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

• reaction of (1-fluorovinyl)magnesium chloride with isopropylmagnesium chloride competed with the FBW rearrangement to give a mixture of alkyne 4a and alkene 10 in 69% and 13% yield, respectively (Table 1, entry 4, Scheme 4a, and Scheme 2c) [20]. Both the sulfoxide/magnesium exchange reaction and bromine

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

• the chemistry of naphthalene. The last one dates from 1887 and deals with the formation of isomers in the electrophilic aromatic substitution of naphthalene with chlorine and bromine [32]. This work was done in collaboration with Pietro Biginelli (1860–1937), the only collaborator of Guareschi who

• bromine in the presence of other halogens [67]. The test is based on the action of sulfitic leucobases of triphenylmethane dyes, such the decolorized fuchsine (Schiff reagent), which develops a deep violet color in the presence of traces of bromine. The reaction is very sensitive and selective for bromine

• chemist Georges Denigès (1859–1951), who, however, published his discovery of the same reaction six months after the disclosure by Guareschi. The ability of the test to distinguish between iodine and bromine is remarkable and difficult to explain in the light of the mechanism by which the Schiff reagent

Structural effects of meso-halogenation on porphyrins

• Keith J. Flanagan,
• Maximilian Paradiz Dominguez,
• Zoi Melissari,
• Hans-Georg Eckhardt,
• René M. Williams,
• Dáire Gibbons,
• Caroline Prior,
• Gemma M. Locke,
• Alina Meindl,
• Aoife A. Ryan and
• Mathias O. Senge

Beilstein J. Org. Chem. 2021, 17, 1149–1170, doi:10.3762/bjoc.17.88

• affected by both halogen type and metal insertion. In compound 1 the main motifs seen are the face-to-face stacking at 3.326(4) Å (Figure 2A) and the tilted edge-on interaction (≈64°) (Figure 2B). The other motif seen is the inline interactions where layers of porphyrins are lined up with the bromine atoms

• porphyrin conformation are observed due to the metal center insertion. The first of these is the stacking between the porphyrin rings (at 3.581(3) Å), which now features the bromine atoms pointing in opposite directions with a ruffled conformation of the porphyrin macrocycle (Figure 3A). Moreover, a similar

• motif of bromine atoms pointing towards the phenyl rings is visible in this structure and seems to be a staple of this series (Figure 3B). Secondly, the edge-on interaction in this structure has changed, where the pyrrole moiety is pointing towards the face of the porphyrin macrocycle as seen in Figure

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

• using DMF as solvent. After addition, a subsequent intramolecular cyclization involving the resulting amide and the vicinal carbon with bromine atoms took place. By contrary, when the reaction was carried out in THF, the elimination process was suppressed, leading exclusively to enantiomerically pure α

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

• gram scale. The introduced bromine atom can be converted into fluorine and allyl groups. Keywords: bromination; C–H transformation; hydrogen abstraction; manganese; radical; Introduction Organic halides are versatile precursors for various synthetic protocols and are frequently used to introduce a

• high temperatures in the absence of a catalyst (Scheme 1a) [14][15][16]. However, these reactions do not exhibit any selectivity due to the indiscriminate attack of bromine radicals on the C–H bonds in the substrate, which leads to the formation of a mixture of halogenated products. Electrophilic and

• reaction proceeded regioselectively at the methine C(sp3)–H bond of isoamyl benzoate (1b) to give 2b in 64% yield. Isoamyl benzoates bearing halogen atoms, such as fluorine, chlorine, or bromine, on the phenyl ring were also suitable substrates and gave C(sp3)–H brominated products 2c–e in 49–60% yields

Synthesis of dibenzosuberenone-based novel polycyclic π-conjugated dihydropyridazines, pyridazines and pyrroles

• Ramazan Koçak and
• Arif Daştan

Beilstein J. Org. Chem. 2021, 17, 719–729, doi:10.3762/bjoc.17.61

• complete conversion to 4l, revealing its ease of oxidation compared to the chloro derivative 3k. In addition, dihydrotetrazines 6k and 6l could not be isolated, as probably compound 6k decomposed completely in the reaction medium and 6l decomposed following a bromine transfer to dibenzosuberenone (1

• mechanism illustrated in Scheme 4, tetrazine 6l first tautomerizes into 7, from which dibenzosuberenone (1) receives bromine to give 5l via bromonium 8. As tetrazine 9 was unstable under the current reaction conditions, it decomposed and could not be observed [65]. In the second part of the study

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

• -(methylsulfonyl)-1-phenyl-1H-tetrazole with substitution of bromine and methylsulfonyl groups giving the corresponding tetrazolium salts or conjugate aminides. The obtained mesoionic tetrazoles have been characterized by elemental analysis, FTIR, NMR, and UV–vis spectroscopy, TGA/DSC analysis and for 1,3-di-tert

• tetrazole-5-aminides were carried out as a part of studies of mesoionic compounds [22][23][24]. Earlier, we reported the facile preparation of 1,3-di-tert-butyltetrazolium-5-aminide [25], which was later used for the synthesis of the first tetrazolium halocuprate [26] and also shown to react with bromine

• and 5-(methylsulfonyl)-1-phenyl-1H-tetrazole and substitute bromine and methylsulfonyl groups giving tetrazolium salts or conjugate aminides. The obtained mesoionic tetrazoles have been characterized by elemental analysis, FTIR, NMR and UV–vis spectroscopy, TGA/DSC analysis, and for 1,3-di-tert

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

• brominated derivatives 72-Br, the corresponding side-chain arylation reaction occurred at −60 °C, but a further hydrodehalogenation led to the bromine-free derivatives 75. For the chlorinated derivatives 72-Cl, a similar side-chain arylation−hydrodehalogenation sequence occurred, but an additional Friedel

Diels–Alder reaction of β-fluoro-β-nitrostyrenes with cyclic dienes

• Savva A. Ponomarev,
• Roman V. Larkovich,
• Alexander S. Aldoshin,
• Andrey A. Tabolin,
• Sema L. Ioffe,
• Jonathan Groß,
• Till Opatz and
• Valentine G. Nenajdenko

Beilstein J. Org. Chem. 2021, 17, 283–292, doi:10.3762/bjoc.17.27

• one of the most widely used fluorine-containing building blocks [48][49]. Recently, we have developed an efficient stereoselective synthesis of β-fluoro-β-nitrostyrenes 1 based on the radical nitration of 2-bromo-2-fluorostyrenes [50]. This process takes place with simultaneous elimination of bromine

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

• yield from the α-bromopyridine-substituted N-Boc-3,4-dehydropiperidine. When the same reaction was attempted on the bromine-free analog, the yield was only 22% [43]. The difluorocyclopropanation of an alkenyl trifluoroborate using the TMSCF3–NaI system afforded the boronate derivative 37 [44]. The

• compounds were synthesized in this way. The reaction with bromine proceeded through the breaking of the distal bond of the cyclopropyl ring affording the final fluorine-containing compound 140 (Scheme 60) [111]. Cleavage of the proximal bond: Cheng investigated the ring-opening reactions of difluoro

Tuning the solid-state emission of liquid crystalline nitro-cyanostilbene by halogen bonding

• Subrata Nath,
• Alexander Kappelt,
• Matthias Spengler,
• Bibhisan Roy,
• Jens Voskuhl and
• Michael Giese

Beilstein J. Org. Chem. 2021, 17, 124–131, doi:10.3762/bjoc.17.13

• azopyridines with molecular iodine or bromine [9]. Interestingly, the broadest mesophase temperature ranges were found for the bromine-based assemblies and not as anticipated, for the iodine system which yields a stronger halogen bond. In order to prove that the halogen bond plays a crucial role for the

Progress in the total synthesis of inthomycins

• Bidyut Kumar Senapati

Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7

• bromine in acetic acid, and then triethyl phosphite. Next, compound 28 was treated with sodium hydride followed by aldehyde 29 [37] to give (E,E)-dienyl stannane 30 in 50% yield. The key Stille coupling between 30 and vinyl iodide 31, prepared by Takai reaction [38] of phenylacetaldehyde, in presence of

Synthesis of tetrafluorinated piperidines from nitrones via a visible-light-promoted annelation reaction

• Vyacheslav I. Supranovich,
• Igor A. Dmitriev and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2020, 16, 3104–3108, doi:10.3762/bjoc.16.260

• photocatalyst and stoichiometric quantities (1.2 equiv) of a reducing system (ascorbic acid/collidine). In this reaction no products were formed with reactant 2a remaining unconsumed (Table 1). To obtain a more reactive fluorinated halide, the bromine atom residing at the fluorinated moiety was exchanged for

An atom-economical addition of methyl azaarenes with aromatic aldehydes via benzylic C(sp³)–H bond functionalization under solvent- and catalyst-free conditions

• Divya Rohini Yennamaneni,
• Vasu Amrutham,
• Krishna Sai Gajula,
• Rammurthy Banothu,
• Murali Boosa and
• Narender Nama

Beilstein J. Org. Chem. 2020, 16, 3093–3103, doi:10.3762/bjoc.16.259

• ) gave the expected product 3c along with the dehydrated product 4c (Table 2, entry 3). Substrates containing a halogen, such as fluorine, chlorine, and bromine, were efficiently reacted to afford the products 3e–h in successively moderate yields (Table 2, entries 5–8). Notably, 3-fluorobenzaldehyde (2e

Construction of pillar[4]arene[1]quinone–1,10-dibromodecane pseudorotaxanes in solution and in the solid state

• Xinru Sheng,
• Errui Li and
• Feihe Huang

Beilstein J. Org. Chem. 2020, 16, 2954–2959, doi:10.3762/bjoc.16.245

• in the solid state. From single crystal X-ray diffraction, the linear guest molecules thread into cyclic pillar[4]arene[1]quinone host molecules in the solid state, stabilized by CH∙∙∙π interactions and hydrogen bonds. The bromine atoms at the periphery of the guest molecule provide convenience for

• bonds. Specifically, there are four hydrogen atoms on the guest molecule to form multiple CH∙∙∙π interactions with the 1,4-diethoxybenzene subunits of the host. In addition, the two bromine atoms at the periphery of the guest molecule are outside the host cavities and form moderate hydrogen bonds with

• between H and G were weak and that there was a complexation competition with solvent molecules. Furthermore, the addition of G did not change the maximum UV–vis absorption wavelength of H. The bromine atoms at the periphery of the guest molecule provide convenience for the further capping of the

Changed reactivity of secondary hydroxy groups in C8-modified adenosine – lessons learned from silylation

• Jennifer Frommer and
• Sabine Müller

Beilstein J. Org. Chem. 2020, 16, 2854–2861, doi:10.3762/bjoc.16.234

• [25]. Therefore, we decided to start the synthesis with the preparation of the C8-brominated derivative. Halogenation with bromine was achieved in good yields, however, the following Sonogashira reaction reproducibly proceeded with very low yields (data not shown). Therefore, we changed the used

Chan–Evans–Lam N1-(het)arylation and N1-alkеnylation of 4-fluoroalkylpyrimidin-2(1H)-ones

• Viktor M. Tkachuk,
• Oleh O. Lukianov,
• Mykhailo V. Vovk,
• Isabelle Gillaizeau and
• Volodymyr A. Sukach

Beilstein J. Org. Chem. 2020, 16, 2304–2313, doi:10.3762/bjoc.16.191

• the bromine atom at position 5 of the 4-trifluoromethylpyrimidin-2(1H)-ones 1g,h did not disturb the course of the reaction and the products 9f,g bearing the corresponding functionalities are applicable as building blocks in further syntheses. The 6-methyl substituent had a negative effect on the N

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

• have also reported the functionalized sumanene derivatives 73–75 at the convex side of the internal carbon commencing from the bromination of the hydroxysumanene 68 using NBS and subsequent nucleophilic substitution reaction [47][48]. To their surprise, when they used molecular bromine instead of NBS

• reaction as the critical step [54]. Towards this goal, they started with the hexabromination of sumanene using bromine and iron powder in nitrobenzene to provide the desired compound 94 in 61% yield. Having the bromosumanene 94 in hand, it was then subjected to the Suzuki coupling with several arylboronic

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

• major isomer were obtained by recrystallization. The X-ray diffraction analysis clearly showed that the bromine atom was located on the carbon trans to the fluorine atom resulting in the major product with the E-geometry (see Supporting Information File 1). It should be noted that longer reaction times

• corroborated by 1D NOESY experiments in which after selective irradiation of the protons α to the nitrogen atom, a response was observed only for the protons α to the bromine atom, thus indicating their spatial proximity. In order to elucidate the selectivity control in this ring-opening reaction displayed by

• between fluorine and bromine limited the intermolecular ring-opening reaction by bromide in favor of a faster intramolecular reaction involving the ester group leading to 14. Indeed, a competitive cyclization reaction occurred forming 14 with HBr/AcOH and confirmed when the reaction was performed in the

Regiodivergent synthesis of functionalized pyrimidines and imidazoles through phenacyl azides in deep eutectic solvents

• Paola Vitale,
• Luciana Cicco,
• Ilaria Cellamare,
• Filippo M. Perna,
• Antonio Salomone and
• Vito Capriati

Beilstein J. Org. Chem. 2020, 16, 1915–1923, doi:10.3762/bjoc.16.158

• to “neutral” (Me), electron-withdrawing (Cl, Br, CN) and electron-donating (MeO, OH) substituents as the desired imidazoles 3b/3b'–3h were isolated in 78–98% yield. The presence of additional halogen groups such as chlorine and bromine in 3c/3c' and 3d allows further downstream diversification by

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

Clickable azide-functionalized bromoarylaldehydes – synthesis and photophysical characterization

• Dominik Göbel,
• Marius Friedrich,
• Enno Lork and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2020, 16, 1683–1692, doi:10.3762/bjoc.16.139

• with a quantum yield of ΦP = 2.9% in the crystalline state: this behavior was caused by intermolecular halogen bonds from the carbonyl-oxygen atom to an adjacent bromine atom (Figure 1a). Despite multifarious examples of RTP in the crystalline state, purely organic compounds showing RTP in solution are

• of the ortho-bromine substituent was again accomplished by metalation using TMPMgCl·LiCl and subsequent reaction with 1,2-dibromotetrachloroethane to afford 11 in 76% yield. A second bromination at the benzylic position provided the dibrominated derivative 12 in 66% yield. The substitution reaction

Azidophosphonium salt-directed chemoselective synthesis of (E)/(Z)-cinnamyl-1H-triazoles and regiospecific access to bromomethylcoumarins from Morita–Baylis–Hillman adducts

• Soundararajan Karthikeyan,
• Radha Krishnan Shobana,
• Kamarajapurathu Raju Subimol,
• J. Helen Ratna Monica and
• Ayyanoth Karthik Krishna Kumar

Beilstein J. Org. Chem. 2020, 16, 1579–1587, doi:10.3762/bjoc.16.130

• outcome of this process was the phosphonium-protected MBH moiety Ib and hydrazoic acid. The counter ion bromine facilitated the nucleophilic attack at the vinylic centre of Ib and the spontaneous removal of triphenylphosphine oxide to yield IIb. A consecutive intramolecular nucleophilic attack of the

Photoredox-catalyzed silyldifluoromethylation of silyl enol ethers

• Vyacheslav I. Supranovich,
• Vitalij V. Levin and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2020, 16, 1550–1553, doi:10.3762/bjoc.16.126

• carbon–bromine bond. Keywords: difluoroalkylation; organofluorine compounds; photocatalysis; radical addition; silicon reagents; Findings Fluorinated silicon reagents have found widespread use for the introduction of fluorinated fragments [1][2][3][4][5]. Typically, these reagents work under strongly

• strongly reducing catalysts may be associated with the ability of gold to interact with the bromine atom of silane 1 followed by inner-sphere electron transfer [27]. The radical then attacks silyl enol ether 2, and the subsequent silyloxy-substituted radical is oxidized by the photocatalyst to generate the

• carbon-based radical via cleavage of the carbon–bromine bond by a gold photocatalyst. Reaction of silyl enol ethers. Yields refer to isolated yields. aReaction time 24 h; b1.0 equiv of silane 1 was used; cketone was isolated. Reactions of (bromodifluoromethyl)trimethylsilane (1). Optimization studies

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