Synthesis and photovoltaic properties of novel organic sensitizers containing indolo[1,2-f]phenanthridine for solar cell

Organic dyes containing indolo[1,2-f]phenanthridine unit are a promising new class of sensitizers for dye-sensitized solar cells, as a result of their broad and intense visible absorptions. Under standard global AM 1.5 solar condition, the JK-61 sensitized cell gave a short circuit photocurrent density (J_sc) of 15.81 mA cm⁻², an open circuit voltage (V_oc) of 0.73 V, a fill factor of 0.72, corresponding to an overall conversion efficiency of 8.34%.     

Synthesis, in vitro antiproliferative activities, and Chk1 inhibitory properties of dipyrrolo[3,4-a:3,4-c]carbazole-triones

The syntheses of dipyrrolo[3,4-a:3,4-c]carbazole-1,4,6-triones and dipyrrolo[3,4-a:3,4-c]carbazole-3,4,6-triones are reported. These compounds can be considered as granulatimide analogues in which a maleimide replaces the imidazole moiety and a five-membered lactam ring replaces the upper maleimide. The Chk1 inhibitory properties of the more soluble compounds have been evaluated and their in vitro antiproliferative activities toward three tumor cell lines: murine leukemia L1210, and human colon carcinoma HT29 and HCT116. Due to their insolubility, the biological activities of the other compounds in this series could not be evaluated. All the tested compounds proved to be potent Chk1 inhibitors.     

Synthesis of dipyrrolo[3,4-a:3,4-c]carbazoles: new kinase inhibitors

Two dipyrrolo[3,4-a:3,4-c]carbazole stereoisomers were unexpectedly obtained by Diels–Alder dimerization of 3-indolylmaleimide. Three dimensional structures of both stereoisomers were confirmed by X-ray analysis. Moreover compound 4 inhibits protein kinases in vitro, especially Pim-3, in the sub-micromolar range.     

Preparation of novel pyridine-fused tris-heterocycles; pyrido[4,3-e]pyrrolo-/pyrido[4,3-e]furano[2,3-c]pyridazines and pyrido[3,4-b]pyrrolo[3,2-d]pyrrole

Three novel pyrido-fused tris-heterocycles have been prepared based on a Suzuki coupling and subsequent cyclisation approach. Pyrido[4,3-e]pyrrolo[2,3-c]pyridazine (3b, 77%) and pyrido[4,3-e]furano[2,3-c]pyridazine (5b, 76%) were obtained by intramolecular diazocoupling. Successful diazocoupling of furan (5b) is thus reported for the first time by NOBF₄ generation of the diazonium intermediate. N-TIPS-pyrido[3,4-b]pyrrolo[3,2-d]pyrrole (TIPS-4b) was synthesised by thermal cyclisation of pyridyl nitrene in considerably higher yield (71%) than previously experienced from similar cyclisations, due to TIPS-activation.     

5-Phenyl-iminostilbene based organic dyes for efficient dye-sensitized solar cells

Four new 5-phenyl-iminostilbene dyes (ISB-3–6) containing electron-withdrawing benzo-[c][1,2,5]thiadiazole have been designed and synthesized for use as DSSCs. Their absorption properties and electrochemical and photovoltaic performances have been investigated systematically. Among these dyes, DSSCs based on a dye containing benzo-[c][1,2,5]thiadiazole and benzene moieties (ISB-4) showed the best performance: a short-circuit photocurrent density (J_sc) of 13.69 mA cm⁻², an open-circuit photovoltage (V_oc) of 722 mV, and a fill factor (FF) of 0.71, which corresponds to a power conversion efficiency (PCE) of 6.71%, under optimized conditions. Additionally, long-term stability of the ISB-4 based DSSCs with ionic-liquid electrolytes was demonstrated under 1000 h of light soaking, the photovoltaic performance is up to 5.75%. The results suggest that 5-phenyl-iminostilbene containing dyes are promising candidates for application in DSSCs.     

Synthesis of novel dipyrazolo[3,4-b:3,4-d]pyridines and study of their fluorescence behavior

A convenient route was successfully developed for the synthesis of novel heterocycles such as pyrazolo[3,4-h][1,6]naphthyridine and dipyrazolo[3,4-b:3,4-d]pyridine (DPP) from pyrazolo[3,4-b]pyridine in good yield. The DPP derivatives synthesized were further studied for their fluorescence properties.     

Substituted chromones in [3+2] cycloadditions with nonstabilized azomethine ylides: synthesis of 1-benzopyrano[2,3-c]pyrrolidines and 1-benzopyrano[2,3-c:3,4-c′]dipyrrolidines

Chromones bearing electron-withdrawing substituents at the 2- or 3-position react with nonstabilized azomethine ylides to produce 1-benzopyrano[2,3-c]pyrrolidines in good yields. Reactions of 3-cyanochromones proceed diastereoselectively to give 1-benzopyrano[2,3-c]pyrrolidines and tetrahydro-1H-spiro[chromeno[2,3-c]pyrrol-9,5′-oxazolidine]-9a-carbonitriles, depending on the reactant ratio, as a result of a 1,3-dipolar cycloaddition of the azomethine ylide at the double bond and carbonyl group of the chromone system. The latter undergoes demethylenation and recyclization into a novel hexahydrochromeno[2,3-c:3,4-c′]dipyrrole tetracyclic system on heating with hydrochloric acid.     

Synthesis of dipyrrolo[3,4-a:3,4-c]carbazole-1,3,4,6-tetraones bearing a sugar moiety

The synthesis of a series of dipyrrolo[3,4-a:3,4-c]carbazole-1,3,4,6-tetraones, structurally related to the G2 checkpoint inhibitor granulatimide and bearing a sugar moiety, is described. Substitutions were carried out at the 6-position of the glycosyl unit to lead to an amino substituent as observed in many biologically active compounds such as anthracyclins or staurosporines.     

Synthesis of new pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidines and related heterocycles

The reaction between 5-amino-4-imino-1(2)-substituted-1(2)H-4,5-dihydropyrazolo[3,4-d]pyrimidines and several commercially available reactants afforded new heterocycles with a conserved pyrazolo[3,4-d]pyrimidine nucleus. The key intermediates employed proved to be suitable compounds by virtue of their two vicinal amino and imino groups that were used to obtain five, six and seven-membered rings.     

Preparation of new pyrido[3,4-b]thienopyrroles and pyrido[4,3-e]thienopyridazines

Two new types of pyrido-fused tris-heterocycles (1a,b and 2a,b) have been prepared from 3-aminopyridine in five/six steps. A synthetic strategy for the preparation of the novel pyrido[3,4-b]thieno[2,3- and 3,2-d]pyrroles (1a,b) and pyrido[4,3-e]thieno[2,3- and 3,2-c]pyridazines (2a,b) has been studied. The Suzuki cross coupling of the appropriate 2- and 3-thienoboronic acids (3,4) and 4-bromo-3-pyridylpivaloylamide (9) afforded the biaryl coupling products (10,11) in high yields (85%). Diazotization of the hydrolysed (2-thienyl)-coupling product (12) and azide substitution gave the 3-azido-4-(2-thienyl)pyridine intermediate (72%, 14). 3-Azido-4-(3-thienyl)pyridine (15) was prepared by exchanging the previous order of reactions. The desired β-carboline thiophene analogues (1a,b) were obtained via the nitrene by thermal decomposition of the azido precursors (14,15). By optimising conditions for intramolecular diazocoupling, the corresponding pyridazine products (72-83%, 2a,b) were afforded.     

Short and efficient access to imidazo[1,2-a]pyrrolo[3,2-c]pyridine derivatives

Access to N-protected or N-free imidazo[1,2-a]pyrrolo[3,2-c]pyridine derivatives as potential antiviral compounds was achieved in good yields from N-protected 7-amino-8-halo-2-methylimidazo[1,2-a]pyridines by catalytic coupling of terminal acetylenes under mild conditions using [PdCl₂(PPh₃)₂] or [Cu(Phen)(PPh₃)₂]NO₃.     

Novel 6-substituted benzothiazol-2-yl indolo[1,2-c]quinazolines and benzimidazo[1,2-c]quinazolines

The synthetic route to and a preliminary biological evaluation of novel indolo[1,2-c]quinazolines (8) and benzimidazo[1,2-c]quinazolines (9) are described. The products were obtained by condensation of the appropriate diamines (e.g. 2-(2-aminophenyl)indole or 2-(2-aminophenyl)benzimidazole) with 2-cyanobenzothiazoles. This work further demonstrates the general applicability of microwaves for a facile and rapid access to original heterocycles with potential pharmaceutical value.     

Synthesis of pyrrolo[3,4-b]pyrroles and perhydrothiazolo[3′,4′-2,3]pyrrolo[4,5-c]pyrroles

The 1,3-dipolar cycloaddition reactions of various N-tethered alkenyl aldehydes with some cyclic and acyclic amino acids have been studied. Some key sulfonamides having strategically positioned aldehyde and olefinic tether have been synthesized and effectively subjected to intramolecular azomethine ylide cycloaddition reaction resulting in a series of pyrrolo[3,4-b]pyrrole and its N-1-C-2 derivatives, and a series of novel heterotricyclic compounds, perhydrothiazolo[3′,4′-2,3]pyrrolo[4,5-c]pyrroles, in good yields. The intramolecular cycloaddition reaction was found to be highly stereoselective to form only cis-fused cycloadducts in all cases.     

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.     

A facile synthesis of chromeno[3,4-c]spiropyrrolidine-oxindoles via 1,3-dipolar cycloadditions

A facile one-pot synthesis of chromene bearing novel spiropyrrolidine-oxindoles has been accomplished by the [3+‏2]-cycloaddition reaction of 3-acetyl-2H-chromen-2-ones with azomethine ylides derived in situ from isatin or N-methyl isatin with sarcosine.     

3-Cyanochromones in [3+2] cycloadditions with an azomethine ylide derived from sarcosine and formaldehyde. A short synthesis of 1-benzopyrano[2,3-c:3,4-c′]dipyrrolidines

Reactions of 3-cyanochromones with sarcosine and paraformaldehyde proceed diastereoselectively to give 1-benzopyrano[2,3-c]pyrrolidines and tetrahydro-1H-spiro[chromeno[2,3-c]pyrrol-9,5′-oxazolidine]-9a-carbonitriles, depending on the reactant ratio, as a result of a 1,3-dipolar cycloaddition of the intermediate nonstabilized azomethine ylide at the double bond and carbonyl group of the chromone system. The latter undergoes demethylenation and recyclization into a novel hexahydrochromeno[2,3-c:3,4-c′]dipyrrole tetracyclic system on heating with hydrochloric acid.     

Synthesis of mesoionic[1,2,3]triazolo[5,1-d][1,2,5]triazepines

Intramolecular cyclization of 1-amino-3-phenacyl-4-carbohydrazido-1,2,3-triazolium-5-olates has been shown to take place via selective interaction of the carbonyl group with the terminal amino function of the hydrazido group to form a 1,2,5-triazepine ring. Minor products, resulting from the interaction of the α-nitrogen atom of the hydrazido group with the carbonyl function, having a N-amino-pyridazine structure were also detected and isolated. A general method for the synthesis of novel mesoionic 2-amino-7-aryl-4-oxo-2,4,5,8-tetrahydro[1,2,3]triazolo[5,1-d][1,2,5]triazepin-9-ium-3-olates was developed.     

Microwave-assisted chemoselective synthesis of novel pyrazolo[3,4-b]thieno[3,4-e]pyridines: substitution induced axial chirality

A microwave-assisted chemoselective synthesis of novel pyrazolo[3,4-b]thieno[3,4-e]pyridines has been achieved via tandem Michael addition–cyclization–tautomerization–oxidative aromatization sequence of reactions. Compounds with ortho-substituted phenyl rings exhibited axial chirality due to restricted rotation around C–C single bond.     

Synthesis of hexahydro[2]benzopyrano[3,4-c]pyrroles as serotonin 5-HT2C receptor agonists via intramolecular hetero Diels-Alder reactions

[2]Benzopyrano[3,4-c]pyrroles were synthesized via an intramolecular hetero Diels-Alder reaction. The reaction was applicable to a wide range of substrates and the products could be easily converted into serotonin 5-HT_2C receptor agonists.     

2-Oxobenzo[h]chromene: a novel entry for the concise and efficient synthesis of indeno[1,2-c]phenanthrenes

An efficient and concise synthesis of 7-sec-amino-5,13-dihydro-6H-indeno[1,2-c]phenanthrene-8-carbonitriles is described through base catalyzed ring transformation of 4-sec-amino-2-oxo-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles with 1-indanone in moderate to good yields.