Photoinduced Synthesis Research Articles

Highly scalable photoinduced synthesis of silanols via untraversed pathway for chlorine radical (Cl•) generation

The emergence of visible light-mediated synthetic transformations has transpired as a promising approach to redefine traditional organic synthesis in a sustainable way. In this genre, transition metal-mediated photoredox catalysis has led the way and recreated a plethora of organic transformations. However, the use of photochemical energy solely to initiate the reaction is underexplored. With the direct utilization of photochemical energy herein, we have established a general and practical protocol for the synthesis of diversely functionalized organosilanols, silanediols, and polymeric siloxanol engaging a wide spectrum of hydrosilanes under ambient reaction conditions. Streamlined synthesis of bio-active silanols via late-stage functionalization underscores the importance of this sustainable protocol. Interestingly, this work also reveals photoinduced non-classical chlorine radical (Cl•) generation from a readily available chlorinated solvent under aerobic conditions. The intriguing factors of the proposed mechanism involving chlorine and silyl radicals as intermediates were supported by a series of mechanistic investigations.

Photo-induced synthesis of star poly(DL-Lactide)-templated Au and Ag nanoparticles and evaluation of their catalytic performance

In this report, photochemical synthesis of monodispersed gold (Au) and silver (Ag) nanoparticles (NPs) was reported using cholic acid functionalized star poly(DL-lactide) (CA-(PDLLA)) as a capping and reducing agent. CA-(PDLLA) was synthesized by ring-opening polymerization (ROP) of DL-lactide with a feed ratio of 1:120 (cholic acid: DL-lactide). The molecular weight of CA-(PDLLA) was measured by using the gel permeation chromatography (GPC) technique. The thermal properties of the polymer and its nanocomposite materials were studied by thermogravimetric analysis (TGA). The optical properties of Ag and Au NPs were studied by UV–visible absorption spectroscopy. Morphological studies and size of the polymer-nanocomposites were assessed by using field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) techniques. The percentage composition of Au and Ag present in the polymer-nanocomposites was calculated using energy-dispersive X-ray spectroscopic (EDX) analysis. Finally, the synthesized polymer-metal nanocomposites were used as heterogeneous catalysts for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) as a model reaction and the apparent rate constant (kapp) values of CA-(PDLLA)-AuNPs and CA-(PDLLA)-AgNPs were found to be 5.76 × 10−4 s−1 and 19.7 × 10−4 s−1, respectively.

Photo-induced organoselenium-catalyzed synthesis of 2-substituted quinazoline derivatives

Herein, a method for the synthesis of 2-substituted quinazoline derivatives from 2-aminobenzylamines and benzylamines using the synergistic action of visible light and organoselenium catalysts was established. Under visible light, the process employs diphenyl diselenide (PhSe)2 as a photocatalyst to achieve the best yield of 97 % in 3 h without the use of other powerful oxidants or selective fluorine excitation, and tolerated a variety of substrates with yields ranging from 60 % to 97 %. Moreover, substitution of benzylamine with benzaldehyde, benzoylformic acid or mandelic acid expanded the substrate scopes for synthesis of 2-substituted quinazolines and quinazolinones. This opens new avenues for further study of the catalytic reaction of organic selenium and promotes the development of green synthetic chemistry.

Photoinduced Pd-Catalyzed Synthesis of Chiral Piperidine 2-Carboxyamides

Photoinduced Pd-Catalyzed Synthesis of Chiral Piperidine 2-Carboxyamides

Riboflavin and Eosin Y Supported on Chromatographic Silica Gel as Heterogeneous Photocatalysts.

The application of photocatalysis for organic synthesis, both in the laboratory and on an industrial scale, will depend on the achieving of good yields and the ease with which it can be applied. Selective irradiation of the photocatalyst with LED light has made it possible to activate the reactions easily, without the need for UV or heat filters. However, a common problem is the need to separate the photocatalyst from the reaction products through extraction and chromatography isolation processes. These procedures make it difficult to recover and reuse the catalyst, which is not compatible with scale-up applications. Photocatalysts attached to heterogeneous supports resulted in an alternative, which facilitates their removal and reuse. In this study, we use chromatographic silica gel as a low-cost heterogeneous support to bind photosensitizers such as Riboflavin or Eosin Y. The modified silica gel was analyzed by FTIR-ATR and diffuse reflectance UV-visible spectroscopy, thermogravimetric analysis, and optical microscopy. These hybrid materials have a suitable size for easy separation by decantation and were found to be photoactive against two photooxidation reactions. These easy-to-handle materials open the door to effective applications for photoinduced organic synthesis methods at medium to large scale.

Photoinduced Reaction of α‐Bromoacetophenone with Thiosulfonate: Synthesis of β‐Keto Thiosulfone

AbstractA photoinduced synthesis of β‐keto thiosulfone/β‐keto selenosulfone by the reaction of α‐bromoacetophenone with thiosulfonate/selenosulfonate under metal‐free and visible light irradiation conditions is developed. Two C−S bonds or one C−S bond and one C−Se bond were constructed simultaneously.

Photo-induced synthesis, stereochemistry and antitumor activity of natural cyclopeptide Hikiamide B analogs

Peptide cyclization has been recognized as capable of overcoming the shortcomings of linear peptides such as poor stability, short half-life, low selectivity and low affinity to receptors, and the modification of cyclic peptides to achieve specific activity requirements is receiving increasing attention. Hikiamide B is a cyclic pentadepsipeptide that can induce the expression of peroxisome-proliferator-activated receptor-γ (PPAR-γ). Considering that PPAR-γ can effectively regulate the expression of genes related to tumorigenesis, and is a potential tumor target, in this paper, we have prepared several Hikiamide B analogs by intramolecular photo-induced single-electron-transfer (SET) reaction to find novel antitumor drugs The stereochemistry and the in vitro antitumor activity against HepG-2 and HeLa cells were investigated. We found that the compound with stronger intramolecular hydrogen bonds (compound 2) than other compounds showed more promising antitumor activity, and the cyclic compounds present stronger bioactivity than that of their linear precursors. In vitro studies of apoptosis mechanisms and mitochondrial membrane potential following cyclopeptide 2 treat have shown that the cyclopeptide may induce apoptosis in tumor cells. Finally, in silico ADME analysis has shown the potential of compound 2 for practical application.

Влияние электрического поля на рекомбинационную люминесценцию коллоидных квантовых точек сульфида серебра

The paper studies the effect of external electric field on the optical properties of the spherical Ag2S quantum dots. Colloidal Ag2S nanoparticles passivated with 2-mercaptopropionic acid were obtained by photoinduced synthesis in the ethylene glycol. The nanoparticles shape and characteristic size were determined using the transmission electron microscopy. To analyze the external electric field influence, a series of samples was prepared based on the optically passive polymer film, where the nanoparticles were embedded. The films were placed between two glasses coated with the transparent electrodes based on the indium tin oxide (ITO). Intensity value of the external electric field created in such structures reached 500 kV/cm. The photoluminescence signal was registered using the CCD fiber spectrometer with spectral resolution of 1.16 nm. Spectrally resolved nanoparticles photoluminescence kinetics was measured by time-corre-lated counting of the separate photons. It was found that the presence of a field led to an increase in intensity and rate of the photoluminescence relaxation due to the surface states. This fact is related to acceleration of the free holes transportation to the recombination centers in the external electric field. It is shown that under long-term exposure to laser radiation with a wavelength of 405 nm and the average power of 5 mW, the nanocrystal photoluminescent properties could degrade, as it occurs due to formation of new centers of non-radiative recombination and photoionization of the quantum dots

Sodium Salt of Partially Carboxymethylated Sodium Alginate-g-Poly(acrylonitrile): I. Photo-Induced Synthesis, Characterization, and Alkaline Hydrolysis.

An efficient redox initiating system, ceric ammonium nitrate/nitric acid, has been employed for the first time to carry out photo-induced graft copolymerization of acrylonitrile (AN) onto sodium salt of partially carboxymethylated sodium alginate, having an average degree of substitution value to be 1.10. The photo-grafting reaction conditions for maximum grafting have been systematically optimized by varying the reaction variables such as reaction time, temperature, the concentration of acrylonitrile monomer, ceric ammonium nitrate, and nitric acid, as well as the amount of the backbone. The optimum reaction conditions are obtained with a reaction time of 4 h, reaction temperature of 30 °C, acrylonitrile monomer concentration of 0.152 mol/L, initiator concentration of 5 × 10-3 mol/L, nitric acid concentration of 0.20 mol/L, amount of backbone of 0.20 (dry basis) and the total volume of the reaction system of 150 mL. The highest percentage of grafting (%G) and grafting efficiency (%GE) achieved are 316.53% and 99.31%, respectively. The optimally prepared graft copolymer, sodium salt of partially carboxymethylated sodium alginate-g-polyacrylonitrile (%G = 316.53), has been hydrolyzed in an alkaline medium (0.7N NaOH, 90-95 °C for ~2.5 h) to obtain the superabsorbent hydrogel, H-Na-PCMSA-g-PAN. The chemical structure, thermal characteristics, and morphology of the products have also been studied.

Photocatalyst-Free, Visible-Light-Mediated C–H Perfluoroalkylation of Quinazolin-4(3H)-ones with perfluoroalkyl Iodides

AbstractA practical and sustainable photocatalyst-free protocol for photoinduced synthesis of perfluoroalkylated quinazolin-4(3H)-ones is described starting from quinazolin-4(3H)-ones. A wide range of substituted or fused-quinazolinones is found to be compatible, providing the corresponding mono- and bis-perfluoroalkylated compounds in moderate yields. This visible-light-mediated C–H perfluoroalkylation allows an environmentally friendly and straightforward access to an array of unprecedented functionalized quinazolinone scaffolds, presenting attractive features for drug discovery. Control experiments demonstrated that a radical mechanism is involved in the reaction mechanism.

Highly E-Selective Olefin Synthesis Catalysed by Novel Quinoxalinone Photocatalyst under Visible Light Conditions.

In photo-induced olefin synthesis, the photocatalysts with high triplet energy could cause the isomerization of olefins. This study demonstrates a new quinoxalinone photocatalytic system for highly stereoselective alkenes preparation from alkenyl sulfones and alkyl boronic acids. Our photocatalyst could not convert the thermodynamically favored E-olefin to Z-olefin, guaranteeing the high E-configuration selectivity of the reaction. There is weak interaction between boronic acids and quinoxalinone according to NMR experiments, probably decreasing the oxidation potential of boronic acids. This system can be further extended to the allyl and alkynyl sulfones to give corresponding alkenes and alkynes.

Photoinduced Synthesis of Bisphosphinated Quinoxalines via Radical Cyclization of o-Diisocyanoarenes with Diphosphines.

The cycloaddition reaction of o-diisocyanoarenes with interelement compounds under light is a very important reaction system to clarify whether this reaction proceeds by radical cyclization or by aza-Bergman cyclization. In this study, a series of diphosphines with phosphorus-phosphorus single bonds were selected as interelement compounds, and their cycloaddition reactions with o-diisocyanoarenes under light were investigated in detail to achieve a novel photoinduced synthesis of bisphosphinated quinoxalines via the radical cyclization pathway. In addition, the photoinduced reaction of diphosphines with isocyanides having o-functional groups such as cyano and ethenyl groups allowed us to elucidate the reaction pathway and product selectivity of this bisphosphination. Furthermore, the one-pot synthesis of PdII -quinoxaline complex was successfully achieved by applying the developed reaction.

Photoinduced One-Pot Synthesis of a Chromium Germylyne Complex and Its Formation Mechanism

A chromium germylyne (or germylidyne) complex having a Cr≡Ge triple bond, [Cp*(OC)2Cr≡GeTsi] (1) (Tsi = C(SiMe3)3), was directly synthesized by the photochemical reaction of a methyl chromium complex [Cp*Cr(CO)3Me] and a trihydrogermane (TsiGeH3). Detailed monitoring the reaction by NMR revealed the initial formation of hydrido (hydrogermylene) complex [Cp*(OC)2(H)Cr═Ge(H)Tsi] (2) as an intermediate and its facile release of dihydrogen to afford 1 under UV–vis light irradiation. The intermediate 2 was isolated from another experiment under blue LED light irradiation. The structures of 1 and 2 were confirmed by X-ray crystallography. Based on the analysis of absorption bands of intermediate 2 using TD-DFT calculations, we suggest possible mechanisms for releasing dihydrogen from 2 to afford 1, which includes a process forming a metallogermylene by weakening the Cr–Ge multiple bond.

Photo-induced synthesis, stereochemistry and antitumor activity of valine-based small cyclopeptides

Photo-induced synthesis, stereochemistry and antitumor activity of valine-based small cyclopeptides were studied.

Solvent-free, photoinduced block copolymer synthesis from polymerizable eutectics by simultaneous PET-RAFT and ring-opening polymerization in air

We report the preparation of thermoresponsive block copolymers via the simultaneous RAFT polymerization and anionic ring-opening polymerization (ROP) of N-isopropylacylamide and ε-caprolactone respectively, in the absence of traditional solvents.

Photoinduced synthesis of C2-linked phosphine oxides via radical difunctionalization of acetylene

A photocatalyzed radical difunctionalization of acetylene was achieved, which enables the green synthesis of C2-linked phosphine oxides.

Cascade Synthesis of Phenanthrenes under Photoirradiation

We report a photoinduced phenanthrene synthesis from aryl iodides and styrenes through an arylation/cyclization cascade. Compared to prior methods, this approach obviates the need for hazardous reagents and provides access to unsymmetrical phenanthrenes with good functional group tolerance. Mechanistic studies revealed that photoexcitation of aryl iodides leads to homolytic C-I bond cleavage. Arylation of styrenes with the formed aryl radical species furnishes stilbene derivatives, which undergo photoinduced cyclization promoted by iodine generated in situ to yield phenanthrene products.

Photo-Induced Microfluidic Production of Ultrasmall Glyco Gold Nanoparticles.

Ultra-small gold nanoparticles (UAuNPs) are extremely interesting for applications in nanomedicine thanks to their good stability, biocompatibility, long circulation time and efficient clearance pathways. UAuNPs engineered with glycans (Glyco-UAuNPs) emerged as excellent platforms for many applications since the multiple copies of glycans can mimic the multivalent effect of glycoside clusters. Herein, we unravel a straightforward photo-induced synthesis of Glyco-UAuNPs based on a reliable and robust microfluidic approach. The synthesis occurs at room temperature avoiding the use of any further chemical reductant, templating agents or co-solvents. Exploiting 1 H NMR spectroscopy, we showed that the amount of thiol-ligand exposed on the UAuNPs is linearly correlated to the ligand concentration in the initial mixture. The results pave the way towards the development of a programmable synthetic approach, enabling an accurate design of the engineered UAuNPs or smart hybrid nano-systems.

Photoinduced Promiscuity of Cyclohexanone Monooxygenase for the Enantioselective Synthesis of α-Fluoroketones.

The development of mild, efficient, and enantioselective methods for preparing chiral fluorinated compounds has been a long-standing challenge. Herein, we report a promiscuous cyclohexanone monooxygenase (CHMO) for the photoinduced synthesis of chiral α-fluoroketones via enantioselective reductive dehalogenation of α,α-halofluoroketones. Wild-type CHMO from Acinetobacter sp. possesses this promiscuous ability innately; however, the yield and stereoselectivity are low. A structure-guided rational design of CHMO improved the yield and stereoselectivity remarkably. Mechanistic studies and molecular simulations demonstrated that this photoinduced CHMO catalyzes the reductive dehalogenation via a novel electron transfer (ET)/proton transfer (PT) mechanism, distinct from that of previously reported reductases with similar promiscuity. This methodology was expanded to various substrates, and desirable chiral α-fluoroketones were obtained in high yields (up to 99 %) and e.r. values (up to 99:1).

Photoinduced Promiscuity of Cyclohexanone Monooxygenase for the Enantioselective Synthesis of α‐Fluoroketones

AbstractThe development of mild, efficient, and enantioselective methods for preparing chiral fluorinated compounds has been a long‐standing challenge. Herein, we report a promiscuous cyclohexanone monooxygenase (CHMO) for the photoinduced synthesis of chiral α‐fluoroketones via enantioselective reductive dehalogenation of α,α‐halofluoroketones. Wild‐type CHMO from Acinetobacter sp. possesses this promiscuous ability innately; however, the yield and stereoselectivity are low. A structure‐guided rational design of CHMO improved the yield and stereoselectivity remarkably. Mechanistic studies and molecular simulations demonstrated that this photoinduced CHMO catalyzes the reductive dehalogenation via a novel electron transfer (ET)/proton transfer (PT) mechanism, distinct from that of previously reported reductases with similar promiscuity. This methodology was expanded to various substrates, and desirable chiral α‐fluoroketones were obtained in high yields (up to 99 %) and e.r. values (up to 99:1).