Deselenylative Acylation and Nitration of Monoselenides.

A deselenylative protocol that enables the construction of the C-C and C-N bonds has been disclosed. By using acyl chloride/AgOTf as an efficient acylation reagent, diarylselenides smoothly undergo deselenylative acylation to produce a series of aroyl compounds. In addition, deselenylative nitration can be enabled by a mild nitration reagent consisting of TsCl and AgNO3, furnishing a diverse array of nitroaromatic compounds.

Transition-metal-free four-component reaction of nitriles and disulfides/diselenides.

One-pot synthesis of structurally diverse sulfurized/selenated 4-aminopyrimidines has been reported via t-BuOK/K2S2O8-promoted four-component reaction of mixed nitriles and disulfides/diselenides. Mechanistic studies indicate that the reaction proceeds through radical and ionic pathways, and an alkenyl sulfide serves as a key intermediate.

Solid-State Luminescence Stimulus-Responsive Property and Doped RTP Emission of Novel 7a,8,10,11-Tetrahydro-9H- pyrido[2',1':2,3][1,3]oxazino[6,5,4-ij]isoquinoline Derivative.

A novel 7a,8,10,11-tetrahydro-9H-pyrido[2',1':2,3][1,3]-oxazino[6,5,4-ij]isoquinoline derivative (POIQ) is accidentally obtained from an isoquinoline derivative and iodine in dimethyl sulfoxide, which is demonstrated to undergo a mechanism of demethylation and thus intramolecular nucleophilic substitution. POIQ with twisted molecular conformation and loose stacking arrangement shows multifunctional optical properties including dual-state emission, mechanochromic, and solid-state acidochromic activities. Furthermore, an organic room temperature phosphorescence (RTP) doped system with green afterglow of 2 s is constructed using POIQ as the guest and easily available phenyl benzoate as the host, in which the host molecules assist in the transfer of the triplet excitons of the guest molecules. Rewritable optical recording media and information encryption are also realized based on multifunctional optical properties of this compound. This work provides inspiration for the development of N,O-containing fused-ring compounds with fluorescence/RTP properties.

Palladium-Catalyzed Ring-Opening Reaction of Cyclopropenones with Vinyl Epoxides.

We report herein the Pd-catalyzed selective ring-opening reaction of cyclopropenones with vinyl epoxides. By using a commercially available Pd2(dba)3·CHCl3-BINAP catalyst, a wide range of conjugated alkadienyl carboxylates could be accessed in good yield and excellent regioselectivity. The new application of zwitterionic π-allyl palladium intermediates has been demonstrated in organic synthesis.

An (NH4)2S2O8-promoted cross-coupling of thiols/diselenides and sulfoxides for the synthesis of unsymmetrical disulfides/selenosulfides.

An (NH4)2S2O8-promoted cross-coupling of thiols/diselenides and sulfoxides to construct unsymmetrical disulfides/selenosulfides is disclosed. Control experiments demonstrate that (NH4)2S2O8 acts as an acid and an oxidant, while both ionic and radical routes are involved in the reaction. The KIE experiments reveal that C-H bond cleavage of sulfoxides was involved in the turnover-limiting step.

Construction of Mechanofluorochromic and Aggregation-Induced Emission Materials Based on 4-Substituted Isoquinoline Derivatives.

Although many organic mechanofluorochromic (MFC) materials have been reported, the design strategy and formation mechanism are still unclear, and thus some of their discoveries are based on chance or a result of blind screening of some compounds. Herein, we show a strategy for constructing MFC materials from a multisubstituted isoquinoline compound with excellent crystallinity. The introduction of bromine atom at 4-position realizes the morphological change from crystalline state to amorphous state under the stimulation of external pressure, but it is not enough to generate MFC phenomenon. Similarly, although naphthalene, benzofuran, and benzothiophene endow the resultant isoquinolines with twisted molecular conformations and aggregation-induced emission (AIE) activities, no obvious solid-state emission color changes are observed. However, the introduction of 2-benzylidenemalononitrile and (E)-2-cyano-3-phenylacrylate leads not only to the AIE activities of IQ-M and IQ-A, but also to their outstanding and reversible MFC properties. The MFC activities of these two derivatives are demonstrated to come from more twisted molecular conformations, larger deformation spaces, and stronger intramolecular charge transfer compared with the other isoquinolines. This work offers important reference value for the construction of MFC and AIE materials from traditional fluorophores.

Cascade Ring-Opening Dual Halogenation of Cyclopropenones with Saturated Oxygen Heterocycles.

Represented is a CuX2- or I2-promoted ring-opening dual halogenation of cyclopropenones with saturated oxygen heterocycles, providing an efficient method for the synthesis of 3-haloacrylates. The ring-opening reaction enables the construction of two C-X (X = Cl, Br, or I) bonds and a C-O bond as well as the cleavage of two C-O bonds and a C-C bond in a single step. This protocol is highly atom economical, has an excellent substrate scope, and exhibits the ability for gram-scale reaction.

α-Selective C(sp3)-H Thio/Selenocyanation of Ketones with Elemental Chalcogen.

A facile method is disclosed for the synthesis of α-thio/selenocyanato ketones through regioselective C-H thio/selenocyanation of ketones. The advantages include the use of easily available starting materials, high efficiency, simple operation, and easy scale-up. Control experiments provide evidence that the reaction proceeded via a radical way, while kinetic isotope effect experiments reveal that the cleavage of the C-H bond serves as the rate-limiting step.

Palladium-catalyzed coupling reaction of 2-iodobiphenyls with alkenyl bromides for the construction of 9-(diorganomethylidene)fluorenes.

An atom economical protocol for the construction of 9-(diorganomethylidene)fluorenes through palladium-catalyzed coupling reactions of 2-iodobiphenyls with alkenyl bromides has been reported. The reaction proceeds through the C-H activation/oxidative addition/reduction elimination/intramolecular Heck coupling reaction to afford a series of 9-(diorganomethylidene)fluorenes with good yields. Control experiments demonstrate that a five-membered palladacycle acts as a key intermediate and ß-H elimination serves as the rate-limiting step.

Excitation-Dependent Triplet-Singlet Intensity from Organic Host-Guest Materials: Tunable Color, White-Light Emission, and Room-Temperature Phosphorescence.

A series of organic host-guest materials with multifunctional luminescence were constructed. Four isoquinoline derivatives were used as the guests, and benzophenone was used as the host. The doped system exhibited excellent dual emission with cyan fluorescence and orange-yellow room-temperature phosphorescence, and the dual emission could be combined into almost pure white-light emission. Importantly, the relative intensity of the fluorescence-phosphorescence could be adjusted by changing the excitation wavelength, with the phosphorescence intensity being significantly higher than the fluorescence intensity under shorter excitation wavelengths and vice versa under longer excitation wavelengths. Therefore, three-color emission switching among cyan, white, and orange could be achieved by simply adjusting the excitation wavelength. The results of experimental and theoretical calculations indicated that the excitation-dependent emission colors were caused by different transfer paths for excitons under different excitation wavelengths. These materials with multifunctional luminescence could be used as writable inks for advanced anticounterfeiting.

Metal-Free Synthesis of Aryl Selenocyanates and Selenaheterocycles with Elemental Selenium.

This work reports a green method for the synthesis of aryl selenocyanates via a three-component reaction of arylboronic acids, Se powder, and trimethylsilyl cyanide (TMSCN) under metal-free and additive-free conditions. Remarkably, TMSCN acts as not only the substrate, but also the catalyst. Various selenaheterocycles can be also accessed with a catalytic amount of TMSCN.

Efficient synthesis of 2-aryl-2H-indazoles by base-catalyzed benzyl C-H deprotonation and cyclization.

A straightforward and efficient method for the preparation of 2-aryl-2H-indazoles from ortho-alkyl substituted azoxybenzenes is presented. The reaction proceeds through base-catalyzed benzyl C-H deprotonation and cyclization to afford 2-aryl-2H-indazoles in good yields. This synthetic strategy can be applied to the construction of several fluorescent and bioactive molecules.

Multifunctional properties of a star-shaped triphenylamine-benzene-1,3,5-tricarbohydrazide fluorescent molecule containing multiple flexible chains.

A star-shaped triphenylamine-benzene-1,3,5-tricarbohydrazide molecule with a twisted molecular conformation was found to display amazing multifunctional optical properties. The design of peripheral triphenylamine units and a central benzene connected with hydrazide groups leads to the formation of rare polymorphic properties in the presence of multiple flexible chains. Two polymorphs with different fluorescence colors exhibited bathochromic mechanofluorochromic activities with high contrast due to a crystalline-to-amorphous transition.

Tunable Phosphorescence/Fluorescence Dual Emissions of Organic Isoquinoline-Benzophenone Doped Systems by Alkoxy Engineering.

Dual/multi-component organic doped systems with room-temperature phosphorescence (RTP) properties have been developed. However, the unknown luminescence mechanism still greatly limits the development of the doped materials. Herein, a new doped system exhibiting phosphorescence/fluorescence dual emission (Φphos =4-24 % and τphos =101-343 ms) is successfully constructed through prediction and design. A series of isoquinoline derivatives with different alkoxy chains were selected as the guests. Benzophenone was chosen as the host owing to the characteristics of low melting point and good crystallinity. The alkoxy chain lengths of the guests are first reported to be used to control the fluorescence and phosphorescence intensities of the doped materials, which results in different prompt emission colors. Additionally, the doped ratio of the guest and host can also control the luminous intensities of the materials. In particular, the doped materials still exhibit phosphorescent properties even if the ratio of the guest/host is as low as 1:100 000.

Three-Component Reactions of Alkynone o-Methyloximes, Element Selenium, and Boronic Acids Leading to 4-Organoselenylisoxazoles.

We report an Ag-catalyzed one-pot three-component reaction of alkynone o-methyloxime, element selenium, and boronic acid, providing a facile route to selenated isoxazole product. This protocol features high efficiency, wide substrate scope, and the use of selenium powder as the selenium source.

An Unexpected 4,5-Diphenyl-2,7-naphthyridine Derivative with Aggregation-Induced Emission and Mechanofluorochromic Properties Obtained from a 3,5-Diphenyl-4H-pyran Derivative.

For a specific fluorescent molecule, the increase of molecular conformation distortion is beneficial to endow it with aggregation-induced emission (AIE) and mechanofluorochromic (MFC) properties. Herein, 3,5-diphenyl-4H-pyran derivative 5 and 4,5-diphenyl-2,7-naphthidine derivative 7 with highly twisted conformations were synthesized. For compound 5, although the introduction of phenyl rings with large steric hindrance at 3 and 5 positions of the 4H-pyran skeleton realized the transformation from aggregation-induced quenching (ACQ)-active molecule to AIE-active molecule, it only showed a low-contrast MFC activity. Compound 7 was accidentally obtained from compound 5 and n-butylamine via a ring-opening and subsequent intramolecular ring-closing mechanism. Compound 7 was confirmed to have a highly twisted molecular conformation by the crystal structural analysis and exhibited AIE activity originated from the restriction of intramolecular rotation. Furthermore, compound 7 exhibited reversible high-contrast MFC activity. Upon grinding, the change of solid-state fluorescence color from orange to yellow was confirmed to be due to the partial destruction of crystal structure. This work provides new ideas for the design and synthesis of novel AIE-active and MFC-active fluorescent molecules based on ACQ-active parent molecules.

Ag2O-promoted ring-opening reactions of cyclopropenones with oximes.

Ag2O-promoted ring-opening reactions of cyclopropenones with oximes is disclosed in this work, providing a direct route to 1,3-oxazinones. This method highlights a new reactivity of cyclopropenones which undergo 1,4-addition with oximes followed by ß-carbon elimination to in situ generate a α-carbonyl ketene intermediate.

Selective [3 + 2] Cycloaddition of Cyclopropenone Derivatives and Elemental Chalcogens.

A highly efficient method is disclosed for the synthesis of 1,2-dichalcogen heterocycles via [3 + 2] cycloaddition of cyclopropenone derivatives and elemental chalcogens. Different from other cyclopropenone derivatives, cyclopropenselenones undergo unprecedented rearrangement with elemental sulfur. The features of this protocol include mild reaction conditions, high efficiency, excellent atom economy, gram-scale ability, and good regioselectivity.

Metal-Free Facile Synthesis of Multisubstituted 1-Aminoisoquinoline Derivatives with Dual-State Emissions.

Although isoquinoline is a good traditional fluorescent structural unit, most of its derivatives emit fluorescence in solution and a few of them can emit solid-state fluorescence as well. Herein, a series of multisubstituted 1-aminoisoquinoline derivatives were synthesized by a simple reaction of a readily available 4H-pyran derivative and secondary amines. The reaction had advantages of metal-free, mild conditions, simple operation, and good yields, which was realized by a ring-opening and sequential ring-closing mechanism. These 1-aminoisoquinoline derivatives were found to exhibit interesting dual-state emissions. In the solution, they emitted strong blue fluorescence at about 458 nm. In the solid state, they emitted solid-state blue fluorescence at 444-468 nm with high fluorescence quantum yields of 40.3-98.1%. Crystal structural analyses indicated that solid-state emissions of these compounds originated from twisted molecular conformations and the resultant loose stacking arrangements. Furthermore, their solid-state fluorescence wavelengths were demonstrated to depend on molecular conformations rather than stacking arrangements. The discovery of these 1-aminoisoquinolines with multiple reaction sites provides new possibilities for the development of solid-state fluorescent materials based on the traditional isoquinoline skeleton.

Synthesis of selenated isochromenones by AgNO3-catalyzed three-component reaction of alkynylaryl esters, selenium powder and ArB(OH)2.

Reported is the AgNO3-catalyzed three-component reaction of alkynylaryl esters, selenium powder and ArB(OH)2, providing a facile entry to selenated isochromenones. This work highlights the use of selenium powder as a selenium reagent in the synthesis of selenated isochromenones for the first time.