Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• oxidation of 4-V by the photoexcited iridium(III) photocatalyst 4-II results in the nickel(III) species 4-VI. Photolysis of 4-VI generates a chloride radical, which rapidly abstracts the α-oxy C(sp3)−H of the ether to provide the alkyl radical species. The alkyl radical rebound to 4-VIII produces the nickel

Cerium-photocatalyzed aerobic oxidation of benzylic alcohols to aldehydes and ketones

• Girish Suresh Yedase,
• Sumit Kumar,
• Jessica Stahl,
• Burkhard König and
• Veera Reddy Yatham

Beilstein J. Org. Chem. 2021, 17, 1727–1732, doi:10.3762/bjoc.17.121

• •−. Photolysis of the CeIV–OBn complex (II), leads to the formation of the corresponding benzyloxy radical (III) and regenerates the CeIII species. A further abstraction of a benzylic hydrogen atom by the peroxide radical then generates the final product 2 [48]. However, at this moment we cannot exclude the

Manganese/bipyridine-catalyzed non-directed C(sp³)–H bromination using NBS and TMSN₃

• Kumar Sneh,
• Takeru Torigoe and
• Yoichiro Kuninobu

Beilstein J. Org. Chem. 2021, 17, 885–890, doi:10.3762/bjoc.17.74

• alcohols with HBr, PBr3, or other brominating reagents [7][8][9][10][11][12][13]. Direct C–H halogenation is one of the most efficient methods used for the synthesis of halogenated organic molecules. This direct method involves the reaction of an alkane with Br2, CBr4, or H2O2–HBr under photolysis or at

[2 + 1] Cycloaddition reactions of fullerene C₆₀ based on diazo compounds

• Yuliya N. Biglova

Beilstein J. Org. Chem. 2021, 17, 630–670, doi:10.3762/bjoc.17.55

• chromatography (HPLC) (methanol/toluene as the eluent) to isolate a reddish-brown powder of methanofullerene 3 in 21% yield (Scheme 4). Similar to photolysis, the thermal rearrangement of kinetic products gives [6,6]-closed isomers that are thermodynamically more stable. After some time, the team of scientists

• % yield [100]. Photolysis of derivatives of para-substituted 3-fluoromethyl-3-phenyldiazirones in the presence of C60 gave phenylmethanofullerenes 53–56 in acceptable yields (Scheme 17) [101]. The electrochemical properties of the products were characterized by cyclic voltammetry and differential pulse

• fullerene based on diazo compounds allows us to state the following: An alternative to the synthesis of methanofullerenes by the Bingel methodology is provided by the thermal [2 + 1] cycloaddition of diazo compounds to the fullerene. Then follows the photolysis or thermolysis of pyrazoline intermediates by

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• ]. Photolytic generation of difluorocarbene: Difluorodiazirine (44) is a convenient photochemical source of difluorocarbene (Scheme 17). The compound readily produces difluorocarbene upon photolysis. N2 is the leaving group and it is good for LFP studies [54]. Furthermore, pyrolysis is also suitable for

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

• Minzan Zuo,
• Krishnasamy Velmurugan,
• Kaiya Wang,
• Xueqi Tian and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• stacked in a slipped anti- or syn-head-to-tail (HT) fashion) to afford the successive photocyclodimerization, which mimics a catalytic antibody. Therefore, various head-to-head (HH)- or HT-photodimers could be obtained. Particularly, the 21–AC complex could be involved in the photolysis and produced the

Metal-free synthesis of biarenes via photoextrusion in di(tri)aryl phosphates

• Hisham Qrareya,
• Lorenzo Meazza,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 3008–3014, doi:10.3762/bjoc.16.250

• iodides) [30][31] or by the direct photolysis of arylazo sulfones [38][39][40] and employed for the desired arylations. These reactions have the advantage of being applied to non-functionalized arenes but have the drawback to require a large excess of the nucleophilic reagent (the arene Ar–H) in up to 10

Controlled decomposition of SF₆ by electrochemical reduction

• Sébastien Bouvet,
• Bruce Pégot,
• Stéphane Sengmany,
• Erwan Le Gall,
• Eric Léonel,
• Anne-Marie Goncalves and
• Emmanuel Magnier

Beilstein J. Org. Chem. 2020, 16, 2948–2953, doi:10.3762/bjoc.16.244

• expensive methods requiring a large input of energy (high temperature, high pressure). Many SF6 decomposition strategies so far developed use photoreduction, plasma discharges or even photolysis processes [10][11]. Beyond the energetic high cost of such processes, they produce side products that are highly

Nocarimidazoles C and D, antimicrobial alkanoylimidazoles from a coral-derived actinomycete Kocuria sp.: application of ¹J_C,H coupling constants for the unequivocal determination of substituted imidazoles and stereochemical diversity of anteisoalkyl chains in microbial metabolites

• Md. Rokon Ul Karim,
• Enjuro Harunari,
• Amit Raj Sharma,
• Naoya Oku,
• Kazuaki Akasaka,
• Daisuke Urabe,
• Mada Triandala Sibero and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 2719–2727, doi:10.3762/bjoc.16.222

• 8 and 9, possessing 4-acetyl and 5- or 2-amino substitutions, respectively, were synthesized for comparison, according to the reported procedures (Scheme 1) [25][26][27]. Compound 8 is known as a photolysis product of 6-methylpurine 1-oxide [28], but we prepared it by the Grignard reaction of a

Access to highly substituted oxazoles by the reaction of α-azidochalcone with potassium thiocyanate

• Mysore Bhyrappa Harisha,
• Pandi Dhanalakshmi,
• Rajendran Suresh,
• Raju Ranjith Kumar and
• Shanmugam Muthusubramanian

Beilstein J. Org. Chem. 2020, 16, 2108–2118, doi:10.3762/bjoc.16.178

• ; potassium persulfate; thiazole; vinyl azide; Introduction Vinyl azide is one of the most versatile and potent building blocks explored in the synthesis of several heterocycles [1][2][3][4][5]. It can undergo photolysis or thermolysis to afford highly strained three-membered 2H-azirine, which can act as the

The biomimetic synthesis of balsaminone A and ellagic acid via oxidative dimerization

• Sharna-kay Daley and
• Nadale Downer-Riley

Beilstein J. Org. Chem. 2020, 16, 2026–2031, doi:10.3762/bjoc.16.169

• reduction using dithionite proved too harsh for the substrate, and like the photolysis of the binaphthyl 16, degradation occurred. However, the use of triethylamine instead of aqueous sodium hydroxide resulted in the isolation of balsaminone A (4) in 13% yield, an overall 7–8% yield over 3 steps, completing

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• interest in g-C3N4 photocatalysts was generated in 2009 by Wang, Domen, and co-workers, who reported the metal-free photolysis of water was possible with the all-organic semiconductor material, a sacrificial electron donor, and visible light irradiation [120]. Prior to this report, poly(p-phenylene) had

[3 + 2] Cycloaddition with photogenerated azomethine ylides in β-cyclodextrin

• Margareta Sohora,
• Leo Mandić and
• Nikola Basarić

Beilstein J. Org. Chem. 2020, 16, 1296–1304, doi:10.3762/bjoc.16.110

• cycloadducts. On the other hand, upon photolysis in the presence of H2O and a base, the photoreaction is about twenty times more efficient, but it delivers simple decarboxylation product 4 only. Attempts to use β-CD to complex both reactants and enhance the efficiency for the cycloaddition failed. In the

• photolysis of 1, β-CD had no effect (Table 1), which may be ascribed to a small size of 1 that cannot fit well in the large cavity of β-CD and form a stable complex. Molecules 2 and 3 are larger, and anticipated to form more stable inclusion complexes with β-CD. Therefore, we performed 1H NMR titrations to

• possible and that photolysis of 2 in such a complex yields 2AMY, which is then readily intercepted with AN in the same complex. Note that cycloadduct 11 was also detected (≈4%), upon irradiation of 3 with AN in the presence of β-CD, suggesting that the photodecarboxylation reaction and subsequent [3 + 2

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

• , arylalkyl, and diaryl oxime radicals was also studied by EPR spectroscopy [53]. Radicals were generated under inert atmosphere directly in the EPR cavity by photolysis of the added di-tert-butyl peroxide (Scheme 1). The authors pointed out the complexity of the processes of iminoxyl radicals’ decomposition

• iminoxyl radical 90. Presumably, the radical 90 underwent cyclization involving the azo group to form indazole 91. During the photolysis of a mixture of di-tert-butyl peroxide with oxime 92 containing an alkenyl fragment at temperatures from −30 to −10 °C, two signals were observed in the EPR spectrum with

• -system. According to EPR data, the authors suggested that iminoxyl radicals 101 generated from oximes 100 by photolysis with the addition of the di-tert-butyl peroxide gave nitroxides 102 [123]. The widespread use of iminoxyl radicals in organic synthesis involving a radical addition to a C=C bond

A simple and easy to perform synthetic route to functionalized thienyl bicyclo[3.2.1]octadienes

• Dragana Vuk,
• Irena Škorić,
• Valentina Milašinović,
• Krešimir Molčanov and
• Željko Marinić

Beilstein J. Org. Chem. 2020, 16, 1092–1099, doi:10.3762/bjoc.16.96

• , which could be accompanied by a photochemical annulation. The photolysis spectra of compound's 3 isomers are shown in Figure 5, as representative examples. Figure 6 presents the UV spectra of products' 3–7 trans-isomers. All the isomers showed an absorption maxima between 300–400 nm. It can be noticed

• bicyclo[3.2.1]octenes/octadienes with cholinesterase inhibitory properties. 1H NMR spectra (CDCl3) for the trans-isomers 3–6. UV spectra in ethanol (95%) of the cis- and trans-isomers of compound 3. Photolysis spectra of cis-3 (a) and trans-3 (b) in ethanol (95%). UV spectra in ethanol (95%) of the trans

• compounds 1, 8, and 9. UV spectra of compounds 1 and 12 in ethanol (95%). Photolysis spectra of compound 12 in ethanol (95%). Synthesis of annulated furobenzobicyclo[3.2.1]octadiene compounds. Synthesis of annulated thiophenebicyclo[3.2.1]octadiene compounds 8-10. Synthesis of compound 11. Synthesis of

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• -butyl ketone (1) yields acetone (4) and propylene (3). Reaction (2) of Scheme 1 refers to a type II intramolecular rearrangement of crotonaldehyde (5) to 3-butenal (7). The triplet state energy donors were quenched by diacetyl and cis-2-butene. In 1970, Cocivera and Trozzollo studied the photolysis of

• the formation of the radical pair mentioned in Scheme 2 or by a triplet state-energy acceptor, such as 2,3-diazabicyclo[2.2.1]hept-2-ene (DBH, 18, Scheme 4). Trying to shed more light on the photolysis of benzaldehyde, Atkins and co-workers studied the photolysis of benzaldehyde (8) with electron spin

• resonance flash photolysis (ESRFP) and CIDNP in various solvents, depending on the efficiency of the solvents as hydrogen donors [19]. More specifically, triplet state benzaldehyde (9) dissolved in an efficient hydrogen donor solvent can lead to an α-hydroxybenzyl radical (11) as the only detectable species

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• photolysis. The mechanism involved in this transformation is shown in Figure 20. Aryl C–H halogenation Aerobic bromination of arenes: In another experiment, Ohkubo et al. reported that for aerobic aryl C–H brominations, HBr can be utilized with photoredox catalyst 2 in the presence of molecular oxygen to

• flash photolysis measurements, and the monobrominated product selectivity was controlled by the difference in electron transfer oxidation reactivity of 127 and 126 of electron transfer state of photocatalyst (Me·+ moiety) and also on the radical cations reactivity with Br−. Recently, König’s group

• bonds in the presence of photoredox catalyst 8, with a similar mechanism as shown in Figure 22, and the photocatalytic mechanism was elucidated by nanosecond laser flash photolysis (Scheme 24) [168]. Fluorine-18 is an important radioisotope used in the radiopharmaceutical industry (e.g., for drug

Synthesis of 3-alkenylindoles through regioselective C–H alkenylation of indoles by a ruthenium nanocatalyst

• Abhijit Paul,
• Debnath Chatterjee,
• Srirupa Banerjee and
• Somnath Yadav

Beilstein J. Org. Chem. 2020, 16, 140–148, doi:10.3762/bjoc.16.16

• photolysis, was characterised by TEM (Figure S1, Supporting Information File 1), which showed polydispersed spherical particles of a size distribution mainly in the range of 10–25 nm, with a mean diameter of 15 nm. The size distribution of the particles from Figure S1, Supporting Information File 1, is

A photochemical determination of luminescence efficiency of upconverting nanoparticles

• Baptiste Amouroux,
• Clément Roux,
• Jean-Claude Micheau,
• Fabienne Gauffre and
• Christophe Coudret

Beilstein J. Org. Chem. 2019, 15, 2671–2677, doi:10.3762/bjoc.15.260

• cyclohexane. Photolysis experiments The description of the setup is summarized in Figure 2. The sample in a thermostated quartz cuvette was irradiated with a fibered, collimated CW 976 nm-laser beam. The transmitted laser intensity was measured using a calibrated power-meter. This measurement informed us

• the freshly prepared actinometer 1-c and nanoparticles. Practically, the preparation of the 1-o/c solution was achieved using bench-top UV source (TLC lamp), either on the UCNP-1 mixture or before mixing the dye with the UCNPs. Concentrations were standardized prior the photolysis experiments using

• 650 nm under CW 976 nm laser at 4.71 W. Initial slope (red line) was determined on the 2nd order polynomial fit of experimental points (dark curve). Parameters of UCNP used in the photolysis experiment. Obtained results. Supporting Information Supporting Information File 540: Experimental details

Arylisoquinoline-derived organoboron dyes with a triaryl skeleton show dual fluorescence

• Vânia F. Pais,
• Tristan Neumann,
• Ignacio Vayá,
• M. Consuelo Jiménez,
• Abel Ros and
• Uwe Pischel

Beilstein J. Org. Chem. 2019, 15, 2612–2622, doi:10.3762/bjoc.15.254

• of 0.2–0.4, reaching in some cases values as high as 0.5–0.6. Laser-flash photolysis provided evidence for the existence of excited triplet states. The dyes form fluoroboronate complexes with fluoride anions, leading to the observation of the quenching of the long-wavelength emission band and

• ratiometric response by the build-up of a hypsochromically shifted emission signal. Keywords: anions; dyes; fluorescence; laser-flash photolysis; organoboron; Introduction Boron-containing tri- and tetra-coordinated chromophores have attracted considerable interest due to their often peculiar and highly

• in some cases very close to the resolution limit of our time-correlated single-photon-counting setup. The LW emission showed considerably longer lifetimes in the 3–6 ns range. The photophysical behavior of the dyes is tentatively summarized in Scheme 4. Laser-flash photolysis The photophysical

Experimental and computational electrochemistry of quinazolinespirohexadienone molecular switches – differential electrochromic vs photochromic behavior

• Eric W. Webb,
• Jonathan P. Moerdyk,
• Kyndra B. Sluiter,
• Benjamin J. Pollock,
• Amy L. Speelman,
• Eugene J. Lynch,
• William F. Polik and
• Jason G. Gillmore

Beilstein J. Org. Chem. 2019, 15, 2473–2485, doi:10.3762/bjoc.15.240

• –oxidation peaks was observed upon multiple scans, representing the reduction and oxidation of the electrogenerated long-wavelength form 1b generated in situ. As expected, either photolysis or multiple CV scans led to the same LW reduction and oxidation peaks (within the error bars indicated in Table 1). We

• for spirocyclic ring-opening exist, leading to 4b or 5b. Thus, we postulated that the electrogenerated LW form was in fact 5b. Having found two distinct LW forms depending on generation by photolysis or electrolysis of SW 3b, we turned our attention to whether a similar phenomenon was observed for 3a

• . Indeed, different redox peaks were observed in the same general LW region for the CV of photolyzed versus electrogenerated LW forms of 3a, consistent with the electrogenerated formation of 5a compared against the known formation of 4a via photolysis. The voltammograms of 3a (Figure 4) did however differ

Excited state dynamics for visible-light sensitization of a photochromic benzil-subsituted phenoxyl-imidazolyl radical complex

• Yoichi Kobayashi,
• Yukie Mamiya,
• Katsuya Mutoh,
• Hikaru Sotome,
• Masafumi Koga,
• Hiroshi Miyasaka and
• Jiro Abe

Beilstein J. Org. Chem. 2019, 15, 2369–2379, doi:10.3762/bjoc.15.229

• emission spectra was measured to separate the fluorescence and phosphorescence. The shutter was controlled by LabVIEW. Nanosecond transient absorption measurements The laser flash photolysis experiments were carried out with a TSP-2000 time resolved spectrophotometer system (Unisoku Co., Ltd.). A 10 Hz Q

Enantioselective Diels–Alder reaction of anthracene by chiral tritylium catalysis

• Qichao Zhang,
• Jian Lv and
• Sanzhong Luo

Beilstein J. Org. Chem. 2019, 15, 1304–1312, doi:10.3762/bjoc.15.129

• cycloadduct 5a in excellent enantioselectivity (97% ee), however, with only 9% yield (Table 1, entry 1). Subsequent efforts to improve the activity by enhancing the dissociation efficiency of latent carbocation through heating or photolysis did not lead to any improvement. We next investigated whether the