Synthesis of 2-arylamino substituted 5,6-dihydropyrido[2,3-d]pyrimidine-7(8H)-ones from arylguanidines

A practical protocol was developed for the synthesis of 2-arylamino substituted 4-amino-5,6-dihydropyrido[2,3-d]pyrimidin-7(8H)-ones from ??,??-unsaturated esters, malononitrile, and an aryl substituted guanidine via the corresponding 3-aryl-3,4,5,6- tetrahydropyrido[2,3-d]pyrimidin-7(8H)-ones. Such compounds are formed upon treatment of 2-methoxy-6-oxo-1,4,5,6-tetrahydropyridine-3-carbonitriles with an aryl substituted guanidine in 1,4-dioxane and are converted to the desired 4-aminopyridopyrimidines with NaOMe/MeOH through a Dimroth rearrangement. The overall yields of this three-step protocol are, generally speaking, higher than the multicomponent reaction, previously developed by our group, between an ??,??-unsaturated ester, malononitrile, and an aryl substituted guanidine.     

Synthesis of highly substituted 2,3-dihydropyrimido[4,5-<Emphasis Type="Italic">d</Emphasis>]pyrimidin-4(1<Emphasis Type="Italic">H</Emphasis>)-ones from 4,6-dichloro-5-formylpyrimidine,amines and aldehydes

A practical strategy was developed for the preparation of highly substituted 2,3-dihydropyrimido[4,5-d]pyrimidin-4(1H)-ones from 4,6-dichloro-5-formylpyrimidine, primary amines, and aldehydes. The key step for this synthesis entails a cyclization reaction involving an intramolecular amide addition to an iminium intermediate formed in situ from 4-amino-pyrimidine-5-carboxamide 2 and aldehydes to form the pyrimido[4,5-d]pyrimidine core with a strategically placed 5-Cl group for further derivatization. The utility of this methodology was demonstrated through the preparation of a 27-membered library of representative 2,3-dihydropyrimido[4,5-d]pyrimidin-4(1H)-ones in moderate to good yields.     

Synthesis of Pyrazolopyridine Annulated Heterocycles and Study the Effect of Substituents on Photophysical Properties

Pyrazolo[3,4-b]pyridines having 4-chloro-5-chloroethyl side chain are synthesized by the reaction of 5-aminopyrazole and cyclic β-formylester gave aminopyrazolodihydrofuranone intermediate, which on cyclization in phosphorous oxychloride exclusively converted in to 4-chloro-5-chloroethyl pyrazolo[3,4-b]pyridines 4(a-b) in major amount. The side chain with acetic acid, thiourea and aromatic amines are used to form angular ring leads to formation of tricyclic Furo[2,3-d]pyrazolo[2,3-b]pyridines 5(a-b), pyrazolo[3,4-b]thieno[2,3-d]pyridines 6(a-b) and pyrazolo[3,4-b]pyrrolo[2,3-d]pyridines 7(a-n) respectively. The substituents effect at C₄ position on fluorescence properties of pyrazolopyridines has been studied. Moreover the effect of electron donor and halogen substituents on fluorescence properties of pyrazolopyrrolopyridines 7(a-n) has been investigated along with their fluorescent quantum yield.     

Electrocatalytic multicomponent assembling of isatins, 3-methyl-2-pyrazolin-5-ones and malononitrile: facile and convenient way to functionalized spirocyclic [indole-3,4′-pyrano[2,3-c]pyrazole] system

Electrochemically induced catalytic multicomponent transformation of isatins, 3-methyl-2-pyrazolin-5-ones and malononitrile in ethanol in an undivided cell in the presence of sodium bromide as an electrolyte results in the formation of spirooxindoles with fused functionalized pyrano[2,3-c]pyrazole system in 78–99} yields. The developed efficient electrocatalytic approach to medicinally relevant spirocyclic [indole-3,4′-pyrano[2,3-c]pyrazoles] is beneficial from the viewpoint of diversity-oriented large-scale processes and represents a novel example of facile environmentally benign synthetic concept for electrocatalytic multicomponent reaction strategy.     

Fluorescence Studies on New Potential Antitumoral Benzothienopyran-1-ones in Solution and in Liposomes

Fluorescence properties of four new potential antitumoral compounds, 3-arylbenzothieno[2,3-c]pyran-1-ones, were studied in solution and in lipid membranes of dipalmitoyl phosphatidylcholine (DPPC), egg yolk phosphatidylcholine (Egg-PC) and dioctadecyldimethylammonium bromide (DODAB). The 3-(4-methoxyphenyl)benzothieno[2,3-c]pyran-1-one (1c) exhibits the higher fluorescence quantum yields in all solvents studied. All compounds present a solvent sensitive emission, with significant red shifts in polar solvents for the methoxylated compounds. The results point to an ICT character of the excited state, more pronounced for compound 1c. Fluorescence (steady-state) anisotropy measurements of the compounds incorporated in liposomes of DPPC, DODAB and Egg-PC indicate that all compounds have two different locations, one due to a deep penetration in the lipid membrane and another corresponding to a more hydrated environment. In general, the methoxylated compounds prefer hydrated environments inside the liposomes. The 3-(4-fluorophenyl)benzothieno[2,3-c]pyran-1-one (1a) clearly prefers a hydrated environment, with some molecules located at the outer part of the liposome interface. On the contrary, the preferential location of 3-(2-fluorophenyl)benzothieno[2,3-c]pyran-1-one (1b) is in the region of lipid hydrophobic tails. Compounds with a planar geometry (1a and 1c) have higher mobility in the lipid membranes when phase transition occurs.     

A new one-pot three-component synthesis of 2,4-diamino-5<Emphasis Type="Italic">H</Emphasis>-chromeno[2,3-<Emphasis Type="Italic">b</Emphasis>]pyridine-3-carbonitrile derivatives

In this study, a three-component one-pot synthesis of new 2,4-diamino-5H-chromeno[2,3-b]pyridine-3-carbonitriles derived from 2-amino-1,1,3-tricyanopropene, salicylic aldehydes and secondary cyclic amines is reported. The reaction is conducted in ethanol at ambient temperature in good-to-excellent yields.     

Cerium oxide-catalyzed multicomponent condensation approach to spirooxindoles in water

An efficient and facile green synthesis of spirooxindole derivatives bearing pyrano[2,3-c]pyrazole moiety has been achieved via a \(\mathrm{CeO}_{2}\)-NPs catalyzed four-component reaction in water. The protocol offers an environmentally benign and effective approach to highly functionalized and biologically interesting spiro[indoline-3,4\(^\prime \)-pyrano[2,3-c]pyrazole] derivatives. The synthesized compounds exhibit potent antioxidant and antibacterial activities.     

A facile and efficient ultrasound-assisted synthesis of novel dispiroheterocycles through 1,3-dipolar cycloaddition reactions

A facile and efficient one-pot three-component procedure for synthesis of novel dispirooxindolecyclo[pyrrolo[1,2-c]thiazole-6,5′-thiazolidine] derivatives without any catalysts under ultrasonic condition has been developed. Combining with the advantages of sonochemistry, such as mild reaction conditions, good yield and short reaction times, we have made a progress on construction of novel disiproheterocyclic compounds via the 1,3-dipolar cycloaddition of azomethine ylides. Several experiments were especially carried out for investigating the acceleration mechanism of ultrasound on the cycloaddition.     

An efficient and facile synthesis of new tetracyclic fused pyrazolo[4,3-<Emphasis Type="Italic">c</Emphasis>][1,2,4]triazino[4,5-<Emphasis Type="Italic">a</Emphasis>]quinolin-4(5<Emphasis Type="Italic">H</Emphasis>)-ones

Reaction of amidrazones 1a–1i with (1,5-dihydro-3-methyl-5-oxo-1-phenyl-4H-pyrazol-4-ylidene)propanedinitrile (2) in ethyl acetate solution in one-step reaction led to the formation of unprecedented pyrazolo[4,3-c][1,2,4]triazino[4,5-a]quinolin-4(5H)-ones 3a–3g along with pyrazolo[4,3-c][1,2,4]triazino[4,5-a]quinolin-12b-oles 3h–3m in moderate to excellent yields. These novel heterocycles were formed via a Michael addition reaction followed by intramolecular cyclization via a dearomatization process.     

Cerium ammonium nitrate (CAN)-catalyzed four-component one-pot synthesis of multi-substituted pyrano[2,3-\varvec{c}]pyrazoles under ultrasound irradiation

A convenient and efficient synthesis of multi-substituted dihydropyrano[2,3-c]pyrazole derivatives is reported. The four-component reaction of 4-hydrazinobenzoic acid, $\beta $ -keto esters, aromatic aldehydes, and malononitrile using 10 mol% CAN catalyst in water under ultrasound irradiation produced the target compounds in good-to-excellent yields. This method has advantages over conventional methods in being economic, non-toxic, and environmentally compatible due to its use of efficient and eco-friendly CAN catalyst and water solvent.     

Sulfamic acid catalyzed solvent-free synthesis of 10-aryl-7,7-dimethyl-6,7,8,10-tetrahydro-9H-[1,3]-dioxolo [4,5- <Emphasis Type="Italic">b</Emphasis>]xanthen-9-ones and 12-aryl-9,9-dimethyl-8,9,10,12-tetrahydro-11H-benzo[<Emphasis Type="Italic">a</Emphasis>]xanthen-11-ones

Three-component one-pot synthesis of some novel 10-aryl-7,7-dimethyl-6,7,8,10-tetrahydro-9H-[1,3]-dioxolo[4,5-b]xanthen-9-ones, which have not been published before, and 12-aryl-9,9-dimethyl-8,9,10,12-tetrahydro-11H-benzo[a]xanthen-11-ones from condensation of 3,4-methylenedioxyphenol or β-naphthol, aldehydes and dimedone under solvent-free conditions at 120 °C is reported.     

A facile one-pot ultrasound assisted for an efficient synthesis of 1H-spiro[furo[3,4-b]pyridine-4,3′-indoline]-3-carbonitriles

A convenient one-pot protocol was developed for the synthesis of 1H-spiro[furo[3,4-b]pyridine-4,3′-indoline]-3-carbonitrile derivatives. This reaction was carried out through a three component condensation reaction of isatins, malononitrile, and anilinolactones in the presence of a catalytic amount of Et₃N as an inexpensive and available basic catalyst in THF under ultrasound irradiation. The products were obtained in high yields and short reaction times. The main advantage of this synthetic method is that the obtained products in ultrasonic irradiations are different from classical heating.     

A diversity oriented, microwave assisted synthesis of N-substituted 2-hydro-4-amino-pyrido[2,3-d]pyrimidin-7(8H)-ones

A protocol for the synthesis of N-substituted 2-hydro-4-amino-pyrido[2,3-d]pyrimidin-7(8H)-ones (11) is described. Thus, the formylation of a 2-aminopyridone 12 in 85% formic acid/Ac₂O, proceeding via in situ cyclization to the intermediate formamide 13, affords the corresponding 2-hydro-4-oxo-pyridopyrimidine 14, which is converted to a 4-chloro-pyridopyrimidine 15 upon treatment with POCl₃. The subsequent transformation to the title compounds is carried by treatment with the corresponding amine in MeOH under microwave irradiation conditions.     

Organic synthesis in water: a green protocol for the synthesis of 2-(cyclohexylamino)-3- aryl- indeno[1,2-b]furan-4-ones

Aldehydes, 1,3-indandione and cyclohexylisocyanide undergo smooth coupling-cyclization in water to produce the corresponding 2-(cyclohexylamino)-3-aryl- indeno [1,2-b] furan-4-ones in good yields. Water was used as a solvent to avoid the use of other highly toxic and environmentally unfavorable solvents for this synthesis.

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Graphical Abstract  A simple and efficient synthesis of 2-(cyclohexylamino)-3-aryl- indeno[1,2-b]furan-4-ones was achieved via a one-pot three-component reaction of cyclohexylisocyanide, aldehydes, and 1,3-indandione in water for 5 h in good yields. zFX

     

High mobility organic thin-film transistors on plastic substrate

We have fabricated organic thin-film transistors (OTFTs) based on di-n-decyldinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (C₁₀-DNTT) on a polyimide gate dielectric coated on a polycarbonate substrate with a bottom-gate, top-contact configuration. Mobilities of the C₁₀-DNTT-based TFTs were as high as 2.4 cm² V^?1 s^?1, which are much better than those of the parent dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT)-based TFTs (mobility ～ 0.5 cm²/V) fabricated on the same substrate. Compared to the C₁₀-DNTT-TFTs on the conventional Si/SiO₂ substrate, the present mobility of C₁₀-DNTT-TFTs are somewhat reduced, which can be attributed to reduced crystallinity on the polyimide gate dielectric, although the crystalline phase on the polyimide is the same as on the Si/SiO₂ substrate.     

Magnetic nanoparticles catalyzed synthesis of diverse N-Heterocycles

A large library of diversified compounds (pyrano [2,3-d]pyrimidines, pyrido[2,3-d] pyrimidines and a variety of spirooxindoles) were synthesized through a very efficient, economical and environmentally benign process utilizing magnetic nanoparticles. Ease of recovery using an external magnetic field is an additional ecofriendly attribute of this catalytic system. Most of the compounds are new; therefore, could be further explored for their pharmaceutical application. Moreover, column chromatography and recrystallisation of the products is not required as the crude products are already highly pure and hence can be used for target oriented synthesis on a wide scale.     

Diastereoselective synthesis of fused [1,3]thiazolo[1,3]oxazins and [1,3]oxazino[2,3-b][1,3]benzothiazoles

An efficient diastereoselective synthesis of 7-ethyl 5,6-dialkyl 7H-[1,3]thiazolo[2,3-b][1,3]oxazin-5,6, 7-tricarboxylates and 2-ethyl 3,4-dialkyl 2H-[1,3]oxazino [2,3-b][1,3]benzothiazole-2,3,4-tricarboxylates via reaction of thiazole and benzothiazole with dialkyl acetylenedicarboxylates in the presence of ethyl pyruvate is described.     

A structurally diverse heterocyclic library: A benzothiazepine-fused β -lactam library derived from reaction of 2,3-dihydro-1,5-benzothiazepines and acyl chlorides: Synthesis and stereochemistry

A 1H-azeto[2,1-d][1,5]benzothiazepin-1-one, -lactam derivatives of dihydrobenzothiazepines library derived from reactions of 2,4-disubstituted 2,3-dihydro-1,5-benzothiazepines and acyl chlorides, including phthalimidoacetyl chloride, chloroacetyl chloride, dichloroacetyl chloride and phenoxyacetyl chloride, was built up through parallel solution-phase synthesis. Stereochemistry of 1H-azeto[2,1-d][1,5]benzothiazepin-1-ones in the reaction process is discussed.     

Structure and linear spectroscopic properties of near IR polymethine dyes

We performed a detailed experimental investigation and quantum-chemical analysis of a new series of near IR polymethine dyes with 5-butyl-7,8-dihydrobenzo[cd]furo[2,3-f]indolium terminal groups. We also synthesized and studied two neutral dyes, squaraine and tetraone, with the same terminal groups and performed a comparison of the spectroscopic properties of this set of “near IR” dyes (polymethine, squaraine, and tetraone) with an analogous set of “visible” dyes with simpler benzo[e]indolium terminal groups. From these measurements, we find that the dyes with dihydrobenzo[cd]furo[2,3-f]indolium terminal groups are characterized by a remarkably large shift ≈300 nm (≈200 nm for tetraone) of their absorption bands towards the red region. We discuss the difference in electronic structure for these molecules and show that the “near IR” dyes are characterized by an additional weak fluorescence band from the higher lying excited states connected with the terminal groups. Absorption spectra for the longest polymethines are solvent-dependent and are characterized by a broadening of the main band in polar solvents, which is explained by ground state symmetry breaking and reduced charge delocalization within the polymethine chromophore. The results of these experiments combined with the agreement of quantum chemical calculations moves us closer to a predictive capability for structure-property relations in cyanine-like molecules.     

Diversity oriented heterocyclizations of pyruvic acids,aldehydes and 5-amino-<Emphasis Type="Italic">N</Emphasis>-aryl-1<Emphasis Type="Italic">H</Emphasis>-pyrazole-4-carboxamides: catalytic and temperature control of chemoselectivity

Heterocyclization reactions of pyruvic acids, aromatic aldehydes and 5-amino-N-aryl-1H-pyrazole-4-carboxamides yielding four different types of final compounds are described. The reactions involving arylidenpyruvic acids lead with high degree of selectivity to either 4,7-dihydropyrazolo[1,5-a]pyrimidine-5-carboxylic acids or 5-[(2-oxo-2,5-dihydrofuran-3-yl)amino]-1H-pyrazoles, depending on the catalyst type or temperature regime. The interactions based on arylpyruvic acids can take place under kinetic or thermodynamic control producing 7-hydroxy-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidine-7-carboxylic acids or 3-hydroxy-1-(1H-pyrazol-5-yl)-1,5-dihydro-2H-pyrrol-2-ones, respectively.