The synthesis of 2-amino-4-aryl-3-ethoxycarbonyl-4H-naphtho[1,2-b]pyrans revisited

An expeditious and unequivocal synthesis of some 2-amino-4-aryl-3-ethoxycarbonyl-4H-naphtho-[1,2-b]pyrans 3 is reported. Previous papers describing the preparation of this type of compound have been amended and a convenient and direct procedure for its preparation is now presented.     

Synthesis of 2-aryl-3H-naphtho[1,2-d]imidazoles containing an adamantane fragment

N ²-[1-(1-Adamantyl)alkyl]naphthalene-1,2-diamines reacted with benzoyl chlorides in chloroform in the presence of triethylamine to give N-{2-[1-(1-adamantyl)alkylamino]naphthalen-1-yl}benzamides which underwent intramolecular cyclization to 2-aryl-3H-naphtho[1,2-d]imidazoles on heating in toluene in the presence of p-toluenesulfonic acid. 3-[(1-Adamantyl)methyl]-2-(3-nitrophenyl)-3H-naphtho[1,2-d]imidazole was synthesized from N ²-[(1-adamantyl)methyl]naphthalene-1,2-diamine and 3-nitrobenzaldehyde.     

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.     

Reaction of 6-methoxybenzo[b]furan-3(2H)-one and benzo[b]thiophen-3(2H)-one with 2-aryl-1,1-dicyanoethylenes as a convenient synthetic route to substituted 2-amino-4-aryl-1,3-dicyano-7-methoxydibenzo[b,d]furans and 2-amino-4-aryl-3-cyano-4H-benzothieno[3,2-b]pyrans

The reactions of 6-methoxybenzo[b]furan-3(2H)-one with 2-aryl-1,1-dicyanoethylenes and malononitrile or with aromatic aldehyde and two moles of malononitrile afford 2-amino-4-aryl-1,3-dicyano-7-methoxydibenzo[b,d]furans. The reactions of benzo[b]thiophen-3(2H)-one with 2-aryl-1,1-dicyanoethylenes or with aromatic aldehyde and one mole of malononitrile produce 2-amino-4-aryl-3-cyano-4H-benzothieno[3,2-b]pyrans.     

Crystal Structure of 2-Amino-5,10-dioxo-4-aryl-5,10-dihydro-4H-naphtho [2,3-b]pyran-3-carboxylic Acid Ethyl Ester

The title compounds have been synthesized via a three-component reaction and their structures were characterized by IR, ^1H NMR, ^13C NMR and X-ray single-crystal diffraction. The crystal of compound 4a belongs to monoclinic, space group P121/c1 with a = 8.575（3）, b = 9.590（3）, c = 21.431（6）A, β = 91.172（3）°, V = 1762.1（9）A^3, Mr = 393.36, Z = 4, Dc= 1.483 g/cm^3, μ（MoKα） = 0.113 mm^-1, F（000） = 816, the final R = 0.0366 and wR = 0.0941. The crystal of compound 4b is of triclinic, space group P-1 with a = 8.6420（17）, b = 9.761（2）, c = 11.132（2） A, α = 97.51（3）, β = 97.86（3）, γ = 92.85（3）°, V = 920.1（3） A^3, Mr = 393.36, Z = 2, Dc = 1.420 g/cm^3, μ（MoKα） = 0.108 mm^-1, F（000） = 408, the final R = 0.0612 and wR = 0.1781. In each molecular structure, the naphthalene rings and pyran rings are almost coplanar with the latter in an envelope conformation. The rings formed by the N-H…O intramolecular hydrogen bonds are almost planar in these compounds. Their crystal packing is stabilized by intermolecular hydrogen bonds together with C-H…π and π-π stacking interactions.     

Three-component synthesis of 4-amino-2-aryl-2H-pyrimido-[1,2-b][1,3]benzazole-3-carbonitriles and 4H-pyrimido-[2,1-b][1,3]benzazoles in the presence of magnesium oxide and 12-tungstophosphoric acid as catalysts

A simple and convenient approach was suggested for the synthesis of 4-amino-2-aryl-2H-pyrimido[1,2-b][1,3]benzimidazole-3-carbonitriles or -benzothiazole-3-carbonitriles through a three-component reaction of 2-aminobenzimidazole or 2-aminobenzothiazole, aldehyde, and malononitrile in the presence of magnesium oxide (MgO) and 12-tungstophosphoric acid as catalysts. Three-component reactions of aldehyde, β-ketoester, and 2-aminobenzimidazole or 2-aminobenzothiazole with the formation of 4H-pyrimido[2,1-b]benzimidazole or 4H-py-rimido[2,1-b]benzothiazole derivatives, respectively, were also studied. These approaches have the advantage of high yields, rapid and pure course of the reactions, as well as the use of cheap and available catalysts.     

Synthesis of 2-aryl-3-hydroxypyrazolo-[4, 3-b]quinuclidines

The reaction of 2-ethoxycarbonyl-3-ketoquinuclidine with arylhydrazines has been examined It is shown that the first stage in the reaction is the formation of 2-ethoxycarbonyl-3-(-arylhydrazino)-²-dehydroquinuclidines, which are then converted into 2-aryl-3-hydroxy-pyrazolo[4, 3-b]quinuclidines (III). The O-methyl- and O-benzoyl- derivatives of III have been synthesized.Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1261–1263, September, 1970.     

Synthesis of 6-amino-2-aryl-1,2-dihydro-3H-pyrido[2,3-d]pyrimidin-4-one derivatives

This paper reports the synthesis of new pyrido[2,3-d]pyrimidin-4-one derivatives as diuretic agents. Starting with 1,2-dihydro-5-nitro-2-oxo-3-pyridinecarboxylic acid 1 , ethyl 2-ethoxy-5-nitro-3-pyridincarboxylate 4 was obtained. Compound 4 reacts with ammonia, methylamine or S-methylpseudothiourea to give the respective 2-amino-5-nitro-3-pyridinecarboxamide derivatives 5 and 6 or 2-methylthio-6-nitro-3H-pyrido[2,3-d]pyrimidin-4-one 8. Treating carboxamide 5 with arylaldehydes and zinc dichloride, new 2-aryl-1,2-dihydro-6-nitro-3H-pyrido[2,3-d]pyrimidin-4-ones 9 were synthetised. These compounds reduced with iron(II) hydroxide gave 6-amino-2-aryl-1,2-dihydro-3H-pyrido[2,3-d]pyrimidin-4-ones 10 as expected.     

One-step synthesis of 5-acetyl-2-amino-4-aryl-3-cyano-4H-pyrano[3,2-b]indoles. Molecular and crystal structure of 5-acetyl-2-amino-4-(4"-chloro-3"-nitrophenyl)-3-cyano-4H-pyrano[3,2-b]indole

A one-step procedure was developed for the synthesis of 5-acetyl-2-amino-4-aryl-3-cyano-4H-pyrano[3,2-b]indoles involving the three-component reaction of 1-acetylindol-3(2H)-one with aromatic aldehydes and malononitrile in ethanol in the presence of triethylamine as the catalyst. The structure of 5-acetyl-2-amino-4-(4"-chloro-3"-nitrophenyl)-3-cyano-4H-pyrano[3,2-b]indole was established by X-ray diffraction analysis.     

An alternative route to 2H-naphtho[1,2-b]thiete and its cycloaddition products

2-(1H-Benzotriazol-1-ylmethyl)-1-naphthalenol ( 1 ) can be transformed in high yields to the corresponding thiol 4 . Flash vacuum pyrolysis of 4 leads to 2H-naphtho[1,2-b]thiete ( 5 ). The benzotriazolyl group proved to be a good leaving group; however, a subsequent nitrogen extrusion takes place under flash vacuum pyrolysis conditions and cyclopentadienecarbonitriles 6a,b are formed by a ring contraction (Scheme 1). Cycloaddition reactions of 5 and dienophiles or heterodienophiles yield the naphtho-condensed sulfur heterocycles 8, 10, 12 and 14 (Scheme 2).     

One-step synthesis of substituted 6-amino-5-cyanospiro-4-(piperidine-4')- 2H,4H-dihydropyrazolo[3,4-b]pyrans

Three-component condensation of 4-piperidinones (7), 5-pyrazolones (8), and malononitrile (4) proceeds chemically and electrochemically and is a convenient one-step means of synthesis of substituted 6-amino-5-cyanospiro-4-(piperidine-4')-2H,4H-dihydropyrazolo[3,4-b]pyrans (12). The electrochemical reactions proceed under milder conditions and with yields 12-15% greater than those of the reactions catalyzed by chemical bases.     

A novel 2-C reactivity studies of 1-aroyl-1,2-dihydro-3H-naphtho[2,1-b]pyran-3-ones

The 2-C, methylene group of 1-aroyl-1,2-dihydro-3H-naphtho[2,1-b]pyran-3-ones (2) have been showed to possess a superior reactivity towards many of organic reagents. The naphthopyrones (2) condensed with aromatic aldehydes to give the 2-arylidine derivatives (3). Bromination of 2 gave 1,2-dibromo (4) or 5-bromo (5) derivatives depending on the reaction conditions. The base catalyzed addition or cycloaddition of naphthopyrones (2) to 4-methoxy benzalacetophenone gave the expected Michael adduct (6) or the cyclic adducts (7–9) depending on the type of catalytic base and reaction conditions. Structures of the products have been established by elemental analyses, IR and ¹H NMR spectroscopic methods.     

One-pot synthesis of 3-amino-4-aryl- and 3-amino-4-hetarylfurazans

A “one pot” method for the synthesis of 3-amino-4-aryl- and 3-amino-4-hetarylfurazans from β-aryl- and 4-β-hetaryl-β-oxo acid esters was developed. Dedicated to Corresponding Member of the Russian Academy of Sciences E. P. Serebryakov on the occasion of his 70th birthday. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 1030–1032, April, 2005.     

Concerning the “synthesis of 2-amino-5-aryl-5H-thiazolo[4,3-b]-1,3,4-thiadiazoles”

Compounds described previously as 2-amino-5-aryl-5H-thiazolo[4,3-b]-1,3,4-thiadiazoles were found to be thiosemicarbazones of aromatic aldehydes. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya No. 6, pp. 1228–1229, June, 1997.     

The synthesis and cytotoxic activity of N-unsubstituted 3-aryl-4-(trifluoromethyl)-4H-spiro[chromeno[3,4-c]pyrrolidine-1,11'-indeno[1,2-b]quinoxalines]

Chemistry of Heterocyclic Compounds - A method for a regio- and stereoselective synthesis of N-unsubstituted...     

Reaction of ketenes with N,N-disubstituted α-aminomethyleneketones. XVIII. Synthesis of N,N-disubstituted 4-amino-3-phenyl-2H-naphtho[1,2-b]pyran-2-ones

1,4-Cycloaddition of phenylchloroketene to N,N-disubstituted 2-aminomethylene-3,4-dihydro-1(2H)naphthalenones gave the corresponding adducts, namely N,N-disubstituted 4-amino-3-chloro-3,4,5,6-tetrahydro-3-phenyl-2H-naphtho[1,2-b]pyran-2-ones II, in the case of aliphatic N,N-disubstitution or aromatic N-monosubstitution. Apart from IIf (NR₂ = NMePh), adducts II were unstable and were dehydrochlorinated in situ with DBN to give N,N-disubstituted 4-amino-5,6-dihydro-3-phenyl-2H-naphtho[1,2-b]pyran-2-ones III in fair overall yields. Compounds III were dehydrogenated with Pd/C in boiling p-cymene to afford the title compounds generally in high yields.     

Facile rearrangement of 2-amino-3-carbethoxy-4-ethylfuro[3,2-b]pyridinium cation to 2-oxo-3-cyano-4-ethyl-4H-furo[3,2-b]pyridine

The rearrangement of 2-amino-3-carbethoxy-4-ethylfuro[3,2-b]pyridinium iodide in basic solution was studied. The reaction product is 2-oxo-3-cyano-4-ethyl-4H-furo[3,2-b]pyridine which was obtained also by alkylation with ethyl iodide and sodium hydride in dimethylformamide of 2-oxo-3-cyano-3H-furo[3,2-b]-pyridine or of p-nitrophenyl-3-acetoxypyridine-2-cyanacetate.     

Synthesis of 2-aryl-6,6-dimethyl-8-oxo-5,6,7,8-tetrahydro-1,2,4-4H-triazolo[3,2-b]benzothiazoles and their 3-aryl-[3,4-b] isomers

Summary Condensation of 3-aryl-5-thio-1,2,4-4H-trizoles (2a–i) and 2-bromodimedone (3) inTHF/benzene gave 2-aryl-6,6-dimethyl-8-oxo-5a-hydroxy-5,5a,6,7,8,8a-hexahydro-1,2,4-4H-triazolo[3,2-b]benzothiazoles (5a–i). These were also obtained by a one step synthesis on heating a mixture of dimedone,NBS, and2a–i in benzene containing a trace of benzoyl peroxide. Thermal dehydration of5a–i inPPA/anhydrous ethanol yielded the corresponding 2-aryl-6,6-dimethyl-8-oxo-5,6,7,8-tetrahydro-1,2,4-4H-triazolo[3,2,b]benzothiazoles (6a–i). The formation of [3,4-b] fused isomers (4a–i) during the reaction of2 with3 was ruled out by an unambiguous synthesis of8a–i. Antibacterial screening of selected compounds againstEscherichia coli andStaphylococcus aureus was not encouraging.

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Synthese von 2-Aryl-6,6-dimethyl-8-oxo-5,6,7,8-tetrahydro-1,2,4-4H-triazolo[3,2-b]benzothiazolen und ihrer 3-Aryl-[3,4-b]-Isomeren

Zusammenfassung Die Kondensation von 3-Aryl-5-thio-1,2,4-4H-triazolen (2a–i) mit 2-Bromdimedon (3) inTHF/Benzol ergab 2-Aryl-6,6-dimethyl-8-oxo-5a-hydroxy-5,5a,6,7,8,8a-hexahydro-1,2,4,-4H-triazolo[3,2-b]benzothiazole (5a–i). Dasselbe Ergebnis wurde durch Erhitzen einer Mischung von Dimedon,NBS und2a–i in Benzol unter Zusatz einer Spur Benzoylperoxid in einer einstufigen Synthese erreicht. Thermische Dehydrierung von5a–i inPPA/Ethanol(abs.) ergab die entsprechenden 2-Aryl-6,6-dimethyl-8-oxo-5,6,7,8-tetrahydro-1,2,4-4H-triazolo[3,2-b]benzothiazole (6a–i). Die Bildung [3,4-b]-kondensierter Isomere (4a–i) während der Reaktion von2 mit3 konnte durch eine eindeutige Synthese von8a–i ausgeschlossen werden. Antibakterielles Screening ausgewählter Verbindungen gegenüberEscherichia coli undStaphylococcus aureus brachte keine ermutigenden Resultate.