Facile and convenient synthesis of new thieno[2,3-b]-thiophene derivatives

A facile and convenient synthesis of bis(2-(1H-benzo[d]imidazol-2(3H)-ylidene)-3-oxopropanenitrile), bis((3-amino-5-(methylthio)-1H-pyrazol-4-yl)methanone) and bis(2-thioxo-1,2-dihydropyrimidine-5-carbonitrile) derivatives incorporating a thieno- [2,3-b]thiophene moiety via versatile, readily accessible diethyl 3,4-dimethylthieno-[2,3-b]thiophene-2,5-dicarboxylate is described.     

Facile synthesis of novel indolo[3,2-b]carbazole derivatives and a chromogenic-sensing 5,12-dihydroindolo[3,2-b]carbazole

Novel indolo[3,2-b]carbazole derivatives and a chromogenic-sensing 5,12-dihydroindolo[3,2-b]carbazole have been synthesized starting from tetra-tert-butylated 6,12-diaryl-5,11-dihydroindolo[3,2-b]carbazoles, which were prepared via an efficient tert-butylation of 6,12-diaryl-5,11-dihydroindolo[3,2-b]carbazoles.     

Facile synthesis of 5-amino- and 7-amino-6-azaoxindole derivatives

An efficient approach for the formation of 5-amino- and 7-amino-6-azaoxindole derivatives was developed. 2-Amino-4-chloro-3-nitropyridine (8), and its 5-nitro-substituted regioisomer (9), respectively, were obtained by reaction with ethyl malonate. The resulting 2-amino-3/5-nitropyridine derivatives substituted in the 4-position with malonic acid diethyl ester (10, 11) were subjected to reductive cyclization yielding 3-ethoxycarbonyl-6-azaoxindole derivatives 4a and 5a. Protection of the amino function was not required. Intermediates 10 and 11 could also be converted to the corresponding 4-acetic acid ethyl esters 12 and 13 by dealkoxycarbonylation with LiCl, and subsequently cyclized under reductive conditions yielding 3-unsubstituted 5-/7-aminooxazindoles.     

An efficient synthesis of 3-aminoisothiazolo[5,4-b] -quinoline from quinoline

Treatment of readily available 3-formylquinoline-2-thiol ( 1 ) with ammoniacal sodium hypochlorite directly afforded isothiazolo[5,4-b]quinoline ( 3 ) in high yield, probably via 3-formylquinoline-2-sulfenamide ( 2 ). Facile conversion of 3 to the corresponding 3-amino derivative ( 7 ) was accomplished by the following sequence: base induced opening of the isothiazole ring to 3-cyanoquinoline-2-thiol ( 5 ), oxidation of 5 to the corresponding stable sulfenamide ( 6 ) and sodium ethoxide catalysed reclosure of the isothiazole ring which provided 3-aminoisothiazolo[5,4-b]quinoline ( 7 ).     

Synthesis of 2,3,4,5-tetrahydropyrimido[2,1-b]-benzothiazoles

1-Thiocarbamoyl-2-phenylpyrazolidines are cyclized to give 2,3,4,5-tetrahydropyrimido[2,-1-b]benzothiazoles, the structure of which was proved by mass spectrometry.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 495–496, April, 1973.     

Facile synthesis of [1,2,4]triazino[4,3-b][1,2,4,5]tetrazepin derivatives by a one-pot reactions using 4-amino-3-hydrazinyl-6-methyl-1,2,4-triazin-5 (4H)-one

<正>4-Amino-3-mercapto-6-methyl-l,2,4-triazin-5(4H)-one 1 converted to 4-amino-6-methy-3-(methylthio)-1,2,4-triazin-5(4H)-one by methylation with methyl iodide.Controlled hydrazination of the resulting compound afforded 4-amino-3-hydrazinyl-6- methyl-l,2,4-triazin-5(4H)-one 2 as a building block,to the synthesis of some novel derivatives of[1,2,4]triazino- [4,3,b][1,2,4,5]tetrazepine 3-6,by the reaction with 3-chloropentane-2,4-dione,chloro acetonitrile,1,3-dichloroacetone,and methyl bromoacetate.This general synthetic procedure can be extended to the preparation of wide variety of tetrazepines using 1,2- bielectrophiles derivatives.     

Convenient synthesis of 6,7-dihydroazolo[5,1-b]quinazolin-8(5H)-one derivatives

Three-component condensation of 3(5)-aminoazoles with benzaldehydes and dimedone in acetonitrile in the presence of montmorillonite KSF as heterogeneous catalyst regioselectively afforded 5,6,7,9-tetrahydroazolo[5,1-b]quinazolin-8(4H)-one derivatives in good yields. Oxidation of the condensation products with ceric ammonium nitrate in acetone gave the corresponding 6,7-dihydroazolo[5,1-b]quinazolin-8(5H)-ones.     

Facile synthesis of thiadiazolo [2,3-b] quinazoline derivatives via the Japp-Klingemann Reaction

Diazotized anathranilic acid and its methyl ester react with substituted α-thiocyanatoacetoacetanilides3a–c to give in both cases the corresponding thiadiazolo [2,3-b] quinazolines6a–c, respectively. A mechanism is proposed and it is substantiated by synthesis of6a from N-(2-car?yphenyl)-C-phenylcarbamoyl hydrazidoyl chloride8a or its N-(2-methoxycarbonylcarbonylphenyl) analogue8d.     

Facile synthesis of some novel triazolo[3,4-b]thiadiazines and triazolo[4,3-b]tetrazines

4-Amino-5-ethyl-4H-1,2,4-triazole-3-thiol was used as a key intermediate for the synthesis of triazolo[3,4-b][1,3,4]thiadiazines, triazolo[4,3-b][1,2,4,5]tetrazines and Schiff’s base via reactions with various hydrazonoyl halides and salicyaldehyde, respectively. Moreover triazolyl-N-N′-triazole derivatives were prepared from reaction of Schiff’s base with various hydrazonoyl halides. The structures of all the newly synthesized heterocyclic compounds were established by considering elemental analysis and spectral data.     

Simple synthesis of 7H-phenaleno[1,2-b]furan-7-one derivatives by one-pot, three-component reactions

The reaction of alkyl isocyanides with various aldehydes and 3-hydroxy-1 H-phenalene-1-one is described. The protocol offers facile and efficient synthesis of biologically interesting 9-(alkyl or arylamino)-7 H-phenaleno[1,2- b]furan-7-one derivatives from readily available starting materials in high yields.     

Synthesis of 6-(4-methyl-1-piperazinyl)-7H-indeno[2,1-c]-quinoline derivatives as potential 5-HT receptor ligands

Two synthetic pathways for the achievement of the title compounds are reported. The key intermediate, namely 3-carboxy-4-phenyl-2(1H)-quinolinone 9 , was directly cyclized into the corresponding 6-chloro-7H-indeno[2,1-c]quinolin-7-one 10 or alternatively it was esterified, reduced to the alcohol, chlorinated and cyclized into the 6-chloro-7H-indeno[2,1-c]quinoline 8 . Further reaction of the chloroindenoquinoline derivatives with N-methylpiperazine afforded the piperazinyl derivatives 4a-c .     

New derivatives of imidazo [5, 1-b] benzothiazole

1-Cyano-3-phenylimidazo[5, 1-b]benzothiazole (II) has been obtained from 1-formyl -3-phenylimidazo[5, 1-b]benzothiazole (I) and from 1-brono-3-phenylimidazo[5, 1-b]benzothiazole (III) and has been converted into the corresponding amide (IV) and thioamide (V). New 1-alkyl-3-phenylimidazo[5, 1-b]benzothiazoles (VI) have been synthesized.     

Synthesis of 6-oxo-6,7,8,9-tetrahydro-10H-pyrimido-[5,4-b][1,4]benzoxazines and 6-oxo-6,7,8,9-tetrahydropyrimido[4,5-b][1,4]benzodioxanes

Reaction of 5-hydroxy-6-aminopyrimidines with 2-bromohydroresorcinol and bromodimedone in DMF in the presence of sodium hydride gave 6,7,8,9-tetrahydro-10H-pyrimido[5,4-b][1,4]benzoxazines. When 4-chloro-5-hydroxy-6-aminopyrimidine was treated with bromodimedone the principal products were 6,7,8,9-tetrahydropyrimido[4,5-b][1,4]benzodioxanes. The nucleophilic substitution of the chlorine atom in position 4 of the tetrahydropyrimidobenzoxazines by amines, sodium alkanoates, and thiourea has been studied and the corresponding amines and alkoxy- and thio derivatives of this tricyclic system obtained. Center for the Chemistry of Medicinal Substances, All Russian Chemico-Pharmaceutical Science Research Institute, Moscow 119815. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1411–1417, October, 1998.     

Tin-free radical cyclizations for the synthesis of 7-azaoxindoles, 7-azaindolines, tetrahydro[1,8]naphthyridines, and tetrahydro-5H-pyrido[2,3-b]azepin-8-ones

[reaction: see text] Compounds containing a pyridine nucleus fused to a saturated nitrogen-containing ring, including 7-azaoxindoles, 7-azaindolines, tetrahydro[1,8]naphthyridines, and tetrahydro-5H-pyrido[2,3-b]azepin-8-ones, were prepared in good yield starting from various 2,6-dichloropyridines. The method hinges on a free-radical xanthate-mediated cyclization or intermolecular addition/cyclization sequence for the construction of the new fused rings.