bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation of halogenated derivatives of thiazolo[5,4‐d]thiazoleviadirect electrophilic aromatic substitution
Authors: Benin Vladimir , Yeates Alan T. , Dudis Douglas 
Published: March 2009

Abstractmagnified imageChlorination and bromination reactions of thiazolo[5,4‐d]thiazole led to the generation of its mono‐ and dihalogenated derivatives. These are the first instances of successful direct electrophilic aromatic substitution in the thiazolo[5,4‐d]thiazole ring system. X‐ray analysis demonstrates that both 2‐bromothiazolo[5,4‐d]‐thiazole and 2,5‐dibromothiazolo[5,4‐d]thiazole are planar structures, with strongly manifested π‐stacking in the solid state. Theoretical analysis of the pyridine‐catalyzed halogenation (MP2/6‐31+G(d)andB3LYP/6‐31+G(d)calculations) reveals that introduction of one halogen actually leads to a slightly enhanced reactivity towards further halogenation. Several halogenation mechanisms have been investigated: 1) The direct C‐halogenation with N‐halopyridine as electrophile; 2) C‐halogenationviaintermediate N‐halogenation, and 3) C‐halogenation following an addition ‐ elimination pathway, with intermediate formation of a cyclic halonium ion. The theoretical studies suggest that the direct C‐halogenation is the favored mechanism.
Synthesis and characterization of substituted (benzo[b]thiophen‐2‐yl)‐4‐methyl‐4,5‐dihydro‐1H‐imidazol‐5‐ones
Authors: Sedlák Miloš , Drabina Pavel , Lánský Václav , Svoboda Jiří 
Published: March 2009

Abstractmagnified imageReactions of 3‐chlorobenzo[b]thiophene‐2‐carbonyl chloride with 2‐alkyl‐2‐aminopropanamides have been used to prepare a series of carboxamides 1a‐d (yields 61‐85%). The products were submitted to base‐catalysed ring closure reactions to give the corresponding 4,5‐dihydro‐1H‐imidazol‐5‐ones 2a‐d (yields 69‐97%). By N‐methylation and N‐benzylation were prepared the corresponding 1‐alkyl derivatives 3a(91%) and 3b (85%). These two alkyl derivatives were studied from the standpoint of potential replacement of 3‐chlorine substituent by piperidine via the Buchwald‐Hartwig reaction. It was found that the reaction gives besides except required products of C‐N coupling 5a (14%) and 5b (12%) also products of reductive dechlorination 4a (max. 57%) and 4b (max. 56%). The reductive dechlorination product 4a is formed exclusively (42%) if butyl‐di‐(1‐adamantyl)phosphine (BDAP) is used.
Synthesis of 1,3‐thiazole and 1,2,4‐oxadiazole substituted spiro[3H‐indole‐3,2′‐thiazolidine]‐2,4′(1H)‐diones
Authors: Mashelkar Uday C. , Rane Deepak M. , Kenny Rajesh S. 
Published: March 2009

Abstractmagnified imageSome new derivatives of spiro[3H‐indole‐3,2′‐thiazolidine]‐2,4′(1H)‐dione with the heterocyclic ring such as substituted thiazole and 1,2,4‐oxadiazole attached to the indolinone ring via CH2 linkage has been synthesized in moderate yields. The synthesis have been carried out by making use of the reactivity of the NH group of the indolinone moiety present in spiro[3H‐indole‐3,2′‐thiazolidine]‐2,4′(1H)‐dione.
Reaction of β‐dimethylaminovinyl ketones with hydroxylamine: A simple and useful method for synthesis of 3‐ and 5‐substituted isoxazoles
Authors: Rosa Fernanda A. , Machado Pablo , Bonacorso Helio G. , Zanatta Nilo , Martins Marcos A. P. 
Published: March 2009

Abstractmagnified imageThe regioselective synthesis of 3‐ and 5‐substituted‐isoxazoles from the reaction of β‐dimethyl‐aminovinyl ketones [R‐C(O)CHCH‐NMe2, where R  Ph, MeO‐4‐C6H4, F‐4‐C6H4, Cl‐4‐C6H4, Br‐4‐C6H4, O2N‐4‐C6H4, fur‐2‐yl, thien‐2‐yl, pyrrol‐2‐yl, Et and CCl3] and hydroxylamine hydrochloride varying only the reaction conditions (with and without the addition of pyridine) is reported.
Synthesis, characterization and studies of new 3‐benzyl‐4H‐1,2,4‐triazole‐5‐thiol and thiazolo[3,2‐b][1,2,4]triazole‐5(6H)‐one heterocycles
Authors: Sarhan Abdelwareth A. O. , Elsherif Hassa N. A. H. , Mahmoud Abdalla M. , Habib Osama M. A. 
Published: March 2009

Abstractmagnified image3‐Benzyl‐4‐phenyl‐1,2,4‐triazole‐5‐thiol (1) was synthesized and used as starting material for preparation of 1,2,4‐triazole bearing substituted thiosemicarbazides moiety (4a‐d) in high yields. The thiosemicarbazides4a‐dwere cyclized in basic medium to give two triazole rings linked by thiomethylene group (5a‐d), while cyclization of thiosemicarbazides4a‐dwith chloroacetyl chloride in the presence of CHCl3and K2CO3afforded the thiazolidinone derivatives6a‐d. The reaction of thiosemicarbazides4a‐cwith phenacyl bromide in the presence of EtOH and fused CH3COONa gave the corresponding thiazoline ring systems7a‐c. Condensation of the 3‐benzyl‐1,2,4‐triazole‐5(1H)‐thiol (1) with chloroacetic acid and aromatic aldehydes (8a‐g) in boiling acetic acid/acetic anhydride mixture in the presence of fused sodium acetate gave one single isomer only, which might be9a‐gor10a‐g. Upon application of Micheal addition reaction on compounds9a‐ewith cyclic secondary amines such as piperidine or morpholine the 2‐benzyl‐6‐(α‐amino‐aryl/methyl)‐1,3‐thiazolo[3,2‐b][1,2,4]‐triazol‐5‐ols (11a‐j) were obtained in good yields The structure of all new compounds were determined using both spectral and elemental analyses.
Synthesis and liquid crystalline properties of novel pyridine derivatives
Authors: Itahara Toshio 
Published: March 2009

Abstractmagnified imageThe treatment of 4‐hydroxypyridine with cholestery p‐(ω‐bromoalkyloxy)benzoates in N,N‐dimethylformamide containing K2CO3 gave cholestery p‐[ω‐(4‐pyridyloxy)alkyloxy]benzoates, which exhibited liquid crystalline properties
Convenient syntheses of 5‐[(2‐methyl‐5‐nitro‐1H‐imidazol‐1‐yl)methyl]‐1,3,4‐oxadiazole‐2(3H)thione and N‐substituted 2‐amino‐5‐[(2‐methyl‐5‐nitro‐1H‐imidazol‐1‐yl)methyl]‐1,3,4‐thiadiazoles
Authors: Mirzaei Javad , Pirelahi Hooshang , Amini Mohsen , Shafiee Abbas 
Published: March 2009

Abstractmagnified imageOxidation of metronidazole (4) with sodium dichromate yielded the corresponding 2‐(2‐methyl‐5‐nitro‐1H‐imidazol‐1‐yl)acetic acid (5) which was esterified with 1‐butanol to give butyl 2‐(2‐methyl‐5‐nitro‐1H‐imidazol‐1‐yl)acetate (8). Reaction of the latter with hydrazine hydrate gave 2‐(2‐methyl‐5‐nitro‐1H‐imidazol‐1‐yl)acetohydrazide (9). Compound 5‐[(2‐methyl‐5‐nitro‐1H‐imidazol‐1‐yl)methyl]‐1,3,4‐oxa‐diazole‐2(3H)‐thione (10) could be obtained through the reaction of compound 9 with carbon disulfide in basic medium. Subsequent alkylation of compound 10 afforded alkyl 2‐(5‐[(2‐methyl‐5‐nitro‐1H‐imidazol‐1‐yl)methyl]‐1,3,4‐oxadiazol‐2‐ylthio)acetate (11) in good yield. Reaction of hydrazide 9 with substituted isothiocynate yielded 1‐[2‐(2‐methyl‐5‐nitro‐1H‐imidazol‐1‐yl)acetyl]‐4‐aryl(or ethyl)thiosemicarbazide (12) which was cyclized in acidic media to N‐substituted 2‐amino‐5‐[(2‐methyl‐5‐nitro‐1H‐imidazol‐1‐yl)methyl]‐1,3,4‐thiadiazole (13).
Synthesis of new 3‐(trifluoromethyl)‐1H‐indoles by reduction of trifluoromethyloxoindoles
Authors: Bastos Moônica M. , Mayer Lúcia M. U. , Figueira Elza C. S. , Soares Marcio , Boechat Núbia , Kover Warner B. 
Published: March 2009

Abstractmagnified imageThis work describes the synthesis of new 3‐trifluoromethylindoles. Different isatins were trifluoromethylated using (trifluoromethyl) trimethylsilane (Me3SiCF3) as a nucleophilic agent giving new 3‐hydroxy‐3‐(trifluoromethyl)indolin‐2‐one. Different “one‐step” procedures to transform the latter compounds into the reduced indoles were attempted, but failed. For the synthesis of the new trifluoromethylindoles the corresponding 2‐oxo‐3‐(trifluoromethyl)indoles were reduced using borane/THF complex to furnish 3‐(trifluoromethyl)indolin‐3‐ol that additionally were dehydrated using thionyl chloride in pyridine to give excellent yields of the desired products.
Studies with 2‐arylhydrazononitriles: Further investigations on reactivity of 2‐arylhydrazononitriles towards hydroxylamine
Authors: Riyadh Sayed M. , Al‐Matar Hamad M. , Elnagdi Mohamed H. 
Published: March 2009

Abstractmagnified imageThe utilization of arylhydrazononitriles (6‐9) for synthesis of azoles is demonstrated. Thus, arylazomalononitriles (6) reacted with hydroxylamine hydrochloride to afford isoxazol‐5‐imine (10), amidoxime (12) and bis‐amidoxime (13) derivatives depending upon both the reaction conditions and molar ratio employed. 2‐Thiazolyl‐2‐arylhydrazononitriles (7) and cyanoformazans (8) gave 1,2,3‐triazole derivatives (15) and (17) respectively upon treatment with hydroxylamine hydrochloride and concomitant loss of water molecule. Formation of novel 1,2,4‐triazin‐5(4H)‐one derivatives (21) has efficiently been carried out by treatment of amidoximes (18) with acetic anhydride in acetic acid.
A convenient synthesis and biological activities of novel 6‐aryl‐3‐(1,2,3,4‐tetrahydroxybutan‐1‐yl)‐7H‐1,2,4‐triazolo‐[3,4‐b][1,3,4]thiadiazines
Authors: Ye Xiao‐Xia , Zhang Jin , Zhang An‐Jiang , Zhang Li‐Xue 
Published: March 2009

Abstractmagnified imageA series of novel 6‐aryl‐3‐(1,2,3,4‐tetrahydroxybutanol‐1‐yl)‐7H‐1,2,4‐triazolo[3,4‐b][1,3,4]thiadiazines were easily synthesized in high yields by means of the reactions of 4‐amino‐5‐(1,2,3,4‐tetrahydroxybutyl)‐2,4‐dihydro‐3H‐1,2,4‐triazole‐3‐thione (1) with substituted ω‐bromoacetophenones or ω‐chloroacetophenone. Nearly all of the title compounds possess plant growth‐promoting activities.
Synthesis and biological evaluation of novel methylene‐bisthiazolidinone derivatives as potential nematicidal agents
Authors: Srinivas A. , Nagaraj A. , Reddy Ch. Sanjeeva 
Published: March 2009

Abstractmagnified imageIn a one pot procedure, a series of novel methylene‐bis‐thiazolidinone derivatives 5 and 6 was prepared by condensation of 5‐(3‐formyl‐4‐methoxybenzyl)‐2‐methoxybenzaldehyde 3 with mercapto acids and primary aromatic amines 4 in presence of ZnCl2 under both microwave irradiation and conventional heating conditions. High yields are achieved even on a gram scale, while reaction times are considerably shortened under microwave irradiation compared to conventional heating conditions. Characterization of new compounds has been done by means of IR, NMR, MS and elemental analysis. The nematicidal and antibacterial activity of the compounds has also been evaluated.
Synthesis of novel 5,7‐disubstituted 8‐hydroxyquinolines
Authors: Himmi Banacer , Kitane Saïd , Eddaif Abdelhamid , Joly Jean‐Pierre , Hlimi Fouzia , Soufiaoui Mohamed , Bahloul Abdelmejid , Sebban Abdelfatah 
Published: March 2009

Abstractmagnified imageSeven new 5,7‐disubstituted oxine derivatives have been synthesized via a Mannich reaction between a sec. amine (e.g. piperidine, pyrrolidine, morpholine, or dibenzylamine,) and 5‐cyano or 5‐azidomethyl‐8‐hydroxyquinoline, which were respectively obtained by nucleophilic displacement of 5‐chloromethyl‐8‐hydroxyquinoline by cyanide or azide anions. In all cases, a single product was isolated in medium to fair yield and characterized on the basis of 1H and 13C‐NMR, MS and IR spectrometric data. The X‐ray structure of the product obtained from 5‐cyanomethyl‐8‐hydroxyquinoline and piperidine is also reported.
I2‐catalyzed reactions of schiff base and alkyl aldehyde towards benzo[f]quinoline derivatives
Authors: Li Qing , Yao Chang‐Sheng , Zhang Mei‐Mei , Tu Shu‐Jiang , Wang Xiang‐Shan 
Published: March 2009

Abstractmagnified imageA mild, efficient, and general method for the synthesis of benzo[f]quinoline derivatives via a molecular iodine‐catalyzed reaction of Schiff base with alkyl aldehydes has been described. The structure of 3o was confirmed by X‐ray diffraction study.
Synthesis and biological activities of novel 1,3‐bis[substituted‐pyridyl (thiazolyl)methyl]‐2‐substitutedmethylideneimidazolidines
Authors: Yan Man , Luo Zai‐Gang , Zhu Xiao‐Fei , Shi De‐Qing 
Published: March 2009

Abstractmagnified imageA series of novel 1,3‐dissubstitutedpyridyl(thiazolyl)methyl‐2‐substituted‐methylideneimidazolidine derivatives 2 and 4 were designed and synthesized via the N‐alkylation of the disubstituted heterocyclic ketene aminal derivative 1. When 1 (R = CN, R' = COOC2H5) was used as the starting materials, mono N‐alkylated reaction can take place in good yields owing to the presence of the intramolecular hydrogen bond. However, as for 1 (R = R' = CN), it is difficult to obtain pure mono N‐alkylated product. The structures of the target compounds were confirmed by IR, 1H NMR, EI‐MS and elemental analyses, and, in the case of 2c, by single crystal X‐ray diffraction. The preliminary bioassay indicated that some of the title compounds possess moderate fungicidal and insecticidal activity.
An efficient microwave‐assisted synthesis furo[3,4‐b]‐[4,7] phenanthroline and indeno[2,1‐b][4,7]phenanthroline derivatives in water
Authors: Shi Feng , Zhou Dianxiang , Tu Shujiang , Shao Qingqing , Li Chunmei , Cao Longji 
Published: March 2009

Abstractmagnified imageA series of furo[3,4‐b][4,7]phenanthroline and indeno[2,1‐b][4,7]phenanthroline derivatives were synthesizedviaa three‐component reaction of aromatic aldehydes, 6‐aminoquinoline and either tetronic acid or 1,3‐indanedione in water, under microwave irradiation without use of any catalyst. This green procedure offers several advantages including operational simplicity, clean reaction, and increased safety for small‐scale high‐speed synthesis.
Heterocondensed thiophenes and thiazoles by THORPE‐ZIEGLER cyclization
Authors: Gruner Margit , Böttcher Gesine , Gewald Karl 
Published: March 2009

Abstractmagnified imageThe syntheses of novel thieno‐pyridones, thiazolo‐pyridones, thiazolo‐pyridines and amino‐ and diamino‐dieno‐pyridines were described. Simultaneously, it was demonstrated that in these compounds and in the related 3‐aminothiophenes the replacement of the methylthio by the morpholino group is possible. The structures were characterized using 1H‐, 13C‐NMR, IR and elemental analysis.
A green and efficient synthesis of furo[3,4‐e]pyrazolo[3,4‐b]‐pyridine derivatives in water under microwave irradiation without catalyst
Authors: Shi Feng , Tu Shujiang , Jiang Bo , Li Chunmei , Zhou Dianxiang , Shao Qingqing , Cao Longji , Wang Qian , Zhou Jianfeng 
Published: March 2009

Abstractmagnified imageA series of furo[3,4‐e]pyrazolo[3,4‐b]pyridine analogues of podophylloxin were synthesized via three‐component reactions of aldehydes, 3‐methyl‐1‐phenyl‐1H‐pyrazol‐5‐amine and tetronic acid in water under microwave irradiation without catalyst. This efficient synthesis not only offers an economical and green synthetic strategy to this class of significant compounds but also enriches the investigations on microwave‐assisted synthesis in water.
Synthesis and biological evaluation of novel methylene‐bis‐[1,5]‐benzodiazepines
Authors: Raghu M. , Nagaraj A. , Reddy Ch. Sanjeeva 
Published: March 2009

Abstractmagnified imageA series of novel methylene‐bis‐chalcones 3 was prepared by the reaction of 5‐(3‐formyl‐4‐hydroxybenzyl)‐2‐hydroxy benzaldehyde 2 with different acetophenones, subsequent treatment of compound 3 with an appropriate o‐phenylenediamine gave the corresponding methylene‐bis‐[1,5]‐benzodiazepines 4/5 in good yields. Characterization of the new compounds has been done by means of IR, 1H NMR, MS and elemental analyses. The antibacterial and antifungal activity of the compounds has also been evaluated.
Synthesis of some novel methylene‐bis‐pyrimidinyl‐spiro‐4‐thiazolidinones as biologically potent agents
Authors: Srinivas A. , Nagaraj A. , Reddy Ch. Sanjeeva 
Published: March 2009

Abstractmagnified imageA series of novel methylene‐bis‐pyrimidinyl‐spiro‐4‐thiazolidinones 6a‐h have been synthesized by cyclocondensation of thioglycolic acid with methylene‐bis‐(N‐cyclohexylidene‐N‐pyrimidine) 5a‐h, which in turn have been prepared by the reaction of cyclohexanone with methylene‐bis‐2‐aminopyrimidines 4a‐h, which are prepared by the reaction of guanidine hydrochloride with methylene‐bis‐chalcones 3a‐h. The compounds 3a‐h have been synthesized by the reaction of 5‐(3‐formyl‐4‐hydroxybenzyl)‐2‐hydroxybenzaldehyde 2 with various acetophenones in presence of KOH. The compound 2 is prepared by the reported method. The structures of the compounds synthesized have been confirmed by their elemental analysis and spectral data. Their antibacterial and antifungal activities have also been evaluated.
Green multicomponent synthesis of 1,2‐dihydro‐pyrimido[1,2‐a]‐benzimidazole‐3‐carbonitrile
Authors: Liu Guangmin , Shao Qingqing , Tu Shujiang , Cao Longji , Li Chunmei , Zhou Dianxiang , Han Baoping 
Published: March 2009

Abstractmagnified image1,2‐dihydro‐pyrimido[1,2‐a]benzimidazole‐3‐carbonitrile derivatives were synthesized via the three‐component reaction of aldehyde, malonodinitrile and 2‐aminobenzimidazole in water under microwave irradiation. The new protocol has the advantages of excellent yield, low cost, reduced environment impact, wide scope and convenient procedure.
Synthesis of a new class of bisheterocycles from phenacylsulfonylacetic acid methyl ester
Authors: Padmavathi Venkatapuram , Mohan Annaji Venkata Nagendra , Mahesh Konda 
Published: March 2009

Abstractmagnified imageNovel bisheterocycles, 1,2,3‐selenadiazoles, thiadiazoles and 2H‐diazaphospholes in combination with oxadiazoles, thiadiazoles and triazoles were prepared from phenacylsulfonylacetic acid methyl ester.
Darzens reaction of 2‐bromo‐4,6‐dimethoxy‐3(2H)‐benzofuranone with aromatic aldehydes to form flavonoids
Authors: Ottersbach Philipp A. , Bolek David , Lepičová Eva , Gütschow Michael , Nieger Martin 
Published: March 2009

Abstractmagnified imageThe applicability of 2‐bromo‐4,6‐dimethoxy‐3(2H)‐benzofuranone (1) to produce flavonoid‐derived epoxides in the course of the Darzens reaction with aldehydes was investigated. However, instead of the epoxides, flavonols 3 and, in certain cases, benzofuranyl‐substituted flavonols 4 were isolated. The generation of 3 is assumed due to a ring expansion of the initially formed epoxides. These flavonols can react with 1 to produce the unexpected 1:2 adducts 4 as minor products. The structure of the hexamethoxy derivative 4b (R1 = H, R2 = R3 = OMe) was confirmed by X‐ray crystallographic analysis.
Synthesis and anti‐HIV‐1 evaluation of 1,5‐disubstituted pyrimidine‐2,4‐diones
Authors: Loksha Yasser M. , Globisch Daniel , Pedersen Erik B. , La Colla Paolo , Collu Gabriella , Loddo Roberta 
Published: March 2009

Abstractmagnified image1,5‐Disubstituted pyrimidine‐2,4‐diones were synthesized by fusion of 5‐bromouracil with an aniline derivative followed by coupling with benzyl halide whereas the opposite synthesis sequence failed. Also 4,6‐dichloro‐N,N,5‐trimethylpyrimidin‐2‐amine was treated with phenols. The products were tested for their activity against HIV‐1.
Facile acidic hydrolysis and displacement reactions of 2‐chloro‐and 2,9‐dichloro‐1,10‐phenanthroline
Authors: Krapcho A. Paul , Sparapani Silvia 
Published: March 2009

Abstractmagnified imageTreatment of 2‐chloro‐ or 2,9‐dichloro‐1,10‐phenanthroline with aqueous HBr or aqueous H2SO4 at 120°C yielded 1,10‐phenanthroline‐2(1H)‐one or 1,10‐dihydro‐1,10‐phenanthroline‐2,9‐dione, respectively. The hydrolysis of 2,9‐dichloro‐1,10‐phenanthroline with 37% aqueous HC1 led to the half hydrolyzed amide and the bis‐amide. Under comparable reactions conditions, using aqueous HBr, H2SO4 or HC1, 2‐chloropyridine was found to be hydrolytically stable. On the other hand, 2‐chloro‐ or 2,9‐dichloro‐1,10‐phenanthroline on heating with 57% aqueous HI afforded the HI salts of 2‐iodo‐ or 2,9‐diiodo‐1,10‐phenanthroline, which could be isolated. These salts on treatment with aqueous ammonium hydroxide led to good yields of 2‐iodo‐ and 2, 9‐diiodo‐1,10‐phenanthroline, respectively. Treatment of 2‐chloropyridine with 57% aqueous HI under similar reaction conditions led to 2‐iodopyridine in a 10% conversion.
An efficient and clean one‐pot synthesis of 3,4‐dihydropyrimidine‐2(1H)‐ones catalyzed by tungstate sulfuric acid in solvent‐free conditions
Authors: Nasr‐Esfahani Masoud , Karami Bahador , Montazerozohori Morteza , Abdi Karim 
Published: March 2009

Abstractmagnified imageTungstate sulfuric acid catalyzes the three component condensation reaction of an aromatic aldehyde, urea and a β‐ketoester under solvent‐free conditions to afford the corresponding dihydropyrimidinones in high to excellent yields at room temperature.
Synthesis of some novel 2‐substituted‐N‐aryl‐benzoxazole‐5‐carboxamides using cobalt dipyridine dichloride as a catalyst
Authors: Sarangapani M. , Sridhar D. , Arjun M. , Chari M. Adharvana 
Published: March 2009

Abstractmagnified imageAn efficient synthesis of some novel 2‐substituted‐N‐aryl‐benzoxazole‐5‐carboxamides from 2‐substituted — 5‐carbomethoxy benzoxazole on treatment with different substituted anilines promoted by cobalt dipyridine dichloride as a catalyst is described. This new approach has the advantage of excellent yields (90%) and short reaction times 1‐2 h.
Highly efficient intramolecular cyclizations of 2′‐hydroxychalcones to 4‐chloro‐2H‐chromenes under vilsmeier conditions
Authors: Li Zhen‐Hua , Zheng Cun , Su Wei‐Ke 
Published: March 2009

Abstractmagnified imageHighly efficient intramolecular cyclization and of 2′‐hydroxychalcones to 4‐chloro‐2H‐chromenes under Vilsmeier conditions have been developed. In comparison with the reported methods, studies carried out indicate that Vilsmeier reagent generated in situ from DMF and bis(trichloromethyl) carbonate (BTC) provides excellent chemselectivity, higher yields and avoids the formation of inorganic phosphorus salts.
An efficient and expeditious microwave‐assisted synthesis of quinoxaline derivatives via nucleophilic heteroaromatic substitution
Authors: Cuenca Angela , Pérez Suhey , Yepez Arlene , Paredes Luisar , Montecinos Luisana , Llovera Ligia , Rodríguez César 
Published: March 2009

Abstractmagnified imageA series of 2‐substituted quinoxaline derivatives including five novel compounds have been successfully synthesized from 2‐chloroquinoxaline using microwave methodology. The yields of the quinoxalines synthesized through this method, were an improvement over the thermal methods usually employed.
Dichloro dicyano quinone (DDQ) as coupling reagent for high yield synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones
Authors: Shobha D. , Chari M. Adharvana , Sadanandam P. , Mukkanti K. 
Published: March 2009

Abstractmagnified imageDDQ catalyzes efficiently the three‐component condensation reaction of aldehyde, β‐ketoester and urea in refluxing acetonitrile to afford the corresponding dihydropyrimidinones. Compared to the classical Biginelli reaction conditions, this new approach consistently has the advantage of excellent yields (80‐92%) and short reaction times 1.5‐2.5 h.
New one‐ pot synthesis of pyrazolo[3,4‐c]pyridazine and isoxazolo‐[5,4‐b]pyridine derivatives from potassium cyanoacetahydroxamate
Authors: El‐Rady Eman A. , Barsy Magda A. 
Published: March 2009

Abstractmagnified imageThe reaction of potassium cyanoacetohydroxamate 1 with ethyl 2‐aryl‐hydrazono‐3‐oxobutyrates 2 gave the unexpected pyrazolo[3,4‐c]pyridazines 7 and isoxazolo[5,4‐b]pyridines 10 via a one‐pot reaction. A mechanistic proof is suggested to account for the products.
An efficient and green synthesis of 3,3′‐benzylidenebis (4‐hydroxy‐6‐methylpyridin‐2(1H)‐one) derivatives through multi‐component reaction in ionic liquid
Authors: Shi Daqing , Ji Shunjun , Shi Daqing , Ni Sainan , Yang Fang 
Published: March 2009

Abstractmagnified imageA series of new 3,3′‐benzylidenebis(4‐hydroxy‐6‐methylpyridin‐2(1H)‐one) derivatives were synthesizedviaa three‐component reaction of an aldehyde, an aniline or ammonium acetate and 6‐methyl‐4‐hydroxypyran‐2‐one in ionic liquid. These heterocyclic compounds produced could be conveniently separated from the reaction mixture without any volatile organic solvents, and the ionic liquid could be readily reused without efficiency loss after simple treatment.