Fritsch–Buttenberg–Wiechell rearrangement of magnesium alkylidene carbenoids leading to the formation of alkynes

• Tsutomu Kimura,
• Koto Sekiguchi,
• Akane Ando and
• Aki Imafuji

Beilstein J. Org. Chem. 2021, 17, 1352–1359, doi:10.3762/bjoc.17.94

• hydroxy group in the adducts, and β-elimination (Scheme 3a) [16]. The 1-bromovinyl p-tolyl sulfoxide 6 was prepared by the deprotonation of sulfoxide 8 with LDA followed by electrophilic bromination with 1,2-dibromo-1,1,2,2-tetrachloroethane. 1-Methoxyvinyl p-tolyl sulfoxide 7 was prepared by a Peterson

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

• as a chiral auxiliary which was then removed by hydrolysis in the final step of the overall seven-step synthesis. Deprotonation of 41 using LiHMDS in THF in a primary reactor was performed at −40 °C and telescoped into a second reactor along with a stream containing the trityl-protected aldehyde, 42

Heterogeneous photocatalytic cyanomethylarylation of alkenes with acetonitrile: synthesis of diverse nitrogenous heterocyclic compounds

• Guanglong Pan,
• Qian Yang,
• Wentao Wang,
• Yurong Tang and
• Yunfei Cai

Beilstein J. Org. Chem. 2021, 17, 1171–1180, doi:10.3762/bjoc.17.89

• byproduct 15 after deprotonation. Conclusion We have demonstrated the application of a heterogeneous CN-K semiconducting photocatalyst in the cyanomethylarylation of alkenes with acetonitrile utilizing a readily available NHPI ester as radical initiator. This transition metal-free protocol tolerates a broad

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• [62][63]. The first asymmetric synthesis of 2,2-dibromoaziridines 15 was achieved by performing the nucleophilic addition of the anion resulting from the deprotonation of bromoform with sodium hexamethyldisilazide (NaHMDS) to chiral N-tert-butanesulfinyl aldimines (RS)-14, at low temperature, and

• found that the reaction of different aromatic and aliphatic chiral imines (SS)-14 with the dienolate resulting from the deprotonation of bromomethyl butenolide 29 in THF at −78 °C led to a mixture of diastereomeric cis-vinylaziridines 30 and 31 with good yields in most cases. Lithium

• hexamethyldisilazide was the base of choice to perform the deprotonation, and it must be added very slowly to the reaction mixture in order to suppress self-dimerization of the butenolide [72]. The structures as well as the absolute and relative stereochemistry of reaction products 30 and 31 were also unambiguously

Synthesis of bis(aryloxy)fluoromethanes using a heterodihalocarbene strategy

• Carl Recsei and
• Yaniv Barda

Beilstein J. Org. Chem. 2021, 17, 813–818, doi:10.3762/bjoc.17.70

• (by direct attack of a aryl oxide nucleophile or deprotonation and loss of chloride in a second carbene generation followed by a second phenoxide attack) would be substantially greater than an aryloxydifluoromethane such as 5, with milder conditions allowing us to avoid the undesired isomer 7

α,γ-Dioxygenated amides via tandem Brook rearrangement/radical oxygenation reactions and their application to syntheses of γ-lactams

• Mikhail K. Klychnikov,
• Radek Pohl,
• Ivana Císařová and
• Ullrich Jahn

Beilstein J. Org. Chem. 2021, 17, 688–704, doi:10.3762/bjoc.17.58

• corresponding acyclic or cyclic allylic amines in very good yields (see Supporting Information File 1 for details). Their subsequent α-deprotonation by LDA followed by treatment with chlorotrimethylsilane at −78 °C [81] resulted in clean C-silylation of the corresponding enolate providing silylacetamides 8a–m

• enolate formation from 8h,i with s-BuLi, a deuterium quenching experiment with D2O was performed. Analysis by 1H NMR spectroscopy revealed 87 and 91% deuterium incorporation, respectively, indicating that a deprotonation occurred, but the epoxide opening was hampered by the combination of a sterically

• equilibrium (Table 4, entries 7 and 11 vs entries 1 and 9). Attempts to influence the diastereomeric ratio of the cyclization products by irreversible stoichiometric deprotonation of the lactams 12d,f,i by LDA at −78 °C and subsequent protonation by methanol did not lead to substantial changes of the initial

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

• and noticeable productivity (TOF = 129 h−1, based on the moles of Zn) at 190°C, EG/PET 4:1, w/w and 5 wt % catalyst [237]. A mechanism was proposed analogous to that depicted in Scheme 6, but in which Zn2+ acts as Lewis acid and dimethylurea acts as base promoter for EG hydroxy deprotonation [238

Mesoionic tetrazolium-5-aminides: Synthesis, molecular and crystal structures, UV–vis spectra, and DFT calculations

• Vladislav A. Budevich,
• Sergei V. Voitekhovich,
• Alexander V. Zuraev,
• Vadim E. Matulis,
• Vitaly E. Matulis,
• Alexander S. Lyakhov,
• Ludmila S. Ivashkevich and
• Oleg A. Ivashkevich

Beilstein J. Org. Chem. 2021, 17, 385–395, doi:10.3762/bjoc.17.34

• -aminides. Results and Discussion Synthesis and chemical transformations Tetrazolium-5-aminides can be prepared by three main approaches: a) by the deprotonation of 5-aminotetrazolium salts, b) by the photochemical transformation of 5-azidotetrazolium salts, and c) by the functionalization of other aminides

• tetrazolium-5-aminide allows to displace halo- and methylsulfonyl groups, whereas 5-aminotetrazoles do not react under analogous conditions. So, we prepared the bistetrazolium salt 9 by the alkylation of aminide 8a with 1,2-dibromoethane (Scheme 2). The obtained salt 9 was subjected to deprotonation to give

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

• nonfluorinated analogues (Eox (PhNMe2) = +0.71 V (SCE)), the radical cation 180 is formed under the reaction conditions, and deprotonation at the methylene unit near the CF3 group is highly favored because of the higher acidity, accounting for the observed high regioselectivity. In addition, the transient

• of 93%, the Pummerer rearrangement of sulfoxide 214 under harsh conditions turned out to be less efficient, affording 204f in only 42% yield. This reaction is thought to proceed stepwise via a first oxidative electron transfer, followed by deprotonation, a second oxidative electron transfer, and

• methoxylation or acetoxylation, respectively (Scheme 53). The driving force in this reaction is assumed to be the deprotonation of radical cation 215, a highly destabilized species due to the presence of the strongly electron-withdrawing CF3 substituent, which leads to radical 216, synergistically stabilized by

Multiswitchable photoacid–hydroxyflavylium–polyelectrolyte nano-assemblies

• Alexander Zika and
• Franziska Gröhn

Beilstein J. Org. Chem. 2021, 17, 166–185, doi:10.3762/bjoc.17.17

• poly(allylamine) at pH 7.0. At this pH value, both the polyelectrolyte and also the photoacid are protonated [81][82]. Upon irradiation, the pKa of the photoacid decreases to pKa = −2.6 leading to deprotonation [82]. In addition to the electrostatic self-assembly of the photoacid and the

• time a peak emerges at λ = 300 nm. In addition, the band corresponding to the photoacid becomes less distinct. These two phenomena indicate the deprotonation of the photoacid and the transformation of Flavy from the A to the B form. After keeping the assemblies in the dark overnight the peak at λ = 550

• suggests that the changes of the structure depend on the deprotonation of the photoacid due to irradiation and the subsequently higher charged molecule. The last two steps for cycle II are as in cycle I and the size and structure of the assemblies switch back to the starting point. Interestingly, these two

Synthesis of aryl 2-bromo-2-chloro-1,1-difluoroethyl ethers through the base-mediated reaction between phenols and halothane

• Yukiko Karuo,
• Ayaka Kametani,
• Atsushi Tarui,
• Kazuyuki Sato,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2021, 17, 89–96, doi:10.3762/bjoc.17.9

• did not occur at all when potassium carbonate was used as a base, because the deprotonation of phenol became slow due to the low basicity (Table 1, entry 9). With the optimal reaction conditions (Table 1, entry 8) in hand, we next examined the scope of the reaction (Table 2). When an electron-rich

Recent progress in the synthesis of homotropane alkaloids adaline, euphococcinine and N-methyleuphococcinine

• Dimas J. P. Lima,
• Antonio E. G. Santana,
• Michael A. Birkett and
• Ricardo S. Porto

Beilstein J. Org. Chem. 2021, 17, 28–41, doi:10.3762/bjoc.17.4

• (1). Alternatively, the (±)-euphococcinine precursor 6 was prepared from 4, via deprotonation, silylation, and finally, silyl ether cleavage. Swern oxidation of alcohols 5 and 6 gave aldehydes 7 and 8, treated with allylmagnesium bromide, to generate secondary alcohols 9 and 10. These alcohols were

Pentannulation of N-heterocycles by a tandem gold-catalyzed [3,3]-rearrangement/Nazarov reaction of propargyl ester derivatives: a computational study on the crucial role of the nitrogen atom

• Giovanna Zanella,
• Martina Petrović,
• Dina Scarpi,
• Ernesto G. Occhiato and
• Enrique Gómez-Bengoa

Beilstein J. Org. Chem. 2020, 16, 3059–3068, doi:10.3762/bjoc.16.255

• very similar numbers, 14.6 kcal⋅mol−1 (from I to TS2) and 14.3 kcal⋅mol−1 (from III to TS3), respectively. We also computed the following steps of deprotonation, protodeauration, and acetate hydrolysis, which would lead to the final product 7, showing that they are not critical for the rate and outcome

• being higher in energy than TS6. As mentioned before, after the slow cyclization step in TS3, we focused our analysis on the transformation of the bicyclic intermediate IV to the final diene product. Basically, the final steps have to include a deprotonation, protodeauration, and in some cases acetate

• hydrolysis. These steps can occur through different pathways; in particular, we considered a single-step intramolecular hydride shift with concomitant C–Au-bond breaking (Figure 5) or a base-mediated deprotonation, followed by Au–C-bond hydrolysis through protodeauration (Figure 6). In the former case, it

Synthesis of imidazo[1,5-a]pyridines via cyclocondensation of 2-(aminomethyl)pyridines with electrophilically activated nitroalkanes

• Dmitrii A. Aksenov,
• Nikolai A. Arutiunov,
• Vladimir V. Maliuga,
• Alexander V. Aksenov and
• Michael Rubin

Beilstein J. Org. Chem. 2020, 16, 2903–2910, doi:10.3762/bjoc.16.239

• , providing a 2,3-dihydro-1H-imidazo[1,5-a]pyridin-4-ium ion 14. After deprotonation, the latter would form the 2,3-dihydroimidazo[1,5-a]pyridine 15, which after the elimination of O-phosphorylated hydroxylamine, would afford the imidazo[1,5-a]pyridines 16 (Scheme 2). To test this idea, nitroethane (1а, 5

Using multiple self-sorting for switching functions in discrete multicomponent systems

• Amit Ghosh and
• Michael Schmittel

Beilstein J. Org. Chem. 2020, 16, 2831–2853, doi:10.3762/bjoc.16.233

• the complex [Zn(49)]2+. The liberated zinc(II) ions replaced the Li+ ions in the nanoswitch [Li(35)]+ and translocated them onto the luminophore 36, thus finally generating the state SelfSORT-II composed of 49•H+, [Zn(35)]2+, and [Li(36)]+. In the return process, the deprotonation of 49•H+ by DBU

Particle size effect in the mechanically assisted synthesis of β-cyclodextrin mesitylene sulfonate

• Stéphane Menuel,
• Sébastien Saitzek,
• Eric Monflier and
• Frédéric Hapiot

Beilstein J. Org. Chem. 2020, 16, 2598–2606, doi:10.3762/bjoc.16.211

• ), the ratio of mono-substituted β-CDMts to poly-substituted β-CDMts derivatives increased over time, as depicted in Figure 7. This result is probably due to the homogeneous diffusion of KOH within the solid mixture facilitating the deprotonation of a larger number of β-CDs rather than only a few of them

• . While the deprotonation/protonation equilibrium preferentially takes place at the 2- and 6-positions of the β-CD [29], the alkoxide located on the primary face at the 6-position is more inclined to react with the bulky mesitylenesulfonate group than the alkoxide on the secondary face at the 2-position

Synthesis of 4-substituted azopyridine-functionalized Ni(II)-porphyrins as molecular spin switches

• Jannis Ludwig,
• Tobias Moje,
• Fynn Röhricht and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2589–2597, doi:10.3762/bjoc.16.210

• the improvement of the switching efficiency. Thiol (σ = 0.15) and thiolethers (σ ≈ 0.0) are less electron donating than methoxy substituents, however, upon deprotonation, the thiolate (σ = −1.2) should considerably improve coordination and potentially restore switchability in water. Carboxylic acids

• notorious problem of porphyrin-based spin switches. To kill two birds with one stone, we introduced acidic substituents in 4-position of the pyridines (1h (R = SH), 1j (R = COOH)). Deprotonation to the corresponding anions should increase the coordination power of the pyridine and increase the solubility of

• of 1e (top), 1h (left) and 1j (right) in acetone water (1:9) (solid line) and after deprotonation using cesium carbonate (dashed line) in the PSS at 505 nm (green) and 435 nm (blue). Synthesis of the nitroso compounds 3 and 6 using the two different methods described by Wegner et al. [19][20][21] and

Thermodynamic and electrochemical study of tailor-made crown ethers for redox-switchable (pseudo)rotaxanes

• Henrik Hupatz,
• Marius Gaedke,
• Hendrik V. Schröder,
• Julia Beerhues,
• Arto Valkonen,
• Fabian Klautzsch,
• Sebastian Müller,
• Felix Witte,
• Kari Rissanen,
• Biprajit Sarkar and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2020, 16, 2576–2588, doi:10.3762/bjoc.16.209

• . Both compounds exhibit two reversible reduction processes. The lariat ether NDIC7 is not suitable for rotaxane synthesis as it forms a complex equilibrium involving the deprotonation of the secondary ammonium axle and does not form 1:1 pseudorotaxanes. Additionally, the pseudorotaxane is hampered by

Synthesis of novel fluorinated building blocks via halofluorination and related reactions

• Attila Márió Remete,
• Tamás T. Novák,
• Melinda Nonn,
• Matti Haukka,
• Ferenc Fülöp and
• Loránd Kiss

Beilstein J. Org. Chem. 2020, 16, 2562–2575, doi:10.3762/bjoc.16.208

• for the formation can be written only from the imides (rac)-11a,b. Apparently, the first step involves a base-catalyzed epimerization into a less-strained cis-annelated system, which undergoes ring inversion, enabling the large halogen atom to be equatorial. This is followed by a deprotonation next to

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• . After deprotonation and oxidation via SET, both catalysts are regenerated and Minisci-type products 120 are released in excellent yields and enantioselectivities (30 examples, up to 99:1 er). Pyridyl substrates are tolerated, but generally required the presence of electron-withdrawing groups for the

• dual catalytic mode. Ooi et al. reported an enantioselective synthesis of 1,2 diamines 247 from tertiary amines 248 and aldimines 249 (Scheme 39) [100]. The proposed mechanism involves a reductive quenching pathway with 248 to produce radical cations 248•+, which following deprotonation and a [1,2

Styryl-based new organic chromophores bearing free amino and azomethine groups: synthesis, photophysical, NLO, and thermal properties

• Anka Utama Putra,
• Deniz Çakmaz,
• Nurgül Seferoğlu,
• Alberto Barsella and
• Zeynel Seferoğlu

Beilstein J. Org. Chem. 2020, 16, 2282–2296, doi:10.3762/bjoc.16.189

• . The pH-sensitive properties of all prepared Schiff bases were examined against TBAOH in DMSO, via deprotonation of the OH group in the salicylidene moiety and their reverse protonation was also investigated using TFA. The Schiff bases exhibited a bathochromic shift upon the addition of TBAOH to their

• /deprotonation processes [23][24][25]. Fluorescent dyes as chemosensors offer unique merits such as low energy consumption, ease of handling, high selectivity, and notable sensitivity [26][27]. Moreover, some fluorescent dyes demonstrate remarkable ICT characteristics, and could therefore serve as NLO dyes [11

• led to the restoration of its emission intensity. Figure 6 shows the deprotonation and reverse protonation of dye 12 by color changes of the dye followed under a UV lamp (λex = 365 nm). Since under the ambient light all solutions seemed to have the same color, a UV lamp was used to observe the color

Reactions of 3-aryl-1-(trifluoromethyl)prop-2-yn-1-iminium salts with 1,3-dienes and styrenes

• Thomas Schneider,
• Michael Keim,
• Bianca Seitz and
• Gerhard Maas

Beilstein J. Org. Chem. 2020, 16, 2064–2072, doi:10.3762/bjoc.16.173

• analogous to 21 could be isolated [56]. A cationic 1,5-cylization converts 21 into cyclopentene 22, from which fulvene 19 is formed by deprotonation and a formal 1,4-shift of the NMe2 group. The details of this rearrangement are not known, an N,N-dimethyldihydropyrrolium intermediate may be involved

Isolation and structure determination of a tetrameric sulfonyl dilithio methandiide in solution based on crystal structure analysis and ⁶Li/¹³C NMR spectroscopic data

• Jürgen Vollhardt,
• Hans Jörg Lindner and
• Hans-Joachim Gais

Beilstein J. Org. Chem. 2020, 16, 2057–2063, doi:10.3762/bjoc.16.172

• from sulfonyl lithio methanides 1 [9] through α-deprotonation [1][2][4], and from arylsulfonyl dilithio methanides 3 [10][11] though ortho,α-transmetallation [10][11][12][13] (Scheme 1). We had found that the α-deprotonation of the lithio methanide 1a with n-butyllithium (n-BuLi) gave the stable silyl

Design, synthesis and application of carbazole macrocycles in anion sensors

• Alo Rüütel,
• Ville Yrjänä,
• Sandip A. Kadam,
• Indrek Saar,
• Mihkel Ilisson,
• Astrid Darnell,
• Kristjan Haav,
• Tõiv Haljasorg,
• Lauri Toom,
• Johan Bobacka and
• Ivo Leito

Beilstein J. Org. Chem. 2020, 16, 1901–1914, doi:10.3762/bjoc.16.157

• increase between pH 2.8 and 6.8 due to the deprotonation of acetic acid (pKa = 4.76) [34], which should result in a decrease in the measured potentials. The measured potentials were then expected to remain constant after pH 6.8 since the activity of acetate should no longer appreciably change with the

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

• undergoes cyclometalation via a concerted metalation–deprotonation (CMD) process furnishing a cyclometalated intermediate. Thereafter, coordination and subsequent insertion of the alkyne into the Co–C bond delivers a seven-membered cobaltacycle. The desired coupling product is then liberated by reductive

• ) catalyst, followed by SET oxidation to provide an Ar–Au(III) intermediate (Figure 43). This Lewis-acidic Au species promotes the regioselective C–H auration of the electron-rich substrate, delivering a cationic intermediate that under deprotonation and subsequent reductive elimination furnishes the

• transfer generate the aryl radical together with a cationic Mn species. The addition of the aryl radical to the (hetero)aromatic substrate affords a radical biaryl intermediate that provides the expected coupling product after oxidation and deprotonation. C–H activation of heterocyclic substrates The panel