Recent advances in controllable/divergent synthesis

• Jilei Cao,
• Leiyang Bai and
• Xuefeng Jiang

Beilstein J. Org. Chem. 2025, 21, 890–914, doi:10.3762/bjoc.21.73

• imides and TMS-alkynes, enabling the rapid construction of S(VI)–C(sp2) or S(VI)–C(sp) bonds efficiently (Scheme 24) [55]. This linkage utilizes the high bond dissociation energy (BDE = 135 kcal/mol) of silicon–fluorine bonds, employing trifluoroborate as a fluorine transfer reagent to simultaneously

A review of recent advances in electrochemical and photoelectrochemical late-stage functionalization classified by anodic oxidation, cathodic reduction, and paired electrolysis

• Nian Li,
• Ruzal Sitdikov,
• Ajit Prabhakar Kale,
• Joost Steverlynck,
• Bo Li and
• Magnus Rueping

Beilstein J. Org. Chem. 2024, 20, 2500–2566, doi:10.3762/bjoc.20.214

Benzylic C(sp³)–H fluorination

• Alexander P. Atkins,
• Alice C. Dean and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 1527–1547, doi:10.3762/bjoc.20.137

• radicals and ions imparted through delocalisation with the adjacent π-system [13][14][15]. In general, the more stabilised the benzylic radical, the weaker the C(sp3)–H bond, as demonstrated when considering the BDEs of a series of phenyl-substituted methanes (Figure 1B). The changes in BDE correlate with

Predicting bond dissociation energies of cyclic hypervalent halogen reagents using DFT calculations and graph attention network model

• Yingbo Shao,
• Zhiyuan Ren,
• Zhihui Han,
• Li Chen,
• Yao Li and
• Xiao-Song Xue

Beilstein J. Org. Chem. 2024, 20, 1444–1452, doi:10.3762/bjoc.20.127

• results of this study could aid in estimating the chemical stability and functional group transfer capabilities of hypervalent bromine(III) and chlorine(III) reagents, thereby facilitating their development. Keywords: BDE; cyclic hypervalent halogen reagents; DFT calculation; graph attention network

• ][45][46][47] have highlighted the critical role of bond dissociation energy (BDE) in understanding the group transfer capabilities and chemical stability of hypervalent iodine(III) reagents. In this context, detailed knowledge of the BDE of hypervalent bromine(III) and chlorine(III) reagents is

• especially crucial for designing novel reagents. Yet, the BDE values of hypervalent bromine(III) and chlorine(III) reagents remain largely elusive, hampering the design and synthesis of novel reagents. In recent years, machine learning has emerged as a promising and cost-effective alternative to traditional

Advancements in hydrochlorination of alkenes

• Daniel S. Müller

Beilstein J. Org. Chem. 2024, 20, 787–814, doi:10.3762/bjoc.20.72

• yield). Metal hydride hydrogen atom transfer reactions vs cationic reactions; BDE (bond-dissociation energy). Mechanism for the cobalt hydride hydrogen atom transfer reaction reported by Carreira. Proposed mechanism for anti-Markovnikov hydrochlorination by Nicewicz. Mechanism for anti-Markovnikov

Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• photochemical instability, as evidenced by their low N–O bond dissociation energy (BDE ≈ 42 kcal/mol) [28], the reliance on toxic tin hydrides as reductants and the undesired radical recombination with reactive 2-pyridylthiyl radicals that leads to (alkylthio)pyridine byproducts [26]. More recently, N

• -hydroxyphthalimide (NHPI) esters (3) have emerged as convenient alternatives to Barton esters (Scheme 1) due in part to their ease of synthesis and greater stability (N–O BDE ≈ 75 kcal/mol) [28]. Their use as radical precursors was first described by Okada and colleagues in 1988 [29], who showed that C(sp3)-centered

• transfer complexes with a donor species 6 or via LUMO lowering activation with Brønsted and Lewis acids 7 (Scheme 2B), collectively offering a number of variables to influence their reactivity. Upon reduction, RAEs give rise to a radical anion 8 with a weakened N–O bond (BDE < 70 kcal/mol) [33]. While

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

DABCO-promoted photocatalytic C–H functionalization of aldehydes

• Bruno Maia da Silva Santos,
• Mariana dos Santos Dupim,
• Cauê Paula de Souza,
• Thiago Messias Cardozo and
• Fernanda Gadini Finelli

Beilstein J. Org. Chem. 2021, 17, 2959–2967, doi:10.3762/bjoc.17.205

• the reaction step with 1 in gas phase and in 1,4-dioxane. The HAT reaction step catalyzed with quinuclidine is exergonic (−8.0 kcal·mol−1), while the reaction step involving DABCO is endergonic (+6.8 kcal·mol−1), in agreement with what would be expected from BDE and BDFE analyses. The solvent effect

• Information File 1 for more details.) The experimental results with DABCO show that the prediction of a mildly endergonic HAT reaction step and the presence of a barrier are not an obstacle to its ability to act as a catalyst. A naïve use of BDE analysis to select HAT catalysts might suggest that DABCO should

• not be appropriate for this reaction. However, our results clearly show that DABCO is a perfectly fit for the job. This apparent contradiction can be more easily understood by recalling that a BDE analysis is essentially thermodynamic, but is connected to the kinetics of the reaction step by means of

Development of N-F fluorinating agents and their fluorinations: Historical perspective

• Teruo Umemoto,
• Yuhao Yang and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

Metal-free glycosylation with glycosyl fluorides in liquid SO₂

• Krista Gulbe,
• Jevgeņija Lugiņina,
• Edijs Jansons,
• Artis Kinens and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 964–976, doi:10.3762/bjoc.17.78

• groups, promoter, solvent and temperature has to be applied. In 1981, Mukaiyama et al. introduced glycosyl fluorides [5] as a new class of glycosyl donors [6]. The C–F bond is one of the strongest single bonds in the realm of organic compounds with a bond dissociation energy (BDE) of 570 kJ/mol [7]. Thus

• , glycosyl fluorides possess a considerably higher thermal and chemical stability compared to the corresponding chlorides (BDE 432 kJ/mol) and bromides (BDE 366 kJ/mol). Due to the advantageous stability during purification, handling and storage, glycosyl fluorides have become widely used glycosyl donors in

Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis

• Shahboz Yakubov and
• Joshua P. Barham

Beilstein J. Org. Chem. 2020, 16, 2151–2192, doi:10.3762/bjoc.16.183

• length is ≈1.35 Å and is one of the strongest bonds known (bond dissociation enthalpy (BDE) of ≈130 kcal⋅mol−1) [11][12]. By C(sp3)–H/C(sp3)–F substitution, adjacent C–C bonds are strengthened while allylic C–C double bonds are weakened [13]. Due to the similar size to the hydrogen atom (rF = 1.47 Å, rH

• dictated by the thermodynamic driving force of the hydrogen atom transfer step (which depends on the stability of the resulting radical) or by the relative BDE of C–H bonds. Thus, it is possible to homolytically cleave stronger C–H bonds in the presence of weaker C–H bonds if the polarity of the stronger C

• monofluorination, albeit in a low (26%) yield, despite its lower BDE (calculated BDE = 63.4 kcal⋅mol−1) than Selectfluor® [196]. gem-Difluorinations using xanthone gave a higher conversion of 26 and a higher yield of 28a with Selectfluor® II rather than with Selectfluor® (Scheme 7), despite their identical N–F

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

• C=N–O angle and a shortened N–O bond compared to the corresponding oximes (Figure 3) [44][52][70]. One of the important quantitative values that determine the reactivity of O radicals is the O–H bond dissociation enthalpy (BDE) in the parent OH compound (Figure 4). This value affects both the ease

• of the generation of radicals from the corresponding OH compounds and the oxidative properties of the O radicals. The O–H BDE values were determined for a number of oximes by the computational [67][70][71] and experimental [70][72] methods. It was established that the BDE decreased with an increase

• should also be noted that there is no noticeable decrease in the O–H BDE in diaryl oximes compared to dialkyl oximes (some examples are shown in Figure 4 [71]), which is consistent with the idea that an unpaired electron is delocalized by the conjugation with a lone pair of the nitrogen atom, but not by

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

• products were obtained with good TON (up to 880) and high selectivity (91–99.5%), even though the aryl C–F bonds present a high bond dissociation energy (BDE) (Scheme 13). Using a similar photocatalytic system, 2-methyl-2,3-dihydrobenzofuran was produced by an intramolecular hydro-functionalization of

p-Pyridinyl oxime carbamates: synthesis, DNA binding, DNA photocleaving activity and theoretical photodegradation studies

• Panagiotis S. Gritzapis,
• Panayiotis C. Varras,
• Nikolaos-Panagiotis Andreou,
• Katerina R. Katsani,
• Konstantinos Dafnopoulos,
• George Psomas,
• Zisis V. Peitsinis,
• Alexandros E. Koumbis and
• Konstantina C. Fylaktakidou

Beilstein J. Org. Chem. 2020, 16, 337–350, doi:10.3762/bjoc.16.33

• characteristics and properties. We note that the adiabatic excitation energy of 12 (including the zero-point energy, ZPE) is Δ0[Τ1 − S0] = 53.40 kcal/mol, which corresponds to a wavelength of 535.6 nm (visible region). The ground state (S0) bond dissociation energies (BDE), D0, for both molecules under

• consideration, are shown in Table 2 and were calculated using Gaussian 09 software program package [77]. The BDE difference between the two compounds is about 10 kcal/mol, while that in their adiabatic excitation energies is 3.9 kcal/mol. Since Δ0 − D0 is higher for 12 than 11 someone would expect 12 to be more

Insertion of [1.1.1]propellane into aromatic disulfides

• Robin M. Bär,
• Gregor Heinrich,
• Martin Nieger,
• Olaf Fuhr and
• Stefan Bräse

Beilstein J. Org. Chem. 2019, 15, 1172–1180, doi:10.3762/bjoc.15.114

• ]. Presumably, there are two factors contributing to the lowered yield. The bond dissociation energy (BDE) of dialkyldisulfides is higher than the BDE of diaryl disulfides [30]. Therefore lower concentrations of thiyl radicals are present to initiate the reaction. The second reason could be the absorption of

• the 4-methoxybenzenethiyl radical is either formed faster and/or reacts more rapidly with 1 than the corresponding benzenethiyl radical. The calculated BDE (DFT calculation) of 10e is slightly lower with 49.0 kcal/mol compared to 10a with 54.5 kcal/mol [32]. This difference hints towards the faster

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• presented in Table 1 because the driving force of its reactivity is more its bond dissociation energy (BDE) than its redox potential. Indeed, this compound obeys to a pure hydrogen transfer mechanism. This corresponds to a hydrogen transfer from (TMS)3SiH to the triplet excited state of the PC. Thus, to

Cp₂TiCl/D₂O/Mn, a formidable reagent for the deuteration of organic compounds

• Antonio Rosales and
• Ignacio Rodríguez-García

Beilstein J. Org. Chem. 2016, 12, 1585–1589, doi:10.3762/bjoc.12.154

• O–H bond, indicating a bond-dissociation energy (BDE) for the intermediate aqua-complex of only 49 kcal/mol. This points to a decrease of almost 60 kcal/mol compared to the calculated BDE of water. Later, Gansäuer et al. proposed a modified structure of the intermediate aqua-complex on the basis of

Ring-whizzing in polyene-PtL₂ complexes revisited

• Oluwakemi A. Oloba-Whenu,
• Thomas A. Albright and
• Chirine Soubra-Ghaoui

Beilstein J. Org. Chem. 2016, 12, 1410–1420, doi:10.3762/bjoc.12.135

• b1g. On the other hand, the Pt 5d AO is more diffuse and consequently more bonding is lost at η4 than its Ni congener. But this cannot be the whole story. Massera and Frenking [23] have shown that there is essentially no energy difference between the bond dissociation energy (BDE) in ethylene–Ni(dpe

• ) and the Pt analog. Furthermore, their calculated BDE for ethylene–Pt(PH3)2 is in very good agreement with that found [23] at the CCSD(T) level with a large basis set. On the other hand, Reinhold, McGrady and Perutz have reported [46] that C6H6 and C6F6–Pt(dpe) BDEs are about 8 kcal/mol less than that

Effective ascorbate-free and photolatent click reactions in water using a photoreducible copper(II)-ethylenediamine precatalyst

• Redouane Beniazza,
• Natalia Bayo,
• Florian Molton,
• Carole Duboc,
• Stéphane Massip,
• Nathan McClenaghan,
• Dominique Lastécouères and
• Jean-Marc Vincent

Beilstein J. Org. Chem. 2015, 11, 1950–1959, doi:10.3762/bjoc.11.211

• character of H2O (BDE = 119 kcal/mol) compared to THF (BDE = 92 kcal/mol), the reactivity of the excited triplet of benzophenone being particularly high toward the THF moiety [29]. At this stage, a reduction mechanism implying the fast generation of the ketyl radical in good hydrogen atom donating solvents

Antioxidant potential of curcumin-related compounds studied by chemiluminescence kinetics, chain-breaking efficiencies, scavenging activity (ORAC) and DFT calculations

• Adriana K. Slavova-Kazakova,
• Silvia E. Angelova,
• Timur L. Veprintsev,
• Petko Denev,
• Davide Fabbri,
• Maria Antonietta Dettori,
• Maria Kratchanova,
• Vladimir V. Naumov,
• Aleksei V. Trofimov,
• Rostislav F. Vasil’ev,
• Giovanna Delogu and
• Vessela D. Kancheva

Beilstein J. Org. Chem. 2015, 11, 1398–1411, doi:10.3762/bjoc.11.151

• : It is evident that in this model DL-α-tocopherol (11) is also the most efficient antioxidant, and ensures the highest oxidative stability of the lipid substrate. The observed lower antioxidant activity of monomers and dimers with respect to 11 is expected as a result of the higher BDE of phenolic –OH

• quantum chemical calculations (see section “Model 4: DFT calculations”) for BDE of 13 and studied compounds in water medium confirm our hypothesis. It is noteworthy that the literature data for individual phenolic compounds acquired with ORAC as a model system are rather poor in comparison with the data

• their possible radicals/biradicals are collected in Table 2. For the monomers similar BDE values are found (the biggest difference is 0.7 kcal·mol−1, i.e., lower than 1 kcal·mol−1), i.e., 2–4 should manifest similar activity and close to that of ferulic acid 5. Two BDE values are calculated for the

Atherton–Todd reaction: mechanism, scope and applications

• Stéphanie S. Le Corre,
• Mathieu Berchel,
• Hélène Couthon-Gourvès,
• Jean-Pierre Haelters and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2014, 10, 1166–1196, doi:10.3762/bjoc.10.117

3-Pyridinols and 5-pyrimidinols: Tailor-made for use in synergistic radical-trapping co-antioxidant systems

• Luca Valgimigli,
• Daniele Bartolomei,
• Riccardo Amorati,
• Evan Haidasz,
• Jason J. Hanthorn,
• Susheel J. Nara,
• Johan Brinkhorst and
• Derek A. Pratt

Beilstein J. Org. Chem. 2013, 9, 2781–2792, doi:10.3762/bjoc.9.313

• synergism to occur among equilibrating phenolic antioxidants it is necessary that the principal antioxidant has both a higher reactivity with peroxyl radicals (kinh) and a higher O–H bond dissociation enthalpy (BDE), as compared to the co-antioxidant. Unfortunately, this is a very demanding requirement

• since kinh and the O–H BDE are inversely correlated according to well-established Evans–Polanyi relationships [2][10]. Over the years, our research groups have developed novel air-stable and highly reactive radical-trapping chain-breaking antioxidants based on either 3-pyridinol (1) or 5-pyrimidinol (2

• sufficiently high O–H BDE to be regenerated by the co-antioxidant, co-AH (vide supra), which was selected among the conventional phenols 10–12. The autoxidation of an organic substrate (e.g. styrene) thermally initiated at a constant rate, Ri, by an azo-initiator will consume oxygen at a constant rate in the

Damage of polyesters by the atmospheric free radical oxidant NO₃^•: a product study involving model systems

• Catrin Goeschen and
• Uta Wille

Beilstein J. Org. Chem. 2013, 9, 1907–1916, doi:10.3762/bjoc.9.225

• studies by Coote et al. clearly revealed that polymers possessing only saturated alkyl chains, for example polyesters, will not propagate autoxidation, particularly because the ROO–H bond-dissociation energy (BDE) is usually less than the BDE for unactivated R–H bonds [6]. Polymer surface coatings, which

• • as propagating step. Thus, although NO3• is not only much more reactive than ROO• [7][8], and the BDE for the O2NO–H bond is with 427 kJ mol−1 also considerably higher than that of the ROO–H bond (which is about 360 ± 20 kJ mol−1) [21], the fact that no hydrogen abstraction from the ester units was

Metal-free aerobic oxidations mediated by N-hydroxyphthalimide. A concise review

• Lucio Melone and
• Carlo Punta

Beilstein J. Org. Chem. 2013, 9, 1296–1310, doi:10.3762/bjoc.9.146

• oxidation of organic substrates [7][8][9][10][11]. NHPI acts as a precursor of the phthalimide N-oxyl (PINO) radical, which is the effective catalyst promoting hydrogen-abstraction processes (Scheme 1). The reactivity of NHPI and PINO is related to the bond dissociation energy (BDE) of the O–H group, which

• was estimated at 88.1 kcal/mol [12]. This value is similar to the BDE of O–H in hydroperoxides, suggesting that the faster reactivity of PINO compared to peroxyl radicals should be attributed to an enhanced polar effect involved in the hydrogen abstraction by this nitroxyl radical [13]. Furthermore

• BDE value (79.2 kcal/mol [12]), NMBHA turned out to be a better candidate than NHPI to act both as autoxidation catalyst, promoting the hydrogen abstraction from the bisallylic C–H position of the fatty esters by means of the corresponding amidoxyl radical, and as a good hydrogen donor (kH = 1.2 × 105

Part 3. Triethylborane- air: a suitable initiator for intermolecular radical additions of S-2-oxoalkyl- thionocarbonates (S-xanthates) to olefins

• Jean Boivin and
• Van Tai Nguyen

Beilstein J. Org. Chem. 2007, 3, No. 47, doi:10.1186/1860-5397-3-47

• . Fortunately, such an increase of reaction temperature enhances route c much more than route b. For planar radicals, Rüchardt and Beckwith established that the C-H bond dissociation energy (BDE) for H-CXYZ compounds displays a good linear correlation with the measured α and β-proton ESR hyperfine splitting

• constants. [17][18][19] When Y = Me, Z = H, the H-C BDE follows the order for X: CH=CH2 < Ph < PhCO = MeCO < CN < CO2Et < Me (Table 3, entries 1–7). The BDE for compounds where Y = Z = H follows the same order, albeit the value is of course slightly higher when compared to their methylated counterparts

• presence of Et3B. Addition of xanthate 1a to decene at r.t., catalysed by Et3B/air Et3B/air catalysed intermolecular radical additions to olefins Selected values of H-C BDE for compounds H-CXYZ from references [17][18][19]. Supporting Information Supporting Information File 117: General procedure for