Unveiling the regioselectivity of rhodium(I)-catalyzed [2 + 2 + 2] cycloaddition reactions for open-cage C₇₀ production

• Cristina Castanyer,
• Anna Pla-Quintana,
• Anna Roglans,
• Albert Artigas and
• Miquel Solà

Beilstein J. Org. Chem. 2024, 20, 272–279, doi:10.3762/bjoc.20.28

• cages. However, in other cases, some of the bonds between the C atoms of the cage are broken and the cage is opened. The first example of an open-cage fullerene was reported in 1995 by Hummelen, Prato, and Wudl [21] through the reaction of C60 with azides followed by photooxygenation. Since then, many

Tandem Hock and Friedel–Crafts reactions allowing an expedient synthesis of a cyclolignan-type scaffold

• Viktoria A. Ikonnikova,
• Cristina Cheibas,
• Oscar Gayraud,
• Alexandra E. Bosnidou,
• Nicolas Casaretto,
• Gilles Frison and
• Bastien Nay

Beilstein J. Org. Chem. 2024, 20, 162–169, doi:10.3762/bjoc.20.15

• one-pot transformation from readily available benzyl(prenyl)malonate substrates. After the photooxygenation of the prenyl moiety, the resulting hydroperoxide was directly engaged in a Hock cleavage by adding a Lewis acid. The presence of an aromatic nucleophile in the reaction mixture and that of a

• mention that allylic hydroperoxides are conveniently produced by the photooxygenation of alkene substrates [14][15][16]. Taking all these informations together, since alkenes can be easier intermediates than aldehydes to handle, we envisaged to use a prenyl (= 3-methyl-2-buten-1-yl) group as an aldehyde

• ), successively involving a Schenck-ene photooxygenation of an alkene A, an acid-catalyzed Hock cleavage of hydroperoxide B generating an aldehyde derivative C, and an acid-catalyzed Friedel–Crafts reaction in the presence of an aromatic nucleophile leading to D [17]. In principle, a second Friedel–Crafts

Efficient synthesis of aziridinecyclooctanediol and 3-aminocyclooctanetriol

• Emine Salamci and
• Ayse Kilic Lafzi

Beilstein J. Org. Chem. 2022, 18, 1539–1543, doi:10.3762/bjoc.18.163

• cyclooctene endoperoxide, prepared by photooxygenation of cis,cis-1,3-cyclooctadiene, with zinc gave a cyclooctenediol and then benzylation of the hydroxy group yielded dibenzylated cyclooctene. Oxidation of the latter compound by OsO4/NMO followed by mesylation of the hydroxy group provided bis(benzyloxy

Stereoselective syntheses of 3-aminocyclooctanetriols and halocyclooctanetriols

• Emine Salamci and
• Yunus Zozik

Beilstein J. Org. Chem. 2021, 17, 705–710, doi:10.3762/bjoc.17.59

• 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 hydroxy group, which gave dioldiacetate by OsO4/NMO oxidation. The cyclooctane dioldiacetate prepared was converted to

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

• functionalization. These functionalizations, beside the addition reaction, could involve photooxygenation reactions (Scheme 5) [1][22][23][24][25], previously studied in our laboratory. These reactions could result in a completely new spectrum of products, with preserved bicyclo[3.2.1.]octadiene skeleton, crucial

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• 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. Keywords: energy transfer; photocatalysis; photooxygenation; photoredox; porphyrins; Introduction In

• , for a broad coverage of different aspects and relevant examples on photooxygenation in organic synthesis, we recommend relevant reviews published by Greer [70] and Crutchley [71]. Undoubtedly, the large-scale preparation of ascaridole, published in 1944 by Schenck and Ziegler [72][73], is a remarkable

• example of the use of chlorophyll a in photooxygenation reactions (Scheme 28). In this seminal scaled-up preparation the authors were able to produce 10 g of ascaridole per batch, showing an additional example of batch numbering up of photoreactors with dozens of glass batch systems scattered in an open

α-Photooxygenation of chiral aldehydes with singlet oxygen

• Dominika J. Walaszek,
• Magdalena Jawiczuk,
• Jakub Durka,
• Olga Drapała and
• Dorota Gryko

Beilstein J. Org. Chem. 2019, 15, 2076–2084, doi:10.3762/bjoc.15.205

• -hydroxylation of aldehydes [14][15]. Recently, we have reported that organocatalytic photooxygenation of aldehydes affords the desired diols (after in situ reduction) in decent yield with either (R)- or (S)-selectivity depending on a catalysts used [14]. In the presence of prolinamides the (R)-enantiomer

• preexisting stereochemical elements influence the stereoselectivity of this reaction. To this end we investigated α-photooxygenation of chiral aldehydes with a stereocenter at the β-position (Scheme 1). In such a case, the outcome should depend on the relationships between the absolute configuration of the

• starting material and the catalyst. Results and Discussion Our previous studies on α-photooxygenation of achiral aldehydes with 1O2 in the presence of chiral amines supported by DFT calculations indicate that the reaction is highly enantioselective only when both enamine structural fragments (substituents

Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• oxygen-transfer (Scheme 8, lower part) [117]. Besides making use of oxygen or air together with a stoichiometric activator/reductant as described above (Scheme 7 and Scheme 8), the photooxygenation of prochiral substrates like β-ketoesters 1 with O2 or air in the presence of a chiral PTC and TPP

A flow reactor setup for photochemistry of biphasic gas/liquid reactions

• Josef Schachtner,
• Patrick Bayer and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2016, 12, 1798–1811, doi:10.3762/bjoc.12.170

• described set-up operates residence times of up to 30 min which cover the typical rates of many organic reactions. The tubular microreactor was successfully applied to the photooxygenation of hydrocarbons (Schenck ene reaction). Major emphasis was laid on the realization of a constant and highly

• gas in the liquid phase which is pressure-dependent according to Henry’s law [69]. Reaction parameters of a model photooxygenation The often poor selectivities of reactions with molecular oxygen (being a triplet biradical in its ground state) [70] have prompted applications of microflow reactors to

• within one day from commercial parts at an overall price of less than 1000 € for the microreactor, less than 5000 € for the peripheral pump and mass flow controller, and less than 500 € for each light source coil. The application of this microreactor system to the visible light-driven photooxygenation of

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• good 92% yield by using Et3N (Scheme 91) [371]. A sequence consisting of a template-mediated photooxygenation and an acid-catalyzed Kornblum−DeLaMare rearrangement of the intermediate endo-peroxides 310 was used in a one-pot transformation of 3-substituted 2-pyridones

2-Hetaryl-1,3-tropolones based on five-membered nitrogen heterocycles: synthesis, structure and properties

• Yury A. Sayapin,
• Inna O. Tupaeva,
• Alexandra A. Kolodina,
• Eugeny A. Gusakov,
• Vitaly N. Komissarov,
• Igor V. Dorogan,
• Nadezhda I. Makarova,
• Anatoly V. Metelitsa,
• Valery V. Tkachev,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2015, 11, 2179–2188, doi:10.3762/bjoc.11.236

• [14][15]. An alternative method [16] involves the photooxygenation of cyclohepta-1,3,5-triene with singlet oxygen in carbon tetrachloride solution, methanolysis of the formed isomeric endoperoxides resulted in 1,2-dihydro-3-hydroxytropone and oxidation of the latter with chromium trioxide. A

Photoinduced 1,2,3,4-tetrahydropyridine ring conversions

• Baiba Turovska,
• Henning Lund,
• Viesturs Lūsis,
• Anna Lielpētere,
• Edvards Liepiņš,
• Sergejs Beljakovs,
• Inguna Goba and
• Jānis Stradiņš

Beilstein J. Org. Chem. 2015, 11, 2166–2170, doi:10.3762/bjoc.11.234

• deprotonated efficiently in the presence of superoxide including Hantzsch 1,4-dihydropyridines [31][32]. Cation radicals have increased acidity comparing to the parent molecules from which they are derived by oxidation [33][34][35]. Consequently, their deprotonation proceeds more efficiently. Photooxygenation

• summer as well as under bright laboratory light the photooxygenation of tetrahydropyridine 1 in the presence of dioxygen proceeds spontaneously in CHCl3, CH2Cl2 or CH3CN solutions. Although much of the light emitted by the sun in UV below 300 nm is absorbed by ordinary glass, the transmitted intensity of

• the sunlight in summer at 300 nm is sufficient to initiate the photooxygenation of 1. Direct reactions of dioxygen with organic substrates in the absence of a catalyst are usually slow, unless the substrate is a particularly good reducing agent. Excited state species are easier to oxidize than the

Stereoselective synthesis of hernandulcin, peroxylippidulcine A, lippidulcines A, B and C and taste evaluation

• Marco G. Rigamonti and
• Francesco G. Gatti

Beilstein J. Org. Chem. 2015, 11, 2117–2124, doi:10.3762/bjoc.11.228

• the synthesis of hernadulcin and its hydroxy derivatives, i.e., the lippidulcines A, B and C and their taste evaluation. Results and Discussion Since our synthetic strategy for the preparation of lippidulcines 3a–c is based on the photooxygenation of 1, it was mandatory to develop and optimize the

• cleavage of the silyl protective group of 11 with tetra-n-butylammonium fluoride (TBAF) in MeCN and at room temperature, the spectroscopic data of 1 were in complete agreement with those reported in literature [6] ([α]D +130° (c 1.6, CHCl3) vs lit. [31] ([α]D +115° (c 0.64, CHCl3)). The photooxygenation

• ) vs lit. [8] [α]D +42.0° (c 3.2, CHCl3)), obtained by treatment of 12 with TBAF in MeCN, resulted very bitter, as usually are the hydroperoxides (Table 3). Thus, the crude material of the photooxygenation was treated with an over stoichiometric amount of TMSCl (Scheme 3). In these conditions, after 24

An improved procedure for the preparation of Ru(bpz)₃(PF₆)₂ via a high-yielding synthesis of 2,2’-bipyrazine

• Danielle M. Schultz,
• James W. Sawicki and
• Tehshik P. Yoon

Beilstein J. Org. Chem. 2015, 11, 61–65, doi:10.3762/bjoc.11.9

• couplings [13][14], and photooxygenation reactions [15][16]. Similarly, Zheng has reported oxidatively initiated indole synthesis [17] and [3 + 2] cycloaddition [18][19] reactions using photocatalyst 2. Finally, a variety of transition metal complexes bearing bipyrazyl ligands have been prepared and

Oxidative phenylamination of 5-substituted 1-hydroxynaphthalenes to N-phenyl-1,4-naphthoquinone monoimines by air and light “on water”

• Julio Benites,
• Juan Meléndez,
• Cynthia Estela,
• David Ríos,
• Luis Espinoza,
• Iván Brito and
• Jaime A. Valderrama

Beilstein J. Org. Chem. 2014, 10, 2448–2452, doi:10.3762/bjoc.10.255

• sensitized solar-induced photooxygenation of 1,5-DHN (1), might undergo in situ phenylamination followed by aerobic oxidation to give the expected target aminojuglone 4a and/or 4b. In order to evaluate the reactions involved in this hypothetical strategy, the solar photosensitized photooxygenation of 1,5-DHN

• (1) and the amination of juglone (2) with 4-hydroxyphenylamine on water were examined separately. It is noteworthy that similar reactions have been recently reported by using a one-flask procedure where juglone 2 was first produced by photoinduced photooxygenation of 1,5-DHN (1) in CH2Cl2/MeOH and

• then in the same flask, the arylamination of 2 to the respective aminoquinones was accomplished [14]. The on-water photooxygenation of 1,5-DHN (1) was carried out for 5 h in round-bottom flasks, under the presence of 1.6 mmol % of rose bengal (RB) as singlet oxygen sensitizer, by using sunlight

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

• Alexander O. Terent'ev,
• Dmitry A. Borisov,
• Vera A. Vil’ and
• Valery M. Dembitsky

Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6

• acetic anhydride and pyridine at room temperature (Scheme 2). It should be emphasized that a mixture of dioxolanes 5 and 6 in a ratio of 7:3 is formed already in the first step [232]. The photooxygenation of oxazolidines 7a–d through the formation of hydroperoxides 8a–d gives spiro-fused oxazolidine

• % yields. 2,4,6-Triphenylpyrylium tetrafluoroborate was used as the sensitizer for singlet oxygen generation (Scheme 54) [301]. It was found that tris(bipyrazyl)ruthenium(II) [(Ru(bpz)3(PF6)2] is an excellent photocatalyst for the synthesis of 1,2-dioxanes by aerobic photooxygenation of α,ω-dienes [302

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

• be made. Keywords: cycloaddition; flow chemistry; photocatalysis; photochemistry; photooxygenation; Introduction The use of ultraviolet light to carry out bond-forming reactions in synthetic organic chemistry has a long history dating back to the mid-19th century. The observation by Trommsdorff [1

• should be noted that an alternative photochemical oxidation using solar radiation was found to be highly efficient, second only to the industrial Dragoco protocol (mercury-arc lamp) [35]. Microflow photochemistry can add a further advantage in photooxygenation reactions through the use of dual-channel

Palladium-catalyzed formation of oxazolidinones from biscarbamates: a mechanistic study

• Benan Kilbas and
• Metin Balci

Beilstein J. Org. Chem. 2011, 7, 246–253, doi:10.3762/bjoc.7.33

• sensitized photooxygenation of the cycloheptatriene derivative 5a5b at room temperature resulted exclusively in the formation of the norcarene endoperoxide 6 [14][17]. The exact configuration of the endoperoxide 6 was determined by the single crystal X-ray analysis of the bisepoxide formed by the thermolysis

• cyanide anion as described in the literature [16]. The tetraphenylporphyrin sensitized photooxygenation of the cycloheptatriene derivative 11a11b at room temperature gave a mixture of norcarene endoperoxides 12–13 in 42 and 33% yields, respectively (Scheme 5) [22]. The exact configuration of the cyano

Synthesis of spiroannulated and 3-arylated 1,2,4-trioxanes from mesitylol and methyl 4-hydroxytiglate by photooxygenation and peroxyacetalization

• Axel G. Griesbeck,
• Lars-Oliver Höinck and
• Jörg M. Neudörfl

Beilstein J. Org. Chem. 2010, 6, No. 61, doi:10.3762/bjoc.6.61

• properties [15][16][17]. In this publication we report the use of the alcohols 3 and 6 to explore further the synthetic approach to spirocyclic fused 1,2,4-trioxanes with a series of other spirofused ring structures. Results and Discussion 3,3-Spiroannulated 1,2,4-trioxanes The photooxygenation reactions via

• benzaldehyde derivatives. 3,3-Spiroannulated 1,2,4-trioxanes by photooxygenation and peroxyacetalization.a Structural features of the 1,2,4-trioxanes 10a–h.a Yields, structural and 13C-NMR properties of 1,2,4-trioxanes 10a–h, and arthemether (AM). Acknowledgements We thank the DFG for project funding and the

Synthesis of a new class of aminocyclitol analogues with the conduramine D-2 configuration

• Latif Kelebekli,
• Yunus Kara and
• Murat Celik

Beilstein J. Org. Chem. 2010, 6, No. 15, doi:10.3762/bjoc.6.15

• . Photooxygenation of trans-7,8-diacetoxy- and cis-7,8-dichlorobicyclo[4.2.0]octa-2,4-diene afforded the bicyclic endoperoxides. Reduction of the latter with thiourea followed by a Pd(0) catalyzed ionization/cyclization reaction gave the corresponding oxazolidinone derivatives. Oxidation of the double bond with

• cyclooctatetraene (8) by the addition of mercury(II) acetate [31]. Tetraphenylporphyrin sensitized photooxygenation of diacetoxydiene 9 with singlet oxygen gave the expected endoperoxide 10. Reduction of the peroxide bond in 10 was performed with thiourea under very mild conditions to give the cis-diol 11 in 99

• in 9 with cis- configured chlorine atoms. This provides a route for the synthesis of other haloaminocyclitol derivatives. cis-Dichlorobicyclooctadiene 19 was synthesized from cyclooctatetraene 8 by the addition of chlorine following the literature procedure [39]. Photooxygenation of cis