Synthesis of [2‐aryl‐6‐oxo‐6H‐chromeno[6,7‐d]oxazol‐8‐yl]‐acetic acid ethyl esters

A number of coumarino[6,7‐d]oxazoles (nitrogen analogs of psoralens) have been synthesized from (7‐hydroxy‐2‐oxo‐2H‐chromen‐4‐yl) acetic acid ethyl ester 1 . The synthetic route began with the nitration of 1 with nitric acid in acetic acid to give (6‐nitro‐7‐hydroxy‐2‐oxo‐2H‐chromen‐4‐yl) acetic acid ethyl ester 2 ; (3,6‐dinitro‐7‐hydroxy‐2‐oxo‐2H‐chromen‐4‐yl) acetic acid ethyl ester 3 and (3,6,8‐trinitro‐7‐hydroxy‐2‐oxo‐2H‐chromen‐4‐yl) acetic acid ethyl ester 4 . The reduction of 2 was accomplished with tin(II) chloride, tin, and concentrated hydrochloric acid in ethanol giving (6‐amino‐7‐hydroxy‐2‐oxo‐2H‐chromen‐4‐yl) acetic acid ethyl ester 5 . After the condensation of aminocoumarin 5 with aromatic aldehyde in glacial acetic acid medium, followed the dehydrocyclization to coumarino[6,7‐d]oxazoles 7a‐k . The intermediate Schiff's bases 6a‐k have been obtained from 5 with aromatic aldehyde in ethanol. Antibacterial and antifungal activities of the compounds have been evaluated.     

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 ).     

An efficient one pot synthesis of 3‐(2‐oxo‐2H‐chromen‐3‐yl)‐6H,8H‐pyrimido[4,5‐c]pyridazine‐5,7‐dionesl

An easy, simple and versatile one step synthesis of 3‐(2‐oxo‐2H‐chromen‐3‐yl)‐6H,8H‐pyrimido[4,5‐c]‐pyridazine‐5,7‐diones is reported by reaction of 3‐acetylcoumarins ( 1 ) with alloxan monohydrate ( 2 ) in acetic acid followed by hydrazine hydrate.     

First synthesis of 2‐(2,4,4‐trimethyl‐3,4‐dihydro‐2H‐benzo[h]chromen‐2‐yl)‐1‐naphthol and 3‐(2,4,4‐trimethyl‐3,4‐dihydro‐2H‐benzo[g]chromen‐2‐yl)‐2‐naphthol from 1‐ and 2‐naphthol derivatives

Two new structurally isomeric, 2‐(2,4,4‐trimethyl‐3,4‐dihydro‐2H‐benzo[h]chromen‐2‐yl)‐1‐naphthol ( 1 ) and 3‐(2,4,4‐trimethyl‐3,4‐dihydro‐2H‐benzo[g]chromen‐2‐yl)‐2‐naphthol ( 3 ) have been synthesized from 2‐acetyl‐1‐naphthol and ethyl‐3‐hydroxy‐2‐naphthoate, respectively, involving Grignard reaction, dehydration of the corresponding tertiary alcohols, and hetero Diels–Alder dimerization. The two benzochromenes ( 1 and 3 ) have been fully characterized by IR, NMR, and HRESIMS data. Their structures are further supported by crystallography of their corresponding acetates ( 2 and 4 ). J. Heterocyclic Chem., (2011).     

Rapid and efficient microwave assisted method for the regioselective synthesis of 8,8′‐methylene‐bis‐4‐oxo‐1H and 2H‐chromeno[4,3‐C]pyrazoles

The ethyl ester of 5,5′‐methylene‐bis‐salicyclic acid 3 was prepared by the esterification of 5,5′‐methylene‐bis‐salicylic acid 2 . The compound 3 on reacting with ethylacetoacetate yields 6,6′‐methylenebis‐(3‐acetyl‐4‐hydroxycoumarin) 4 . The compound 4 was regioselectively converted into either 8,8′‐methylene‐bis‐(4‐oxo‐1H‐chromeno[4,3‐c]pyrazoles) 6 or 8,8′‐methylene‐bis(‐4‐oxo‐2H‐chromeno[4,3‐c]‐pyrazoles) 7 under microwave irradiation. High yields are achieved even on a gram scale, while reaction times are considerably shortened compared to conventional heating conditions.     

Synthesis and Reactions of the Novel 6‐ethyl‐4‐hydroxy‐2,5‐dioxo‐5,6‐dihydro‐2H‐pyrano[3,2‐c]quinoline‐3‐carboxaldehyde

The novel 6‐ethyl‐4‐hydroxy‐2,5‐dioxo‐5,6‐dihydro‐2H‐pyrano[3,2‐c]quinoline‐3‐carboxaldehyde ( 2 ) was efficiently synthesized from Vilsmeier–Haack formylation of 3‐(1‐ethy1‐4‐hydroxy‐2‐oxo‐(1H)‐quinolin‐3‐yl)‐3‐oxopropanoic acid ( 1 ). The aldehyde 2 was allowed to react with some nitrogen nucleophiles producing a variety of hydrazones 3 – 7 . Reaction of aldehyde 2 with hydrazine hydrate and hydroxylamine hydrochloride afforded pyrazole and isoxazole annulated pyrano[3,2‐c]quinoline‐2,5(6H)‐dione, respectively. The reactivity of aldehyde 2 was examined toward some active methylene nitrile, namely, malononitrile, ethyl cyanoacetate, and cyanoacetamide leading to 2‐iminopyrano[2′,3′:4,5]pyrano[3,2‐c]quinolines 10 – 12 , respectively. Also, some novel pyrazolo[4″,3″:5′,6′]pyrano[2′,3′:4,5]pyrano[3,2‐c]quinolines ( 13 , 14 ) and thiazolo[5″,4″:5′,6′]pyrano[2′,3′:4,5]pyrano[3,2‐c]quinolines ( 15 , 16 ) were synthesized. Structures of the new synthesized products were deduced on the basis of their analytical and spectral data.     

New synthesis and reactivity of 3‐bromoacetyl‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one with binucleophilic amines

3‐(Bromoacetyl)‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one was synthesized by the reaction of dehydroacetic acid (DHAA) with bromine in glacial acetic acid. Novel heterocyclic products were synthesized from the reaction of bromo‐DHAA with alkanediamines, phenylhydrazines, ortho‐phenylenediamines, and ortho‐aminobenzenethiol. The obtained new products 3‐(2‐N‐substituted‐acetyl)‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐ones, 4‐hydroxy‐3‐[1‐hydroxy‐2‐(2‐phenylhydrazinyl)vinyl]‐6‐methyl‐2H‐pyran‐2‐one, 1‐(2,4‐dinitrophenyl)‐7‐methyl‐2,3‐dihydro‐1H‐pyrano[4,3‐c]pyridazine‐4,5‐dione, 3‐(3,4‐dihydroquinoxalin‐2‐yl)‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one/3‐(3,4‐dihydroquinoxalin‐2‐yl)‐6‐methyl‐2H‐pyran‐2,4(3H)‐dione, 6‐methyl‐3‐(3,4‐dihydroquinoxalin‐2‐yl)‐2H‐pyran‐2,4(3H)‐dione, and (E)‐3‐(2H‐benzo[b][1,4]thiazin‐3(4H)‐ylidene)‐6‐methyl‐2H‐pyran‐2,4(3H)‐dione were fully characterized by IR, ¹H and ¹³C NMR, and mass spectra. J. Heterocyclic Chem., 2011.     

Quinolone analogues 2. A facile synthesis of novel 3‐substituted 1‐alkyl‐4‐oxo‐1,4‐dihydropyridazino[3,4‐b]quinoxalines

The reaction of the 2‐(1‐alkylhydrazino)‐6‐chloroquinoxaline 4‐oxides 1a,b with diethyl acetone‐dicarboxylate or 1,3‐cyclohexanedione gave ethyl 1‐alkyl‐7‐chloro‐3‐ethoxycarbonylmethylene‐1,5‐dihydropyridazino[3,4‐b]quinoxaline‐3‐carboxylates 5a,b or 6‐alkyl‐10‐chloro‐1‐oxo‐1,2,3,4,6,12‐hexahydroquinoxalino[2,3‐c]cinnolines 7a,b , respectively. Oxidation of compounds 5a,b with nitrous acid afforded the ethyl 1‐alkyl‐7‐chloro‐3‐ethoxycarbonylmethylene‐4‐hydroxy‐1,4‐dihydropyridazino‐[3,4‐b]quinoxaline‐4‐carboxylates 9a,b , whose reaction with base provided the ethyl 2‐(1‐alkyl‐7‐chloro‐4‐oxo‐1,4‐dihydropyridazino[3,4‐b]quinoxalin‐3‐yl)acetates 6a,b , respectively. On the other hand, oxidation of compounds 7a,b with N‐bromosuccinimide/water furnished the 4‐(1‐alkyl‐7‐chloro‐4‐oxo‐1,4‐dihydropyridazino[3,4‐b]quinoxalin‐3‐yl)butyric acids 8a,b , respectively. The reaction of compound 8a with hydroxylamine gave 4‐(7‐chloro‐4‐hydroxyimino‐1‐methyl‐1,4‐dihydropyridazino[3,4‐b]quinoxalin‐3‐yl)‐butyric acid 12 .     

Facile Synthesis of Novel 3‐(4‐phenylisothiazol‐5‐yl)‐2H‐chromen‐2‐one Derivatives as Potential Anticancer Agents

A series of 3‐(4‐phenylisothiazol‐5‐yl)‐2H‐chromen‐2‐one ( 6a – l ) derivatives has been efficiently synthesized by straightforward sequential reactions. Tandem Vilsmeier Hack reaction/cyclization/bromination/Suzuki cross‐coupling reactions were successfully applied to the preparation of title compounds in good‐to‐high yields. In the synthetic sequences, 3‐chloro‐3‐(2‐oxo‐2H‐chromen‐3‐yl)acrylaldehydes ( 2 ) were found to react with ammonium thiocyanate to yield the corresponding 3‐(isothiazol‐5‐yl)‐2H‐chromen‐2‐ones ( 3 ). These derivatives were brominated with N‐bromo succinamide to yield the corresponding regioselective 3‐(4‐bromoisothiazol‐5‐yl)‐2H‐chromen‐2‐one ( 4 ). Finally, compound 4 was treated with various phenyl/pyrazole/7H –pyrrolo[2,3‐d]pyrimidinyl boronic acids 5a – l in the presence of K₂CO₃ and Pd catalyst in dimethylformamide to yield the corresponding title derivatives 6a – l . All the synthesized compounds were characterized by analytical and spectral studies. All the final compounds were screened against different cancer cell lines (A549, PC3, SKOV3, and B16F10), and among these compounds, 6b , 6g , 6h , and 6l displayed moderate cytotoxic activity against the tested cell lines.     

An Efficient,Multicomponent Synthesis of Pyrazolyl Triazolo Thiadiazinyl Chromen ‐ 2 ‐ Ones

One‐pot synthesis of 3‐(3‐(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)‐7H‐[1,2,4]triazolo[3,4‐b][1,3,4]thiadiazin‐6‐yl)‐2H‐chromen‐2‐ones was achieved via the multicomponent reaction of purpald, acetyl acetone, and different derivatives of 3‐(2‐bromo‐acetyl)‐2H‐chromen‐2‐one in absolute ethanol. All the synthesized compounds were characterized by analytical and spectral data.     

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.     

Facile and simple synthesis of some new polyfunctionally heterocyclic derivatives incorporating 2‐imino‐2H‐chromene moiety

1,2‐Dihydro‐2‐imino‐6‐(2‐imino‐2H‐chromen‐3‐yl)‐1,4‐diphenyl‐pyridine‐3‐carbonitrile 4 has been synthesized and reacted with ethyl cyanoacetate to yield the new 5‐amino‐1,7‐dihydro‐2‐(2‐imino‐2H‐chromen‐3‐yl)‐7‐oxo‐1,4‐diphenyl‐1,8‐naphthyridine‐6‐carbonitrile 6 , which consider a good and available starting intermediate for synthesis of series of functionalized chromenes. So, the compound 6 was utilized as a key for the synthesis of some new pyrimido[5,4‐c][1,8]naphthyridinones, pyrido[2,3‐c][1,6]naphthyridinones, triazolo[3′,4′:1,6]triazino][5,4‐c][1,8]naphthyridinones, triazolo[2′,3′:1,6]pyrimido[4,5‐c][1,8]naphthyridinones, triazepino[6,5‐c][1,8]naphthyridinone, and triazino[5,4‐c][1,8]naphthyridinones. The structures of these compounds were established by elemental analysis, IR, MS, and NMR spectral analysis. J. Heterocyclic Chem., (2012).     

Synthesis of 1,3,4‐Oxadiazole Acyclo C‐Nucleosides Bearing 5‐Methylthio{7‐substituted‐1,2,4‐triazolo[1,5‐d]tetrazol‐6‐yl}moieties

Oxidative cyclization of the sugar hydrazones ( 3_a‐f ) derived from {7H‐1,2,4‐triazolo[1,5‐d]tetrazol‐6‐ylsulfanyl}acetic acid hydrazide ( 1 ) and aldopentoses 2_a‐c or aldohexoses 2_d‐f with bromine in acetic acid in the presence of anhydrous sodium acetate, followed by acetylation with acetic anhydride gave the corresponding 2‐(per‐O‐acetyl‐alditol‐l‐yl)‐5‐methylthio{7H‐1,2,4‐triazolo[1,5‐d]tetrazol‐6‐yl}‐1,3,4‐oxadiazoles ( 5_a‐f ). Condensative cyclization of the sugar hydrazones ( 3_a‐f ) by heating with acetic anhydride gave the corresponding 3‐acetyl‐2‐(per‐O‐acetyl‐alditol‐1‐yl)‐2,3‐dihydro‐5‐methylthio{7‐acetyl‐1,2,4‐triazolo[1,5‐d]tetrazol‐6‐yl}‐1,3,4‐oxadiazoles ( 11_a‐f ). De‐O‐acetylation of the acyclo C‐nucleoside peracetates ( 5 and 11 ) with methanolic ammonia afforded the hydrazono lactones ( 7 ) and the acyclo C‐nucleosides ( 12 ), respectively. The structures of new oxadiazole derivatives were confirmed by analytical and spectral data.     

Synthesis,Characterization, and Cytotoxicity Evaluation of Some New Benzo[f]coumarin Derivatives

Interaction of 2‐(bromoacetyl)‐3H‐benzo[f]coumarin ( 1 ) with salicylaldehyde afforded 2‐(2‐oxo‐2‐(3H‐benzo[f]coumarin‐2‐yl)ethoxy)benzaldehyde ( 2 ) which underwent self‐condensation in refluxing dimethylformamide (DMF) to afford 2‐(2‐benzofuroyl)‐3H‐benzo[f]coumarin (3). Treatment of 1 with o‐aminothiophenol ( 4 ) gave 2‐(2‐((2‐aminophenyl)thio)acetyl)‐3H‐benzo[f]coumarin (5) . Refluxing of 5 in DMF led to formation of 2‐(4H‐[1,4]‐benzothiazin‐3‐yl)‐3H‐benzo[f]coumarin (6). Treatment of 1 with aryl amines 7a–d in boiling DMF gave 1‐aryl‐3‐hydroxybenzo[5,6]chromeno[4,3‐b]pyrrol‐4(1H)‐one ( 10a–d ) . Condensation of 11 with o‐phenylenediamine gave 2‐(2‐methyl‐2,3‐dihydro‐1H‐benzimidazol‐2‐yl)‐3H‐benzo[f]coumarin ( 12 ). Interaction of 2‐acetyl‐3H‐benzo[f]coumarin ( 11 ) with arylidene malonononitrile gave 4‐hydroxy‐2‐(3H‐benzo[f]coumarin‐2‐yl)‐5H‐dibenzo[c,f]chromen‐5‐one ( 16) . All reaction products were characterized by analytical and spectral data. Novel compounds bioactivity as antitumor were examined for in vitro cytotoxicity against HepG‐2 and MCF‐7.     

Synthesis anti‐fungal and anti‐bacterial screening of 3‐phenyl‐1,4,5‐trihydro‐pyrazol and 2, 4‐dihydro[ 1,2,4]‐triazol‐3‐one derivatives of 4‐hydroxy‐2‐oxo‐2H‐1‐benzopyran

4‐Hydroxy‐2‐oxo‐2H‐1‐benzopyran‐3‐carboxaldehydes 2a‐d are prepared from 4‐hydroxy‐2‐oxo‐2H‐1‐benzopyrans 1a‐d via the Vielsmeyer Haack reaction. The 4‐hydroxy‐2‐oxo‐3‐(3′oxo‐3′‐phenylprop‐1′‐enyl)‐2H‐1‐benzopyrans 3a‐d are obtained from 2a‐d via the Claisen reaction. Refluxing compounds 3a‐d with hydrazine hydrate gave the 3‐phenyl‐5‐(4‐hydroxy‐2‐oxo‐2H‐1‐benzopyran‐3‐yl)‐1,4,5‐trihydropyra‐zols 4a‐d . Stirring compounds 2a‐d with semicarbazide hydrochloride in acidic medium gave the 4‐hydroxy‐2‐oxo‐2H‐1‐benzopyran‐3‐aldehyde‐semicarbazone 5a‐d , which on cyclisation with ferric chloride hexahydrate gave the 5‐(4‐hydroxy‐2‐oxo‐2H‐1‐benzopyran‐3‐yl)‐2,4‐dihydro[1,2,4]triazol‐3‐ones 6a‐d . All these compounds show significant antibacterial activities.     

An Efficient One‐pot Three‐component Method for the Synthesis of 5‐Amino‐3‐(2‐oxo‐2H‐chromen‐3‐yl)‐7‐aryl‐7H‐thiazolo[3,2‐a]pyridine‐6,8‐dicarbonitriles

A facile, convenient, and adequate method has been developed for the synthesis of novel 5‐amino‐3‐(2‐oxo‐2H‐chromen‐3‐yl)‐7‐aryl‐7H‐thiazolo[3,2‐a]pyridine‐6,8‐dicarbonitriles ( 6 ) by employing 2‐(4‐(2‐oxo‐2H‐chromen‐3‐yl)thiazol‐2‐yl)acetonitrile ( 3 ) as an important precursor. Initially, we have synthesized the target compounds in a stepwise manner and then approached a tandem method to examine the feasibility of one‐pot method. Subsequently, one‐pot three‐component protocol has been established for the synthesis of title compounds by the reaction of 3 with benzaldehyde and malononitrile in refluxing ethanol engender a new six‐membered thiazolo[3,2‐a] pyridine as a hybrid scaffold. Reaction conditions were optimized for this reaction and a broad substrate scope with various aryl and heteroaryl aldehydes make this protocol very practical, attractive, and worthy. Mechanistic aspects for the formation of these compounds were outlined comprehensively. Characterization of these newly synthesized compounds was achieved by means of IR, ¹H NMR, ¹³C NMR, and HRMS.     

New Approaches to the Synthesis of 4‐(2‐Aminophenyl)‐1,3‐dihydro‐2H‐imidazol‐2‐ones and 3‐Ureidoindoles and a Study of Their Interconversion

3‐Alkyl/aryl‐3‐ureido‐1H,3H‐quinoline‐2,4‐diones ( 2 ) and 3a‐alkyl/aryl‐9b‐hydroxy‐3,3a,5,9b‐tetrahydro‐1H‐imidazo[4,5‐c]quinoline‐2,4‐diones ( 3 ) react in boiling concentrated HCl to give 5‐alkyl/aryl‐4‐(2‐aminophenyl)‐1,3‐dihydro‐2H‐imidazol‐2‐ones ( 6 ). The same compounds were prepared by the same procedure from 2‐alkyl/aryl‐3‐ureido‐1H‐indoles ( 4 ), which were obtained from the reaction of 3‐alkyl/aryl‐3‐aminoquinoline‐2,4(1H,3H)‐diones ( 1 ) with 1,3‐diphenylurea or by the transformation of 3a‐alkyl/aryl‐9b‐hydroxy‐3,3a,5,9b‐tetrahydro‐1H‐imidazo[4,5‐c]quinoline‐2,4‐diones ( 3 ) and 5‐alkyl/aryl‐4‐(2‐aminophenyl)‐1,3‐dihydro‐2H‐imidazol‐2‐ones ( 6 ) in boiling AcOH. The latter were converted into 1,3‐bis[2‐(2‐oxo‐2,3‐dihydro‐1H‐imidazol‐4‐yl)phenyl]ureas ( 5 ) by treatment with triphosgene. All compounds were characterized by ¹H‐ and ¹³C‐NMR and IR spectroscopy, as well as atmospheric pressure chemical‐ionisation mass spectra.     

An Efficient Synthesis of Chromeno[4,3‐d]isoxazolo[5,4‐b]pyridin‐6‐one Derivatives

A series of chromeno[4,3‐d]isoxazolo[5,4‐b]pyridin‐6‐one derivatives were easily and efficiently synthesized by the reaction of 3‐acyl‐2H‐chromen‐2‐ones with isoxazol‐5‐amine in acetic acid. Some synthesized compounds were evaluated for their antiproliferative properties in vitro against cancer cells, and these compounds were found to have some activities.     

Synthesis of 3‐Acetyl‐4‐hydroxy‐1‐phenylpyridin‐2(1H)‐one Derivatives

The cyclization of aryl ketone anilides 3 with diethyl malonate to affords 4‐hydroxy‐6‐phenyl‐6H‐pyrano[3,2‐c]‐pyridin‐2,5‐diones 4 in good yields. 3‐Acetyl‐4‐hydroxy‐1‐phenylpyridin‐2(1H)‐ones 5 are obtained by ring‐opening reaction of 4‐hydroxy‐6‐phenyl‐6H‐pyrano[3,2‐c]‐pyridin‐2,5‐diones 4 in the presence of 1,2‐diethylene glycol. The reaction of 3‐acetyl‐4‐hydroxy‐1‐phenylpyridin‐2(1H)‐ones 5 with hydroxylamine hydrochloride produces 4‐hydroxy‐3‐[N‐hydroxyethanimidoyl]‐1‐phenylpyridin‐2(1H)‐ones 6 from which 3‐alkyloxyiminoacetyl‐4‐hydroxy‐1‐phenylpyridin‐2(1H)‐ones 7 are obtained by reacting with alkyl bromides or iodides in the presence of anhydrous potassium carbonate with moderate yields. The similar compounds can be synthesized on refluxing 3‐acetyl‐4‐hydroxy‐1‐phenylpyridin‐2(1H)‐ones 5 with substituted hydroxylamine hydrochloride in the presence of sodium bicarbonate with good yields. Most of the synthesized compounds are characterized by IR and NMR spectroscopic methods.     

Synthesis of New Chromeno[4,3‐b]pyrazolo[4,3‐e]pyridines Derivatives with Antimicrobial Evaluation

A series of 2‐oxo‐2,5‐dihydro‐1H‐chromeno[4,3‐b]pyridine derivatives were obtained by using a one‐pot three component reaction of 2,2‐disubstituted chroman‐4‐one with aromatic aldehydes and 2‐cyanoacetamide in the presence of sodium hydroxide under solvent‐free conditions. Heating chromenopyridine derivatives with phosphoryl chloride gave the corresponding chloro derivatives. The reaction of the chloro derivatives with hydrazine hydrate afforded dihydrochromeno[4,3‐b]pyrazolo[4,3‐e]pyridines derivatives. Condensation of the dimethyl derivative compound with the aromatic aldehydes gave 8‐Arylideneamino‐6,6‐dimethyl‐10H‐chromeno[4,3‐b]pyrazolo[4,3‐e]pyridine.