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The catalytic asymmetric synthesis of P-chiral phosphorus compounds is an important way to construct P-chiral ligands. Herein, we report a new strategy that adopts the pyridinyl moiety as the coordinating group in the cobalt-catalysed asymmetric nucleophilic addition/alkylation of secondary phosphine oxides. A series of tertiary phosphine oxides were generated with up to 99 % yield and 99.5 % ee, and with broad functional-group tolerance. Mechanistic studies reveal that (R)-secondary phosphine oxides preferentially interact with the cobalt catalysts to produce P-stereogenic compounds.

An efficient methodology for the synthesis of dibenzo[a,c]carbazoles via annulation of 2,3-diphenyl-1H-indoles in EtOH under UV light irradiation (λ = 365 nm) along with hydrogen evolution is described. This method exhibits the advantages of mild reaction conditions, no requirement of any oxidants and catalysts, and release of hydrogen as the only byproduct. Notably, the mechanism investigation confirms that the trans-4b,8a-dihydro-9H-dibenzo[a,c]carbazole intermediate could convert into cis-4b,8a-dihydro-9H-dibenzo[a,c]carbazole, which relies on the nitrogen atom of the indole ring. This is followed by intramolecular dehydrogenation which yields the dibenzo[a,c]carbazoles.

A concise and environmentally friendly protocol was developed for the synthesis of 6-phenylbenzo[h]quinolines. 6-Phenylbenzo[h]quinolines were obtained in good yields via irradiation of (E)-2-phenyl-3-styrylpyridines with a 254 nm UV light (64 W) in EtOH under an argon atmosphere in the presence of TFA. The reaction is a dehydrogenative annulation reaction that proceeds through 6π-electrocyclization, a [1,5]-H shift, 1,3-enamine tautomerization, and elimination of a hydrogen molecule to afford 6-phenylbenzo[h]quinolines. The described protocol not only avoids the usage of a transition metal catalyst and an oxidant but also has the advantages of high atom efficiency and mild reaction conditions.

A concise and environmentally friendly protocol has been developed for the synthesis of cis-dihydrochromenones and trans-dihydrochromenones in EtOH at room temperature. Irradiation of 4-phenyl-3-arylcoumarins in EtOH with 313 nm UV light under an argon atmosphere at room temperature gave cis-4b,15c-dihydro-16H-benzofuro[3',2':7,8]phenanthro[9,10-c]chromen-16-ones and cis-8c,14b-dihydro-9H-benzo[11,12]chryseno[5,6-c]chromen-9-ones in good yields. And an analogous treatment of 4-phenyl-3-alkenylcoumarins as 4-phenyl-3-arylcoumarins provided trans-1,2,3,4,4a,14b-hexahydro-5H-phenanthro[9,10-c]chromen-5-ones. The described photorearrangement proceeded smoothly without the addition of any transition metals and additives. The photorearrangement of 4-phenyl-3-arylcoumarins is believed to proceed via 6π-electrocyclization, a [1,3]-hydrogen shift and keto-enol isomerization.

In this paper, two 2H-dibenzo[e, g]indazoles, 6-methoxy-9-isopropoxy-2H-dibenzo[e, g]indazole(1) and 6-fluoro-9-methoxy-2H-dibenzo[e, g]indazole(2) have been one-pot synthesized from the corresponding isoflavones by two dehydration processes. They have been characterized by IR, NMR, HRMS and single crystal X-ray diffraction. Single crystal X-ray diffraction analyses show that 1 crystallizes in the orthorhombic space group P 212121, and 2 in the monoclinic space group P 21. For both structures, intermolecular hydrogen bonding, π…π and C−H…π interactions play an important role in the packing of the molecules. Two 2H-dibenzo[e, g]indazoles, 6-methoxy-9-isopropoxy-2H-dibenzo[e, g]indazole and 6-fluoro- 9-methoxy-2H-dibenzo[e, g]indazole have been one-pot synthesized from the corresponding isoflavones by two dehydration processes. Single crystal X-ray diffraction analyses show that hydrogen bonding, π…π and C–H…π interactions are present in both structures.

A versatile gold(I)-catalyzed cross-coupling reaction of 3-diazooxindoles with diazoesters has been presented, affording (E)-3-alkylideneoxindoles stereoselectively. Density functional theory calculations rationalized the chemo- and stereoselectivity of the reaction, which was in good agreement with experimental observations. In addition, (E)-3-alkylideneoxindoles were converted into their (Z)-isomers under UV-irradiation facilely, indicating the great advantage of this approach in stereoselective synthesis of both (E)- and (Z)-3-alkylideneoxindoles.

The synthesis of a unique type of π-expanded coumarin derivatives, bearing six fused phenyl rings, was achieved via one-pot Suzuki reaction and visible light-driven electrocyclization. The large π-expanded 5H-benzo[12,1]tetrapheno[7,6,5-cde]chromen-5-ones were obtained in good to high yields from 1-bromo-2H-phenaleno[1,2,3-de]chromen-2-ones, and the intriguing optical properties were explored by altering the attached functional groups. 2-Arylaminosubstituted-5H-benzo[12,1]tetrapheno[7,6,5-cde]chromen-5-ones showed a large Stokes shift (4005 cm-1) or excellent fluorescence quantum yield (Φf = 0.75) along with significant bathochromic shift in tetrahydrofuran.

A concise and efficient method for the synthesis of 7-hydroxy-6H-naphtho[2,3-c]coumarin using available 1-(2-hydroxyphenyl)-2-phenylethanone and Meldrum's acid has been developed. This transformation involved a tandem aldol reaction/lactonization/Friedel-Crafts reaction to form a lactone ring and a benzene ring. It showed high atom economy with water and acetone as the byproducts. Mechanism studies demonstrated two roles of Meldrum's acid: (i) as the reagent for the tandem reaction, and (ii) as the catalyst for the Friedel-Crafts reaction. Moreover, the hydroxyl group of 7-hydroxy-6H-naphtho[2,3-c]coumarin was further functionalized efficiently by arylethynyl, aryl, and cyano groups to furnish D-π-A compounds with excellent fluorescence emissions (ΦF = 0.14-0.78).

A general approach for the synthesis of 3-(iso)quinolinyl 4-chromenones and 3-(iso)quinolinyl 4-quinolones from (iso)quinoline N-oxides and ynones under metal-free conditions was developed. The reaction of (iso)quinoline N-oxide with the electron-deficient alkyne first generated an (iso)quinolinyl β-diketone intermediate, which then underwent an intramolecular dehydration, affording 3-(iso)quinolinyl 4-chromenones and 3-(iso)quinolinyl 4-quinolones.

A strategy for the syntheses of benzofuranoquinolines and its analogues via the irradiation of o-phenylfuranyl/thienylpyridines/pyrimidines in DCM with UV light at rt under an argon atmosphere is described. The mechanism of this reaction through the process of 6π-electrocyclization, [1,5]-hydrogen shift, and 1,3-eneamine tautomerism leading to H2 evolution was elucidated. Notably, the syntheses of cis-8b-methyl-8b,13a-dihydrobenzo[f]benzofuro[3,2-h]quinolone via the photoinduced rearrangement of 2-(3-methylbenzofuran-2-yl)-3-phenylpyridine relevant to the mechanism of this reaction highlights the importance of the developed methodology.

A cascade reaction of isoquinoline N-oxides with alkynones was developed, delivering a fluorescent benzoazepino[2,1-a]isoquinoline derivative. The reaction worked smoothly without requirement of any catalyst or additive, making this method economical and easy to handle.

A series of novel C-glycosides of heterocyclic derivatives containing a pyrimidin-2-amine or a 1 H-pyrazolo[3,4- b]pyridine moiety were synthesized using condensation reactions of the substituted puerarin with guanidine or 3-amino-5-hydroxypyrazole in methyl alcohol. Their chemical structures were characterized by Fourier-transform infrared spectroscopy, nuclear magnetic resonance, and high-resolution mass spectrometry. In addition, their biological activity has been demonstrated by in vitro evaluation against the human leukemia cells K562 and human prostate cancer cells PC-3 by MTT-based assays, using the commercially available standard drug of cis-platin as a positive control. The results also demonstrated that most of the compounds showed considerable cytotoxicity to these two cell lines of K562 and PC-3, and indicated that novel C-glycosides of heterocyclic derivatives may be potential leads for further biological screenings and may generate drug-like molecules.

The photo-induced rearrangement of 2'-arylisoflavones (aryl = phenyl, furyl, 3-pyridyl, 1-naphenyl, and 2-naphenyl) for the synthesis of (2-hydroxyphenyl)(fused phenyl)methanones in EtOH under an Ar atmosphere at room temperature has been developed. The described method proceeded smoothly without requiring any transition metal catalyst, oxidant, or additives. Moreover, using ethanol as the solvent is not only cost efficient but also environmentally friendly. Further treatment of methanone analogues with AlCl3 yielded highly conjugated polycyclic aromatic hydrocarbon (PAH) derivatives.

A photochemical C-N coupling of aryl halides with nitroarenes is demonstrated for the first time. Catalyzed by a NiII complex in the absence of any external photosensitizer, readily available nitroarenes undergo coupling with a variety of aryl halides, providing a step-economic extension to the widely used Buchwald-Hartwig C-N coupling reaction. The method tolerates coupling partners with steric-congestion and functional groups sensitive to bases and nucleophiles. Mechanistic studies suggest that the reaction proceeds via the addition of an aryl radical, generated from a NiI /NiIII cycle, to a nitrosoarene intermediate.

A versatile gold(I)-catalyzed cross-coupling reaction of 3-diazooxindoles with diazoesters has been presented, affording (

The synthesis of a unique type of π-expanded coumarin derivatives, bearing six fused phenyl rings, was achieved via one-pot Suzuki reaction and visible light-driven electrocyclization. The large π-expanded 5

A facile and efficient one-pot synthesis of 3-(furan-2-yl)-4-hydroxy-2H-chromen-2-ones was developed. The reaction of ethyl 3-(2-hydroxyphenyl)-3-oxopropanoates and 2,5-dimethoxy-2,5-dihydrofuran were performed in presence of K10 Montmorillonite Clay heterogeneous catalyst under the solvent-free condition at 80 °C for 1 h, and followed by further converted to 3-(furan-2-yl)-4-hydroxy-2H-chromen-2-ones via refluxing in the alkaline EtOH solution for 0.5 h. The demonstrate method not only avoided the usage of any expensive transition-metals, but also eliminated the tedious intermediate purification. Moreover, due to the wide functional group tolerance, it could be applied to various substrates and gave product in good to excellent yields.

A strategy for the syntheses of benzofuranoquinolines and its analogues via the irradiation of

A highly efficient and environmentally friendly synthesis of (2-aminophenyl)(naphthalen-2-yl)methanones was developed. The (2-aminophenyl)(naphthalen-2-yl)methanone derivatives were obtained in high yields (up to 96%) by the irradiation of (E)-3-styrylquinolin-4(1H)-ones in EtOH–H2O (7:1) with UV light (365 nm) at room temperature under Ar atmosphere. The demonstrated photoinduced intramolecular rearrangement has advantages over other transition-metal-catalyzed reactions, e.g. no requirement of additives, green solvent, broad substrate scope, and high atom efficiency.

A concise and efficient one-pot strategy to synthesize 3-fluoroflavones was developed. 1-(2-Hydroxyphenyl)-3-phenylpropane-1,3-diones were fluorinated using selectfluor with a small amount of CH3CN at room temperature, followed by cyclization and dehydration in the presence of a trace amount of conc. H2SO4 to provide 3-fluoroflavones. The desired 3-fluoroflavone analogues were obtained in moderate to excellent yields. This strategy tolerated a wide range of functional groups and did not need sophisticated instruments or tedious substrate preparation.

C14H13F2N3O3, triclinic, P1̄ (no. 2), a = 9.4486(7) Å, b = 12.4694(8) Å, c = 13.8690(8) Å, α = 65.734(6)°, β = 74.523(5)°, γ = 83.726(6)°, V = 1435.63(18) Å3, Z = 4, Rgt (F) = 0.0495, wR ref(F 2) = 0.1249, T = 293(2) K.

C22H21NO8S, triclinic, P1̄ (no. 2), a = 7.095(4) Å, b = 11.882(7) Å, c = 13.661(8) Å, α = 95.004(9)°, β = 104.918(9)°, γ = 107.323(9)°, V = 1045.4(11) Å3, Z = 2, Rgt (F) = 0.0627, wR ref(F 2) = 0.1745, T = 296(2) K.

A series of 3,4-diaryl- 1H -pyrazoles derivatives were designed and synthesized by the reaction of 3-heteroarylchromones and 3-phenylchromones with hydrazine hydrate in good yields. All of those compounds were characterized by 1 H NMR, 13 C NMR, IR, and HRMS. Moreover, 3-(2,4-dihydroxyphenyl)-4-(4-hydroxyphenyl)- 1H -pyrazole and 3-(2,4-dihydroxy phenyl)-4-(4-methoxyphenyl)- 1H -pyrazole were further conformed by the single crystal X-ray diffraction. In addition, the antifungal activity against five phytopathogenic fungi ( Cytospora sp., Colletotrichum gloeosporioides , Botrytis cinerea , Alternaria solani and Fusarium solani ) of 3,4-diaryl- 1H -pyrazoles were evaluated. 3-(2-Hydroxy-4-isopropoxyphenyl)-4-phenyl- 1H -pyrazole was more better and broader inhibitory effect on Cytospora sp., C. gloeosporioides , A. solani and Fusarium solani with IC 50 values of 26.96, 28.84, 16.77 and 22.10 μg/mL, respectively. 4-(4-Fluorophenyl)-3-(2-hydroxy-4-methoxyphenyl)- 1H -pyrazole exhibited fairly effective antifungal activity against Cytospora sp., C. gloeosporioides and A. solani with IC 50 values of 11.91, 14.92 and 16.98 μg/mL, respectively.

A gold-catalyzed synthesis of an important building block, 1-(furan-3-yl)-1,2-diones, from easily available starting materials under mild reaction conditions was reported. Preliminary mechanistic investigation indicated that water was involved as a reactant in the reaction serving as an oxygen source.

The metal-free reactions of 1,4-diynes and 1-en-4-yn-3-ones with isoquinoline and quinoline N-oxides are developed, resulting in the formation of 3,4-dihydro-2H-pyrido[2,1-a]isoquinolines and 2,3-dihydro-1H-pyrido[1,2-a]quinolines via cascade C═O/C═C/C-N bond formation. It is the first report in which in the alkyne oxidation by N-oxides both the oxygen atom of N-oxides and the nitrogen atom are involved in a second C-heteroatom bond formation. The reactions showed a broad substrate scope and functional group tolerance. Furthermore, the products were found to display green-blue fluorescence in DMSO with fluorescence quantum yields up to 0.59.

7-Hydroxy-3-methoxy-6-oxo-6H-benzo[c]- chromene-8-carboxylic acid (3a), 3,7-dihydroxy-6-oxo-6H- benzo[c]chromene-8-carboxylic acid (3b), 1,7-dihydroxy-6-oxo-6H-benzo[c]chromene-8-carboxylic acid (3c) and 2-bromo-7-hydroxy-6-oxo-6H-benzo[c]chromene-8-carboxylic acid (3d) were synthesized and characterized by the method of single crystal X-ray diffraction. Owing to bigger conjugated system and various H-bonds in 7-hydroxy-6-oxo-6H-benzo[c]chromene-8-carboxylic skeleton, 3a–3c have excellent fluorescence in ethanol solution and the solid state. The synthons involved in each crystal are identified, and the fluorescence emission differences leading to molecular recognition are determined.

Vinyl radicals were generated from 3-iodoflavones under a mercury lamp and tandem cyclization reactions occurred with five-membered heteroarenes entailing two consecutive C–C bond formations to synthesize benzo[e]chromeno[2,3-g]indol-13(1H)-one derivatives. The tandem cyclization reactions worked in acetonitrile without any additives such as transition metals, ligands and oxidants, giving rise to a broad variety of novel polycyclic xanthone frameworks in good yield under mild and environmentally friendly reaction conditions.

An efficient photo-induced transition-metal-free direct hydrogen evolution and annulation of 2,3-diphenyl-4H-chromen-4-ones in EtOH–H2O (19 : 1, v/v) at room temperature was described. The reported methodology provided a quick and easy access to the synthesis of dibenzo[a,c]xanthen derivatives, which eliminates the use of any catalysts, oxidants and additives.

Presented here is a new porous tetrahedral Zn(II)-tetrazolate framework, namely [Zn2(mtz)3(OH)]n·n(DMF) (1, Hmtz = 5-methyl-1H-tetrazole, DMF = N,N’-dimethylformamide), has been successfully synthesized under solvothermal conditions. Single crystal X-ray structural analysis reveals that compound 1 features a three-dimensional (3D) porous framework with 4-connected dia-type topology. The 1D channels along the crystallograhical c axis are occupied by the lattice DMF molecules. The desolvated samples show highly adsorption selectivity of CO2 over N2.

An efficient two-step synthesis of π-expanded maleimide derivatives was reported, which proceeded via a photoinduced dehydrogenative annulation of 3,4-diphenylfuran-2(5H)-ones in EtOH at room tempe...

An efficient, oxidant and photocatalyst-free approach for the synthesis of polycyclic-fused isoindolinone derivatives is reported via annulation of 3,4-diphenyl-3-pyrrolin-2-ones along with release of the hydrogen gas under an argon atmosphere in EtOH by irradiation with a 500 W mercury lamp at room temperature. The described approach is atom-economic and environmentally friendly and tolerates various electron-donating and electron-withdrawing groups. In addition, selected annulation products, dibenzo[e,g]isoindole-1-ones, were successfully oxidized into dibenzo[e,g]isoindole-1,3(2H)- diones in DMSO in the presence of CH3ONa at room temperature.

New vertically π-expanded coumarins dyes 1-phenynyl-2H-phenaleno[1,2,3-de] chromen-2-ones and 1-cyano-2H-phenaleno[1,2,3-de]chromen-2-ones were synthesized using 1-bromo-2H-phenaleno[1,2,3-de]chromen-2-one with arylacetylene or cyano reagent via the Sonogashira reaction and cyanide substitution reaction, and obtained in high yields up to 85% from 1-bromo-2H-phenaleno [1,2,3-de]chromen-2-one. The photophysical studies revealed that 1-substituted -2H-phenaleno[1,2,3-de]chromen-2-ones have large Stokes shift (4898 cm−1) and excellent fluorescence quantum yield (Φf = 0.80) along with significant bathochromic shift. The intriguing optical properties of these vertically π-expanded coumarins are discussed on the basis of quantum chemical calculations. Furthermore, 1-cyano-2H-phenaleno[1,2,3-de]chromen-2-one exhibited good biocompatibility by onion skin staining.

Transition-metal-free LiCl-promoted cross-coupling reactions of tetraphenyltin, trichlorophenyl-, dichlorodiphenyl-, and chlorotriphenylstannanes with aryl halides in DMF provided access to biaryls in good to high yields. Up to four phenyl groups were transferred from the organostannanes substrates. The aryls bearing electron-withdrawing groups in either halides or organotin substrates gave coupling products in higher yields. The methodology has been applied for the efficient synthesis of ipriflavones.

5,6-Diarylpyrazolo[1,5-a]pyrimidines (3) and 6,7-diarylpyrazolo[1,5-a]pyrimidines (4) were chemoselectively synthesized by the condensation of isoflavone (1) and 3-aminopyrazole (2). 5,6-Diarylpyrazolo[1,5-a]pyrimidines (3) were obtained via microwave irradiation, and 6,7-diarylpyrazolo[1,5-a]pyrimidines (4) were obtained via conventional heating. In addition, the pyrimidine derivatives 3 and 4 were evaluated against five phytopathogenic fungi (Cytospora sp., Colletotrichum gloeosporioides, Botrytis cinerea, Alternaria solani, and Fusarium solani) using the mycelium growth rate method. Some of them were effective in inhibiting the growth of the five phytopathogenic fungi. For instance, 6,7-diarylpyrazolo[1,5-a]pyrimidines (4j) inhibited the growth of A. solani with an $$\hbox {IC}_{50}$$ value of 17.11 $$\upmu \hbox {g}/\hbox {mL}$$ , and 6,7-diarylpyrazolo[1,5-a]pyrimidines (4h) inhibited the growth of both Cytospora sp. and F. solani with $$\hbox {IC}_{50}$$ values of 27.32 and 21.04 $$\upmu \hbox {g}/\hbox {mL}$$ , respectively. A chemoselective synthesis of 5,6-pyrazolo[1,5-a]pyrimidines 3 derivatives in excellent yields was performed under microwave irradiation and 6,7-pyrazolo[1,5-a]pyrimidines 4 were also prepared using heating method. The antifungal properties of 3 and 4 were tested against Cytospora sp., Colletotrichum gloeosporioides, Botrytis cinerea, Alternaria solani, and Fusarium solani.