The synthesis of 5,6-dihydro-6-methylthiazolo-[2,3-b] [1,3] benzodiazepines, 2,3,10,11-tetrahydro-10-methyl-1H-cyclopenta[4,5] thiazolo[2,3-b] [1,3] benzodiazepine,and 7,8,9,10,12,13-hexahydro-13-methylbenzothiazolo[2,3-b] [1,3]-benzodiazepine via 1,3,4,5-tetrahydro-5-methyl-2H-1,3-benzodiazepine-2-thione

Catalytic reductive scission of 4-methylcinnoline (V) with Raney nickel afforded o-amino-β-methylphenethylamine (IV) in 57% yield. Treatment of IV with carbon disulfide followed by thermal cyclization of the product furnished 1,3,4,5-tetrahydro-5-methyl-2H-1,3-benzodiazepine-2-thione (III). Reaction of III with ethyl chloroacetate, ethyl 2-bromohexanoate, ethyl 2-chloroacetoacetate, 2-bromo-2′-methoxyacetophenone, and 2-bromoacetophenone provided a series of substituted 5,6-dihydro-6-methylthiazolo[2,3-b][1,3]benzodiazepines. Condensation of III with 2-chlorocyclopentanone and 2-chlorocyclohexanone gave 2,3,10,11-tetrahydro-10-methyl-1H-cyclopenta[4,5]thiazolo[2,3-b][1,3]benzodiazepine and 7,8,9,10,12,13-hexahydro-13-methylbenzothiazolo[2,3-b][1,3]benzodiazepine, respectively. Structure assignments are discussed. None of the compounds possessed appreciable biological activity.     

A Useful Synthesis of 2-Methyl-2,3-dihydrofuro [2,3-b] Quinolines

A convenient, general synthesis of 2-methyl-2,3-dihydrofuro [2,3-b] quinolines is described from o-nitrobenzaldehydes. The benzaldehydes (la-c) on reaction with phosphorane 2 provide (E)-ethyl-α-allylcinnamates (3a-c) in high yields. These esters 3a-c on reduction followed by acid catalysed cyclisation give 2,3-dihydrofuro [2,3-b] quinolines (5a-c).     

Synthesis of 3a,4,6,7,11b,12-hexahydro-3a-methyl-7-phenylbenzo[a]furo[2,3-g]quinolizines

By alkylation of stereoisomeric 7a-methyl-2-oxo-5-phenylfuro-[2,3-c]piperidines with phenacyl bromide and subsequent reduction of the keto group by sodium borohydride, amino alcohols were obtained; heating of these products in 70% sulfuric acid affords 3a,4,6,7,11b,12-hexahydro-3a-methyl-7-phenylbenzo[a]furo[2,3-g]quinolizines. It was found that the cis-quinolizidine, upon heating to 150°C in acetic acid, is isomerized to the trans-quinolizidine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1679–1682, December, 1993.     

A facile synthesis of 1-alkylthio and acylthio-2,3-dihydro-1H-naphtho[2,1-b]thiopyrans and 4-alkylthio and acylthio-3,4-dihydro-2H-naphtho[1,2-b]thiopyrans

The reaction of 3-(2-naphthylthio)propionaldehyde ( 3 )and its (1-naphthylthio)isomer (7)with a variety of thiols and thio acids in the presence of sulfuric acid at room temperature afforded 1-alkylthio and acylthio-2,3-dihydro-1H-naphtho[2,1-b]thiopyrans 5 and 4-alkylthio and acylthio-3,4-dihydro-2H-naphtho[1,2-b]thiopyrans 9 in excellent yield.     

Synthesis of 2H-pyrano[2,3-b]quinolines. Part I

3,4-Dihydro-2H-pyrano[2,3-b]quinolines 5a-e and 2H-pyrano[2,3- b ]quinolines 10a-c were synthesised starting from the appropriate ω-chloro-n-valeroylanilides 2a-e . Compounds 10a-c were transformed to analogs of the novel antihypertensive agent Cromakalim ( 1 ).     

Efficient synthesis of cytotoxic quinones: 2-Acetyl-4H,9H-naphtho[2,3-b]furan-4,9-dione (6) and (±)-2-(1-hydroxyethyl)-4H,9H-naphtho[2,3-b]furan-4,9-dione (7)

From the ethanol extract of the stem bark of Tabebuia cassinoides (Lam.) DC (Bignoniaceae), Kingston and Rao [1] isolated two new furonaphthoquinones 6 and 7 that showed activity in KB cell culture assay (ED₅₀ 1.0 and 2.0 μg/ml, respectively). These values may be significant since lapachol, which has an ED₅₀ value of 4.4 μg/ml in the same assay, showed sufficient in vivo activity to reach clinical trial at the National Cancer Institute of the United States. The syntheses of these compounds ( 6 and 7 ) were realized in 36% overall yield starting from furan and phthalic anhydride.     

Furopyridines. XIV. Synthesis of 2-aminoalkyl derivatives of furo[2,3-b]-, furo[3,2-b], furo[2,3-c]- and furo[3,2-c]pyridine

The preparation of 2-aminomethyl- 3a-d , 2-acetamidomethyl- 4a-d , 2-N,N-dimethylaminomethyl- 5a-d , 2-(1-hydroxy-2-nitroethyl)- 6a-d , 2-(1-hydroxyl-2-aminoethyl)- 7a-d and 2-(1-hydroxy-2-N,N-dimethylaminoethyl)- 8b-d derivatives of furo[2,3-b]-, furo[3,2-b]-, furo[2,3-c]- and furo[3,2-c]pyridine is described.     

Reactivity of 1H-pyrrolo[2,3-b]pyridine. I. Synthesis of 3-acetyl-7- azaindole and related compounds

The behaviour of 1H-pyrrolo[2,3-b)pyridine (7-azaindole) towards several acylating reagents are reported. The preparation of 3-acetyl-7-azaindole, 3-chloroacetyl-7-azaindole and 3-(2-hydroxiethyl)-7-azaindole are described.     

Acid-base properties of 2,3,4,5-tetrahydro-1H-naphtho[2,3-b]-1,4-diazepine-2,4,6, 11-tetraone

It is shown that 2,3,4,5-tetrahydro-1H-naphtho[2,3-b]-1,4-diazepine-2,4,6,11-tetraone, which has acid properties, undergoes methylation to give an N,N-di-methyl derivative, whereas it gives products of substitution of the hydrogen atoms of the methylene group in its reactions with bromine and salicylaldehyde. Treatment of 2,3,4,5-tetrahydro-1H-naphtho[2,3-b]-1,4-diazepine-2,4,6,11-tetrone with aqueous alkali or secondary aliphatic amines with heating is accompanied by opening of the diazepine ring to give hydrolysis (2-carboxyacetamido-3-hydroxy-1,4-naphthoquinones) or aminolysis (N-alkylaminomalonyl-2,3-diamino-1,4-naphthoquinones) products.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1132–1136, August, 1978.     

Furopyridines. XI. 13C NMR Spectra of 2- or 3-Substituted Furo[2,3-b]-, Furo[3,2-b]-, Furo[2,3-c]- and Furo[3,2-c]pyridine

The ¹³C nmr spectra of 2- or 3-monosubstituted furo[2,3-b]- 1a-1j , furo[3,2-b]- 2a-2j , furo[2,3-c]- 3a-3j and furo[3,2-c]pyridine derivatives 4a-4j are reported. Effects by change in annelation and substituent effects on ¹³C chemical shifts and carbon-proton coupling constants are discussed. The spectra of benzo[b]furan derivatives 5a-5j having the corresponding substituent are also reported for comparison.     

Synthesis of 6-chlorofuro[2,3-b]pyridine-2-carboxylie acid

A new route was employed to synthesize methyl 6-ehlorofuro[2,8-b]pyridine-2-earboxylate by eoneurrent dehydrohalogenation and dehydration of 3-ehloro-3-(β,β-dichloro-β-ethoxycar-bonylelhyl)-2,6-piperidinedione using methyl phosphonyl chloride.     

A new synthetic route to 2-substituted naphtho[2,3-b]furan-4,9-dione2-Substituted Naphtho[2,3-b]furan-4,9-dione

4,9-Dimethoxynaphtho[2,3-b]furan 9 was obtained in 91% yield via the reductive methylation of naphtho[2,3-b]furan-4,9-dione 2 . After treatment of 9 with butyllithium, the mixture was allowed to react with N,N-dimethylacetamide, followed by oxidization with cerium(IV) diammonium nitrate to give 2-acetylnaphtho[2,3-b]furan-4,9-dione 1 . 2-Formylnaphtho[2,3-b]furan-4,9-dione 13 and 2-trimethylsilyl-naphtho[2,3-b]furan-4,9-dione 14 were also obtained from 9 by a similar method. The halodesilylations of 14 easily gave 2-iodonaphtho[2,3-b]furan-4,9-dione 16 , 2-bromonaphtho[2,3-b]furan-4,9-dione 17 , and 2-chloronaphtho[2,3-b]furan-4,9-dione 18 in 82%, and 93% and 83% yield, respectively. Furthermore, the nitrodesilylation of 14 gave 2-nitronaphtho[2,3-b]furan-4,9-dione 3 in 77% yield.     

Synthesis of 5H-naphtho[2,3-c]phenothiazine-8,13-diones from 1-arylthio-2-azidoanthraquinones

Thermolysis of 1-arylthio-2-azidoanthraquinones in DMSO at 150 °C afforded substituted 5H-naphtho[2,3-c]phenothiazine-8,13-diones. These compounds were also formed upon photolysis of azides at 77 K and were prepared in quantitative yields by the reactions of 1-arylthio-2-azidoanthraquinones with KOH in DMSO at 20 °C.     

Synthesis of 2,3,3a,8 a-tetrahydrofuro[2,3-b] benzofuran-2-one from coumarin

4-Vinyl-3,4-dihydrocoumarin, which is obtained in two steps from 3-(2-benzyloxyphenyl)allyl alcohol, was converted to 2,2,3a,8a-tetrahydrofuro[2,3-b]benzofuran-2-one by oxidation and rearrangement.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 748–750, June, 1976.     

Fluorine-containing heterocycles: Part III. Synthesis of some new furo[2,3-b]-, pyrazolo[3,4-b]- and thieno[2,3-b]pyridines with anticipated biological activities

3-Cyano-6-(2-thienyl)-4-trifluoromethylpyridine-2(1H)-one (1) and its thiono analog 2 were prepared by the reaction of (2-thenoyl)-ω,ω,ω-trifluoroacetone with cyanoacetamide or cyanothioacetamide, respectively. Interaction of compound 1 with ethyl chloroacetate or chloroacetamide led to the regioselective formation of O-alkylated pyridines 3 and 10. The latter compounds underwent some successive reactions to furnish the promising furopyridines (4 and 7–9) and pyrazolopyridines (12–15). The reaction of 2 with chloroacetamides or chloroacetonitrile furnished 2-functionalized 3-amino-6-(2-thienyl)-4-trifluoromethyl-thieno[2,3-b]pyridines (16a, b) which were used as key intermediates in the synthesis of the title thienopyridines. Structures of the newly synthesized compounds were established on the basis of their elemental and spectral (IR, ¹H NMR and mass) analyses.