated in situ from N‐[2‐(Azidomethyl)phenyl] Amides

An efficient method for the preparation of 1‐acyl‐3,4‐dihydroquinazoline‐2(1H)‐thiones 5 has been developed. The reaction of N‐[2‐(azidomethyl)phenyl] amides 3 , easily prepared by a three‐step sequence starting with (2‐aminophenyl)methanols, with Ph₃P, followed by CS₂, allowed generation of N‐[2‐(isothiocyanatomethyl)phenyl]‐amide intermediates 4 , which underwent cyclization on treatment with NaH to furnish the corresponding desired products in generally good yields.     

Synthesis of Novel Spiro Pyrano[2,3‐d]thiazolo[3,2‐a]pyrimidine via 1,3‐Dipolar Cycloaddition of Azomethine Ylide

The reaction involving 4‐phenyl‐octahydro‐pyrano[2,3‐d]pyrimidine‐2‐thione, ethyl chloroacetate and the appropriate aromatic aldehyde yielded 2‐arylmethylidene‐5‐phenyl‐5a,7,8,9a‐tetrahydro‐5H,6H‐pyrano[2,3‐d][1,3]thiazolo[3,2‐a]pyrimidin‐3(2H)‐ones. The 1,3‐dipolar cycloaddition of 2‐arylmethylidene‐5‐phenyl‐5a,7,8,9a‐tetrahydro‐5H,6H‐pyrano[2,3‐d][1,3]thiazolo[3,2‐a]pyrimidin‐3(2H)‐ones with azomethine ylide generated by a decarboxylative route from sarcosine and acenaphthenequinone afforded 4′‐aryl‐1′‐methyl‐5″‐phenyl‐5a″,7″,8″,9a″‐tetrahydro‐2H,5″H,6″H‐dispiro[acenaphthylene‐1,2′‐pyrrolidine‐3′,2″‐pyrano[2,3‐d][1,3]thiazolo[3,2‐a]pyrimidine]‐2,3″‐diones in moderate yields. The structures of the products were determined and characterized thoroughly by NMR, MS, IR, elemental analysis, and X‐ray crystallographic analysis.     

Synthesis of dispiro[oxindole‐pyrrolidine]‐thiazolo[3,2‐a][1,3,5]triazines by 1,3‐dipolar cycloaddition

The 1,3‐dipolar cycloaddition of an azomethine ylide generated by a decarboxylative route from sarcosine and isatin to 7‐arylmethylidene‐3‐aryl‐3,4‐dihydro‐2H‐thiazolo[3,2‐a][1,3,5]triazin‐6(7H)‐ones afforded novel dispiro[oxindole‐pyrrolidine]‐thiazolo[3,2‐a][1,3,5]triazines in moderate yields. The structures of the products were determined and characterized thoroughly by NMR, MS, IR, and elemental analysis. The results of experiment indicated that this 1,3‐dipolar cycloaddition proceeded with high stereoselectivity and regioselectivity. J. Heterocyclic Chem., (2011).     

Preparation and Reactions of 2‐Methyl‐7‐(3‐methyl‐5‐oxo‐1‐phenyl‐2‐pyrazolin‐4‐yl)‐5‐arylthiazolo[3,2‐a]‐pyrimido[4,5‐d]oxazin‐4(5H)‐one

Ethyl 7‐amino‐3‐(3‐methyl‐5‐oxo‐1‐phenyl‐2‐pyrazolin‐4‐yl)‐5‐aryl‐5H‐thiazolo[3,2‐a]pyrimidine‐6‐carboxylate was hydrolyzed with an ethanolic sodium hydroxide and the sodium salt thus formed underwent cyclization with acetic anhydride to afford 2‐methyl‐7‐(3‐methyl‐5‐oxo‐1‐phenyl‐2‐pyrazolin‐4‐yl)‐5‐arylthiazolo[3,2‐a]pyrimido[4,5‐d]oxazin‐4(5H)‐one. This compound was transformed to related heterocyclic systems via its reaction with various reagents. The biological activity of the prepared compounds was tested against Gram positive and Gram negative bacteria as well as yeast‐like and filamentous fungi. They revealed in some cases excellent biocidal properties.     

The psuedo‐michael reaction of 2‐aminoimidazolines 2. Part 1. Synthesis and structure assignment of isomeric 5(1H)‐Oxo and 7(1H)‐Oxo‐2,3‐dihydroimidazo[1,2‐a]pyrimidine‐6‐carboxylates

The pseudo‐Michael reaction of 1‐aryl‐2‐aminoimidazolines‐2 with diethyl ethoxymethylenemalonate (DEEM) was investigated. Extensive structural studies were performed to confirm the reaction course. For derivatives with N1 aromatic substituents, it was found that the reaction course was temperature dependent. When the reaction temperature was held at ?10 °C only the formation of 1‐aryl‐7(1H)‐oxo‐2,3‐dihydroimi‐dazo[1,2‐a]pyrimidine‐6‐carboxylates ( 4 ) was observed in contrast to earlier suggestions. Under the room temperature conditions, the same reaction yielded mixtures, with varying ratio, of isomeric 1‐aryl‐7(1H)‐oxo‐ ( 4a‐4f ) and 1‐aryl‐5(1H)‐oxo‐2,3‐dihydroimidazo[1,2‐a]pyrimidine‐6‐carboxylates ( 5a‐5f ). The molecular structure of selected isomers, 4b and 5c , was confirmed by X‐ray crystallography. Frontal chro‐matography with delivery from the edge was applied for the separation of the isomeric esters. The isomer ratio of the reaction products depended on the character of the substituents on the phenyl ring. The 1‐aryl‐7(1H)‐oxo‐carboxylates ( 4a‐4f ) were preferably when the phenyl ring contained H, 4‐CH₃, 4‐OCH₃ and 3,4‐Cl₂ substituents. Chloro substitution at either position 3 or 4 in the phenyl ring favored the formation of isomers 5a‐5f . The isomer ratios were confirmed both by ¹H NMR and chromatography. The reaction of the respective hydrobromides of 1‐aryl‐2‐aminoimidazoline‐2 with DEEM, in the presence of triethylamine, gave selectively 5(1H)‐oxo‐esters ( 5a‐5f ).