The synthesis of benzofuroquinolines. V. Some benzofuro[3,2-B]quinoline derivatives

Some benzofuro[3,2-b]quinoline derivatives 1a-d and 3a were synthesized by condensation of 2-amino-benzaldehyde, 2-aminoacetophenone, 2-aminobenzophenone, isatin, or 2-aminobenzoic acid with 3(2H)-benzofuranone. The benzofuroquinolinone 3a was also obtained from 2-aminobenzoic acid and phenoxy-acetyl chloride in two steps and converted to 10-chloro derivative 1e . Similarly, some 8-halobenzofuro[3,2-b]-quinoline derivatives 1d,e and 3a (X = F, Cl, Br, I) were synthesized from 5-haloisatin or 2-amino-5-halo-benzoic acid. And benzofuro[3,2-b]quinolines 1a-e thus obtained were converted to corresponding N-oxides 2 .     

The synthesis of benzofuroquinolines. I. Some benzofuro[2,3-b]quinoline and benzofuro[3,2-c]quinoline derivatives

Benzofuro[2,3-b]quinoline ( Ia ) and its 11-methyl derivative ( Ib ) were synthesized by demethylcyclization of 3-(o-methoxyphenyl)-1,2-dihydroquinolin-2-ones (VIa,b). Benzofuro[2,3-b]quinoline-11-carboxylic acid (Id) was synthesized by chlorination followed by the action of potassium hydroxide of a lactone (IX) prepared by demethyl-cyclization of 3-(o-methoxyphenyl)-2-oxo-1,2-dihydroquinoline-4-carboxylic acid (VIII). Isomeric benzofuro[3,2-c]quinoline (Ha) and its 6-methyl derivative (IIb) were synthesized by demethyl-cyclization of 3-(o-methoxyphenyl)-1,4-dihydroquinolin-4-ones (XIa,b). Both the methyl derivatives (Ib and IIb) were converted to the carboxylic acids (Id and IId) through condensation with benzaldehyde followed by oxidation. The benzofuroquinolines (Ia,b,d and IIa,b) thus obtained were oxidized to the corresponding N-oxides (IIIa,b,d and IVa,b).     

On the mechanism of the conversion of 6-chloropyrido[2,3-B]pyrazine into 1h-lmidazo[4,5-b] pyridine by potassium amide in liquid ammonia

The synthesis of a number of 2-R₁, 3-R₂-6-X-pyrido[2,3-b]pyrazines (1) is reported and their reaction with potassium amide in liquid ammonia investigated. Ring contraction into a 2-R-1H-imidazo[4,5-b]pyridine was found to occur with X = Cl, R₁ = H, R₂ = C₆H₅ (1b); X = Cl, R₁ = R₂ = C₆H₅ ( 1c ); X = Cl, R₁ = H, R₂ = t-C₄H₉ ( 1d ). Besides ring contraction, an increasing amount of dechlorination of 1 was found: 1a , 20%; 1b , 30%; 1d , 40%; 1c , 60%; 1g , 95%. 1e (X = Cl, R₁ = t-C₄H₉, R₂ = H) yields the unreactive anionic σ-adduct at C-3 i.e., 3-amino-2-t-butyl-6-chloro-3,4-dihydropyrido[2,3-b]pyrazine. The ring contraction only proceeds with X = Cl. 1b (X = F) gives an amino-defluorination, 1b (X = Br) exclusively undergoes reductive debromination. The ring contraction of 1a (X = Cl, R₁ = R₂ = H) is investigated by ¹⁵N- and ¹³C-labelling. It is concluded that the conversion into 1H-imidazo[4,5-b]pyridine proceeds via the reactive anionic σ-adduct at C-2, under exclusive elimination of C-2.     

Synthesis of 12-aryl-1-oxo-1,2,3,4,5,12-hexahydroindolo-[2,1-b]quinazoline-6-carbonitriles by recyclization of 11-aryl-1-oxo-2,3,4,5,10b,11-hexahydro-1H-indolo[2,3-b]quinoline-10b-carbonitriles

A general and convenient method for the synthesis of 12-aryl-1-oxo-1,2,3,4,5,12-hexahydroindolo[2,1-b]quinazoline-6-carbonitriles was proposed. The method is based on the recyclization of 11-aryl-1-oxo-2,3,4,5,10b,11-hexahydro-1H-indolo[2,3-b]quinoline-10b-carbonitriles. The structure of 12-(3-methoxyphenyl)-8-methyl-1-oxo-1,2,3,4,5,12-hexahydroindolo[2,1-b]quinazoline-6-carbonitrile was studied by X-ray diffraction analysis.     

The synthesis of benzofuroquinolines. III. Two dihydroxybenzofuroquinolinones

Two dihydroxybenzofuroquinolinones, 3,9-dihydroxy-5H-benzofuro[3,2-c]quinolin-6-one (V) and 3,8-dihydroxy-6H-benzofuro[2,3-b]quinolin-11-one (VI), were obtained by the demethyl-cyclization of 3-(2,4-dimethoxyphenyl)-4-hydroxy-7-methoxy-1H-quinolin-2-one (IV). By the methylation with diazomethane, V gave a dimethylated compound (VII), while VI gave a trimethylated compound (VIII).     

Photocyclization of 2-[1]benzothien-3-yl)-3-phenylpropenoic acids

Photocyclization of the substituted 2-([1]benzothien-3-yl)-3-phenylpropenoic acids 3a-c in the presence of iodine and air in a benzene-cyclohexane mixture afforded a separable mixture of three compounds, benzo[b]naphtho[2,1-d]thiophene-6-carboxylic acids 4a-c , 6H-benzo[b]naphtho[2,3-d]thiopyran-6-ones 5a-c , and 10-methoxy-2-methyl-6H-benzo[b]naphtho[2,3-d]pyran-6-one ( 6 ).     

Synthesis of tricyclic isoindoles and thiazolo[3,2-c][1,3]benzoxazines

The thermolysis of (3R,9bS)-5-oxo-2,3,5,9b-tetrahydrothiazolo[2,3-a]isoindole-3-carboxylic acids in Ac₂O led to novel 3-methylene-2,5-dioxo-3H,9bH-oxazolo[2,3-a]isoindoles and chiral (9bS)-5-oxo-2,3,5,9b-tetrahydrothiazolo[2,3-a]isoindoles were obtained on FVP. Starting from l-cysteine methyl ester (3R,10bR)-5-oxo-2,3-dihydro-10bH-[1.3]thiazolo[3,2-c][1,3]benzoxazines were obtained as single stereoisomers. The thermolysis of (3R,10bR)-5-oxo-2,3-dihydro-10bH-[1.3]thiazolo[3,2-c][1,3]benzoxazine-3-carboxylic acid in Ac₂O gave 5-acetyl-2-phenyl-2,3-dihydrothiazole. The structures of methyl (3R,9bS)-5-oxo-2,3,5,9b-tetrahydrothiazolo[2,3-a]isoindole-3-carboxylate 1a and methyl (2R,4R)-N-chlorocarbonyl-2-(2-hydroxyphenyl)thiazolidine-4-carboxylate 9 were determined by X-ray crystallography.     

Five-membered 2,3-dioxoheterocycles: LXXXIV. [4+2]-Cycloaddition of styrene to 4,5-diaroyl-1H-pyrrole-2,3-diones. Crystal and molecular structures of 7a-(2,5-dimethylbenzoyl)-4-(2,5-dimethylphenyl)-1-(4-methoxyphenyl)-6-phenyl-7,7a-dihydropyrano[4,3-b]-pyrrole-2,3(1H,6H)-dione

1-Aryl-4,5-diaroyl-1H-pyrrole-2,3-diones react with styrene to form substituted 7,7a-dihydropyrano[4,3-b] pyrrole-2,3(1H,6H)-diones whose structure was confirmed by XRD analysis. The crystal and molecular structure of 7a-(2,5-dimethylbenzoyl)-4-(2,5-dimethyl-phenyl)-1-(4-methoxyphenyl)-6-phenyl-7,7a-dihydropyrano[4,3-b] pyrrole-2,3(1H,6H)dione was examined.     

Synthesis of Benzofuro[3,2-e][1,4]diazepines

A synthesis of 4-N-oxides and of 3-hydroxy derivatives of 1,3-dihydro-2H-benzofuro[3,2-e][1,4]diazepin-2-ones and of 2,3-dihydro-1H-benzofuro[3,2-e][1,4]diazepines is described. Condensation of 2-acetyl- and 2-benzoyl-3-ethoxycarbonylaminobenzofurans with acrylonitrile gave derivatives of 1,2-dihydro- and of 1,2,3,4-tetrahydrobenzofuro[3,2-b]pyridine.     

3-Methyl[1,3,4]thiadiazino[2,3-b]quinazolin-6-ones

4H,6H-[1,3,4]Thiadiazino[2,3-b]quinazolin-6-one with a methyl group in position 3 (6a) has been synthesised by the condensation of 3-amino-2-mercapto-3H-quinazolin-4-one (1) with allyl bromide (2) followed by treatment with bromine and subsequent dehydrohalogenation of the brominated product (4) with ethanolic sodium hydroxide. Its isomeric 3-methyl-2H,6H-[1,3,4]thiadiazino[2,3-b]quinazolin-6-one (6b) has also been obtained by condensation of1 and bromoacetone (7) followed by cyclisation of the intermediates (8 or9) with hydrobromic acid or with concentrated sulphuric acid. The structures have been established on the basis of IR and PMR data.

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3-Methyl[1,3,4]thiadiazino[2,3-b]chinazolin-6-one

Zusammenfassung Zur Synthese von 4H,6H-[1,3,4]thiadiazino[2,3-b]chinazolin-6-on (6a) wurde die Kondensation von 3-Amino-2-mercapto-3H-chinazolin-4-on (1) mit Allylbromid mit nachfolgender Behandlung mit Brom und Dehydrohalogenierung des bromierten Produktes4 mit ethanolischer Natronlauge herangezogen. Das zu6a isomere 2H,6H-Produkt6b wurde ebenfalls durch Kondensation von1 mit Bromaceton und nachfolgender Cyclisierung der Zwischenprodukte8 bzw.9 mit HBr oder H₂SO₄ erhalten. Die Strukturen wurden mittels IR und NMR abgesichert.

     

1, 3-dipolar cycloaddition of diazomethane to azolopyridazines. The synthesis of 8-methyl-8H- and 9-methyl-9H-pyrazolo[3, 4-d]-s-triazolo[4, 3-b]pyridazine and 1-methyl-1H- and 2-methyl-2H-imidazo[1, 2-b]pyrazolo[3, 4-b]pyridazine derivatives

The transformations of 7-methyl-7H- and 8-methyl-8H-pyrazolo[4, 3-d]tetrazolo[1, 5-b]pyridazines 1, 2, 9 and 10 into 8-methyl-8H- and 9-methyl-9H-pyrazolo[3, 4-H]-s-triazolo[4, 3-b]pyridazines 7 and 8 , and 1-methyl-1H-and 2-methyl-2H-imidazo[1, 2-b]pyrazolo[3, 4-d]pyridazines 13 and 14 are described.     

The synthesis of monomethoxy[1]benzothieno[2,3-c]quinolines

A series of monomethoxy[1]benzothieno[2,3-c]quinolines 24-28 were prepared by photocylization of the appropriate 3-chloro-N-phenylbenzo[b]thiophene-2-carboxamides 9–13 to [1]benzothieno[2,3-c]quinolin-6(5H)-ones 14-18 followed by chlorination to 6-chloro[1]benzothieno[2,3-c]quinolines 19-23 then dechlorination resulting in the title compounds except for 25 which was achieved by direct reduction of 15 . Reaction of 24-28 with methyl iodide provided the corresponding N-methyl quaternary salts 29-33 . Also, conversion of 4-meth-oxy[1]benzothieno[2,3-c]quinolin-6(5H)-one 16 to 4-methoxy-6-methylthio[1]benzothieno[2,3-c]quinoline 35 and 4,6-dimethoxy[1]benzothieno[2,3-c]quinoline 36 is described.     

K-region oxides and imines of benzo[b]phenanthro[2,3-d]thiophene and benzo[b]phenanthro[3,2-d]thiophene

The syntheses of the K-oxides and K-imine derivatives of benzo[b]phenanthro[2,3-d]thiophene and benzo-[b]phenanthro[3,2-d]thiophene are described. The parent hydrocarbons 1 and 2 were oxidized with osmium tetroxide and sodium metaperiodate, and the dialdehydes 12 and 18 so formed, cyclized to the corresponding epoxides 1a,12b-dihydrobenz[b]oxireno[9,10]phenanthro[2,3-d]thiophene ( 7 ) and 1a,12b-dihydrobenz-[b]oxireno[9,10]phenanthro[3,2-d]thiophene ( 13 ). Reaction of the oxiranes with sodium azide gave mixtures of azido-alcohols that, in turn, were transformed to the thiaarene imines 1a,12b-dihydro-1H-benz[b]azirino-[9,10]phenanthro[2,3-d]thiophene ( 8 ) and 1a,12b-dihydro-1H-benz[b]azirino[9,10]phenanthro[3,2-d]thiophene ( 14 ), respectively, with the aid of tri-n-butylphosphine.     

The photochemical synthesis of novel heterocyclic compounds from s-triazolo[4,3-b]pyridazine (II)

s-Triazolo[4,3-b Jpyridazine (I) photochemically reacted with dihydropyran; 2,3-dihydro-p-dioxin; 2,5-dihydrofuran; 2,5-dimethoxy-2,5-dihydrofuran; and 1,3-dioxep-5-ene to give a new series of substituted pyrrolo[1,2-b]-.s-triazoles (II-IX). In most reactions, two or more products were formed. The following compounds have been prepared from I: 9-methylene-4a,5,6,7,8a,9-hexahydropyrano[2,3 :4,5]pyrrolo[1,2-b]-s-triazole (Ha), the corresponding 9-cyanomethyl product (III), and 9-methylene-4a,7,8,8a-tetrahydro-6H,9H-pyrano[3′,2′:4,5]pyrrolo[1,2-b]-s-triazole (IIb) from dihydropyran; 9-methylene-4a,6,7,8a-tetrahydro-9H-p-dioxino[2′,3′:4,5]-pyrrolo[1,2-6]-s-triazole (IV) from 2,3-dihydro-p-dioxin; 8-methylene-4a,5,7a,8-tetrahydro-7H-furo[3′,4′:4,5]pyrrolo[1,2-b]-s-triazole (V) and the corresponding 8-cyanomethyl product (VI) from 2,5-dihydrofuran; 8-cyanomethyl-5,7-dimethoxy-4a,5,7a,8-tetrahydro-7H-furo[3′,4′:4,5]-pyrrolo[1,2-6]-s-lriazole (VII) from 2,5-dimethoxy-2,5-dihydrofuran; and 10-methylene-4a,5,9a,10-tetrahydro-9H-[1,3]dioxepino[5′,6′:4,5]pyrrolo[1,2-b]-s-triazole (VIII) and the corresponding 10-cyanomethyl product (IX) from 1,3-dioxep-5-ene. The addition of several other compounds (1,2,3,6-tetrahydropyridine, 1-acetylimidazole, 3-sulfolene, 2,3-dihydro-p-dithiin, and vinylene carbonate) was attempted, but no reactions were observed.     

Molecular Engineering of Isomeric Benzofurocarbazole Donors for Photophysical Management of Thermally Activated Delayed Fluorescence Emitters

Benzofurocarbazole moieties are commonly used donor structures in the design of thermally activated delayed fluorescence (TADF) emitters. However, only 5 H-benzofuro[3,2-c]carbazole (34BFCz) has been reported and, to the best of our knowledge, no other benzofurocarbazole derivatives have been covered in the literature. In the present study, two further benzofurocarbazole moieties, 12 H-benzofuro[3,2-a]carbazole (12BFCz) and 7 H-benzofuro[2,3-b]carbazole (23BFCz), have been synthesized to investigate the effect of the donor structure on the photophysics and device parameters of TADF emitters. Two benzofurocarbazole-derived TADF emitters, 12-(2-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-12 H-benzofuro[3,2-a]carbazole (o12BFCzTrz) and 7-(2-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-7 H-benzofuro[2,3-b]carbazole (o23BFCzTrz), have been compared with 5-(2-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-5 H-benzofuro[3,2-c]carbazole (oBFCzTrz). The benzofurocarbazole donor structure governs the TADF characteristics, such as charge-transfer property and emission color. The 12BFCz donor has proved to be effective in blue-shifting the emission color, and 34BFCz has proven useful for improving the external quantum efficiency (EQE). The 12BFCz-derived o12BFCzTrz showed blue-shifted color coordinates of (0.159, 0.288), compared to (0.178, 0388) for o23BFCzTrz and (0.169, 0.341) for oBFCzTrz. The 34BFCz-derived oBFCzTrz exhibited an EQE of 22.9 %, compared to 19.2 % for o12BFCzTrz and 21.1 % for o23BFCzTrz.     

Pyrrolo[2,3-d] pyrimidines. I. 5-hydroxypyrrolo[2,3-d] pyrimidines

5-Hydroxy-7-alkyl-2-phenyl-7H-pyrrolo[2,3-d]pyrimidine-6-carbonitriles (VIIb-d) and 5-hydroxy-2-phenyl-7H-pyrrolo[2,3-d]pyrimidine-6-carboxylic acid, ethyl ester (VIIa) were prepared from 5-carbethoxy-4-chloro-2-phenylpyrimidine (IV) via 4-[(cyanomethyl)alkylamino[-2-phenyl-5-pyrimidinecarboxylic acid, ethyl esters (Vb-d) and 4-[(carboxymethyl)amino]-2-phenyl-5-pyrimidinecarboxylic acid, diethyl ester (Va), respectively. The hydroxy group of the pyrrolo-[2,3-d]pyrimidines could be methylated, acetylated and tosylated. Hydrolysis of 5-methoxy-7-methyl-2-phenyl-7H-pyrrolo[2,3-d]pyrimidine-6-carbonitrile (IX) afforded the corresponding amide (X).     

Synthesis of furo[2,3-b]pyridine

Two routes were employed to synthesize unsubstituted furo[2,3-b]pyridine (IV). The first method started with ethyl 5-aminofuro[2,3-b] pyridine-2-carboxylate (1) and involved successive deamination, hydrolysis, and decarboxylation. The second method began with 5-nitrofuro[2,3-b ]-pyridine-2-carboxylic acid (V) and consisted of successive decarboxylation, reduction, and deamination reactions.     

Pyrrolopyridine analogs of nalidixic acid. 1. Pyrrolo[2,3-b]pyridines

A series of 4,7-dihydro-4-oxo-1H-pyrrolo[2,3-b]pyridine-5-carboxylic acids was synthesized from ethyl 5-methyl(or 5H)-2-aminopyrrole-3-carboxylate. The starting pyrroles were obtained by reaction of carbethoxyacetamidine with bromoacetone or chloroacetaldehyde. One compound ( 10 ) showed antibacterial activity in vitro.     

Synthesis of 1H-thieno[3,4-c]pyrazoles,thieno[3,4-b]furans,selenolo[3,4-b]furans and pyrrolo[3,4-d]thiazoles

Starting from the readily available aryl 2-methyl-5-phenyl-3-furyl ketones, 5-methyl-1H-1-phenylpyrazole-4-yl ketones and 4-methyl-2-phenyl-5-thiazolylcarboxaldehyde, a series of 2-phenyl-4-arylthieno[3,4-b]-furan, 2-phenyl-4-(p-methoxyphenyl)selenolo[3,4-b]furan, 4-aryl-1H-1-phenylthieno[3,4-c]pyrazole and 5-benzyl-2-phenylpyrrolo[3,4-d]thiazole were prepared in high yield.     

Synthesis and transformations of 3-(1H-pyrrol-1-yl)thieno[2,3-b]pyridines

Reactions of 2,5-dimethoxytetrahydrofuran with 3-aminothieno[2,3-b]pyridines afford a number of substituted 3-(1H-pyrrol-1-yl)thieno[2,3-b]pyridines. The possibility of the reaction and the yield of the product are determined by the character of a substituent in position 2 of thieno[2,3-b]pyridine. The Curtius rearrangement of 2-acylazido-3(1H-pyrrol-1-yl)thieno[2,3-b]pyridines yields 4,5-dihydropyrido[3",2":4,5]thieno[2,3-e]pyrrolo[1,2-a]pyrazin-4-ones. The molecular and crystal structures of ethyl 4-methoxymethyl-6-methyl-3-(1H-pyrrol-1-yl)thieno[2,3-b]pyridine-2-carboxylate were determined by X-ray diffraction analysis.