Preparing a liquid crystalline dispersion of carbon nanotubes with high aspect ratio

• Keiko Kojima,
• Nodoka Kosugi,
• Hirokuni Jintoku,
• Kazufumi Kobashi and
• Toshiya Okazaki

Beilstein J. Org. Chem. 2024, 20, 52–58, doi:10.3762/bjoc.20.7

• polarizers (white double arrows). Scale bars are 400 µm. (c) Polarized optical absorption spectra with different angles ranging from 0° (red) to 90° (blue). The sear direction and polarizer are parallel at 0°. (d) SEM image of the DWCNT film. Blue outlined arrows indicate the shear direction of bar-coating

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• bonds of unactivated aryls or aromatic sulfenylation by electrophilic aromatic substitution (SEAr) has also recently received attention [38]. In recent years, N-(aryl/alkylsulfenyl)succinimides and N-(arylsulfenyl)phthalimides have been widely employed as new alternative sulfenylating reagents in the

Facile and diastereoselective arylation of the privileged 1,4-dihydroisoquinolin-3(2H)-one scaffold

• Dmitry Dar’in,
• Grigory Kantin,
• Alexander Bunev and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2022, 18, 1070–1078, doi:10.3762/bjoc.18.109

• ). Mechanistically, the arylation of diazo substrates 10 likely proceeds via the protonation of the diazo moiety and elimination of a nitrogen molecule, whereby carbocation 17 is generated. The latter can either be deprotonated to give byproduct 15 or be intercepted by an arene molecule in SEAr fashion to give

Regioselectivity of the S_EAr-based cyclizations and S_EAr-terminated annulations of 3,5-unsubstituted, 4-substituted indoles

• Jonali Das and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2022, 18, 293–302, doi:10.3762/bjoc.18.33

• approaches toward such compounds have been developed. Among these, cyclization and annulation of 3,5-unsubstituted, 4-substituted indoles involving an electrophilic aromatic substitution (SEAr) as the ring closure are particularly attractive, because they avoid the use of 3,4- or 4,5-difunctionalized indoles

• summarizing recent relevant literature reports. Keywords: annulation; cyclization; fused indoles; regioselectivity; SEAr; Introduction Over the decades, countless cyclization and annulation reactions of substituted arenes/heteroarenes involving an electrophilic aromatic substitution (SEAr) reaction as the

• an SEAr reaction as the ring-closure step can generate indole 3,4-fused cabo- and heterocycles or/and their indole 4,5-fused counterparts (Scheme 1B). This is primarily due to the fact that such substrates have two proximal nucleophilic sites: the indole C5 as the ortho position and intrinsically

Synthesis of highly substituted fluorenones via metal-free TBHP-promoted oxidative cyclization of 2-(aminomethyl)biphenyls. Application to the total synthesis of nobilone

• Ilya A. P. Jourjine,
• Lukas Zeisel,
• Jürgen Krauß and
• Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2668–2679, doi:10.3762/bjoc.17.181

• through inductive effects, and on amides, which should be more prone to engage in the cyclization owing to the high reactivity of expected N-acyliminium ions 4a (R1 = alkyl, R2 = acyl) in SEAr reactions. In the second screening round, we determined the isolated yields of the promising reactions identified

• unsuccessful, fluorenone (3) was not formed under either of these conditions, suggesting the involvement of radicals in the cyclization reaction rather than an SEAr mechanism as proposed in Scheme 3. A more detailed investigation might be required to fully understand the mechanism of this oxidative benzylamine

Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

• Ranadeep Talukdar

Beilstein J. Org. Chem. 2021, 17, 2102–2122, doi:10.3762/bjoc.17.137

• excess of the indole reactant. It is seen that in the presence of a base the C-2 deprotonation becomes very fast in 9 (for regaining aromaticity) so the boron at the initial C-3-borylated intermediate 8 (formed via SEAr) cannot migrate fast enough, leading to a C-3 borylation product 10a (unlike Pd) [38

• challenging strategies depending on the central tethering atom involved. As time progresses, research on the synthesis and application of this class of molecules will be more broadened. Synthesis of 2,2’-bis(indole)borinic ester 3. Synthesis of 2,2’-bisindole NHC·boranes by an SEAr mechanism. Syntheses of

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

• Pezhman Shiri,
• Ali Mohammad Amani and
• Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

• aryl selenide anion to the antimony atom takes place to give 5-selanyltriazole 85 and Ph2Sb–SeAr. Ph2Sb–SeAr is hydrolyzed in aqueous medium to give selenol 90 and Ph2SbOH. Selenol 90 is oxidized in air and transformed into diselenide 84. Therefore, only 0.5 equiv of diaryl diselenide were necessary

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

• electrophilic attack takes place at the more reactive angular position of the aromatic ring, but in case of a substantial steric hindrance, the linear isomer is formed (Scheme 27). Later, this SEAr reactivity was used for the synthesis of pyrroloquinazoline from 5-aminoindole [63]. Contrary to the one-pot

• except for one single use of silver dicyanamide [65]. Further investigations in this direction might help to soften the conditions and improve the yields. An interesting reactivity was reported with subsequent SEAr cyclization or 1,2,4-oxadiazole formation. However, these applications seem sparse with

In silico rationalisation of selectivity and reactivity in Pd-catalysed C–H activation reactions

• Liwei Cao,
• Mikhail Kabeshov,
• Steven V. Ley and
• Alexei A. Lapkin

Beilstein J. Org. Chem. 2020, 16, 1465–1475, doi:10.3762/bjoc.16.122

• : a) electrophilic aromatic substitution (SEAr) mechanism and b) proton abstraction (PA) mechanism. The key step for the electrophilic aromatic substitution is an electrophilic attack by Pd(II) onto the aromatic substrate that also defines the regioselectivity of the overall process [24]. The key

• predictions. Employing the Python module [20] and OpenBabel executables [28], the 3D structures of the most stable conformers were generated from the 2D structure of a substrate. Subsequently, structures of all possible palladium intermediates representing both mechanisms (PA and SEAr) were built for each

•  1, and introducing the ipso-complex stability parameter. We define this parameter to be the energy difference between the most stable intermediate of the SEAr mechanism and the one of the PA mechanism. By comparing the computational results obtained to the literature experimental data, the two

Acid-catalyzed rearrangements in arenes: interconversions in the quaterphenyl series

• Sarah L. Skraba-Joiner,
• Carter J. Holt and
• Richard P. Johnson

Beilstein J. Org. Chem. 2019, 15, 2655–2663, doi:10.3762/bjoc.15.258

• ][8]. Every student of organic chemistry is taught the importance of arenium ions in the classic two step SEAr mechanism for electrophilic aromatic substitution. Addition of an electrophile to an arene leads to a bound species, sometimes called a σ-complex, which then loses a proton at the site of

Superelectrophilic carbocations: preparation and reactions of a substrate with six ionizable groups

• Sean H. Kennedy,
• Makafui Gasonoo and
• Douglas A. Klumpp

Beilstein J. Org. Chem. 2019, 15, 1515–1520, doi:10.3762/bjoc.15.153

• providing pentacation 13 then the hexacation 14. The product forming steps occur through either 13 or 14. For the arylation product 10, charge delocalization at the carbocation leads to nucleophilic attack at the para-position of the phenyl group. This SEAr step is followed by protonation at the methine

Atom-economical group-transfer reactions with hypervalent iodine compounds

• Andreas Boelke,
• Peter Finkbeiner and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2018, 14, 1263–1280, doi:10.3762/bjoc.14.108

• ) in an SEAr reaction to give the diarylated isoindolin-1-one 9. A drawback of these reaction conditions is the use of excess (3 equiv) mesityl(aryl)iodonium salt 1a to achieve satisfying yields. This dramatically lowers the atom-economy to only 29% (for R = H, Ar = Ph), instead of theoretical 75%, if

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

Conjugated nitrosoalkenes as Michael acceptors in carbon–carbon bond forming reactions: a review and perspective

• Yaroslav D. Boyko,
• Valentin S. Dorokhov,
• Alexey Yu. Sukhorukov and
• Sema L. Ioffe

Beilstein J. Org. Chem. 2017, 13, 2214–2234, doi:10.3762/bjoc.13.220

• oximes 67 and 68 can occur not only via an SEAr mechanism, but also through an alternative [4 + 2]-cycloaddition/elimination pathway (for cycloaddition chemistry of nitrosoalkenes see reviews and accounts: [6][7][8][9][10][57][58]). In the recent work by Palacios and co-workers, the reaction of

Nitration of 5,11-dihydroindolo[3,2-b]carbazoles and synthetic applications of their nitro-substituted derivatives

• Roman A. Irgashev,
• Nikita A. Kazin,
• Gennady L. Rusinov and
• Valery N. Charushin

Beilstein J. Org. Chem. 2017, 13, 1396–1406, doi:10.3762/bjoc.13.136

• ], including elaboration of convenient synthetic ways to construction and modification of ICZ derivatives [34][35][36][37][38][39][40][41]. Taking into account the electron-donating character of the ICZ system, there is no doubt that electrophilic aromatic substitution (SEAr) reactions are the most attractive

• opportunities for design of ICZ-cored molecules. ICZ-cored materials for organic electronic devices. General positions for SEAr in ICZs 1. X-ray single crystal structure of compound 2a. Thermal ellipsoids of 50% probability are presented. X-ray single crystal structure of compounds 9b and 10b. Thermal

Palladium-catalyzed picolinamide-directed iodination of remote ortho-C−H bonds of arenes: Synthesis of tetrahydroquinolines

• William A. Nack,
• Xinmou Wang,
• Bo Wang,
• Gang He and
• Gong Chen

Beilstein J. Org. Chem. 2016, 12, 1243–1249, doi:10.3762/bjoc.12.119

• γ-arylpropylpicolinamides were then selectively iodinated at the remote ε-C(sp2)−H position via a rarely precedented PA-directed electrophilic aromatic substitution (SEAr) reaction (Scheme 1, reaction 2) [21][22]. Copper-catalyzed intramolecular C−N cyclization of these ortho-iodinated intermediates

• provided PA-coupled THQ products in good yields. Although ε-C−H iodination via directed SEAr proceeds with excellent yield and mono-selectivity for many γ-arylpropylpicolinamides, the scope of these PA-directed SEAr reactions is limited to arenes bearing moderate electron-donating or withdrawing groups

• . Arene substrates bearing strongly electron-donating substituents typically gave substantial amounts of undesired iodinated side products via competing innate SEAr processes, and arene substrates bearing strongly electron-withdrawing substituents were often unreactive. Herein, we report our development

Synthesis and nucleophilic aromatic substitution of 3-fluoro-5-nitro-1-(pentafluorosulfanyl)benzene

• Javier Ajenjo,
• Martin Greenhall,
• Camillo Zarantonello and
• Petr Beier

Beilstein J. Org. Chem. 2016, 12, 192–197, doi:10.3762/bjoc.12.21

• , nitro(pentafluorosulfanyl)benzenes are widely-available primary industrial products and starting materials to other SF5-benzenes which were prepared by reduction followed by condensation or diazotization chemistry [8][14][15][16], SEAr [17], SNAr [18][19][20][21][22][23][24], or metal-catalyzed cross

New developments in gold-catalyzed manipulation of inactivated alkenes

• Michel Chiarucci and
• Marco Bandini

Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294

• indoles to alkenes. Intermolecular [Au(III)]-catalyzed hydroarylation of alkenes with benzene derivatives and thiophene. a) Intramolecular [Au(III)]-catalyzed hydroarylation of alkenes. b) A SEAr-type mechanism was hypothesized by the authors. Intramolecular [Au(I)]-catalyzed hydroalkylation of alkenes

Utilizing the σ-complex stability for quantifying reactivity in nucleophilic substitution of aromatic fluorides

• Magnus Liljenberg,
• Tore Brinck,
• Tobias Rein and
• Mats Svensson

Beilstein J. Org. Chem. 2013, 9, 791–799, doi:10.3762/bjoc.9.90

• and industrially important SNAr and SEAr reactions (nucleophilic and electrophilic aromatic substitution, respectively) [3][4][5]. The putative mechanism for the SNAr reaction involves attack of a nucleophile and the formation of an intermediate σ-complex (also called the Meisenheimer complex

Highly selective synthesis of (E)-alkenyl-(pentafluorosulfanyl)benzenes through Horner–Wadsworth–Emmons reaction

• George Iakobson and
• Petr Beier

Beilstein J. Org. Chem. 2012, 8, 1185–1190, doi:10.3762/bjoc.8.131

• the only known SEAr of 1 or 2 is the nitration of 2 under harsh conditions and in low yield [14], we have recently described SNAr of the nitro group in compounds 1 and 2 with alkoxides and thiolates [15], vicarious nucleophilic substitution (VNS) of the hydrogen with carbon [16], oxygen [17] and

• nitrogen [18] nucleophiles, and the oxidative nucleophilic substitution with Grignard and alkyllithium reagents [19]. Reduction of the nitro group in 1 or 2 to (pentafluorosulfanyl)anilines followed by acylation, SEAr halogenation or diazotization (with follow-up reactions) has also been described [11][20

Recent advances in direct C–H arylation: Methodology, selectivity and mechanism in oxazole series

• Cécile Verrier,
• Pierrik Lassalas,
• Laure Théveau,
• Guy Quéguiner,
• François Trécourt,
• Francis Marsais and
• Christophe Hoarau

Beilstein J. Org. Chem. 2011, 7, 1584–1601, doi:10.3762/bjoc.7.187

• ) [66]. Palladium- and copper-catalyzed direct (hetero)arylation with halides: Progress in mechanisms Regarding the C5>C4>C2-reactivity scale of electron-rich azoles under electrophilic reaction, Miura proposed an SEAr-type mechanism for selective C5-arylation of imidazoles, thiazoles and oxazoles. [40

Directed aromatic functionalization

• Victor Snieckus

Beilstein J. Org. Chem. 2011, 7, 1215–1218, doi:10.3762/bjoc.7.141

• Victor Snieckus Department of Chemistry, Queen's University, Kingston, Ontario, K7L 3N6, Canada 10.3762/bjoc.7.141 The title of this Thematic Series brings to the minds of most organic chemists the beautifully logical aromatic electrophilic substitution (SEAr) [1][2][3][4][5] and, to a lesser

• heteroaromatics [15][16][17]. While comparison with SEAr and SNAr should never be denied, the DoM approach offers incontestable ortho regioselectivity, mild conditions, and perhaps most significantly, broad post-DoM synthetic potential. As a result, it has been called upon, with increasing favor and frequency, by

• exchange) chemistry, alternative and competitive combinational metal amide bases are rapidly appearing [47][48]. The first successful glimpses of the much sought after complementary, cleaner, regiodefined, and milder procedures to ortho, para versus meta SEAr reactions are being seen in Cu-catalyzed meta

Enantiospecific synthesis of [2.2]paracyclophane- 4-thiol and derivatives

• Gareth J. Rowlands and
• Richard J. Seacome

Beilstein J. Org. Chem. 2009, 5, No. 9, doi:10.3762/bjoc.5.9

• of enantiomerically pure 4-hydroxy[2.2]paracyclophane or application of our own sulfoxide-metal exchange protocol [31] would permit enantiospecific variants of either route, but neither has been reported. An elegant entry to a variety of racemic alkyl sulfides and sulfoxides by an SEAr reaction