Cyclocondensation reactions of heterocyclic carbonyl compounds XII. The double course of cyclization of 3‐(2‐aminobenzyl)‐1,2‐dihydro‐quinoxaline‐2‐one

The cyclocondensation reaction of compound 1 in boiling hydrochloric acid had an unexpected course. Instead of supposed 5,11‐dihydro‐quinoxalino[2,3‐b]quinoline 6a , 2‐(indol‐2‐yl)‐benzimidazole 4 was isolated as the major product.     

Unusual structures derived from N‐acridin‐9‐yl methyl N′‐acridin‐9‐yl thiourea based on the propensity of N‐10 to retain H

N‐Acridin‐9‐yl methyl N′‐acridin‐9‐yl thiourea spontaneously spiro cyclises via nucleophilic attack of the methylene carbon onto the C‐9 of the other acridine moiety. The thiourea, upon reaction with bromoacetonitrile, provided a spiro fused‐bicyclic product displaying unusual dynamic behavior.     

Aromatization of 1,4‐dihydropyridines in the presence of methanesulfonic acid/NaNO2/wet SiO2 under both heterogeneous and solvent free conditions

A combination of methanesulfonic acid and sodium nitrite in the presence of wet SiO₂ was used as an effective oxidizing agent for the oxidation of 1,4‐dihydropyridines to the corresponding pyridine derivatives under mild and heterogeneous conditions in excellent yields.     

Synthesis and spectral data of new 1,2‐bis‐(2‐hetaryl‐4‐oxothiazolidin‐3‐yl)ethanes and 1,4‐bis‐(2‐hetaryl‐4‐oxothiazolidin‐3‐yl)butanes

New αω‐bis‐(2‐hetaryl‐4‐oxothiazolidin‐3‐yl)alkanes were prepared via a common two step procedure using N,N‐bis‐hetarylidenamines condensation with α‐mercaptoacetic acid. The used bis‐aldimines were obtained from reaction between ethylenediamine or putrescine and benzaldehyde or the isomeric pyridinecarboxyaldehydes. The bis‐(2‐phenyl‐4‐oxothiazolidin‐3‐yl)alkanes were prepared by one‐pot three component reaction of diamine, aldehyde and α‐mercaptoacetic acid under very mild conditions.     

Synthesis of meso‐tetrakis(4‐chlorocoumarin‐3‐yl)porphyrins

meso‐Tetrakis(4‐chlorocoumarin‐3‐yl)porphyrins were prepared by condensation of corresponding 4‐chlorocoumarin‐3‐carboxaldehydes and pyrrole in the presence of trifluoro acetic acid (TFA) in dichloromethane followed by oxidation with 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ). These porphyrins exhibited the atropisomerism due to ortho substituent of meso aryl groups. The atropisomers of meso‐tetrakis(4‐chloro‐6‐methylcoumarin‐3‐yl)porphyrin were separated and identified by ¹H‐nmr spectra. Zinc complexes of these porphyrins were synthesized and characterized by ms, ¹H nmr, ir and uv‐vis spectra.     

Ring expansion of isopropenyldihydrofuran derivatives

Lactonization of 2‐(hydroxymethyl)‐5‐isopropenyl‐4,5‐dihydrofuran‐3‐carboxylic acids 1a,b,c with dicyclohexylcarbodiimide gave the corresponding furano‐lactones, 5‐isopropenyl‐5,6‐dihydro‐1(3H)‐furo[3,4‐b]furanone 2a,b,c , which were readily converted to the corresponding oxepino‐lactones, 6‐methyl‐5,8‐dihydro‐1(3H)‐furo[3,4‐b]oxepinone 3a,b,c by respective thermal ring expansions.     

One‐pot synthesis of hexahydroquinolines Via a four‐component cyclocondensation under microwave irradiation in solvent free conditions: A green chemistry strategy

Four‐component cyclocondensation of aromatic aldehydes, malononitrile, dimedone and ammonium acetate proceeds under microwave irradiation in solvent free conditions to give highly functionalized hexahydroquinolines in excellent yields.     

Synthesis and further studies of chemical transformation of the 2‐aryl‐3‐halogenoquinolin‐4(1H)‐one derivatives

The C‐3 brominated and iodinated derivatives were prepared from the corresponding 2‐arylquinolin‐4(1H)‐ones and their NMe‐4‐oxo derivatives using pyridinium tribromide in acetic acid or iodine‐Na₂CO₃ mixture in THF. The results of further studies of chemical transformation of the prepared α‐haloenones and preliminary antitumour activity of the 3‐bromo NH‐4‐oxo and NMe‐4‐oxo derivatives are also described.     

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.     

The dipolar route to naphtho[2,1‐c]isoxazoles from the baylis‐hillman adducts of 2‐alkynylbenzaldehydes

A new synthesis of 4‐carbomethoxynaphtho[2,1‐c]isoxazoles 4a‐d from methyl 3‐(alkynylphenyl)‐2‐nitromethyl‐2‐propenoates 2a‐d by the intramolecular nitrile oxide cycloaddition is described. The latter are readily obtained from 2‐alkynylbenzaldehydes through the Baylis‐Hillman adduct acetates 1a‐d followed by nucleophilic substitution of nitrite anion.     

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.     

Novel derivatives of the benzo[b][1,6]naphthyridine system

An efficient synthesis of 2‐hydroxy‐6‐methylbenzo[b][1,6]naphthyridin‐1(2H)‐one was devised. The hydroxy group was alkylated, acylated and replaced by hydrogen. Electrophilic nitration, bromination and chlorosulfonation occurred readily in the 4‐position. From the last, various sulfonamide derivatives were prepared. A selection of the products was screened by the National Cancer Institute. Cytotoxicities were generally low.     

Synthesis and tautomerization of 6,7‐dihydro‐(1,2,3)‐triazolo[1,5‐a]pyrimidines

The condensation of 5‐amino‐4‐phenyl‐1,2,3‐triazole ( 1 ) with chalcones 2a‐e or 3‐dimethylamino‐propiophenone ( 4f ) leads to the 6,7‐dihydro‐(1,2,3)‐triazolo[1,5‐a]pyrimidines 3a‐f. The equilibrium of 3 and the tautomeric 4,7‐dihydro‐(1,2,3)‐triazolo[1,5‐a]pyrimidines 3′ is described.     

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.     

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 and alkylation of 5‐(3‐chlorobenzo[b]thien‐2‐yl)‐4H‐1,2,4‐triazole‐3‐thiol under classical and microwave conditions. AM1 semiemperical calculations for investigating the regioselectivity of alkylation

Under microwave irradiation (MWI), 5‐(3‐chlorobenzo[b]thien‐2‐yl)‐4H‐1,2,4‐triazole‐3‐thiol ( 3 ) was synthesized in a good yield by intramolecular cyclization of the carbonyl thiosemicarbazide 2. A regioselective S‐alkylation of 3 with benzyl chloride or allyl bromide has been achieved by using triethylamine as a base, while other different basic conditions led to a mixture of bis(alkylated) derivatives N⁴, S‐ and S, N²‐, under both of classical and MWI conditions. The relative stabilities, charge densities, dipole moments and electronic energies of reactants, transition states and intermediates were calculated by the AM1 method and used for investigating the regioselectivity.     

Reactions of cephalosporin sulfones 3. Synthesis of 2‐phenylhydrazonocephem‐sulfones. A new potential entry to 2‐aminocephems

Reaction of cephem sulfones 1a‐e with aryldiazonium salts gives the 2‐azo compounds which immediately rearrange into the corresponding 2‐hydrazono derivatives 2a‐e .     

A clean synthesis of polyhydroacridine and indenoquinoline derivatives catalyzed by triethylbenzylammonium chloride in aqueous media

An efficient and convenient synthesis of benzo[a]acridines and indeno[1,2‐b]benzo[f]quinolines was achieved in high yields by the reaction of N‐arylidenenaphthalen‐2‐amine with 1,3‐dicarbonyl compounds catalyzed with triethylbenzylammmonium chloride (TEBAC) in aqueous media. The structures were established by spectroscopic data and further confirmed by X‐ray analysis. This method provides several advantages such as neutral conditions, high yields and simple work‐up procedure. In addition, water was chosen as a green and recyclable solvent.     

An efficient synthesis of new thiazolopyrimidinones under microwave irradiation

7‐Chloromethyl‐6‐nitro‐5H‐thiazolo[3,2‐a]pyrimidin‐5‐one ( 2 ) is obtained by cyclocondensation of 2‐aminothiazole with ethyl 4‐chloroacetoacetate. This product was shown to react with various nitronate or malonate anions under microwave irradiation to give potentially bioactive 6‐nitro‐5H‐thiazolo[3,2‐a]pyrimidin‐5‐ones. Extension to other anions centered on S atom allows for the generalization this synthetic procedure.     

Structure determination of N‐methyl‐tetrahydro‐5H‐indazol‐5‐ones

This paper communicates the (regio) synthesis and a convenient NMR structural assignment method for N‐methyl‐tetrahydro‐5H‐indazol‐5‐one isomers. The cyclization reaction of 7‐(hydroxymethylene)‐1,4‐dioxaspiro[4,5]decan‐8‐one ( 3 ) with methylhydrazine yields, after de‐protection predominately the N‐2 methyl isomer 2 . Analysis of the product ratio and structural assignments are based on NMR data including NOE difference experiments and subsequently confirmed with X‐ray crystallography. These findings are in sharp contrast with the literature. The experimental conditions used to optimize the synthesis of the individual isomers are discussed.