Rh(III)-Catalyzed Reaction of 4-Diazoisochroman-3-imines with (2-Formylaryl)boronic Acids To Access a Straightforward Construction of 5H-Isochromeno[3,4-c]isoquinolines.

An Rh(III)-catalyzed one-pot synthesis of 5H-isochromeno[3,4-c]isoquinolines from readily available 4-diazoisochroman-3-imines and (2-formylphenyl)boronic acids is reported. The cascade annulation involves a Rh(III)-catalyzed cross-coupling and an intramolecular nucleophilic addition-elimination process. A series of biologically important 5H-isochromeno[3,4-c]isoquinolines were obtained in good to excellent yields. The method can be extended to synthesize 7H-isochromeno[3,4-b]thieno[3,2-d]pyridines and 7H-isochromeno[3,4-b]thieno[2,3-d]pyridines from the corresponding heteroaryl boronic acids.

Design and Synthesis of Benzoheterodiazole-based Fluorescent Compounds for Emitting Applications.

Benzoheterodiazole-based fluorophores with aggregation-induced emission (AIE) properties are synthesized and their photophysical properties in different states (solution, film, and powder) are investigated. These compounds present excellent thermal stability, and the decomposition temperature is above 300 °C. Among these compounds, the fluorophores with triphenylamine (TPA) group present better fluorescent emissions in solutions as well as in aggregated states, and the highest solution fluorescent efficiency is up to 75.2% in solution. Meanwhile, the fluorescent compounds terminated with triphenylethene (TPE) exhibit the classical AIE properties. Furthermore, these compounds might be used as emissive layers for the fabrication of red, orange and green organic light emitting diodes.

Synthesis of Functionalized Indolobenzazepinones via Sc(OTf)3-Induced Ring Expansion/Annulation Reactions of 4-Diazoisoquinolin-3-ones with Isatins.

Herein, we report an unexpected cascade ring expansion/annulation reaction between 4-diazo-1,4-dihydroisoquinolin-3-ones and a variety of isatin derivatives in the presence of Sc(OTf)3 catalyst. A series of novel indolobenzazepinones were synthesized in good to excellent yields with the exclusion of nitrogen and carbon dioxide gases. High bond-forming efficiency, novel reaction mechanism, readily available starting materials, commercially available cheap catalyst, broad substrate scope, and mild reaction conditions are the prominent features of this method.

Rh(II)-catalyzed synthesis of 5H-isochromeno[3,4-b]indolizines from 4-diazoisochroman-3-imines and pyridines.

A Rh(II)-catalyzed (3 + 2) annulation of pyridines with 4-diazoisochroman-3-imines leading to 5H-isochromeno[3,4-b]indolizines is presented. This methodology provides straightforward access to a wide variety of substituted 5H-isochromeno[3,4-b]indolizines with moderate to good yields (up to 84%) and complete regioselectivity.

Olefination of 3-Diazoindolin-2-imines with Hydrazones: An Approach toward Stereoselective Synthesis of (E)-3-Arylideneindolin-2-imines.

Stereoselective synthesis of (E)-3-arylideneindolin-2-imines from 3-diazoindolin-2-imines and hydrazones was achieved using copper bromide as the catalyst. The olefination reaction proceeded via copper-catalyzed aerobic oxidation of hydrazones to diazo compounds and copper-catalyzed cross coupling of two different diazo components in a tandem manner.

Cu(II)-Catalyzed Synthesis of 4-(1,4,5,6-Tetrahydropyridin-3-yl)-1,4-dihydroisoquinolin-3-ones from 4-Diazoisoquinolin-3-ones.

We report a simple, efficient, and highly selective C-H bond insertion of copper carbenes generated in situ from 4-diazo-1,4-dihydroisoquinolin-3-ones into ß-C(sp2)-H bonds of N-sulfonyl enamides, which gave a series of 4-(1,4,5,6-tetrahydropyridin-3-yl)-1,4-dihydroisoquinolin-3(2H)-ones in good to excellent yields. Operationally simple and mild reaction conditions, a cheap catalyst, readily accessible starting materials, and a broad substrate scope are the merits of this reaction.

Preparation and Photoluminescent Properties of Amino 2,1,3-Benzoxadiazoles (Am-BODs) with D-A-D and D-A-A Conjugation Systems.

A series of D-A-D and D-A-A conjugated compounds composed of a benzoxadiazole core and corresponding amino moiety were synthesized. Their photoluminescent properties in different states were investigated as well. In the solution state, some compounds were observed to possess the usual anti-Kasha's emission in toluene and the solvatofluorochromic phenomenon. Meanwhile, compound 1 a could be utilized as fluorescent chemosensor for the environmental acidity, and 2 c could be developed for detecting fluoride anion. Moreover, they were emissive in powders and films, and 2 d could be applied to the emissive layer in red OLEDs.

Rh(III)-Catalyzed C-H bond activation/annulation reactions of arylacyl ammonium salts with 4-diazoisochroman-3-imines and 4-diazoisoquinolin-3-ones.

Herein, we report a C-H bond functionalization strategy for the construction of oxo- and aza-spirocyclic compounds from diazo compounds as coupling partners. Our method comprises ortho sp2 C-H bond activation of arylacyl ammonium salts, followed by coupling with two types of cyclic diazo compounds i.e. 4-diazoisochroman-3-imines and 4-diazoisoquinolin-3-ones, respectively. The mechanism involves the formation of dual metal carbene intermediates in situ with the breakage of oxidizing C-N bonds in arylacyl ammonium salts. The cascade C-H activation/annulation process gave a variety of novel spiro[indene-1,4'-isochromane]-3,3'(2H)-diones and spiro[indene-1,4'-isoquinoline]-3,3'(2H)-diones in good to excellent yields. Readily available starting materials, broad substrate scope, and operationally simple and mild reaction conditions are the prominent features of this method.

Syntheses of 4-allyl-/4-allenyl-4-(arylthio)-1,4-dihydroisoquinolin-3-ones via the photochemical Doyle-Kirmse reaction.

Facile synthesis of 4-allyl-/4-allenyl-4-(arylthio)-1,4-dihydroisoquinolin-3-ones via the visible-light-induced Doyle-Kirmse reaction of 4-diazo-1,4-dihydroisoquinolin-3-ones with allyl-/propargyl sulfides is reported. The reaction proceeds via the generation of free carbenes from cyclic diazo compounds followed by in situ formation of sulfonium ylide intermediates, which subsequently undergo [2,3-sigmatropic rearrangement] to give highly functionalized dihydroisoquinolinones in moderate to good yields. Broad substrate scope, and catalyst-free and mild conditions are the merits of this reaction.

Photocatalytic Approach for Construction of 5,6-Dihydroimidazo[2,1-a]isoquinolines and Their Luminescent Properties.

A visible-light-driven photoredox reaction of tetrahydroisoquinoline with 2H-azirines is described. 4,7-Bis(4-methoxyphenyl)benzo[c][1,2,5]thiadiazole, a benzothiadiazole (BTD) derived fluorophore, is used as an organic photoredox catalyst, and the reaction offers an efficient access to 5,6-dihydroimidazo[2,1-a]isoquinolines with a broad range of functional groups. The resulting 5,6-dihydroimidazo[2,1-a]isoquinolines present strong photoluminecence in solutions and powders and could be applied in the fabrication of blue OLED devices.

Visible-Light-Induced Photocatalyst-Free Aerobic Hydroxyazidations of Indoles: A Highly Regioselective and Stereoselective Synthesis of trans-2-Azidoindolin-3-ols.

A visible-light-promoted aerobic hydroxyazidation of indole derivatives with TMSN3 is described. The reaction proceeded under photocatalyst-free conditions to furnish trans-2-azidoindolin-3-ols with high regioselectivity and stereoselectivity. The protocol is operationally simple, and the starting materials (e.g., 1-(pyrimidin-2-yl) indoles, azidotrimethylsilane, and air) are readily available. The proposed mechanism in which substrates act as photocatalysts upon excitation using blue light-emitting diodes (LEDs) was supported by experimental studies.

Visible-Light-Induced C(sp2)-C(sp3) Coupling Reaction for the Regioselective Synthesis of 3-Functionalized Coumarins.

A photocatalysis strategy for the regioselective synthesis of 3-functionalized coumarins is reported. With visible light irradiation, a direct and regioselective C(sp2)-C(sp3) coupling reaction of 3-(2-hydroxyphenyl)acrylates with ethers or thioethers occurs by using Ru(bpy)3Cl2·6H2O as a photocatalyst and TBHP as an oxidant. The cascade process involves alkenylation of the C(sp3)-H bond of ethers and lactonization, furnishing 3-alkylated coumarins as the final products. This approach is characterized by a broad substrate scope, mild reaction conditions, and simplified operation. The synthesis of 3-alkylated coumarins could be realized by a one-pot procedure, starting from commercially available salicylaldehyde.

Base Promoted Three-Component Annulation of 4-Diazoisochroman-3-imines with Dimethylsulfonium Ylides: Synthesis of Highly Functionalized Isochromeno[4,3-c]pyridazines.

A novel method has been developed to synthesize a unique class of highly functionalized isochromeno[4,3-c]pyridazines. This reaction features an intermolecular functionalization of terminal nitrogen atom of diazo group of 4-diazoisochoman-3-imine with two dimethylsulfonium ylide components, followed by a base promoted 6-exo-trig cyclization step. Readily available starting materials, a broad substrate scope, and operationally simple, mild, and catalyst-free reaction conditions are the prominent features of this method.

Preparation and Photoluminescent Properties of Three 5-Amino Benzothiadiazoles (5-amBTDs).

Three D-A compounds were designed and synthesized based on a benzothiadiazole acceptor. Azepane (AP), iminodubenzyl (IDB) and iminostilbene (ISB) were used, respectively, as donors and installed on the 5-position of BTD to afford 1, 2 and 3, respectively. Their photophysical properties in different states (solution, film, crystal, and powder) are systematically investigated. Among them, AIE-active compounds 2 and 3 were found to have good sensitivity toward viscosity and display quite good linear relationship with an increase in viscosity. Compound 2 displayed dual emission in solutions which largely depended on the polarity of the solvent. Meanwhile, compound 2 exhibits a mechanochromic character with disappearance and reappearance of a dual-emissive peak induced by mechanical grinding and solvent fuming. Furthermore, these three compounds can be used in the fabrication of blue OLED devices.

TfOH-promoted synthesis of 4,5-dihydrooxazolo[5,4-c]isoquinolines via formal [3 + 2] cycloaddition of 4-diazoisoquinolin-3-one and benzonitriles.

A facile and efficient method for the synthesis of novel 2-substituted 4-tosyl-4,5-dihydrooxazolo[5,4-c]isoquinolines from 4-diazoisoquinolin-3-ones and nitriles is reported. The reaction proceeded through a TfOH-promoted formal [3 + 2] cycloaddition and the products could be conveniently converted to 2-aryloxazolo[5,4-c]isoquinolines and the subsequent 2-(oxazolo[5,4-c]isoquinolin-2-yl)phenol which emitted bright green light in dilute dichloromethane solution and in solid form as well. Simple operation, metal-free and mild reaction conditions, short reaction time and broad substrate scope are the prominent features of this methodology.

Syntheses of 2-Iminoindolin-3-ones and 2-Alknyl-2,3-dihydroquinazolin-4(1H)-ones from 3-Diazoindolin-2-imines.

3-Diazoindolin-2-imines reacted with nitrones to furnish 2-iminoindolin-3-ones through a Au(I)-catalyzed cascade oxygen transfer/imine exchange process. The prepared 2-iminoindolin-3-ones could be further transformed into 2-alknyl-2,3-dihydroquinazolin-4(1H)-ones through a Ag(I)-catalyzed reaction with terminal alkynes. A MeOH-triggered ring expansion mechanism involving cyclic iminium formation and nucleophilic addition is proposed for this novel alkynylation reaction. This two-step procedure provides a general and convenient approach to 2-alknyl-2,3-dihydroquinazolin-4(1H)-ones, which are privileged structures in medicinal chemistry.

Synthesis of 8-Alkoxy-5H-isochromeno[3,4-c]isoquinolines and 1-Alkoxy-4-arylisoquinolin-3-ols through Rh(III)-Catalyzed C-H Functionalization of Benzimidates with 4-Diazoisochroman-3-imines and 4-Diazoisoquinolin-3-ones.

Rh(III)-catalyzed C-H activation/annulation of benzimidates with 4-diazoisochroman-3-imines furnished 8-alkoxy-5H-isochromeno[3,4-c]isoquinolines in moderate to excellent yields with a broad range of substrate scope. The reaction was carried out under mild reaction conditions and could be scaled up with practical usage. Similar reaction between benzimidates and 4-diazoisoquinolin-3-ones provided 1-alkoxy-4-arylisoquinolin-3-ols in excellent yields. Moreover, the synthesized products could be conveniently transformed to the corresponding heterocycles with a 1,8-naphthyridinone or isochromenopyridinone core, which are privileged structures in medicinal chemistry.

Preparation and photophysical properties of quinazoline-based fluorophores.

The donor-acceptor design is a classic method of synthesizing new fluorescent molecules. In this study, a series of new fluorescent compounds (1-10) were synthesized based on 2-(3,5-bis(trifluoromethyl)phenyl)-quinazoline acceptor and various amino donors. The fluorescent emissions of 1-10 cover the spectrum from 414 nm to 597 nm in cyclohexane solutions with various amino donors on 4- or 7-positions of quinazoline. Ultimately, compounds 1 and 2 presented the highest photoluminescence quantum yield (QY) over 80%, while compound 10 provided the largest Stokes shift (161 nm) in cyclohexane. Most of them have strong emissions in aggregated states such as in nanoparticles, in powders, in crystals and in films. Mechanochromic properties were observed for compounds 1, 2, 4 and 7. Furthermore, blue OLEDs were fabricated by using compound 2 or 7 as the active layer.

Preparation of 4-Diazoisoquinolin-3-ones via Dimroth Rearrangement and Their Extension to 4-Aryltetrahydroisoquinolin-3-ones.

4-Diazoisoquinolin-3-ones were prepared efficiently via TBAB-promoted rearrangement of 4-diazoisochroman-3-imines under mild reaction conditions. The resulted 4-diazoisoquinolin-3-ones could be conveniently applied for the synthesis of 4-aryltetrahydroisoquinolin-3-ones either by the TfOH-catalyzed reaction with electron-rich arenes or by the BF3-promoted reaction with aryl aldehydes.

Preparation of spiro[imidazolidine-4,3'-indolin]-2'-imines via copper(i)-catalyzed formal [2 + 2 + 1] cycloaddition of 3-diazoindolin-2-imines and triazines.

We report a facile and efficient synthesis of spiro[imidazolidine-4,3'-indolin]-2'-imines via a copper(i)-catalyzed cascade reaction of 3-diazoindolin-2-imines with 1,3,5-triazines. The reaction proceeds under very mild conditions and tolerates a variety of functional groups. The cascade process involves the formation of a copper-carbene intermediate and a formal [2 + 2 + 1] cycloaddition.