Visible-light-induced decarboxylative alkynylation of carboxylic acids in batch and continuous flow

A green efficient photoredox-catalyzed decarboxylative alkynylation of carboxylic acids with alkynyl bromides has been developed.This broadly applicable protocol is presented whereinα-amino,aliphatic andα-oxy acids are converted into useful alkynylation products.The commercially-available organic photocatalyst 4CzIPN is used as the photocatalyst,organic base DBU is utilized as the base,and DMSO serves as solvent.This strategy features mild conditions,is metal-free,and is environmentally friendly.The batch and continuous-flow protocols described were applied to obtain a broader substrate scope of functionalization(more than 50 examples).Furthermore,we demonstrate that the use of microflow technology enhanced and intensified the reaction process,achieving significantly reduced reaction times(i.e.,10 min of residence time).

Dearomative spirocyclization via visible-light-induced reductive hydroarylation of non-activated arenes

A visible-light-induced spirocyclizative hydroarylation via reductive dearomatization of a series of non activated arenes including 2-phenyl indoles and naphthalene derivatives under mild conditions is de scribed.An intriguing chemoselective dearomative hydroarylation of 2-phenyl indoles is presented.Th dearomative hydroarylation protocol rapidly delivers valuable spirocycles with carbon-carbon doub bonds from readily accessible aromatic precursors in a single step.

Visible-light-induced chemoselective reactions of quinoxalin-2(1H)-ones with alkylboronic acids under air/N_(2) atmosphere

A visible-light-induced chemoselective reactions of quinoxalin-2(1 H)-ones with alkylboronic acids in the presence of air(O_(2)) and N_(2)atmosphere was developed under transition-metal free conditions, providing 3-alkylquinoxalin-2(1H)-ones and 3,4-dihydroquinoxalin-2(1H)-ones, respectively. The overall strategy accommodates a broad scope of substituted quinoxalin-2(1H)-ones and alkylboronic acids with good to excellent product yields.

Visible-light-induced photoredox-catalyzed synthesis of benzimidazo[2,1-a]iso-quinoline-6(5H)-ones

A simple and efficient visible-light-induced photo redox-catalyzed diarylation of N-methacryloyl-2-arylbenzoimidazoles with aryl diazonium salts was developed.The reaction provides a conve nient access to a variety of benzimidazoisoquinolinones through the construction of two C-C bonds in one step under mild reaction conditions.

Visible-light-induced novel cyclization of 2-(2-(arylethynyl)benzylidene)-malononitrile derivatives with 2,6-di(tert-butyl)-4-methylphenol to bridged spirocyclic compounds

A green and highly efficient strategy for the preparation of bridged spirocyclic compounds via visible-light-induced cyclization of 2-(2-(arylethynyl)benzylidene)malononitrile derivatives with 2,6-di(tert-butyl)-4-methylphenol(BHT)at room temperature was developed.The photoinduced radical reactions generated the corresponding products in good yields under simple and mild reaction conditions.

Facile oxalic acid-assisted construction of laminated porous N-deficient graphitic carbon nitride: Highly efficient visible-light-driven hydrogen evolution photocatalyst

The laminated porous N-deficient g-C3N4(CN–H)is successfully synthesized by a facile two-step hydrothermal calcination method using oxalic acid-assisted melamine as the precursor.Compared with pristine g-C3N4(224μmol g-1h-1),the CN–H shows superior photocatalytic hydrogen production activity(up to 728μmol g-1h-1),which is three times higher than the unmodified counterpart.To draw out the multifaceted influences of oxalic acid modification on the visible-light-induced photocatalytic activity,various techniques are utilized to investigate the formation mechanism,structural characteristics and photoelectrical properties of CN–H.The results indicate that the addition of a trace amount of oxalic acid to the precursor melamine results in a g-C3N4 structure possessing the advantage of both nitrogen defects and laminated porosity.These properties can enlarge specific surface areas of g-C3N4,enhance an efficient separating of photogenerated electron-hole pairs and extend the range of spectral response,all contributing to the enhancement of the visible-light-induced photocatalytic activity.

Novel continuous single-step synthesis of nitrogen-modified TiO_2 by flame spray pyrolysis for photocatalytic degradation of phenol in visible light

A novel rapid and continuous process has developed for the synthesis of nitrogen-doped TiO2（N-TiO2）with flame spray pyrolysis（FSP） method. The nitrogen incorporation into TiO2 was achieved by a facile modification（addition of dilute nitric acid） in the precursor for the synthesis. The catalysts were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. The doping of nitrogen into the TiO2 was confirmed by X-ray photoelectron spectroscopy（XPS） and energy dispersive X-ray（EDX） spectroscopy. The UV-vis spectra of the modified catalysts（with primary N source） exhibited band-gap narrowing for 4 N-TiO2 with band gap energy of 2.89 eV, which may be due to the presence of nitrogen in TiO2 structure. The introduction of secondary N-source（urea） into TiO2 crystal lattice results in additional reduction of the band gap energy to 2.68 eV and shows a significant improvement of visible light absorption. The N-TiO2 nanoparticles modified by using secondary N-source showed significant photocatalytic activity under visible light much higher than TiO2. The higher activity is attributed to the synergetic interaction of nitrogen with the TiO2 lattice. The lowering of the band-gap energy for the flame made N-doped TiO2 materials implies that the nitrogen doping in TiO2 by aerosol method is highly effective in extending the optical response of TiO2 in the visible region. The nitrogen atomic percentage has increased monotonically（0.09%-0.15%）with the increase in primary nitrogen source（nitric acid）, and significantly boosted to 0.97% when secondary nitrogen source（urea） was introduced. The highest rate of phenol degradation was obtained for catalysts with secondary N source due to increase in N content in the catalyst.

Two transition-metal-modified Nb/W mixed-addendum polyoxometalates for visible-light-mediated aerobic benzylic C–H oxidations

The visible-light-induced selective oxidation of ubiquitous C–H bonds into valuable C=O bonds under aerobic conditions is one of the most attractive approaches for the construction of carbonyl-containing molecules.In this work,two transition metal-containing Nb/W mixed-addendum POMs dimers with the formula of K_(2)Na_(2)H_(5)[(Fe(H_(2)O)_(4))_(3)(P_(2)W_(15)Nb_(3)O_(62))_(2)]·24H_(2)O(POM[Fe])and K_(2)Na_(3)H_(4)[(Cr(H_(2)O)_(4))_(3)(P_(2)W_(15)Nb_(3)O_(62))_(2)]·32H_(2)O(POM[Cr])have been synthesized and characterized by various analytical and spectral techniques.POM[Fe]was proved to be an efficient photocatalyst for benzylic C–H oxidation under visible light and using oxygen as an oxidant to produce the corresponding carbonyl complex in good yields.A plausible mechanism involving superoxide radical was proposed for the catalytic reaction.POM[Fe]showed good reusability in the recycling experiments.IR spectroscopy and XRD analysis indicate that POM[Fe]can retain its integrity after catalysis.