Synthesis of 1H-pyrrolo[3,2-c]quinoline derivatives via palladium-catalyzed heteroannulation of 2-aryl-3-iodo-4-(phenylamino)quinolines and 4-(N,N-allylphenylamino)-2-aryl-3-iodoquinolines

Palladium(0)/copper iodide catalyzed Sonogashira cross-coupling of 2-aryl-3-iodo-4-(phenylamino)quinolines with terminal alkynes afforded series of 1,2,4-trisubstituted 1H-pyrrolo[3,2-c]quinolines in a single-step operation. Conversely, the 4-(N,N-allylphenylamino)-2-aryl-3-iodoquinoline derivatives were found to undergo PdCl₂(PPh₃)₂/CuI catalyzed intramolecular Heck reaction to yield the corresponding 1,3,4-trisubstituted 1H-pyrrolo[3,2-c]quinolines.     

Synthesis of 8-R-9c-alkyl-1-aryl-2-benzyl-1-hydroxy-1,2,9b,9c-tetrahydro-5-oxa-2-aza-cyclopenta[2,3]cyclopropa[1,2-a]naphthalene-3,4-diones and reaction thereof with acetic anhydride

The reaction of zinc enolates synthesized from 1-aryl-2,2-dibromoalkanones and zinc with 6-R-2-oxochromene-3-carboxylic acid N-benzylamide affords 8-R-9c-alkyl-1-aryl-2-benzyl-1-hydroxy-1,2,9b,9c-tetrahydro-5-oxa-2-aza-cyclopenta[2,3]cyclopropa[1,2-a]naphthalene-3,4-diones. Acylation of these compounds is accompanied by an unexpected rearrangement producing a sole geometrical isomer of 4′-alkyl-5′-aryl-1′-benzyl-3,4,2′,3′-tetrahydro-2,2′-dioxospiro[chroman-3,3′-pyrrol]-4-yl acetates.     

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 study of the reactions of 2-aryl-4-hydroxy-6H-1,3-thiazin-6-ones with chromone-3-carboxaldehydes

Reaction of 3-formylchromones with 2-aryl-4-hydroxy-6H-1,3-thiazin-6-ones in the presence of pyridine leads to formation of a mixture of novel N-thioaroyl-5-hydroxy-2H,5H-pyrano[3,2-с]chromen-2-one-3-carboxamides and 2-aryl-5-(4′-oxochromen-3′-yl)-6,7-dihydro-4H,5H-pyrano[2,3-d][1,3]thiazine-4,7-diones. The yields of these compounds clearly depend on the nature of the substituent on the 3-formylchromone and on the reaction conditions.     

Reactions of 4-acyl-1-alkoxyaryl-5-aryl-3-hydroxy-2,5-dihydro-1H-pyrrol-2-ones with nucleophilic reagents

4-Acetyl-1-alkoxyaryl-5-aryl-3-hydroxy-2,5-dihydro-1H-pyrrol-2-ones reacted with amines to give 1-alkoxyaryl-5-aryl-4-(1-R-aminoethylidene)pyrrolidine-2,3-diones. Reactions of amines with 4-benzoyl-substituted analogs involve nucleophilic attack on the C³ atom in the heteroring to produce the corresponding 3-R-amino-1-alkoxyaryl-5-aryl-4-benzoyl-2,5-dihydro-1H-pyrrol-2-ones. Reactions of the title compounds with hydrazine hydrate, regardless on the substituent on C₄, afforded 4-aryl-3-methyl(phenyl)-5-[2(4)-methoxyphenyl]-4,6-dihydropyrrolo[3,4-c]pyrazol-6-ones.     

Five-membered 2.3-dioxo heterocycles: LXVIII. Three pathways in the reaction of methyl 3-aroyl-1-aryl-4,5-dioxo-4,5-dihydro-1H-pyrrole-2-carboxylates with 3-amino-5,5-dimethylcyclohex-2-en-1-one

Methyl 3-aroyl-1-aryl-4,5-dioxo-4,5-dihydro-1H-pyrrole-2-carboxylates reacted with 3-amino-5,5-dimethylcyclohex-2-en-1-one having no substituent on the nitrogen atom to give 3-aroyl-4-arylamino-6′,6′-dimethyl-6′,7′-dihydro-5H-spiro[furan-2,3′-indole]-2′,4′,5′(1′H,5′H)-triones or methyl 12-aroyl-11-aryl-9-hydroxy-5,5-dimethyl-3,10-dioxo-8,11-diazatricyclo[7.2.1.0^2,7]dodec-2(7)-ene-1-carboxylates. The latter underwent thermal recyclization to 3′-aroyl-1′-aryl-4′-hydroxy-6,6-dimethyl-6,7-dihydrospiro[indole-3,2′-pyrrole]-2,4,5′(1H,1′H,5H)-triones.     

Copper-mediated Chan-Evans-Lam N-arylation of 5-methylene-4-aryl-1,5-dihydro-2H-pyrrol-2-one derivatives

A simple and efficient procedure for the synthesis of N-aryl 5-methylene-4-aryl-1,5-dihydro-2H-pyrrol-2-one derivatives has been developed through copper-mediated CN bond formation. The synthetic protocol allows for versatile and robust CN arylation with a range of readily available boronic acids under mild conditions.     

Synthesis of ethyl 2-[(1-aryl-1H-1,2,4-triazol-3-yl)oxy]propionates and related derivatives

Alkylation of 1-aryl-1H-1,2,4-triazol-3-ols with ethyl 2-bromopropionate under basic conditions resulted in the formation of 2-[(1-aryl-1H-1,2,4-triazol-3-yl)oxy]propionic acid, ethyl esters. No N-alkylated products were detected. Similar alkylation of 2-oxo-5-phenyl-1,3,4-thiazole and the corresponding 1,3,4-oxadiazole gave only N-alkylated derivatives. With 4-hydroxy-6-phenylpyrimidine and 2-oxo-4-phenylthiazole, both O- and N-alkylation occurred. Structure assignments were based on ir and ¹³C nmr spectral data.     

4-aryl-2-hydroxy-4-oxobut-2-enoic acids <Emphasis Type="Italic">N</Emphasis>-(2-pyridyl)amides in reactions with diazo compounds

Reactions of 4-aryl-2-hydroxy-4-oxobut-2-enoic acids N-(2-pyridyl)amides with diazomethane, diazoethane, diaryldiazomethanes, and diazofluorene lead to the formation of 2-alkoxy-4-aryl-4-oxobut-2-enoic acids N-(2-pyridyl)amides, 3-aroyl-5-methylpyrazole-4-carboxylic acids N-(2-pyridyl)amides, and 3-alkoxy-3-(2-aryl-2-oxoethyl)-2,3-dihydro-2-oxoimidazo[1,2-a]pyridines. The composition and structure of compounds obtained depend on the nucleophilic nature of the diazo compound and on the character of substituents in the aryl and pyridine parts of the substrate.     

The triflic acid-mediated cyclisation of N-benzylcinnamanilides

N-Benzylcinnamanilides cyclise with triflic acid to form 1-benzyl-4-aryl-2,4-dihydro-1H-quinolin-2-ones and 2,5-diaryl-benzazepin-3-ones. The product ratio is determined by the preferred orientation of the amide and by the electronics of the substituents. With ortho-substituted anilides, N-debenzylation also occurs to give 4-aryl-2,4-dihydro-1H-quinoline-2-ones.     

An efficient synthesis of functionalized tetrahydro-lH-indeno[2, 1-c]pyridine derivatives by a PPh3-promoted condensation reaction between acetylene esters and 1,3-dioxo-N-aryl-2,3- dihydro-1 H-indene-2-carboxamides

A reaction between 1,3-dioxo-N-aryl-2,3-dihydro-lH-indene-2-carboxamides, dialkyl acetylenedicar- boxylates, and triphenylphosphine or trimethylphosphite is described as a simple and efficient method for the synthesis of 5-hydroxy-4-aryl-2,5-dihydrofuran-2,3-dicarboxylate derivatives.     

Synthesis of 5-alkyl-5-aryl-1-pyrroline N-oxides from 1-aryl-substituted nitroalkanes and acrolein via Michael addition and nitro reductive cyclization

A general method for accessing 5-alkyl-5-aryl-1-pyrroline N-oxides (AAPOs) has been established using readily available aryl bromides, nitroalkanes, and acrolein as the starting materials. The palladium-catalyzed arylation of nitroalkanes gave the 1-aryl-substituted nitroalkanes, which underwent the Et₃N-catalyzed Michael addition with acrolein at room temperature to afford the 4-aryl-4-nitroaldehydes. The latter were then subjected to the nitro reductive cyclization using Zn–HOAc in EtOH at 0 °C followed by warming the reaction mixture to room temperature for 24 h, furnishing the 5-alkyl-5-aryl-1-pyrroline N-oxides in good overall yields. Selected examples of 1,3-dipolar cycloaddition of the cyclic nitrones with methyl methacrylate were also described.     

Oxidative hydrolysis of a cyclic 1,N-propano-2′-deoxyguanosine, an adduct of 2′-deoxyguanosine with acetaldehyde or crotonaldehyde

The SO₄⁻-oxidation of cyclic 1,N²-propano-2′-deoxyguanosine, chemo- and regioselectively produced in the reaction of 2′-deoxyguanosine with excessive acetaldehyde or crotonaldehyde, resulted in the smooth formation of (4-hydroxy-5-hydroxymethyltetrahydrofuran-2-ylimino)-(4-hydroxy-6-methyltetrahydropyrimidin-2-ylideneamino)acetic acid, 3-(4-hydroxy-5-hydroxymethyltetrahydrofuran-2-yl)-6-methyl-3H-1,3,4,5,8a-pentaazacyclopenta[b]naphthalen-9-one, and 2′-deoxyguanosine even under neutral conditions. The formation of the guanine-ring opened product during the reaction is very interesting and appears to closely relate to the mechanisms for the point-mutations of DNA by these mutagenic and carcinogenic aldehydes.     

Two-pot synthesis of N,N-disubstituted 4H-3,1-benzothiazin-2-amines from aryl(2-isothiocyanatophenyl)methanones and secondary amines

A convenient synthesis of N,N-disubstituted 4H-3,1-benzothiazin-2-amines from aryl(2-isothiocyanatophenyl)methanones using a two-pot procedure has been developed. Thus, treatment of these isothiocyanato ketones with secondary amines gave the corresponding keto thioureas, which were allowed to react with sodium borohydride or methylmagnesium bromide to afford 1,1-dialkyl-3-{2-[aryl(hydroxy)methyl]phenyl}thioureas or 1,1-dialkyl-3-[2-(1-aryl-1-hydroxyethyl)phenyl]thioureas, respectively, in one pot. Hydrobromic acid-mediated cyclization of these hydroxy thiourea precursors provided the desired 4H-3,1-benzothiazin-2-amines.     

Synthesis of 4-aryl-2-hydroxy-4-oxo-2-butenoic (Aroylpyruvic) acids N-(4-Acetylaminosulfonylphenyl)amides

Methyl aroylpyruvates react with sodium 4-aminobenzenesulfonylacetamide in acetic acid to afford 4-aryl-2-hydroxy-4-oxo-2-butenoic acids N-(4-acetylaminosulfonylphenyl)amides. The latter were studied in reactions with hydrazine hydrate.     

A novel annulation reaction of N-substituted-2-nitrosoanilines with esters of α-isocyano acids. A one-pot,two-step route to 2-benzimidazole-substituted esters of α-amino acids

A BF₃-promoted α-addition of isocyanides to both nitrogen atoms of N-aryl-2-nitrosoanilines leads to stable BF₃-complexes of 3-N-hydroxy-(2-alkylimino)benzimidazole derivatives, which, after reduction with Zn in AcOH produce 1-N-aryl-2-alkylaminobenzimidazoles. This two-step annulation proceeds efficiently in a one-pot protocol with isocyanides derived from esters of α-amino acids. The chirality of the latter remains unaffected in the reaction.     

N-Nitroso-2-aryl-1,3-oxazolidines catalyzed aromatization of Hantzsch 1,4-dihydropyridines

A catalytic amount of N-nitroso-2-aryl-1,3-oxazolidines leading to the aromatization of Hantzsch 1,4-dihydropyridines (DHPs) was successfully achieved. A catalytic mechanism for the reaction is proposed.     

Cycloacylation of N-phenyl-N′-R-thioureas with 3-aryl-2-propenoyl chlorides

Cycloalkylation of N-phenyl-N′-R-thiourea with 3-aryl-2-propenoyl chlorides in acetone gives as products 6-aryl-3-phenyl-2-(R-imino)-2,3,5,6-tetrahydro-4H-1,3-thiazin-4-one and their hydrochlorides. The same reaction carried out in acetone in the presence of K₂CO₃ leads to the formation of 6-aryl-3-phenyl-2-(R-imino)-2,3,5,6-tetrahydro-4H-1,3-thiazin-4-ones, N-(3-aryl-2-propenoyl)-N-phenylthioureas, 3-aryl-2-propenoylanilides, and phenyl isothiocyanate.     

Efficient synthesis of 6-aryl-4-trifluoromethyl/ethoxycarbonyl-2H-pyran-2-ones through self-condensation of penta-2,4-dienenitriles

An efficient synthesis of two new series of 6-aryl-4-trifluoromethyl-2H-pyran-2-ones and 6-aryl-4-carboxyethyl-2H-pyran-2-ones, obtained through the self-condensation reaction of 5-aryl-5-methoxy-3-(trifluoromethyl)penta-2,4-dienenitriles 3 and ethyl 4-aryl-2-(cyanomethylene)-4-methoxybut-3-enoates 4 respectively, is reported. The self-condensation reaction of the enoates 4 was performed in water in the presence of hydrochloric acid whereas the self-condensation reaction of the penta-2,4-dienenitriles 3 required the use of zinc bromide and hydrochloric acid in order to give the respective 2H-pyran-2-ones. Products were obtained up to 97% yield.     

Anodic formation of 3,6-diaryl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazoles and 2(3-aryl-5-methyl-1H-[1,2,4]triazol-1-yl)-5-aryl-1,3,4-thiadiazoles

3,6-Disubstituted 1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles together with the unknown systems 2-(3-aryl-5-methyl-1H-[1,2,4]triazol-1-yl)-5-aryl-1,3,4-thiadiazoles were obtained by anodic oxidation, under aprotic conditions, of aryl aldehyde N-(5-aryl-1,3,4-thiadiazol-2-yl) hydrazones. Mechanistic proposals are given.