Photodecarboxylative addition of carboxylates to phthalimides: a concise access to biologically active 3-(alkyl and aryl)methylene-1H-isoindolin-1-ones

A series of 3-(alkyl and aryl)methyleneisoindolin-1-one derivatives were synthesized in a simple two-step procedure using a recently established photodecarboxylative addition of carboxylates to phthalimides as the key-step. Subsequent acid-catalyzed dehydration and deprotection furnished the desired target compounds with high E-selectivity. The reaction sequence was applied to the synthesis of the known bioactive phenylethylene derivative, AKS-186. Different analogues, including heteroatom-containing isosteres were also synthesized using this approach.     

The solar-chemical photo-Friedel-Crafts heteroacylation of 1,4-quinones

Photochemical reactions between 1,4-benzo- and 1,4-naphthoquinone and several heteroaromatic carbaldehydes were investigated under solar irradiation conditions. These reactions gave the corresponding heteroacylated hydroquinones in the range 71%-92% yield.     

Influence of supporting ligand microenvironment on the aqueous stability and visible light-induced CO-release reactivity of zinc flavonolato species

The visible light-induced CO-release reactivity of the zinc flavonolato complex [(6-Ph₂TPA)Zn(3-Hfl)]ClO₄ (1) has been investigated in 1?:?1 H₂O?:?DMSO. Additionally, the effect of ligand secondary microenvironment on the aqueous stability and visible light-induced CO-release reactivity of zinc flavonolato species has been evaluated through the preparation, characterization, and examination of the photochemistry of compounds supported by chelate ligands with differing secondary appendages, [(TPA)Zn(3-Hfl)]ClO₄ (3; TPA = tris-2-(pyridylmethyl)amine) and [(bnpapa)Zn(3-Hfl)]ClO₄ (4; bnpapa = N,N-bis((6-neopentylamino-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine)). Compound 3 undergoes reaction in 1?:?1 H₂O?:?DMSO resulting in the release of the free neutral flavonol. Irradiation of acetonitrile solutions of 3 and 4 at 419 nm under aerobic conditions results in quantitative, photoinduced CO-release. However, the reaction quantum yields under these conditions are lower than that exhibited by 1, with 4 exhibiting an especially low quantum yield. Overall, the results of this study indicate that positioning a zinc flavonolato moiety within a hydrophobic microenvironment is an important design strategy toward further developing such compounds as CO-release agents for use in biological systems.     

Photosensitized addition of isopropanol to furanones in a continuous-flow dual capillary microreactor

A novel continuous-flow photoreactor with parallel capillaries was constructed and successfully tested for the DMBP-sensitized addition of isopropanol to furanones. Complete conversions were achieved after a maximum of 10 min of irradiation with a single 350 nm lamp. The results were compared to analogous batch experiments using a conventional Rayonet chamber reactor equipped with 16 UVA lamps. The capillary tower generally showed higher space-time yields.     

Microflow photochemistry—a reactor comparison study using the photochemical synthesis of terebic acid as a model reaction

The continuous-microflow photochemical synthesis of terebic acid from maleic acid was investigated in two different microreactor set-ups. The results were subsequently compared to analogue experiments in a conventional chamber reactor. Based on conversion rates, reactor design and energy efficiency calculations, the simple microcapillary reactor showed the best overall performance.     

A stable chemiluminophore,adamantylideneadamantane 1,2-dioxetane: from fundamental properties to utilities in mechanochemistry and soft crystal science

Chemiluminescence (CL) is a luminescence phenomenon originated by a “chemical reaction.” CL provides a basis for real-time imaging technology in materials science. In fact, a CL reaction is easily triggered in general and makes it possible to track its progress in a target material by highly sensitive photon detection. Recently, real-time CL imagings became breakthrough techniques for analyzing the molecular mechanisms of failures of polymeric materials and of reactions and phase transitions in soft crystals. In the CL imaging techniques, adamantylideneadamantane 1,2-dioxetane (Adox) has been adopted as a stable core structure of chemiluminophores. That is, Adox is an essential seed compound to design a chemiluminophore with a desired molecular function. To support developments of real-time CL imaging techniques, we review the chemistry of Adox as a representative stable chemiluminophore including scientific history and utilities of Adox and its derivatives.     

Plasmon heating mediated Friedel-Crafts alkylation of anisole using supported AuNP@Nb2O5 catalysts

Two different hybrid materials composed of gold nanoparticles (AuNPs) supported on either commercial niobium oxide HY 340 or mesoporous niobium oxide catalyzed the Friedel-Crafts alkylation of anisole by benzyl chloride. Excitation of the surface plasmon of the supported AuNPs allowed the reaction to occur at lower temperatures by acting as an alternative heat source. The localized heating produced via plasmon excitation permitted the acid catalyzed reaction to occur - at the Lewis acid sites on the Nb₂O₅ support - at 80 °C while thermal-dark reactions using a conventional heat source, required temperatures of 120 °C or higher. The catalytic activity of the tested hybrid materials decreased with storage time. However, the deactivation showed to be reversible upon lyophilisation indicating that the nature of the deactivation could be due to water adsorption.     

Design, synthesis and photo-cross-linking of a new photosensitive macromonomer from tetra-branched poly(ethylene oxide)s

A general procedure to increase the amount of photoreactive chromophore groups per oligoether chain is presented. In this work, a photoreactive macromonomer with four functionalities was synthesized by a four-step synthetic pathway with high yield. The photochemical behavior of this compound was studied with a view to obtaining polymeric networks. The significant advantage in this strategy is that the preparation of this material has as last operation, the obtaining and processing of polymer as thin film. In this way, the synthetic strategy based on assembling: (i) the polyether chains, (ii) a film forming backbone, and (iii) a photoactive moiety to be used for cross-linking, seems a viable solution to the problem of the continuous processing of materials.     

Parahydrogen-based NMR methods as a mechanistic probe in inorganic chemistry

The study of reactions by NMR spectroscopy is normally limited by the poor detection limits offered by the method. An overview is presented of how chemical reactions can be studied using parahydrogen-assisted NMR spectroscopy, where detected signals can have strengths that exceed those normally available by factors that approach 31,000.     

Synthesis and photochemical properties of photo-cleavable crosslinkers

We report herein the synthesis and the development of homo-bifunctional photo-cleavable sulfhydryl group cross-linkers that are able to react and then to photorelease two cysteines leading to the photoregulation of cross-linkers cleavage.