A new route for the synthesis of 1-deazaguanine and 1-deazahypoxanthine

• Raphael Bereiter,
• Marco Oberlechner and
• Ronald Micura

Beilstein J. Org. Chem. 2022, 18, 1617–1624, doi:10.3762/bjoc.18.172

• reports found in the literature suffer from the requirement of hazardous intermediates and harsh reaction conditions. Here, we report a new six-step synthesis for c1G base, starting from 6-iodo-1-deazapurine. The key transformations are copper catalyzed C–O-bond formation followed by site-specific

• 3,4-dihydropyran in dimethylformamide to obtain the corresponding tetrahydropyranyl-protected amine 17. Subsequently, a copper-catalyzed C–O bond formation at C6 using benzyl alcohol in the presence of caesium carbonate, copper(I) iodide, and 1,10-phenanthroline furnished benzyl ether 18 in excellent

• ) starts from the tetrahydropyranyl-protected 6-iodo-1-deazapurine 17 which was converted into the O6-benzyl derivative 31 using the copper-catalyzed C–O-bond formation as described above (Scheme 6). Without purification the crude product was treated with hydrochloric acid in methanol to remove the

A Streptomyces P450 enzyme dimerizes isoflavones from plants

• Run-Zhou Liu,
• Shanchong Chen and
• Lihan Zhang

Beilstein J. Org. Chem. 2022, 18, 1107–1115, doi:10.3762/bjoc.18.113

• ’’-coupled dimer (Table S5, Supporting Information File 1). For the dimer 3, three hydroxy and fifteen sp2 protons indicated a C–O bond linkage. An analysis of 1H,1H-COSY and HMBC spectra suggested it to be a 3’–O–7’’-coupled dimer (Table S6, Supporting Information File 1). The absolute configuration of 1

On Reuben G. Jones synthesis of 2-hydroxypyrazines

• Pierre Legrand and
• Yves L. Janin

Beilstein J. Org. Chem. 2022, 18, 935–943, doi:10.3762/bjoc.18.93

• isomer 4{1,2} made it impossible to obtain a complete 13C NMR spectrum. On the other hand, following a sample recrystallization from acetic acid, an X-ray derived structure was obtained as seen with the ORTEP depiction in Figure 1. In this structure, the C–O bond length of 1.2425 Å is typical of a double

Synthesis of bis-spirocyclic derivatives of 3-azabicyclo[3.1.0]hexane via cyclopropene cycloadditions to the stable azomethine ylide derived from Ruhemann's purple

• Alexander S. Filatov,
• Olesya V. Khoroshilova,
• Anna G. Larina,
• Vitali M. Boitsov and
• Alexander V. Stepakov

Beilstein J. Org. Chem. 2022, 18, 769–780, doi:10.3762/bjoc.18.77

• -protonated 1 and C-protonated 1'' tautomers do not contain an enol functional group. It is therefore likely that the lowest stability of the O-protonated form 1' compared to tautomers 1 and 1'' is due to the favorability of the C=O bond over the C=C bond. Next, using the equations recommended by Parr [47

Unusual highly diastereoselective Rh(II)-catalyzed dimerization of 3-diazo-2-arylidenesuccinimides provides access to a new dibenzazulene scaffold

• Anastasia Vepreva,
• Alexander S. Bunev,
• Andrey Yu. Kudinov,
• Grigory Kantin,
• Mikhail Krasavin and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2022, 18, 533–538, doi:10.3762/bjoc.18.55

• method for the preparation of this class of compounds [2] and showed that DAS can undergo Rh(II)-catalyzed insertion reactions into the heteroatom–H bonds [3]. In 2020, it was shown that under Rh(II) catalysis, DAS can enter insertion reactions into the C–O bond of ethers [4], a rare transformation for

A photochemical C=C cleavage process: toward access to backbone N-formyl peptides

• Haopei Wang and
• Zachary T. Ball

Beilstein J. Org. Chem. 2021, 17, 2932–2938, doi:10.3762/bjoc.17.202

• tested alkenyl ether 6 as a model of C–O-bond cleavage. Photoirradiation of the ether 6 similarly provided a mixture of C9-containing products 3, 4, and 5. Under these reaction conditions, the C–X cleavage products (MeOH or 2) were observed, but no formyl products were formed. The C9 byproducts – the

α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions

• Scott Benz and
• Andrew S. Murkin

Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172

• intermediate 117. C–O bond cleavage produces an α-iminol intermediate 118, which proceeds to rearrange by ring expansion to ultimately yield 119 (Figure 21a). Using the benzoate ester of 118 (R = Ph; X = CH2) as the substrate and N-methylindole as the heteroarene, optimal reaction conditions (95% yield) were

Visible-light-mediated copper photocatalysis for organic syntheses

• Yajing Zhang,
• Qian Wang,
• Zongsheng Yan,
• Donglai Ma and
• Yuguang Zheng

Beilstein J. Org. Chem. 2021, 17, 2520–2542, doi:10.3762/bjoc.17.169

• copper-catalyzed C–O cross-coupling reaction. Results of mechanistic studies indicated that in this case a CuI–phenoxide complex is a competent intermediate in the photoinduced C–O bond formation. In 2020, Nguyen and co-worker [90] reported copper-catalyzed C–O cross-coupling of glycosyl bromides with

In-depth characterization of self-healing polymers based on π–π interactions

• Josefine Meurer,
• Julian Hniopek,
• Johannes Ahner,
• Michael Schmitt,
• Jürgen Popp,
• Stefan Zechel,
• Kalina Peneva and
• Martin D. Hager

Beilstein J. Org. Chem. 2021, 17, 2496–2504, doi:10.3762/bjoc.17.166

• , indicating a strengthening of the carbon-oxygen bond. This is caused by a weakening of inter-perylene C–H–O interactions that also contribute to the stacking behavior [28][29], which in turn increases the electron density in the C=O bond. In addition to these shifts in band positions, all bands show

Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

• Yi Liu,
• Puying Luo,
• Yang Fu,
• Tianxin Hao,
• Xuan Liu,
• Qiuping Ding and
• Yiyuan Peng

Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163

• ) was also tolerated efficiently under the standard conditions to afford the desired product 46k in 64% yield. In addition, tert-butyldimethylsilyl (TBS)-substituted enynyl azide provided the target product 46l in 34% yield. The transformation involves a sequence of C−N/C−O bond formation, and the

A novel methodology for the efficient synthesis of 3-monohalooxindoles by acidolysis of 3-phosphate-substituted oxindoles with haloid acids

• Li Liu,
• Yue Li,
• Tiao Huang,
• Dulin Kong and
• Mingshu Wu

Beilstein J. Org. Chem. 2021, 17, 2321–2328, doi:10.3762/bjoc.17.150

• , which further implied that the halogenation reaction with haloid acids had occurred. On the basis of this study and the early related reports [30][35], an SN1 mechanism for this transformation is proposed as illustrated in Scheme 5. Initially, the C–O bond of the C-3 position of a diethyl (2-oxoindolin

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

• catalysts (Scheme 11) [63]. Here, the use of a zinc-based Lewis acid (LA) was found to activate α-hydroxy C‒H bonds by forming alkoxide (O‒LA) and suppressing the C‒O bond formation by inhibiting the formation of a nickel alkoxide species. The authors also claimed that the use of the zinc-based LA also

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

A straightforward conversion of 1,4-quinones into polycyclic pyrazoles via [3 + 2]-cycloaddition with fluorinated nitrile imines

• Greta Utecht-Jarzyńska,
• Karolina Nagła,
• Grzegorz Mlostoń,
• Heinz Heimgartner,
• Marcin Palusiak and
• Marcin Jasiński

Beilstein J. Org. Chem. 2021, 17, 1509–1517, doi:10.3762/bjoc.17.108

• -quinones, competitive reaction courses involving either ethylenic C=C or carbonyl C=O bonds were observed. For example, the more polar arylnitrile oxides and 1,4-benzoquinones reacted via addition to the C=C bond to give fused isoxazole derivatives [10][11][12] as well as with the C=O bond yielding

• either onto the C=C or C=O bond. The present work should also be considered as an extension of our earlier studies focused on the exploration of 1,4-quinones in the [3 + 2]-cycloaddition and hetero-Diels–Alder reaction performed with thiocarbonyl S-methanides and thiochalcones, respectively [37][38

Valorisation of plastic waste via metal-catalysed depolymerisation

• Francesca Liguori,
• Carmen Moreno-Marrodán and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

• reactions of PET were developed mostly using Ru metal-based catalysts, due to their higher affinity for C=O bond (ester) hydrogenation compared to other metals (Scheme 2) [181][182]. Thus, a 73% BDM yield was obtained using a soluble Ru(II)–PNN complex at 110 °C in THF/anisole solvent, 50 bar of hydrogen

• , based on the activation of the C=O bond by the IL Lewis acid cation and of the hydroxy group in EG by the IL anion (Scheme 6). The IL catalysts could be easily separated by distillation and reused up to six times with no significant efficiency drop. Catalytic glycolysis by heterogenised, metallated

1,2,3-Triazoles as leaving groups: S_NAr reactions of 2,6-bistriazolylpurines with O- and C-nucleophiles

• Dace Cīrule,
• Irina Novosjolova,
• Ērika Bizdēna and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 410–419, doi:10.3762/bjoc.17.37

• -yl)purine with dimethylamine, sodium methoxide and sodium thiomethoxide [39]. Earlier, the use of 6-(1,2,4-triazol-1-yl)purine derivatives in SNAr reactions has been reported [40]. An alternative method for the synthesis of O6-alkylpurines is Pd catalyzed C–O bond formation starting from 6

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• benzylic alcohols 61 did not undergo further arylation and were stable under the reaction conditions. In agreement with computational studies [97], this behavior was assigned to the presence of the CF3 group, which induces a shortening of the C–O bond in the product (dC–O = 1.426 Å) compared to the CH3

Ring-closing metathesis of prochiral oxaenediynes to racemic 4-alkenyl-2-alkynyl-3,6-dihydro-2H-pyrans

• Viola Kolaříková,
• Markéta Rybáčková,
• Martin Svoboda and
• Jaroslav Kvíčala

Beilstein J. Org. Chem. 2020, 16, 2757–2768, doi:10.3762/bjoc.16.226

• considered for the dihydropyran 12b, namely all combinations of equatorial or axial positions of the but-2-ynyl substituent, three staggered conformations of the prop-1-ynyl group with respect to the C–O bond of the ring, and three conformations of the dienyl system (s-trans and two tilted s-cis

Vicinal difluorination as a C=C surrogate: an analog of piperine with enhanced solubility, photostability, and acetylcholinesterase inhibitory activity

• Yuvixza Lizarme-Salas,
• Alexandra Daryl Ariawan,
• Ranjala Ratnayake,
• Hendrik Luesch,
• Angela Finch and
• Luke Hunter

Beilstein J. Org. Chem. 2020, 16, 2663–2670, doi:10.3762/bjoc.16.216

• which the C–F bonds align gauche (I and II, Figure 1) [22]. Separately, the presence of fluorine on the α-carbon of a tertiary amide is known to restrict the Cα–C(O) bond to a small set of low-energy rotamers (III–V, Figure 1) [23]. Intriguingly, studies of simple molecules containing either F–C–C–F or

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• 71 with methanol provided methoxysumanenone 73 in an overall good yield (Scheme 16). From their studies they observed that compound 74 is unstable to both heat as well as light, may be due to instability of the internal C–O bond. In this regard, very recently they transformed this unstable compound

Lipophilicity trends upon fluorination of isopropyl, cyclopropyl and 3-oxetanyl groups

• Benjamin Jeffries,
• Zhong Wang,
• Robert I. Troup,
• Anaïs Goupille,
• Jean-Yves Le Questel,
• Charlene Fallan,
• James S. Scott,
• Elisabetta Chiarparin,
• Jérôme Graton and
• Bruno Linclau

Beilstein J. Org. Chem. 2020, 16, 2141–2150, doi:10.3762/bjoc.16.182

• difference in lipohilicity between D4 and D5. Aliphatic compounds containing a CF2H group are frequently less lipophilic than to their nonfluorinated equivalent [20][31] (except in presence of a vicinal C–O bond [22][32]), which is what is found here for D4. The CF3-containing D5 is more lipophilic than the

Selective preparation of tetrasubstituted fluoroalkenes by fluorine-directed oxetane ring-opening reactions

• Clément Q. Fontenelle,
• Thibault Thierry,
• Romain Laporte,
• Emmanuel Pfund and
• Thierry Lequeux

Beilstein J. Org. Chem. 2020, 16, 1936–1946, doi:10.3762/bjoc.16.160

• conformational changes [11][12][13]. For the latter, nucleoside analogues (Figure 2, VI) containing a trans-butenyl moiety where the endocyclic C–O bond was replaced by a C=C bond are recognized by kinases as dUMP surrogate (V) [11]. However, there is no existing data for the corresponding fluoroalkene (VII), as

One-pot synthesis of oxazolidinones and five-membered cyclic carbonates from epoxides and chlorosulfonyl isocyanate: theoretical evidence for an asynchronous concerted pathway

• Esra Demir,
• Ozlem Sari,
• Yasin Çetinkaya,
• Ufuk Atmaca,
• Safiye Sağ Erdem and
• Murat Çelik

Beilstein J. Org. Chem. 2020, 16, 1805–1819, doi:10.3762/bjoc.16.148

• reaction of CSI with epoxides in different solvents under mild conditions and compared the reaction mechanism with previously proposed mechanisms using theoretical calculations. Keshava Murthy and Dhar [41] postulated a mechanism involving a zwitterionic intermediate. C–O bond cleavage in this unstable and

• ′ (Figure 2). Therefore, attack by N4 of CSI on the C2 of epoxide is found to be energetically the most favored approach. The epoxide ring opening and formation of the O–C(=O) bond are almost completed before the C–N bond is formed. The changes in bond lengths along the intrinsic reaction coordinate (IRC

• corresponding barrier was calculated to be 13.0 kcal/mol relative to initial reactant complex RC6 (7f+CSI) (Figure 7). Elimination of 18, accompanied by C=O bond formation, constitutes the final step of the reaction observed. Optimized structures are given in Figure 10. The elimination reaction, via the

Photocatalyzed syntheses of phenanthrenes and their aza-analogues. A review

• Alessandra Del Tito,
• Havall Othman Abdulla,
• Davide Ravelli,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 1476–1488, doi:10.3762/bjoc.16.123

• photocatalyzed reduction of acyloximes 14.1a,b offered a smooth entry to iminyl radicals (Scheme 14) [76]. The process took place at room temperature and involved the cleavage of a C–O bond, followed by a cyclization to give access to the benzo[c]phenanthridine alkaloids noravicine (14.2a) and nornitidine (14.2b

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

• radicals with the formation of a C–O bond (dimer 4b, oxidation of diisopropyl oxime 1b), an O–N bond (dimer 4c, oxidation of benzophenone oxime 1c), and an N–N bond (dimer 4d, oxidation of benzaldoxime 1d, see also [58]) was observed. As a rule, the initial dimers of iminoxyl radicals are unstable, which

• rule, a C–O bond is formed in intermolecular reactions, intramolecular cyclization generally occurs with the formation of a five-membered cycle of isoxazoline (C–O bond formation) or nitrone (C–N bond formation). Application of the oxime radicals in organic synthesis: intermolecular reactions Selective