Use of nanoporous Na+-montmorillonite sulfonic acid (SANM) as an eco-benign, efficient and reusable solid acid catalyst for the one-pot synthesis of 14-aryl-14-H-dibenzo[a,j]xanthenes and 1,8-dioxo-dodecahydroxanthene derivatives

Nanoporous Na⁺-montmorillonite sulfonic acid was found to be an efficient and green catalyst for the synthesis of various 14-aryl-14H-dibenzo[a,j]xanthenes and 1,8-dioxo-dodecahydroxanthene derivatives by the reaction of aldehydes with 2-naphthol and 1,3-cyclohexanedione, respectively. This novel synthetic method has the advantages of high yields, short reaction times and recyclability of the catalyst, simplicity and easy workup compared to the conventional methods reported in the literature.     

A clean synthesis of oxazino[5,6-f]quinolinone and naphtho[1,2-e]oxazinone derivatives

A clean, simple, one-pot, and efficient synthesis of 1,2-dihydro-1-aryl[1,3]oxazino[5,6-f]quinolin-3-one and 1,2-dihydro-1-arylnaphtho[1,2-e]-[1,3]oxazine-3-one derivatives was accomplished in good yields via reaction between 6-quinolinol or 2-naphthol, aromatic aldehydes, and methyl carbamate in aqueous medium catalyzed by TEBA (triethylbenzylammonium chloride).     

BF3·SiO2: an efficient alternative for the synthesis of 14-aryl or alkyl-14H-dibenzo[a,j]xanthenes

Silica-supported boron trifluoride (BF₃·SiO₂) is an efficient, readily available, and reusable catalyst for the synthesis of 14-aryl or alkyl-14H-dibenzo[a,j]xanthenes by condensation of 2-naphthol and aldehydes. This reaction under heating or sonication conditions is very simple, affording good to excellent yields of products.     

Synthesis and conformational analysis of new naphth[1,2-e][1,3]oxazino[3,4-c]quinazoline derivatives

A new highly functionalized aminonaphthol derivative, 1-(amino(2-aminophenyl)methyl)-2-naphthol (4), was synthesized by the reaction of 2-naphthol, 2-nitrobenzaldehyde and tert-butyl carbamate or benzyl carbamate, followed by reduction and/or removal of the protecting group. The aminonaphthol derivative thus obtained was converted in ring-closure reactions with formaldehyde, benzaldehyde and/or phosgene to the corresponding naphth[1,2-e][1,3]oxazino[3,4-c]quinazoline derivatives. The conformational analysis of some derivatives by NMR spectroscopy and accompanying molecular modelling are also reported.     

A new strategy for the synthesis of pyrazolo[4,3-e][1,2,4]triazolo[4,3-c]pyrimidines and pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidines

A series of pyrazolo[4,3-e][1,2,4]triazolo[4,3-c]pyrimidines were prepared via oxidative cyclization of aldehyde N-(1,3-diphenylpyrazolo[3,4-d]pyrimidin-4-yl)hydrazones. Dimroth rearrangement of such a series yielded pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidines.     

Solvent-free synthesis of 14-Aryl-14H-dibenzo[a,j]xanthenes catalyzed by recyclable and reusable iron(III) triflate

A solvent-free and efficient synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes through the one-pot condensation of β-naphthol and aldehydes catalyzed by recyclable and reusable Iron(III) triflate was reported. Notably, the presented method features short reaction time, excellent yield, and simple experimental procedure.     

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.     

A clean synthesis of oxazino[5,6-<Emphasis Type="Italic">f</Emphasis>]quinolinone and naphtho[1,2-<Emphasis Type="Italic">e</Emphasis>]oxazinone derivatives

A clean, simple, one-pot, and efficient synthesis of 1,2-dihydro-1-aryl[1,3]oxazino[5,6-f]quinolin-3-one and 1,2-dihydro-1-arylnaphtho[1,2-e]-[1,3]oxazine-3-one derivatives was accomplished in good yields via reaction between 6-quinolinol or 2-naphthol, aromatic aldehydes, and methyl carbamate in aqueous medium catalyzed by TEBA (triethylbenzylammonium chloride). Correspondence: Mohammad Hossein Mosslemin, Department of Chemistry, Islamic Azad University, Yazd 8916871967, Iran.     

Heterogeneous catalyst: Amberlyst-15 catalyzes the synthesis of 14-substituted-14H-dibenzo[a,j]xanthenes under solvent-free conditions

A one-pot condensation of β-naphthol with aldehydes in the presence of Amberlyst-15 to give 14-substituted-14H-dibenzo[a,j]xanthenes under solvent-free condition is described.     

Sulfamic acid: a novel and efficient catalyst for the synthesis of aryl-14H-dibenzo[a.j]xanthenes under conventional heating and microwave irradiation

A simple and convenient procedure for the synthesis of aryl-14H-dibenzo[a.j]xanthenes is described through a one-pot condensation of β-naphthol with aryl aldehydes in the presence of sulfamic acid as the catalyst in a solvent-free media using both conventional heating and microwave irradiation.     

Iodine Catalyzed Microwave-Assisted Synthesis of 14-Aryl（Alkyl）-14H-dibenzo[a,j]xanthenes

A straightforward and effective procedure for the synthesis of 14-aryl（alkyl）-14H-dibenzo[aj]xanthenes was described using a catalytic amount of molecular iodine under microwave irradiation to afford the corresponding xanthenes in good yields.     

A novel synthesis of 14-(hydroxymethylalkyl) derivatives of dibenzoxanthenes and 3,3-dimethyl-4-(2-hydroxy-1-naphthyl)benzo[f]chroman

Several reactions of 2-naphthol with 2-alkyl-2-hydroxymethylaldehydes have been investigated. Novel synthesis of 14-(hydroxymethyl)alkyldibenzo[a,j]xanthenes and 3,3-dimethyl-4-(2-hydroxy-1-naphthyl)benzo[f]chroman has been realized.     

Simple access to pentacyclic oxazinoisoquinolines via an unexpected transformation of aminomethylnaphthols

Unexpected reactions between 1-α-aminobenzyl-2-naphthol, 1-aminomethyl-2-naphthol, N-benzyl-1-α-aminobenzyl-2-naphthol and 6,7-dimethoxy-3,4-dihydroisoquinoline to furnish naphth[1,2-e][1,3]oxazino[2,3-a]isoquinolines are reported. The reaction conditions involved classical heating at 80 °C in MeCN for 22 h (57-62%), or the use of microwave conditions (100 °C), which allowed a reduction of the reaction time to 90 min and resulted in somewhat higher yields (73-82%).     

Bis(aldehydes): Versatile precursors for novel bis(14H-dibenzo[a,j]xanthenes), bis(pyrano[3,2-c:5,6-c']dichromenedione), and bis(dihydrobenzo[a]xanthenones) via multicomponent reactions

A synthesis of novel bis(4-(14H-dibenzo[a,j]xanthenes) and bis(dihydro-8H-benzo[a]xanthenones) was performed in good yields via pseudo-multicomponent, or multicomponent reactions, of bis-aldehydes with four equivalents of β-naphthol or with a mixture of two equivalents of each β-naphthol and dimedone in the presence of a catalytic amount of p-toluenesulfonic acid. Bis(pyrano[3,2-c:5,6-c′]dichromenediones) or tetrakis(4-hydroxy-2H-chromen-2-ones) could also be obtained in good yields through pseudo-multicomponent reactions of bis(aldehydes) with four molar ratio of 4-hydroxycoumarin.     

[3 + 2]-Cycloaddition of azomethine ylide at 1,3-dimethyl-6-(2-oxo-1,2-dihydro-3H-indol-3-ylidene)-3a,9a-diphenyl-3,3a,9,9a-tetrahydroimidazo[4,5-e][1,3]thiazolo[3,2-b][1,2,4]triazine-2,7(1H,6H)-diones

[3 + 2]-Cycloaddition of azomethine ylide generated from formaldehyde and sarcosine at the double bond of 1,3-dimethyl-6-(2-oxo-1,2-dihydro-3H-indol-3-ylidene)-3a,9a-diphenyl-3,3a,9,9a-tetrahydroimidazo[4,5e][1,3]thiazolo[3,2-b][1,2,4]triazine-2,7(1H,6H)-diones occurs stereospecifically at the face opposite to the phenyl substituents. Product 3a crystallizes as a conglomerate.     

Selective construction of indeno[1,2-b]phenothiazine and indeno[2,1-c]phenothiazine via tandem annulation reaction

AcOH promoted annulation reaction of 2-arylideneindane-1,3-diones with methyl 2-(benzo[b][1,4]thiazin-3-ylidene)acetate in refluxing ethanol afforded pentacyclic tetrahydroindeno [1,2-b]phenothiazine in satisfactory yields and with high diastereoselectivity according to the unexpected tandem annulation process. When the above reaction was carried out in refluxing acetic acid, isomeric dihydroindeno [1,2-b]phenothiazines and dihydroindeno [2,1-c]phenothiazines were obtained in comparable yields according to alternate tandem annulation process.     

One-pot,expeditious and chromatography-free synthesis of new chromeno[4,3-e][1,3]oxazine derivatives catalyzed by reusable TiO2 nanopowder at room temperature

An expeditious, one-pot, pseudo four-component coupling reaction between 3-hydroxy coumarin, formaldehyde, and amine catalyzed by reusable TiO₂ nanopowder in ethanol at room temperature (25–28 °C) under stirring condition to synthesize the chromeno[4,3-e][1,3]oxazine derivatives has been described. A wide range of substrate variation, environmentally benign reaction procedure, easy work-up, chromatography free synthesis, and excellent yields with reusability of the catalyst make the methodology highly effective for the synthesis of chromeno[4,3-e][1,3]oxazine derivatives. To the best of our knowledge, this is the first Letter for the synthesis of chromeno[4,3-e][1,3]oxazines using 3-hydroxy coumarin.     

New syntheses of [1,2,5]oxadiazolo[3,4-e][1,2,3,4]tetrazine 4,6-dioxide

New methods were developed for the synthesis of [1,2,5]oxadiazolo[3,4-e][1,2,3,4]tetrazine 4,6-dioxide from 4-(tert-butyl-NNO-azoxy)-N-nitro-1,2,5-oxadiazol-3-amine or its alkali metal salts and acid anhydrides (or chlorides) in the presence of strong acids. The yield of [1,2,5]oxadiazolo[3,4-e][1,2,3,4]tetrazine 4,6-dioxide in acetic anhydride in the presence of sulfuric acid or sulfuric anhydride at 20°C in 20 min attained 83%. A general mechanism was proposed for the reactions under study. Acetyl group behaved for the first time as departing group in the synthesis 1,2,3,4-tetrazine 1,3-dioxides, and [1,2,5]oxadiazolo[3,4-e][1,2,3,4]tetrazine 4,6-dioxide was obtained in 47% yield from N-[4-(acetyl-NNO-azoxy)-1,2,5-oxadiazol-3-yl]acetamide.     

Fused pyrimidine systems: XIII. Synthesis and some transformations of 1,3-thiazolo(thiazino)-fused pyrido[3,4-d]pyrimidines

2-[Allyl(propargyl)sulfanyl]pyrido[3,4-d]pyrimidin-4-ones at heating in polyphosphoric acid undergo an intramolecular cyclization with the formation of pyrido[4,3-e]thiazolo-[3,2-a]pyrimidin-5-ones of angular structure. Under similar conditions the cyclization of 2-(cinnamylsulfanyl)pyrido[3,4-d]-pyrimidin-4-one results in a linear pyrido[3′,4′:4,5]pyrimido-[2,1-b][1,3]thiazin-6-one. The iodocyclization of the same substrates affords the corresponding 9-(iodomethyl)(iodomethylidene)pyrido[4,3-e][1,3]thiazolo-[3,2-a]pyrimidin-5-ones and 3-iodopyrido[3′,4′:4,5]pyrimido[2,1-b][1,3]thiazin-6-one of angular structure. 9-(Iodomethyl)-8,9-dihydro-5H-pyrido[4,3-e][1,3]thiazolo[3,2-a]pyrimidin-5-one treated with sodium azide gave 9-(azidomethyl) derivative whose cyclization with substituted alkynes in the presence of copper compounds provided pyrido [4,3-e][1,3]thiazolo[3,2-a]pyrimidinylmethyltriazoles.     

A convenient synthesis of new pyrido[3,2-e][1,4]diazepine-2,5-diones and pyrido[2,3-e][1,4]diazepine-2,5-diones

A convenient synthesis of a series of pyrido[3,2-e][1,4]-diazepine-2,5-diones 8 and pyrido[2,3-e][1,4]diazepine-2,5-diones 9, is reported using the condensation of α-amino acid methyl ester derivatives with 1H-pyrido[3,2-d][1,3]oxazine-2,4-dione and 1H-pyrido[2,3-d][1,3]oxazine-2,4-dione. Compounds 8 and 9 were also synthesized by peptide coupling of α-amino acid methyl ester derivatives with β-amino acids (2 or 3) followed by the cyclisation in tetrahydrofuran with sodium hydride (NaH).