Reactivity of (2‐methylsulfanyl‐4‐oxo‐6‐phenyl‐4h‐pyrimidin‐3‐yl)‐acetic acid methyl ester towards hydrazine hydrate and benzylamine

The title ester 1 reacted with hydrazine hydrate to give hydrazide 2 , which underwent intramolecular cyclization to yield 1‐amino‐7‐phenyl‐1H‐imidazo[1,2‐a]pyrimidine‐2,5‐dione ( 3 ) or took place in a substitution reaction with benzylamine to form N‐benzyl‐2‐(2‐benzylamino‐4‐oxo‐6‐phenyl‐4H‐pyrimidin‐3‐yl)‐acetamide ( 4 ). The reaction of ester 1 with benzylamine gave corresponding amide 7 , disubstituted derivative 4 or 1‐benzyl‐7‐phenyl‐1H‐imidazo[1,2‐a]pyrimidine‐2,5‐dione ( 8 ) depending on the reaction conditions.     

A practical synthesis of 5‐(4′‐methylbiphenyl‐2‐yl)‐1H‐tetrazole

Practical synthesis of 5‐(4′‐methylbiphenyl‐2‐yl)‐1H‐tetrazole, key intermediate in several angiotensin II receptor antagonists from 2‐fluorobenzonitrile in excellent yields and very high purity is described.     

Synthesis of some new 4‐substituted‐3, 5‐bis(2‐pyridyl)‐1h‐pyrazole

Several 4‐substituted‐3, 5‐bis(2‐pyridyl)‐1H‐pyrazoles, where the substituent is chloro, bromo, iodo, nitro, diazo, were synthesized under mild reaction conditions in high yields. The structures of the products were characterized by ¹H NMR, ¹³C NMR, ESI‐MS, IR and elemental analyses.     

Synthesis and characterization of 4‐aryl‐5‐(1‐aryl‐2‐methyl‐2‐nitropropyl)‐1,2,3‐selenadiazoles

The synthesis of a new set of selenadiazoles, 4‐aryl‐5‐(1‐aryl‐2‐methyl‐2‐nitropropyl)‐1,2,3‐selenadiazoles ( 4 ) derived from 2‐[4‐methyl‐4‐nitro‐1,3‐diarylpentylidene]‐1‐hydrazinecarboxamide ( 3 ) has been reported. THF has been found to be the solvent of choice for this reaction. Structural features of 3 and 4 have been analyzed by NMR and X‐ray techniques.     

Synthesis of fluorine containing N‐benzyl‐1,2,3‐triazoles and N‐methyl‐pyrazoles from conjugated alkynes

1, 3‐Dipolar‐cycloaddition reaction of fluoro substituted 3‐aryl‐propynenitriles 1 with benzyl azide 2 afforded the expected 3‐benzyl‐5‐aryl‐3H‐[1,2,3]triazole‐4‐carbonitrile 3 and 1‐benzyl‐5‐aryl‐1H‐[1,2,3]‐triazole‐4‐carbonitrile 4 in good yield. However, 1,3‐dipolar cycloaddition of diazomethane 5 with 3‐aryl‐propynenitriles 1 resulted in the exclusive formation of N‐methyl‐pyrazole derivatives 6 and 7 .     

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.     

Transformation of 4‐oxo‐4H‐[1]‐benzopyran‐3‐carboxaldehydes into pyrazolo[3,4‐B]pyridines

Reaction of 6‐methyl‐4‐oxo‐4H‐[1]‐benzopyran‐3‐carboxaldehyde 1 with 5‐amino‐3‐methyl‐1‐phenylpyrazole 2 in alcoholic reaction media in the presence of 4‐toluenesulfonic acid as catalyst afforded 5‐(2‐hydroxy‐5‐methylbenzoyl)‐3‐methyl‐1‐phenyl‐1H‐pyrazolo[3,4‐b]pyridine 3 and 2‐methoxy‐6‐methyl‐3‐(3‐methyl‐1‐phenylpyrazol‐5‐ylaminomethylene)chroman‐4‐one 7 . We explain the mechanism of formation of both products on the basis of kinetic study of individual reaction steps.     

Convenient synthesis of some new substituted pyrazolyl‐1,3,4‐oxadiazoles and pyrazolyl‐1,2,4‐triazoles

A simple and versatile method for the synthesis of pyrazol‐3‐yl‐1,3,4‐oxadiazole, pyrazol‐3‐yl‐1,2,4‐triazole, (1,5‐diphenylpyrazol‐3‐yl)‐(3,5‐dimethyl‐1‐carbonyl)pyrazole and (1,5‐diphenylpyrazol‐3‐yl)‐(5‐hydroxy‐3‐metheyl‐1‐carbonyl)pyrazole derivatives from 1,5‐diphenylpyrazole‐3‐carboxylic acid hydrazide has been developed.     

The [3 + 2] cycloaddition route to 5‐carbomethoxy‐4h‐1,2,3‐triazolo[1,5‐a][1]benzazepines from baylis‐hillman acetates of 2‐azidobenzaldehydes

A new, simple synthesis of 5‐carbomethoxy‐4H‐1,2,3‐triazolo[1,5‐a][1]benzazepines from the reaction of several Baylis‐Hillman acetates of 2‐azidobenzaldehydes with alkynide Grignard reagents such as phenylethynyl‐, 1‐propynyl‐ and ethynylmagnesium bromides followed by cycloaddition reaction has been described.     

Synthesis of 1‐(substituted phenylcarbonyl/sulfonylamino)‐1,2,3,6‐tetrahydropyridine‐5‐carboxylic acid diethylamides as potential anti‐inflammatory agents

Fifteen novel 1‐(substituted phenylcarbonyl/sulfonylamino)‐1,2,3,6‐tetrahydro‐ pyridine‐5‐carboxylic acid diethylamide ( 7, 15 ) were synthesized in fair to good yields via sodium borohydride reduction of the corresponding 1‐(substituted phenylcarbonyl/ sulfonylimino)‐3‐diethylcarbamoyl pyridinium ylides ( 6, 14 ) in absolute ethanol.     

Synthesis of 2‐amino‐4‐aryl‐7,7‐dimethyl‐5‐oxo‐4H‐5,6,7,8‐tetrahydrobenzo[b]pyran derivatives in ionic liquid medium

In this paper, preparation of 2‐Amino‐4‐aryl‐7,7‐dimethyl‐5‐oxo‐4H‐5,6,7,8‐tetrahydrobenzo[b]pyran derivatives from aromatic aldehyde, malononitrile or cyanoacetate and 5,5‐dimethyl‐1,3‐cyclohexanedione in ionic liquid [bmim⁺][BF₄^?] was described. Compared with other methods, this new method has the advantages of easier work‐up, milder reaction conditions, high yields and environmentally benign procedure.     

1,3‐Dipolar cycloaddition or nucleophilic addition: Influence of solvents and nature of substituents in the reagent and substrate molecules on the reaction of 4,5‐dihydro‐1H‐imidazole 3‐oxides with alkynes

Two competitive processes ‐ 1,3‐dipolar cycloaddition and nucleophilic addition ‐ in the reaction of 4,4,5,5‐tetramethyl‐4,5‐dihydro‐1H‐imidazole 3‐oxides with asymmetrically substituted alkynes were shown to occur. The influence of solvents and the nature of substituents in the reagent and substrate molecules on the rate ratio of these competitive processes were studied.     

Synthetic approaches to bridgehead nitrogen methanesulfonamide derivatives of 3‐amino‐2‐thioxo‐2,3‐dihydrothieno[2,3‐d]pyrimidin‐4(1H)‐ones,potential cox‐2 selective inhibitors

Methane sulfonamide derivatives of 3‐amino‐2‐thioxo‐2,3‐dihydrothieno[2,3‐d]pyimidin‐4(1H)‐one, potential selective COX‐2 inhibitors, were synthesized and their structural elucidation is here reported. Some derivatives, at 10 μM concentration, showed a significant percentage of inhibition in some in vitro experiments.     

Transformations of phenylhydrazones of 5‐acyl‐1,2,4‐triazines to pyrazolo[4,3‐e][1,2,4]triazines or 4‐cyanopyrazole

A simple and high yielding preparation of pyrazolo[4,3‐e][1,2,4]triazines and 4‐cyano‐3‐methyl‐1‐phenylpyrazole derivatives from corresponding phenylhydrazones of 5‐acyl‐1,2,4‐triazines by melt under acidic medium and by thermal heating, respectively.     

Microwave induced synthesis of the thiazolidine‐2,4‐dione motif and the efficient solvent free‐solid phase parallel syntheses of 5‐benzylidene‐thiazolidine‐2,4‐dione and 5‐benzylidene‐2‐thioxo‐thiazolidine‐4‐one compounds

Novel microwave induced method for the synthesis of thiazolidine‐2,4‐dione motif under solvent phase conditions is developed. Further we report an efficient, microwave assisted method for the parallel syntheses of biologically important 5‐benzylidene‐thiazolidine‐2,4‐dione and 5‐benzylidene‐2‐thioxothiazolidine‐4‐one compounds under solid‐phase and solvent‐free conditions. A comparative study between the developed microwave methods and the conventional methods is described. We have also illustrated the possible mechanism behind to address the reason why piperidine, acetic acid and silica gel enhanced the Knoevenagel condensation reaction.     

One‐pot synthesis of 2‐acylimino‐3‐aryl‐1,3‐thiazoline derivatives in aqueous media

The one‐pot two‐step synthesis for acyliminothiazolines by treatment of N,N'‐substituted thioureas with α‐bromocarbonyl compounds under aqueous media was described. Compared to classical reaction in organic solvents, this method consistently has the advantages of short reaction time and being environmentally friendly.     

1,3‐Dipolar cycloaddition reaction of 4,5‐dihydro‐1H‐imidazole 3‐oxides with alkynes

4,5‐Dihydro‐1H‐imidazole 3‐oxides bearing different substituents at positions 1 and 2 of the heterocycle were shown to react with a wide range of acceptor‐substituted alkynes forming corrsponding cycloadducts ‐ derivatives of 1,2,3,7a‐tetrahydroimidazo[1,2‐b]isoxazole. High regioselectivity of this process stipulated by conjugation of the nitrogen atom with the nitrone group was revealed.     

Synthesis and intramolecular cyclization of 2‐methylsulfany‐4‐oxo‐3(4H)‐quinazolinyl)acetohydrazide

Treatment of ambident sodium salt of 2‐methylsulfanyl‐4(3H)‐quinazolinone with methyl bromoacetate resulted in N₍₃₎‐alkyl ester formation. Reaction of the resulted ester with hydrazine hydrate gave 2‐methylsulfanyl‐4‐oxo‐3(4H)‐quinazolinyl)acetohydrazide, which underwent intramolecular cyclization under heating in dimethylformamide to give 1‐aminoimidazo[2,1‐b]quinazoline‐2,5(1H,3H)‐dione. The latter took place in acylation reaction and in condensation with aromatic aldehydes.     

Chemistry and application of 4‐oxo‐4H‐1‐benzopyran‐3‐carboxaldehyde

The Chemistry and application of the title aldehyde and some simple derivatives thereof are reviewed.