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

• ′-tetramethylethylenediamine (TMEDA) as shown in the Scheme 1. Having the compound 4 in hand, it was subjected to the cyclization in the presence of boron trifluoride to provide the tricyclohexyl-fused benzene derivative which on further dehydrogenation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) afforded 1,5,9

• accessible compound, namely norbornadiene (10) by involving oxidative aromatization in the presence of DDQ via an intermediate 17, as displayed in Scheme 2. As can be seen from an inspection of Scheme 2, they first performed a single step cyclotrimerization of 10 using n-BuLi and t-BuOK in 1,2-dibromoethane

• hexahydrosumanene 17 which on subsequent aromatization using DDQ furnished the desired molecule sumanene (2) in good yield. To their surprise, tandem metathesis for achieving compound 17 from 13 (anti) was fruitless may be because of the endothermic reaction by 37.4 kcal/mol as compared to the exothermic (51.4 kcal

Highly selective Diels–Alder and Heck arylation reactions in a divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles from 2-formylpyrrole

• Carlos H. Escalante,
• Eder I. Martínez-Mora,
• Carlos Espinoza-Hicks,
• Alejandro A. Camacho-Dávila,
• Fernando R. Ramos-Morales,
• Francisco Delgado and
• Joaquín Tamariz

Beilstein J. Org. Chem. 2020, 16, 1320–1334, doi:10.3762/bjoc.16.113

• ). However, the use of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) at 25 °C for 48 h led to the aromatized compound 21a in high yield (Table 4, entry 3). Under similar reaction conditions, the series of pyrrolo[3,4-e]indole-1,3-diones 21b–g was resulted in high yields (Table 4, entries 4 and 6–10

• using manganese oxide or DDQ as the oxidizing reagents, or even including Pd/C at high temperatures (250 °C) [45], failed to obtain the series of indoles 23. It is likely that the electron withdrawing effect of the formyl group at the C-7 position counterbalance the delocalization direction of the

• aromatization of pentacycles 11 was explored. Although the use of DDQ under the oxidative reaction conditions shown in Table 4 was efficient for the preparation of derivatives 21, the conversion of 11a into 12 was unsuccessful (Scheme 7). The action of active MnO2 in toluene at high temperature was able to

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

• quinazolinone 73a (Scheme 27) [118]. The method for oxidative cyclization of thiohydroximic acids 75 under the action of DDQ and p-TsOH with the formation of the corresponding 1,4,2-oxathiazoles 76 was developed (Scheme 28) [119]. The authors noted that reaction in the absence of p-TsOH proceeded with lower

• yield of 76. A radical mechanism was proposed in which the oxime moiety is oxidized by DDQ to the iminoxyl radical 77, which undergoes 1,5-HAT to give a C-centered radical 78 stabilized by a sulfur atom. 78 is oxidized by DDQ to a carbocation 79, followed by the closure of the oxathiazole ring (Scheme

•  29). Later, DDQ-mediated oxidative cyclization of amidoximes with the formation of 1,2,4-oxadiazoles (analogous transformation with K3PO4/O2 system was shown above in Scheme 26) was realized without the addition of TsOH [120]. Isoxazolines 82 were synthesized by a one-pot sequence, which included the

Synthesis and properties of tetrathiafulvalenes bearing 6-aryl-1,4-dithiafulvenes

• Aya Yoshimura,
• Hitoshi Kimura,
• Kohei Kagawa,
• Mayuka Yoshioka,
• Toshiki Itou,
• Dhananjayan Vasu,
• Takashi Shirahata,
• Hideki Yorimitsu and
• Yohji Misaki

Beilstein J. Org. Chem. 2020, 16, 974–981, doi:10.3762/bjoc.16.86

• ion complexes with DDQ or iodine were reported [17][18][19][20][21][22][23][24]. Peripherally thiophene-functionalized TTFs, as potential precursors to conducting polymers, and organic metals were also prepared and characterized [25][26][27][28][29]. To design more tempting molecules, the attachment

Direct borylation of terrylene and quaterrylene

• Haruka Kano,
• Keiji Uehara,
• Kyohei Matsuo,
• Hironobu Hayashi,
• Hiroko Yamada and
• Naoki Aratani

Beilstein J. Org. Chem. 2020, 16, 621–627, doi:10.3762/bjoc.16.58

• with AlCl3 reproducibly provided a pure terrylene [8]. Scholl reaction using a superacid catalyst in combination with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as oxidant provides a scalable preparation of quaterrylene [9], but unfortunately the low solubility prevents 1H NMR characterization

• calculations showed a good agreement with the observed absorption spectra. Taking the successful result of the terrylene borylation, next we tried to perform the same reaction to quaterrylene (Scheme 2). The quaterrylene was prepared by the oxidative condensation reaction of perylene with TfOH and DDQ [9

Regioselectively α- and β-alkynylated BODIPY dyes via gold(I)-catalyzed direct C–H functionalization and their photophysical properties

• Takahide Shimada,
• Shigeki Mori,
• Masatoshi Ishida and
• Hiroyuki Furuta

Beilstein J. Org. Chem. 2020, 16, 587–595, doi:10.3762/bjoc.16.53

• mixture was treated with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to give the α,α'-diethynyl-substituted dipyrrin 7a. Subsequent boron complexation in the presence of trimethylsilyl chloride (TMSCl) as a fluoride scavenger afforded 4a in 16% yield over three steps. Separately, α-ethynyl

Efficient synthesis of 3,6,13,16-tetrasubstituted-tetrabenzo[a,d,j,m]coronenes by selective C–H/C–O arylations of anthraquinone derivatives

• Seiya Terai,
• Yuki Sato,
• Takuya Kochi and
• Fumitoshi Kakiuchi

Beilstein J. Org. Chem. 2020, 16, 544–550, doi:10.3762/bjoc.16.51

• dehydrogenative cyclization using DDQ and FeCl3 (Scheme 2b) [44]. However, 3,6,13,16-tetrasubstituted tetrabenzo[a,d,j,m]coronenes have not been reported using these reported methods. Here, we describe a convenient method for the synthesis of 3,6,13,16-tetrasubstituted tetrabenzo[a,d,j,m]coronenes based on a

Synthesis of triphenylene-fused phosphole oxides via C–H functionalizations

• Md. Shafiqur Rahman and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2020, 16, 524–529, doi:10.3762/bjoc.16.48

• (trifluoroacetoxy)iodo]benzene] (PIFA) and BF3·OEt2 in dichloromethane at −78 °C afforded, after 12 h, the desired cyclized product 8a in 59% yield. The reaction could be performed on a 0.5 mmol scale in a similar yield of 58%. Note that other typical reagents used for the Scholl reaction, such as DDQ/CF3CO2H

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• of substituted phenols using QuCN. Synthesis of substituted phenols with DDQ (5). Aerobic bromination of arenes using an acridinium-based photocatalyst. Aerobic bromination of arenes with anthraquinone. Chlorination of benzene derivatives with Mes-Acr-MeClO4 (2). Chlorination of arenes with 4CzIPN

Synthesis of 3-alkenylindoles through regioselective C–H alkenylation of indoles by a ruthenium nanocatalyst

• Abhijit Paul,
• Debnath Chatterjee,
• Srirupa Banerjee and
• Somnath Yadav

Beilstein J. Org. Chem. 2020, 16, 140–148, doi:10.3762/bjoc.16.16

• purification [17][18]. As an example for the second category, Jiao and co-workers developed an organocatalytic C3–H alkenylation of indoles by the reaction of indoles with α,β-unsaturated aldehydes in presence of morpholin-4-ium trifluoroacetate as a catalyst and a stoichiometric amount of DDQ to achieve

Convenient synthesis of the pentasaccharide repeating unit corresponding to the cell wall O-antigen of Escherichia albertii O4

• Tapasi Manna,
• Arin Gucchait and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2020, 16, 106–110, doi:10.3762/bjoc.16.12

• presence of tetrabutylammonium bromide (TBAB) followed by oxidative removal [33] of the PMB group using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to give trisaccharide acceptor 13 in 72% yield. Trisaccharide acceptor 13 was then allowed to couple with ʟ-rhamnosyl trichloroacetimidate donor 5 in the

• , THF, room temperature, 6 h; (c) DDQ, CH2Cl2/H2O (9:1), room temperature, 2 h, 72% in two steps; (d) HClO4/SiO2, CH2Cl2, −10 °C, 1 h, 76%; (e) 0.1 M CH3ONa, CH3OH, room temperature, 2 h, 94%; (f) NIS, HClO4/SiO2, MS 4 Å, CH2Cl2, –15 °C, 1 h, 70%; (g) CH3COSH, pyridine, room temperature, 16 h; (h

Construction of trisubstituted chromone skeletons carrying electron-withdrawing groups via PhIO-mediated dehydrogenation and its application to the synthesis of frutinone A

• Qiao Li,
• Chen Zhuang,
• Donghua Wang,
• Wei Zhang,
• Rongxuan Jia,
• Fengxia Sun,
• Yilin Zhang and
• Yunfei Du

Beilstein J. Org. Chem. 2019, 15, 2958–2965, doi:10.3762/bjoc.15.291

• also be realized by DDQ-mediated dehydrogenation of chromanones under heating in dioxane (Scheme 1b) [3][59][60]. In 2005, Yang and co-workers reported that chromones could be formed by microwave irradiation of the corresponding chromanone reactants and N-bromosuccinimide (NBS) in the presence of a

Chemical synthesis of the pentasaccharide repeating unit of the O-specific polysaccharide from Escherichia coli O132 in the form of its 2-aminoethyl glycoside

• Debasish Pal and
• Balaram Mukhopadhyay

Beilstein J. Org. Chem. 2019, 15, 2563–2568, doi:10.3762/bjoc.15.249

• -position of the donor led exclusively to the 1,2-cis glycoside [19]. Finally, the oxidative removal of the naphthyl group using DDQ [20] afforded the trisaccharide acceptor 11 in 83% yield (Scheme 2). The known galactofuranosyl derivative 12 [21] was prepared by following a literature procedure. It was

Functional panchromatic BODIPY dyes with near-infrared absorption: design, synthesis, characterization and use in dye-sensitized solar cells

• Quentin Huaulmé,
• Cyril Aumaitre,
• Outi Vilhelmiina Kontkanen,
• David Beljonne,
• Alexandra Sutter,
• Gilles Ulrich,
• Renaud Demadrille and
• Nicolas Leclerc

Beilstein J. Org. Chem. 2019, 15, 1758–1768, doi:10.3762/bjoc.15.169

• dyes. Synthetic scheme of the selected materials. a) hydroxylamine hydrochloride, NaHCO3, DMSO, 60 °C then acetylene, KOH, DMSO, 110 °C, 24% over the two steps; b) 4-iodobenzoyl chloride, DCM, rt then DDQ, DCM, rt then NEt3, BF3·OEt2, 0 °C to rt, 35%; c) piperidine, cat. PTSA, toluene, 130 °C, 5: 35

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

Synthesis of pyrrolo[1,2-a]quinolines by formal 1,3-dipolar cycloaddition reactions of quinolinium salts

• Anthony Choi,
• Rebecca M. Morley and
• Iain Coldham

Beilstein J. Org. Chem. 2019, 15, 1480–1484, doi:10.3762/bjoc.15.149

• adduct 10 was performed using the oxidant 2,3-dichloro-5,6-dicyanoquinone (DDQ) to give the fully unsaturated product 13. To expand the range of products and explore the scope of the reaction further, we prepared the salts 14a and 14b (from 6-chloroquinoline and 6-bromoquinoline) and these were heated

Extending mechanochemical porphyrin synthesis to bulkier aromatics: tetramesitylporphyrin

• Qiwen Su and
• Tamara D. Hamilton

Beilstein J. Org. Chem. 2019, 15, 1149–1153, doi:10.3762/bjoc.15.111

• milder conditions by promoting the establishment of an equilibrium for the cyclization step, then adding a gentle oxidizer (p-chloranil or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)) in a second step to obtain irreversibly the aromatized porphyrin [11]. The symmetrical tetra-meso-substituted

• work on mechanochemical porphyrin synthesis has demonstrated that it is possible to synthesize tetraphenylporphyrin (TPP) by grinding benzaldehyde and pyrrole (two liquids) in the presence of an acid catalyst, followed by oxidation with DDQ in minimal amounts of solvent [19]. TPP was produced in a

• several weeks brought about the appearance of TPP in small amounts. More immediate oxidation of this power, by dissolving in chloroform and stirring with DDQ for 2 hours, allowed isolation of TPP in 28% yield [19]. Appearance of TPP upon oxidation confirms that mechanochemistry successfully brought about

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• acid derivative as one of the substrates of the reaction, together with an amine and a third reagent that provides the carbon atom needed to complete the cyclic moiety. Thus, Shi et al. [76] reacted benzoic acid derivatives 1, amides 2 and DMSO (3) in the presence of DDQ as oxidant and without any

Efficient synthesis of 4-substituted-ortho-phthalaldehyde analogues: toward the emergence of new building blocks

• Clémence Moitessier,
• Ahmad Rifai,
• Pierre-Edouard Danjou,
• Isabelle Mallard and
• Francine Cazier-Dennin

Beilstein J. Org. Chem. 2019, 15, 721–726, doi:10.3762/bjoc.15.67

• cyclisation in a basic medium of 2 then occurred to generate 4,5-dihydroisobenzofuran-5-ol (3) [19]. At this step, Cao et al. [17] have chosen the direct oxidation of 4,5-dihydroisobenzofuran-5-ol (3) to obtain 4-HO-OPA by using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as an oxidant. However, the yield

• initiated in order to evaluate the stability of the protected RO-OPA and to certify the absence of OPA contamination [20]. Two major oxidants, SeO2 and DDQ were chosen for 5-methoxy and 5-acetoxy-4,5-dihydroisobenzofuran oxidation. As illustrated in Scheme 3, the reaction occurred with both reactants but

• -phthalaldehyde (5a) and 78% of OPA (Table 2, entry 2). As for 5-methoxy-4,5-dihydroisobenzofuran (4b), it was totally converted to 4-hydroxyphthalic acid (7, Table 2, entry 3). In regard to these results, oxidation with SeO2 leads to the unwanted products OPA and 7, so oxidation with DDQ was initiated to avoid

Catalyst-free assembly of giant tris(heteroaryl)methanes: synthesis of novel pharmacophoric triads and model sterically crowded tris(heteroaryl/aryl)methyl cation salts

• Rodrigo Abonia,
• Luisa F. Gutiérrez,
• Braulio Insuasty,
• Jairo Quiroga,
• Kenneth K. Laali,
• Chunqing Zhao,
• Gabriela L. Borosky,
• Samantha M. Horwitz and
• Scott D. Bunge

Beilstein J. Org. Chem. 2019, 15, 642–654, doi:10.3762/bjoc.15.60

• reactions could also be carried out in water (at circa 80 °C) but with chemoselectivity favoring (Ar1Ar1Ar2)CH over (Ar1Ar2Ar3)CH. The molecular structure of a representative (Ar1Ar2Ar3)CH triad was confirmed by X-ray analysis. Model tris(heteroaryl/aryl)methylium salts were generated by reaction with DDQ

• attempts to cleanly generate the salts by hydride abstraction with trityl-BF4 were unsuccessful [61], presumably due to extreme steric crowding, the reaction with DDQ/HPF6 (Scheme 8) [62][63][64][65] was successful and the methylium-PF6 salts 10{4,4,8} and 10{4,4,11}, respectively, precipitated from DCM as

• and 9, respectively, packed with up to three different pharmacophors in a single molecule. The ability to perform these reactions in ethanol and even in water, with no catalysts is noteworthy. Representative methylium salts generated by ionization with DDQ/HPF6 exhibited 1H NMR signal broadening

A chemoenzymatic synthesis of ceramide trafficking inhibitor HPA-12

• Seema V. Kanojia,
• Sucheta Chatterjee,
• Subrata Chattopadhyay and
• Dibakar Goswami

Beilstein J. Org. Chem. 2019, 15, 490–496, doi:10.3762/bjoc.15.42

• conversion to the appropriate intermediates and subsequent acylation with lauric acid furnished the target compound. Keywords: AD mix-β; [bmim][PF6]; DDQ; HPA-12; lipase; Introduction Ceramides belong to the family of sphingolipids (SLs) and are synthesized de-novo in the endoplasmic reticulum (ER) [1

• -alcohol [53]. However, unlike in our case, the reaction proceeded with poor diastereoselectivity irrespective of the dihydroxylating agent used. To confirm the 1,3-anti diol stereochemistry of 7a, it was debenzylated using DDQ/CH2Cl2–H2O to furnish the trihydroxy compound 7a'. The 1H and 13C NMR spectra

• to product 9b, which was undesirable. A similar elimination was earlier observed by Sharf et al. during hydrogenolysis of dibenzyl ether [55]. To avoid this, an oxidative debenzylation of 9a using DDQ/CH2Cl2–H2O was carried out. However, this led to a very poor yield of the target compound 2 (Scheme

Convergent synthesis of the pentasaccharide repeating unit of the biofilms produced by Klebsiella pneumoniae

• Arin Gucchait,
• Angana Ghosh and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2019, 15, 431–436, doi:10.3762/bjoc.15.37

• removal of acetyl groups and benzylation using benzyl bromide and sodium hydroxide in one-pot [37] followed by removal of the p-methoxybenzyl group using DDQ [38] in 84% overall yield. Finally, stereoselective glycosylation of disaccharide trichloroacetimidate donor 18 with trisaccharide acceptor 23 in

• conditions: (a) TMSOTf, CH2Cl2, −10 °C, 30 min, 45%; (b) NIS, TMSOTf, MS 4 Å, CH2Cl2, −10 °C, 30 min, 40%. Reagents and conditions: (a) NIS, TMSOTf, MS 4 Å, CH2Cl2, −50 °C, 2 h, 70%; (b) benzyl bromide, NaOH, TBAB, DMF, 3 h; (c) DDQ, CH2Cl2/H2O, room temperature, 84%; (d) TMSOTf, CH2Cl2, −10 °C, 30 min, 70

Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

• Guillaume Ernouf,
• Jean-Louis Brayer,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

• -hindered face of the olefin was obtained predominantly (73/73’ = 90:10) albeit with lower diastereocontrol compared to the protected alcohol 58a. Cleavage of the PMB ether in 58a was achieved purposely with DDQ so that a hydroxy-directed hydrogenation of the resulting α-hydroxy ester 74 could be carried

Stereodivergent approach in the protected glycal synthesis of L-vancosamine, L-saccharosamine, L-daunosamine and L-ristosamine involving a ring-closing metathesis step

• Pierre-Antoine Nocquet,
• Aurélie Macé,
• Frédéric Legros,
• Jacques Lebreton,
• Gilles Dujardin,
• Sylvain Collet,
• Arnaud Martel,
• Bertrand Carboni and
• François Carreaux

Beilstein J. Org. Chem. 2018, 14, 2949–2955, doi:10.3762/bjoc.14.274

• strategy based on an Evans’ aldol reaction. Mildly oxidizing conditions using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) were used for the removal of the p-methoxybenzyl (PMB) group to provide alcohols 14 (Scheme 3). Several palladium(II) catalysts have been tested for the conversion of alcohols to

• the syn diastereomer 18 in high stereoselectivity (93:7). After silylation of the free hydroxy group, the cleavage of the PMB ether with DDQ led to alcohol 20 in 77% yield for the two steps. Ring-closing metathesis of diene 21, obtained by O-vinylation of 20, gave the dihydropyran 22 in 53% overall

Transition metal-free oxidative and deoxygenative C–H/C–Li cross-couplings of 2H-imidazole 1-oxides with carboranyl lithium as an efficient synthetic approach to azaheterocyclic carboranes

• Lidia A. Smyshliaeva,
• Mikhail V. Varaksin,
• Pavel A. Slepukhin,
• Oleg N. Chupakhin and
• Valery N. Charushin

Beilstein J. Org. Chem. 2018, 14, 2618–2626, doi:10.3762/bjoc.14.240

• involve the use of DDQ as oxidant and refluxing of the reaction mixture in argon atmosphere for 1 h (Table 2, entry 12). It has also been observed that further increase in the exposure time does not improve yields (39–52%) of the target carboranyl-substituted imidazole 1-oxides 5a–d (Scheme 1). Besides