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The tricyclic azepino[1,2-a]indole acetates 7, readily accessible by visible-light-driven catalytic photooxygenation of cyclohepta[b]indoles 1, are convenient precursors to novel and uncommon cyclic C,N-diacyliminium ions 3. We report here the first Lewis acid-catalyzed C-C bond forming reactions of these species with TMSCN and silyl enol ethers as nucleophiles and utilizing TIPSOTf as well as Sc(OTf)3 as catalysts. Employing Sc(OTf)3/pybox complexes as a chiral catalyst system, regio- and enantioselective asymmetric alkylations with silyl enol ethers were achieved.

Scospirosins A (1) and B (2), two unprecedented spiro ent-clerodane dimers with 6/6/10/6 and 6/6/6/6/6 ring systems, respectively, were isolated from Isodon scoparius. Their structures were unambiguously established by spectroscopic, X-ray crystallographic, and chemical approaches. A bioinspired protecting-group-free strategy for their synthesis was achieved on a gram scale and featured the application of green methods, including neat reaction, sensitized photooxygenation, and electrochemical oxidation. 2 exhibited selective immunosuppressive activity against the proliferation of T lymphocytes (IC50 = 1.42 μM).

Cage-opened bisfulleroids are one of suitable building blocks for making a large hole on fullerenes. This work focuses on the Diels-Alder reaction of C60 with azines, among synthetic methods developed thus far, to provide bisfulleroids. Surprisingly, the computational study predicted that the reaction proceeds with normal electron demand in contrast to hitherto considered inverse-electron-demand pathway. The benzoannulation to the pyridazine ring, i. e., phthalazine, resulted in the remarkably shortened reaction time due to the better interaction between the HOMO of phthalazine and the LUMO of C60 as well as stronger 2,3-diaza-1,3-butadiene character in the phthalazine as confirmed crystallographically. Contrary to expectations, the benzobisfulleroid was converted into corresponding orifice-enlarged derivative via the photooxygenation slightly faster than the fulleroid derived from pyridazine.

We report the shortest synthesis of glycosidase inhibitor (+)-hyacinthacine A1 using a highly chemoselective N-heterocyclic carbene-catalyzed cross-benzoin reaction as well as a furan photooxygenation-amine cyclization strategy. This is the first such cyclization on a furylic alcohol, an unprecedented reaction due to the notorious instability of the formed intermediates. The photooxygenation strategy was eventually incorporated into a three-step one-pot process that formed the requisite pyrrolizidine framework of (+)-hyacinthacine A1.

Chemobiocatalytic selective transformation is an attractive yet challenging task, due to the incompatibility issues between different types of catalysts. In this work, one-pot, multi-step cascades integrating biocatalysis with organo-, base- and photocatalysis in a plug-and-play fashion were constructed for the controllable synthesis of eight C4 chemicals from furfural. Furfural was converted to 5-hydroxy-2(5H)-furanone (HFO) by sequential biocatalytic oxidation and photooxygenation in phosphate buffer, in >90% yields. Ring opening and concurrent isomerization of HFO to fumaric semialdehyde (FSA) were readily realized under mild conditions by a weakly basic resin (e.g., DVB resin). The versatile intermediate FSA could be oxidized to fumaric acid (FA) using a laccase–2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) system, which was further upgraded to amino acids including L-aspartic acid (L-Asp) and β-alanine (β-Ala) by whole-cell catalysis. Notably, amino acids were obtained from biobased furfural in a one-pot, four-step process with yields of up to 75%, without the isolation of any intermediates. Besides, the scale-up synthesis of L-Asp was demonstrated. This work demonstrates the great potential of the combination of chemo- and biocatalysis for selective furfural valorization.

Three unprecedented cytochalasan homodimers, bisaspochalasins A-C (1-3), and two known monomers, aspochalasins B and D (4 and 5), were isolated from an endophytic Aspergillus flavipes. Bisaspochalasin A (1) contains a 13-hydroxy-3,24-dioxatricyclo[11.10.11,13.02,15]tetracos-4-one cross-linkage, representing an unprecedented carbon skeleton. Bisaspochalasins B (2) and C (3) share a thioether bridge, while 3 has a peroxy modification at C-7, which may be generated by Schenck-ene photooxygenation. Their structures, including their absolute configurations, were elucidated by HRESIMS, NMR, chemical transformation, and X-ray crystallography. Bisaspochalasin A showed inhibitory activity against human T cell proliferation with an IC50 value of 15.8 μM while maintaining low cytotoxicity to T cells.

In this review we present relevant and recent applications of porphyrin derivatives as photocatalysts in organic synthesis, involving both single electron transfer (SET) and energy transfer (ET) mechanistic approaches. We demonstrate that these highly conjugated photosensitizers show increasing potential in photocatalysis since they combine both photo- and electrochemical properties which can substitute available metalloorganic photocatalysts. Batch and continuous-flow approaches are presented highlighting the relevance of enabling technologies for the renewal of porphyrin applications in photocatalysis. Finally, the reaction scale in which the methodologies were developed are highlighted since this is an important parameter in the authors’ opinion.

Lavender oil, obtained from the flowers of Lavandula angustifolia (Family: Lamiaceae) by steam distillation, The major component of lavender oil is linalyl acetate was isolated and subjected to oxidation thermally and photochemically using (mcpba and H2O2) respectively to produce mixture of 6,7-epoxy-3,7-dimethyl-1-octene-3-yl acetate (3) and 1,2-epoxy-3,7-dimethyl-6-octene-3-yl acetate (4) photochemically, while produced epoxide 4 only thermally. On the other hand, photooxygenation of 1 using different singlet oxygen sensitizers gave two hydroperoxide derivatives of 6-hydroperoxy-3,7-dimethylocta-1,7-diene-3-yl acetate (5) and 7-hydroperoxy-3,7-dimethylocta-1,5-diene-3-yl acetate (6) in the presence of tetraphenyl porphin (TPP), whereas gave hydroperoxide 6 only using hematoporphyrin (HP). Studies on the antimicrobial especially Microsporum canis and Microsprum gallinna showed that linalyl acetate and its epoxide and hydroperoxide derivatives have a good antibacterial action. Keywords: Medicinal plants, Monoterpene, Linalyl acetate, Essential oil, Epoxidation, Antibacterial, m-Chloroperbenzoic acid, Photooxygenation, Epoxide

Petrochemical based polymers, paints and coatings are cornerstones of modern industry but our future sustainable society demands for greener processes and renewable feedstock materials. A challenge is to access platform monomers from biomass resources while integrating the principles of Green Chemistry in their chemical synthesis. Here, we present a synthesis route starting from biomassderived furfural towards the commonly used monomers maleic anhydride and acrylic acid, implementing environmentally benign photooxygenation, aerobic oxidation and ethenolysis reactions. Maleic anhydride and acrylic acid, transformed into sodium acrylate, were isolated in yields of 85% (2 steps) and 81% (4 steps), respectively. With minimal waste and high atom efficiency, this biobased route provides a viable alternative to access key monomers.

Misfolded proteins produce aberrant fibrillar aggregates, called amyloid, that contain cross-beta-sheet higher order structures. The species generated in the aggregation processes (i.e., oligomers, protofibrils, and fibrils) are cytotoxic and can cause various diseases. Interfering with the amyloid formation of proteins could be a drug development target for treating diseases caused by aberrant protein aggregation. In this review, we introduce a variety of chemical catalysts that oxygenate amyloid proteins under light irradiation using molecular oxygen as the oxygen atom donor (i.e., photooxygenation catalysts). Catalytic photooxygenation strongly inhibits the aggregation of amyloid proteins due to covalent installation of hydrophilic oxygen atoms, and attenuates the neurotoxicity of the amyloid proteins. Recent in vivo studies in disease-model animals using the photooxygenation catalysts showed promising therapeutic effects, such as memory improvement and lifespan extension. Moreover, photooxygenation catalysts with new modes of action, including interfering with the propagation of amyloid core seeds and enhancing the metabolic clearance of amyloids in the brain, have begun to be identified. Manipulation of catalytic photooxygenation with secured amyloid-selectivity is indispensable for minimizing the side effects in clinical application. Here we describe several strategies for designing catalysts that selectively photooxygenate amyloid without reacting with other non-amyloid biomolecules.

A new series of 1,2,4-trioxanes 9a1-a4, 9b1-b4, 10–13 and 9c1-c4 were synthesized and evaluated against multidrug-resistant Plasmodium yoelii nigeriensis in Swiss mice via oral and intramuscular (i.m.) routes. Adamantane-based trioxane 9b4, the most active compound of the series, provided 100% protection to the infected mice at the dose 48 mg/kg × 4 days and 100% clearance of parasitemia at the dose 24 mg/kg × 4 days via oral route. Adamantane-based trioxane 9b4, is twice active than artemisinin. We have also studied the photooxygenation behaviour of allylic alcohols 6a-b (3-(4-alkoxynaphthyl)-but-2-ene-1-ols) and 6c (3-[4-(tert-butyl-dimethyl-silanyloxy)-naphthalen-1-yl]-but-2-en-1-ol). Being behaving as dienes, they furnished corresponding endoperoxides, while behaving as allylic alcohols, they yielded β-hydroxyhydroperoxides. All the endoperoxides (7a-c) and β-hydroxyhydroperoxides (8a-c) have been separately elaborated to the corresponding 1,2,4-trioxanes, except from endoperoxide 7c. It is worthy to note that TBDMS protected naphthoyl endoperoxide 7c unable to deliver 1,2,4-trioxane, which demonstrated the strength of the O-Si bond is not easy to cleave under acidic condition.

The photooxygenation of naphthalene to the corresponding endoperoxide (EPO) under various conditions is described. Substantial conversion is only observed at -10 degrees C and after more than two days, indicating that the [4+2] cycloaddition of singlet oxygen to this acene proceeds much more slowly than corresponding reactions of substituted naphthalenes, a rate constant of k = 5.4 +/- 0.3 M(-1)s(-1) was determined by competition kinetics. Another problem is the thermal lability and photochemical cleavage of the naphthalene EPO. We investigated the mechanism of this radical process depending on the light source and sensitizer in comparison to known cyclohexadiene EPO. Thus, bisepoxides and keto epoxides are formed after homolysis of the O-O bond by irradiation with sodium lamps or blue LEDs and subsequent cyclization. This process is accelerated by the sensitizers methylene blue and 9,10-dicyanoanthracene, indicating an electron transfer mechanism. Finally, the cleavage of the peroxidic bond is inhibited with red LEDs, and photooxygenation under such conditions affords 20 % EPO. Thus, we could demonstrate that contrary to literature statements singlet oxygen does indeed react with naphthalene.

There is an ongoing interest in 1 O2 sensitizers, whose activity is selectively controlled by their interaction with DNA. To this end, we synthesized three isomeric pyridinium alkynylanthracenes 2 o-p and a water-soluble trapping reagent for 1 O2 . In water and in the absence of DNA, these dyes show a poor efficiency to sensitize the photooxygenation of the trapping reagent as they decompose due to electron transfer processes. In contrast, in the presence of DNA 1 O2 is generated from the excited DNA-bound ligand. The interactions of 2 o-p with DNA were investigated by thermal DNA melting studies, UV/vis and fluorescence spectroscopy, and linear and circular dichroism spectroscopy. Our studies revealed an intercalative binding with an orientation of the long pyridyl-alkynyl axis parallel to the main axis of the DNA base pairs. In the presence of poly(dA : dT), all three isomers show an enhanced formation of singlet oxygen, as indicated by the reaction of the latter with the trapping reagent. With green light irradiation of isomer 2 o in poly(dA : dT), the conversion rate of the trapping reagent is enhanced by a factor >10. The formation of 1 O2 was confirmed by control experiments under anaerobic conditions, in deuterated solvents, or by addition of 1 O2 quenchers. When bound to poly(dG : dC), the opposite effect was observed only for isomers 2 o and 2 m, namely the trapping reagent reacted significantly slower. Overall, we showed that pyridinium alkynylanthracenes are very useful intercalators, that exhibit an enhanced photochemical 1 O2 generation in the DNA-bound state.

Organocatalytic α-oxygenation of chiral aldehydes with photochemically generated singlet oxygen allows synthesizing chiral 3-substituted 1,2-diols. Stereochemical results indicate that the reaction in the presence of diarylprolinol silyl ethers is highly diastereoselective and that the configuration of a newly created stereocenter at the α-position depends predominantly on the catalyst structure. The absolute configuration of chiral 1,2-diols has been unambiguously established based on electronic circular dichroism (ECD) and TD-DFT methods.

The photochemical behavior of several dienones was studied under aerobic conditions. 2-Allylidene-1,3-cycloalkanediones prepared via Knoevenagel-type condensation between simple readily available 1,3-dicarbonyl substrates and á,â-unsaturated aldehydes afforded 1,2,4-trioxane derivatives upon UVA irradiation in the presence of oxygen. This domino self-sensitized photooxygenation cascade of conjugated carbonyl systems proceeds stereoselectively and involves the formation of two new oxa-cycles, three new bonds (two C-O), and three stereocenters. Fil: Riveira, Martín Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentina Fil: Martiren, Nadia Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentina Fil: Mischne, Mirta Paulina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentina

A continuous flow photooxygenation of 7-aminothieno[3,2-c]pyridin-4(5H)-ones to produce 7-iminothieno[3,2-c]pyridine-4,6(5H,7H)-diones has been developed, utilizing ambient air as the sole reactant. N-H Imines are formed as the major products, and excellent functional group tolerance and conversion on gram-scale without the need for chromatographic purification allow for facile late-stage diversification of the aminothienopyridinone scaffold. Several analogs exhibit potent in vitro inhibition of the cancer-associated protein tyrosine phosphatase PTP4A3, and the SAR supports an exploratory docking model.

A series of C-2' modified cinchonine-derived phase-transfer catalysts were synthesized and used in the enantioselective photo-organocatalytic aerobic oxidation of β-dicarbonyl compounds with excellent yields (up to 97%) and high enantioselectivities (up to 90% ee). Furthermore, the reaction was carried out in a flow photomicroreactor, in which the heterogeneous gas-liquid-liquid asymmetric photocatalytic oxidation reaction was performed affording good yields (up to 97%) and enantioselectivities (up to 86% ee) within 0.89 min.

Five different model reactions (photodecarboxylation, inter- and intramolecular [2+2] cycloadditions, TiO2 photocatalytic reduction and type II photooxygenation) were investigated in the advanced Vapourtec UV-150 photo reactor with their conversion and throughput potentials reported. Compared to known batch reactions in laboratory reactors, significantly higher calculated productivities were achieved despite a rather small 10 mL reactor coil. The device enables rapid, convenient, reliable and reproducible flow photochemistry studies across the entire wavelengths spectrum and on flexible scales.

International audience; The quest for molecules able to trap, store and release singlet oxygen is of utmost interest due to their applicability in various domains such as materials science and photomedicine. The aim of this study was to prepare and to study a new family of singlet oxygen donors based on the 1,2-dihydropyridine motif. The experiments demonstrated the influence of substituents and solvents on the photooxygenation rate constants. The process can be operated reversibly by thermolysis of the in-situ formed endoperoxide leading to a release of singlet oxygen and formation of the parent 1,2 dihydropyridine compound. A bifunctional structure based on a phenalenone photosensitizer covalently connected to a 1,2 dihydropyridine module was synthesized via a multi-step sequence. Upon irradiation with blue light, singlet oxygen was produced leading to the formation of the endoperoxide intermediate. In the dark cycle, the endoperoxide underwent cycloreversion reaction affording the parent 1,2-dihydropyridine unit paving the way to a continuous production of singlet oxygen during the light/dark cycles.

Photooxygenation reactions involving singlet oxygen (1O2) are utilized industrially as a mild and sustainable access to oxygenated products. Due to the usage of organic dyes as photosensitizers, these transformations can be successfully conducted using natural sunlight. Modern solar chemical reactors enable outdoor operations on the demonstration (multigram) to technical (multikilogram) scales and have subsequently been employed for the manufacturing of fine chemicals such as fragrances or biologically active compounds. This review will highlight examples of solar photooxygenations for the manufacturing of industrially relevant target compounds and will discuss current challenges and opportunities of this sustainable methodology.

International audience; This review aims to showcase the high potential of beta-hydroperoxy alcohols (HPA) as intermediates in molecular chemistry in both academic and industrial areas. In particular, these are crucial intermediates for the synthesis of 1,2,4-trioxanes, essential motifs in numerous anti-malarial drugs including the lead artemisinin. The aim of this review is to report the main pathways of preparation of HPAs, more particularly highlighting the selective opening of epoxides by hydrogen peroxide solutions or the use of singlet oxygen for the photooxygenation of allylic alcohols. (C) 2021 Elsevier Science. All rights reserved. (C) 2021 Published by Elsevier Ltd.

The synthesis of glycosides and modified nucleosides represents a wide research field in organic chemistry. The classical methodology is based on coupling reactions between a glycosyl donor and an acceptor. An alternative strategy for new C-nucleosides is used in this approach, which consists of modifying a pre-existent furyl aglycone. This approach is applied to obtain novel pyridazine C-nucleosides starting with 2- and 3-(ribofuranosyl)furans. It is based on singlet oxygen [4+2] cycloaddition followed by reduction and hydrazine cyclization under neutral conditions. The mild three-step one-pot procedure leads stereoselectively to novel pyridazine C-nucleosides of pharmacological interest. The use of acetyls as protecting groups provides an elegant direct route to a deprotected new pyridazine C-nucleoside.

The price of the currently best available antimalarial treatment is driven in large part by the limited availability of its base drug compound artemisinin. One approach to reduce the artemisinin cost is to efficiently integrate the partial synthesis of artemisinin starting from its biological precursor dihydroartemisinic acid (DHAA) into the production process. The optimal design of such an integrated process is a complex task that is easier to solve through simulations studies and process modelling. In this article, we present a quantitative kinetic model for the photooxygenation of DHAA to an hydroperoxide, the essential initial step of the partial synthesis to artemisinin. The photooxygenation reactions were studied in a two-phase photo-flow reactor utilizing Taylor flow for enhanced mixing and fast gas-liquid mass transfer. A good agreement of the model and the experimental data was achieved for all combinations of photosensitizer concentration, photon flux, fluid velocity and both liquid and gas phase compositions. Deviations between simulated predictions and measurements for the amount of hydroperoxide formed are 7.1 % on average. Consequently, the identified and parameterized kinetic model is exploited to investigate different behaviors of the reactor under study. In a final step, the kinetic model is utilized to suggest attractive operating windows for future applications of the photooxygenation of DHAA exploiting reaction rates that are not affected by mass transfer limitations.

The efficient synthesis of two new stereoisomeric 3-aminocyclooctanetriols and new halocyclitol derivatives of them starting from cis,cis-1,3-cyclooctadiene are reported. Reduction of cyclooctene endoperoxide, obtained by photooxygenation of cis,cis-1,3-cyclooctadiene, with zinc yielded a cyclooctene diol followed by acetylation of the hydroxyl group, which gave dioldiacetate by OsO4/NMO oxidation. The cyclooctane dioldiacetate prepared was converted to the corresponding cyclic sulphate via the formation of a cyclic sulphite in the presence of catalytic RuO4. Reaction of this cyclic sulphate with a nucleophilic azide followed by the reduction of the azide group provided the target, 3-aminocyclooctanetriol. The second key compound, bromotriol, was prepared by epoxidation of the cyclooctene diol with m-chloroperbenzoic acid followed by hydrolysis with HBr(g) in methanol. Treatment of bromotriol with NaN3 and the reduction of the azide group yielded the other 3-aminocyclooctanetriol desired. Hydrolysis of the epoxides with HCl(g) in methanol gave stereospecifically new chlorocyclooctanetriols.

For the inhibition of myostatin, which is an attractive strategy for the treatment of muscle atrophic disorders including muscular dystrophy, myostatin-binding peptides were synthesized with an on/off-switchable photooxygenation catalyst at different positions on the peptide chain. These functionalized peptides oxygenated and inactivated myostatin upon irradiation with near-infrared light. Among the peptides tested, a peptide (5) with the catalyst moiety at the 16 position induced myostatin-selective photooxygenation, and efficiently inhibited myostatin. These peptides exhibited low phototoxicity. Such functionalized peptides would provide a precedented strategy for myostatin-targeting therapy, in which myostatin is irreversibly and catalytically inactivated by photooxygenation.

French National Research Agency (ANR) ANR-18-CE07-0013-01 French National Research Agency (ANR) Universite de Nantes Centre National de la Recherche Scientifique (CNRS) FONDEQUIP EQM160099

The synthesis of the biologically active alkaloid simulenoline, isolated from the roots of Zanthoxylum simulans, is reported. The natural product was assembled from simple commercial reagents via initial domino Knoevenagel/oxa-6p-electrocyclization followed by a one-pot singlet-oxygen ene-reaction/reduction sequence. New insights of singlet oxygen reactivity with olefinic substrates have been revealed. Fil: Riveira, Martín Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentina

Substrate selectivity by means of synthetic catalysts remains a challenging topic in chemistry. Here, a catalytic system combining an iodo-BODIPY photosensitizer and quinine was evaluated in the competitive photooxygenation of non-hydrogen and hydrogen-bond-donor substrates. The ability of quinine to activate hydrogen-bond-donor substrates towards photooxygenation was reported and the results were benchmarked with photooxygenation experiments in the absence of quinine.

Dye-sensitized photooxygenation reaction of bio-based double bond-containing substrates is proposed as sustainable functionalization of terpenes and terpenoids to transform them into polyoxygenated compounds to be employed for the synthesis of new bio-based polyesters. As proof of concept, citronellol 1 has been regioselectively converted into diol 4 using singlet oxygen (O-1(2)), a traceless reagent that can be generated from air, visible light and zeolite supported-photosensitizer (Thionine-NaY). With our synthetic approach, diol 4 has been obtained in two-steps, with good regioselectivity, using green reagents such as light and air, and finally a solvent-free oxidation step. From this compound, a citronellol-based copolyester of poly(butylene succinate) (PBS) has been synthesized and fully characterized. The results obtained evidence that the proposed copolymerization of PBS with the citronellol-based building blocks allows to obtain a more flexible and functionalizable material, by exploiting a largely available natural molecule modified through a green synthetic path.

The last decade has witnessed a remarkable development towards improved and new photochemical transformations in response to greener and more sustainable chemical synthesis needs. Additionally, the availability of modern continuous flow reactors has enabled widespread applications in view of more streamlined and custom designed flow processes. In this focused review article, we wish to evaluate the standing of the field of continuous flow photochemistry with a specific emphasis on the generation of bioactive entities, including natural products, drugs and their precursors. To this end we highlight key developments in this field that have contributed to the progress achieved to date. Dedicated sections present the variety of suitable reactor designs and set-ups available; a short discussion on the relevance of greener and more sustainable approaches; and selected key applications in the area of bioactive structures. A final section outlines remaining challenges and areas that will benefit from further developments in this fast-moving area. It is hoped that this report provides a valuable update on this important field of synthetic chemistry which may fuel developments in the future. University College Dublin

In the present study, (3aR,7aS)-1,3,3a,4,7,7a-hexahydroisobenzofuran was submitted to photooxygenation and two isomeric hydroperoxides were successfully obtained. Without any further purification, reduction of the hydroperoxides with titanium tetraisopropoxide catalyzed by dimethyl sulfide gave two alcohol isomers in high yields. After acetylation of alcohol with Ac2O in pyridine, epoxidation reaction of formed monoacetates with m-CPBA, then chromatographed and followed by hydrolysis of the acetate groups with NH3 in CH3OH resulted in the formation of epoxy alcohol isomers respectively. These epoxy alcohol isomers were subjected to trans-dihydroxylation reaction with acid (H2SO4) in the presence of water to afford triols. Acetylation of the free hydroxyl groups produced benzofuran triacetates in high yields. Ring-opening reaction of furan triacetates with sulfamic acid catalyzed in the presence of acetic acid/acetic anhydrate and subsequently hydrolysis of the acetate groups with ammonia gave the targeted cyclohexane carbasugar-based pentols. All products were separated and purified by chromatographic and crystallographic methods. Structural analyses of all compounds were conducted by spectral techniques including NMR and X-ray analyses. The biological inhibition activity of the target compounds was tested against glycosidase enzymes, α- and β-glucosidase.

For consumer safety reasons, cosmetics that are exposed to light are evaluated with respect to phototoxicity and/or photoallergy (photosensitization). For perfumes/aftershaves, however, these tests are not performed with the cosmetic product but only with single fragrance compounds, which may influence the outcome. In the presence of a sensitizer, photoinduced oxidation of unsaturated fragrances might result in the formation of unwanted products. Therefore, using real samples, we studied the photodegradation of the common fragrance octahydro tetramethyl naphthalenylethanone (OTNE) under in vitro irradiation, during indoor storage, and after application on skin. OTNE and its photoproducts were determined by liquid chromatography (LC) coupled to diode array detection (DAD). Whereas OTNE itself was photostable, irradiation in the presence of a sensitizer and of aftershave/perfume samples resulted in a strong degradation. Photooxygenation was identified as the major degradation reaction for all three trials. OTNE photooxidation products were characterized by LC-high resolution mass spectrometry (LC-HRMS) and by high-performance thin-layer chromatography (HPTLC) after derivatization with titanium ethoxide and nitrobenzyl pyridine. Both HPTLC and HRMS data indicate that OTNE hydroperoxides are formed during irradiation.

For the first time 5,7-di-tert-butyl-1,3-dimethyl-3a,9a-diphenyl-3,3a-dihydro-1H-benzo[5,6][1,4]dioxino[2,3-d]imidazol-2(9aH)-one 13 and complex 9 of 4,6-di-tert-butyl-3-nitrobenzene-1,2-diol with 1,3-dimethyl-4,5-diphenyl-1H-imidazol-2(3H)-one 10a were prepared by the reactions of 3-alkylthio-5,7-dimethyl-4a,7a-diphenyl-4a,5,7,7a-tetrahydro-1H-imidazo[4,5-e]-1,2,4-triazin-6(4H)-ones with 3,5-di-tert-butyl-1,2-benzoquinone 1 and 4,6-di-tert-butyl-3-nitro-1,2-benzoquinone 2, respectively. Photochemical transformations of compounds 9 and 10a as well as products of its photooxygenation involving singlet oxygen under UV irradiation: urea 16, isomeric 1,3-dimethyl-4,5-diphenylimidazolidin-2-ones 17 and 17′, and compound 18 were studied by the spectral-kinetic method. Data on the absorption and fluorescence properties of synthesized compounds and their photoproducts were obtained.

An oxidative cleavage of a C–C double bond is developed from the photochemical [2+2]-cycloaddition of diaryl N-tosyl enamides, aryl heteroaryl N-tosyl enamides, and N-tosyl cyclic enamides with singlet molecular oxygen, followed by a ring-opening reaction mediated by Cs2CO3 under air and sunlight without the use of photosesitizer, producing symmetrical and unsymmetrical diaryl, heterodiaryl, and cyclic ketones in good to excellent yields. Moreover, the oxidative cleavage of C–C triple bonds from 1-alkynes is demonstrated for the synthesis of symmetrical and unsymmetrical ketones from the Cu-catalyzed [3+2]-cycloaddition, Rh-catalyzed alkoxyarylation, photooxygenation, and ring-opening reaction in one-pot. Because the synthesis of the symmetrical and unsymmetrical diaryl and/or heterodiaryl ketones bearing an electron-donating group is not easy, the present method is notable.

We report tetrahalogenoferrate(III) complexes as a new kind of iron photocatalyst. These complexes are easily prepared from FeCl3 with lithium bromide or ammonium bromides, and have a good and tunable photo-sensitivity in the visible light region. Their distinct catalytic mode with FeCl3 enables a highly chemoselective photooxygenation of benzylic sp3 C–H, providing a series of carbonyls in moderate to excellent yields. The method has also been employed in the challenging aerobic oxidative transposition of vinyl halides, thus facilitating a mild and highly efficient approach to access significant α-halo ketones with a broad substrate scope. The disclosure of tetrahalogenoferrate(III) complex photocatalysts should provide inspiration for their expansion to new aerobic oxidative reactions and even anaerobic variations.

Photooxygenation of Δ8 tetrahydrocannabinol (Δ8-THC), Δ9 tetrahydrocannabinol (Δ9-THC), Δ9 tetrahydrocannabinolic acid (Δ9-THCA) and some derivatives (acetate, tosylate and methyl ether) yielded 24 oxygenated derivatives, 18 of which were new and 6 were previously reported, including allyl alcohols, ethers, quinones, hydroperoxides, and epoxides. Testing these compounds for their modulatory effect on cannabinoid receptors CB1 and CB2 led to the identification of 7 and 21 as CB1 partial agonists with Ki values of 0.043 μM and 0.048 μM, respectively and 23 as a cannabinoid with high binding affinity for CB2 with Ki value of 0.0095 μM, but much less affinity towards CB1 (Ki 0.467 μM). The synthesized compounds showed cytotoxic activity against cancer cell lines (SK-MEL, KB, BT-549, and SK-OV-3) with IC50 values ranging from 4.2 to 8.5 μg/mL. Several of those compounds showed antimicrobial, antimalarial and antileishmanial activities, with compound 14 being the most potent against various pathogens.

A series of novel iodinated NO2-substituted aza-BODIPYs have been synthesized and characterized. Highly desirable photophysical and photochemical properties were induced in NO2-substituted aza-BODIPYs by iodination of the pyrrole rings. In particular, high values of singlet oxygen quantum yields (ΦΔ) ranging from 0.79 to 0.85 were measured. The photooxygenation process proceeds via Type II mechanism under the experimental conditions applied. The compounds studied exhibited an absorption band within the so-called "therapeutic window", with λmax located between 645 nm to 672 nm. They were non-fluorescent at room temperature with excited singlet state lifetimes within the picosecond range as measured by femtosecond transient absorption. Nanosecond laser flash photolysis experiments revealed T1 → Tn absorption spanning from ca. 400 nm to ca. 500 nm and allowed determination of the triplet state lifetimes. The estimated triplet lifetimes (τT) in deaerated acetonitrile ranged between 2.74 μs to 3.50 μs. As estimated by the CV/DPV measurements, all iodinated aza-BODIPYs studied exhibited one irreversible oxidation and two quasi-reversible reductions processes. Estimation of the EHOMO gave the value of - 6.06 to - 6.26 eV while the ELUMO was found to be located at ca. - 4.6 eV, respectively. Thermogravimetric (TGA) analysis revealed that iodinated aza-BODIPYs were stable up to approximately 300 °C. All compounds studied exhibit high photostability in toluene solution.

A method for the synthesis of 1,2-diketones through the mild and metal-free catalytic photooxygenation of alkynes is described. This reaction, using 9,10-dicyanoanthracene as a catalytic sensitizer with/without biphenyl as a co-sensitizer, readily furnished a variety of desired products upon visible-light irradiation. Mechanistic studies indicated that a radical cation process might have been involved. This report provides the first examples of the transformation of alkynes via acetenyl radical cation intermediates, which have thus far not been explored in organic synthesis.

A multicatalytic photooxygenation of substituted phenols in the presence of rose bengal and cesium carbonate under green LED light is reported. This transformation enabled the introduction of both atoms of singlet oxygen and led to the one-pot synthesis of epoxyquinols in a stereoselective way.