A new total synthesis of an indolo[3,2-j]phenanthridine alkaloid calothrixin B

A new total synthesis of calothrixin B is described. The key step is an allene-mediated electrocyclic reaction involving the indole 2,3-bond for the construction of a suitable 4-oxygenated 2,3,4-trisubstituted carbazole ring system.     

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%.     

A convenient approach to the design and synthesis of indolo[3,2-c]coumarins via the microwave-assisted Cadogan reaction

3-(4,5-Dimethoxy-2-nitrophenyl)coumarins bearing various substituents on the benzene ring of the coumarin system have been prepared from salicylaldehydes and 2-(4,5-dimethoxy-2-nitrophenyl)acetonitrile by means of the Perkin condensation. Further cyclization of these 3-aryl coumarins through the microwave-assisted Cadogan reaction afforded the corresponding indolo[3,2-c]coumarins in good to excellent yields.     

Synthesis and alkylation of indolo[3,2-b]carbazoles

Double Fischer cyclisation was used to prepare indolo[3,2-b]carbazole and its 2,8-di-OMe, OH, Br and F-derivatives. N-monosubstituted derivatives of indolo[3,2-b]carbazole (methyl, hydroxymethyl, dimethylaminoethyl) were obtained starting from 5,11-di-Boc-indolo[3,2-b]carbazole.     

Enantioselective synthesis of chelidonine, a B/C-cis-11-hydroxyhexahydrobenzo[c]phenanthridine alkaloid

Both enantiomers of chelidonine, a B/C-cis-11-hydroxyhexahydrobenzo[c]phenanthridine alkaloid, were synthesized by manipulation of the B/C-dehydro ring juncture of benzo[c]phenanthridine skeleton using Sharpless asymmetric dihydroxylation and stereospecific catalytic hydrogenation after introduction of oxygen functions on the C ring as key reaction steps for the construction of stereogenic centers.     

Synthesis and properties of hole-transporting indolo[3,2-b]carbazole-based hydrazones with reactive functional groups

The synthesis of indolo[3,2-b]carbazole-based mono- and dihydrazones with reactive vinylbenzyl or vinyloxyethyl functional groups at the nitrogen atom of hydrazine moiety is reported. The thermal, optical, photophysical, electrochemical and photoelectrical properties of the synthesized compounds are described. They exhibit moderate thermal stability with 5% weight loss temperatures ranging from 273 to 343 °C. Self-polymerization of the monomers with vinylbenzyl functional groups starts at around 180 °C. The values of ionization potentials of the compounds measured by cyclic voltammetry are in the range of 4.94–5.00 eV and those estimated by electron photoemission in air range from 4.99 to 5.21 eV. Electron affinities range from −2.28 to −2.23 eV. The molecular structure of these hydrazones allows stable amorphous films to be prepared and the hole drift mobilities of the films exceed 10⁻³ cm²/V s at high electric fields.     

Synthesis, photophysical and electrochemical properties and theoretical studies on three novel indolo[3,2-b]carbazole derivatives containing benzothiazole units

Three novel indolo[3,2-b]carbazoles derivatives were successfully synthesized by condensation reaction and structurally characterized by elemental analysis, mass spectrometry and proton nuclear magnetic resonance spectroscopy methods, which belong to donor-π-acceptor systems comprising an indolo[3,2-b]carbazole group as an electron donor and two benzothiazole rings as electron acceptors. The thermal, electrochemical and photophysical properties of the compounds were characterized by thermogravimetric analysis combined with electrochemistry, UV-vis absorption spectroscopy and fluorescence spectroscopy. On the other hand, the geometries, molecular orbitals, charge-injection and transport properties were determined by quantum chemical calculations. The results show that the compounds synthesized exhibit good thermal stability and high fluorescence quantum yields, indicating the potential application as optoelectronic materials.     

A facile synthesis of the novel thiazolo[3,2-a]pyrimidine derivatives

2-Bromomethyl- and 2-iodomethyl-2,3-dihydrothiazolo[3,2-a]pyrimidin-5-ones are prepared via the reaction of 3-allyl-2-thiouracil derivatives with bromine or iodine chloride, respectively. The 6-bromo and 6-nitro derivatives are synthesized by an electrophilic substitution at C-6 of the thiazolopyrimidine system. As a result, novel 2,3-dihydrothiazolo[3,2-a]pyrimidin-5-one derivatives are obtained. Hydrogen halide elimination from the 2-halomethyl-2,3-dihydrothiazolo[3,2-a]pyrimidin-5-ones is also reported.     

One pot synthesis of imidazo[2,1-b]thiazoles and benzo[d]thiazolo[3,2-a]imidazoles

A series of imidazo[2,1-b]thiazole and benzo[d]thiazolo[3,2-a]imidazole analogues were synthesized by stirring an equimolar mixture of dibenzoylacetylene with imidazole/thiazole derivatives in toluene or acetonitrile at room temperature. The products were generated in good yields and characterized by standard analytical techniques such as IR, ¹H NMR, ¹³C NMR and mass spectrometry. The structure of products 19, 20, 22, 24 and 25 were also unambiguously confirmed by single crystal X-ray analysis.     

Zyzzyanone A, a novel pyrrolo[3,2-f]indole alkaloid from the Australian marine sponge Zyzzya fuliginosa

A new dipyrroloquinone, zyzzyanone A 1, having a pyrrolo[3,2-f]indole-4,8(1H,7H)-dione skeleton, was isolated from the Australian marine sponge Zyzzya fuliginosa, along with the known pyrroloquinoline alkaloids, makaluvamines C, E, G, H, and L, and damirones A and B. The structure of 1 was determined by spectroscopic data. Zyzzyanone A 1 shows moderate cytotoxic activity against mouse Ehrlich carcinoma cells (IC₅₀ 25 μg/mL), inhibits the cell division of fertilized sea urchin eggs at a concentration of 25 μg/mL, and exhibits UV-A and UV-B absorbing activity.     

Ophiuroidine, the first indolo[2,1-b]quinazoline alkaloid from the Caribbean brittle star Ophiocoma riisei

A new indoloquinazoline alkaloid, ophiuroidine 1, having an indolo[2,1-b]quinazoline-6,12-dione skeleton, was isolated from the Caribbean ophiuroid, Ophiocoma riisei. The structure of 1 was determined as 4,8,9-trihydroxyindolo[2,1-b]quinazoline-6,12-dione from spectroscopic data. Ophiuroidine 1 is the first example of an indoloquinazoline alkaloid found in a marine invertebrate.     

A facile synthesis of indolo[3,2,1-jk]carbazoles via palladium-catalyzed intramolecular cyclization

A new efficient synthesis of indolo[3,2,1-jk]carbazoles by the palladium-catalyzed cyclization of N-(2-bromoaryl)carbazoles is described. The reaction involves intramolecular C-C bond formation, coupled with the cleavage of a C-X bond and a C-H bond on carbazole ring. Substitutions on N-aryl core with either electron-donating or electron-withdrawing groups are introduced, and different reaction factors for cyclization are evaluated.     

Thiadiazole fused indolo[2,3-a]carbazoles as new building blocks for optoelectronic applications

New indolo[2,3-a][1,2,5]thiadiazolo[3,4-c]carbazoles including functional groups (halide or hydroxyl groups) on the meta positions relative to the nitrogen atoms which are known to be the most conjugated, have been synthesized following two synthetic routes. The characterizations of their optical and electrochemical properties evidence their potential as new building blocks for optoelectronic materials.     

Synthesis,photophysical and electrochemical properties of novel 6,12-di(thiophen-2-yl) substituted indolo[3,2-b]carbazoles

Novel 5,11-dialkyl-6,12-di(thiophen-2-yl) substituted 5,11-dihydroindolo[3,2-b]carbazoles have been obtained and plausible ways for their further modifications via the Friedel–Crafts reaction are presented. The formylation of these indolo[3,2-b]carbazoles with dichloromethyl alkyl esters catalysed by Lewis acids leads to the formation of the corresponding 2,8-diformyl derivatives. Applicability of this formylation method for modification of indolo[3,2-b]carbazoles bearing electron-rich aromatic substituents at C-6 and C-12 has also been demonstrated. The Knoevenagel condensation of 2,8-dialdehydes with active methylene nitriles has been studied. The measurements of optical and redox properties for a number of new indolo[3,2-b]carbazoles have been performed.     

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.     

Reduction of indolo[2,3-b]quinoxalines

Reduction of indolo[2,3-b]quinoxalines with zinc in the presence of an anhydride gave N,N-diacyl trapped 6,11-dihydroindolo[2,3-b]quinoxalines in 43-92% yields. When the reduction with zinc was performed in TFA/TFAA, an unexpected ring opened product was isolated in 49% yield. The structure of this product could be identified as 1,2-dihydro-1-trifluoroacetyl-3-[(2-trifluoroacetylamino)phenyl]quinoxaline.     

Furo[3,2-h]isochroman, furo[3,2-h]isoquinoline, isochroman, phenol, pyranone, and pyrone derivatives from the sea fan-derived fungus Penicillium sp. PSU-F40

Nine new fungal metabolites, penicisochromans A-E, penicipyrone, penicipyranone, peniciphenol, and penicisoquinoline, were isolated from the sea fan-derived fungus Penicillium sp. PSU-F40 together with five known compounds. Their structures were determined by spectroscopic analysis. Their antibacterial activity against the standard Staphylococcus aureus ATCC 25923 and methicillin-resistant S. aureus was evaluated.     

Synthesis of dihydrochromeno[4,3-b]pyrrolo[3,2-f]quinolines via intramolecular aza Diels-Alder reaction

An efficient and convenient one-pot intramolecular aza Diels-Alder approach for the synthesis of dihydrochromeno[4,3-b]pyrrolo[3,2-f]quinolines has been reported. Particularly valuable features of this methodology include simple execution, inexpensive catalyst, and good product yields.     

Unexpected nitrilimine cycloaddition of thiazolo[3,2-a]pyrimidine derivatives

1,3-Dipolar cycloaddition of 2-arylidene-6,7-dihydro-5H-thiazolo[3,2-a]pyrimidine-3(5H)-ones to diphenylnitrilimine (generated in situ by triethylamine dehydrohalogenation of the N′-phenylbenzohydrazonoyl chloride) proceeded regio- and site-selectively affording a mixture of two unexpected isomer products at reflux temperature. The cycloaddition/ring-opening/rearrangement/substitution, mechanism of the reaction was also discussed.     

Synthesis of the dibenzopyrrocoline alkaloid skeleton: indolo[2,1-a]isoquinolines and related analogues

The indolo[2,1-a]isoquinoline and pyrrolo[2,1-a]isoquinoline nuclei have been synthesized from N-benzylindole or ethyl 1H-indol-1-ylacetate and N-benzylpyrrole precursors, respectively. Firstly, at C-2 of either the indole or pyrrole nucleus, aromatic rings containing a carbonyl substituent ortho to the newly formed biaryl axis were introduced using the Suzuki-Miyaura coupling reaction. Thereafter, under basic conditions the nucleophile that formed at the acidic methylene protons of the N-benzylindole, ethyl 1H-indol-1-ylacetate or N-benzylpyrrole intermediate reacted with the internal aromatic carbonyl to yield (after the expulsion of water) the title compounds. For example, exposure of ethyl 2-(2-(2-formylphenyl)-1H-indol-1-yl)acetate to potassium tert-butoxide resulted in the formation of ethyl indolo[2,1-a]isoquinoline-6-carboxylate.