Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

Advances in the synthesis of functionalised pyrrolotetrathiafulvalenes

• Luke J. O’Driscoll,
• Sissel S. Andersen,
• Marta V. Solano,
• Dan Bendixen,
• Morten Jensen,
• Troels Duedal,
• Jess Lycoops,
• Cornelia van der Pol,
• Rebecca E. Sørensen,
• Karina R. Larsen,
• Kenneth Myntman,
• Christian Henriksen,
• Stinne W. Hansen and
• Jan O. Jeppesen

Beilstein J. Org. Chem. 2015, 11, 1112–1122, doi:10.3762/bjoc.11.125

• -benzoquinone (DDQ) gives 6, which is purified by column chromatography, in 52% overall yield (22.5 g) from 12. We have also consistently obtained comparable yields of around 55% using the same method at approximately half this scale. The ability to isolate multigram quantities of 6, which can be stored for

• . Reagents and conditions: a) PhMe, reflux, 19 h, 74%; b) LiBr, NaBH4, THF, MeOH, −10 °C → rt, 20 h, 77%; c) PBr3, THF, 0 °C → rt, 20 h, 75%; d) (i) 13, MeCN, DMF, 80 °C, 15 min, (ii) Hg(OAc)2, CHCl3, AcOH, rt, 24 h, (iii) DDQ, PhCl, reflux, 4 h, 52% (from 12). Preparation of 7. Reagents and conditions: a

Glycoluril–tetrathiafulvalene molecular clips: on the influence of electronic and spatial properties for binding neutral accepting guests

• Yoann Cotelle,
• Marie Hardouin-Lerouge,
• Stéphanie Legoupy,
• Olivier Alévêque,
• Eric Levillain and
• Piétrick Hudhomme

Beilstein J. Org. Chem. 2015, 11, 1023–1036, doi:10.3762/bjoc.11.115

• onto compound 11 [34]. The hydroquinone moieties were subjected to a dehydrogenation reaction using DDQ in THF to reach desired glycolurildiquinone 13 [35] in 91% yield. The Diels–Alder cycloaddition was carried out by treatment of bis-dienophile 13 with TTF derivative 14 [36], able to give rise in

Discrete multiporphyrin pseudorotaxane assemblies from di- and tetravalent porphyrin building blocks

• Mirko Lohse,
• Larissa K. S. von Krbek,
• Sebastian Radunz,
• Suresh Moorthy,
• Christoph A. Schalley and
• Stefan Hecht

Beilstein J. Org. Chem. 2015, 11, 748–762, doi:10.3762/bjoc.11.85

• ), BF3·Et2O, DDQ, CHCl3, rt; b) Zn(OAc)2, CHCl3/MeOH, rt; c) dipyrromethane 6, BF3·Et2O, DDQ, CHCl3, rt; d) Zn(OAc)2, CHCl3/MeOH, rt; e) 1. benzylamine, trimethyl orthoformate, rt, 2. NaBH4, THF/MeOH, rt; f) Boc2O, triethylamine, CH2Cl2, rt; g) 1. ethynyltrimethylsilane, CuI, PPh3, Pd(PPh3)4, TEA

• , 3,4-dihydroxybenzaldehyde, DMF, 85 °C; d) 1. pyrrole (4), propionic acid, 140 °C, 2. Zn(OAc)2, MeOH/CHCl3, rt; e) 1. dipyrromethane (6), BF3·Et2O, DDQ, CHCl3, rt, 2. Zn(OAC)2, MeOH/CHCl3, rt. Supporting Information Supporting Information File 370: Detailed synthetic procedures. Acknowledgements The

Bis(vinylenedithio)tetrathiafulvalene analogues of BEDT-TTF

• Erdal Ertas,
• İlknur Demirtas and
• Turan Ozturk

Beilstein J. Org. Chem. 2015, 11, 403–415, doi:10.3762/bjoc.11.46

• of 52 was prepared with the acceptor 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) 53 (1:1) in dichloromethane at room temperature to investigate the optical constant and optical band gap of the complex (Scheme 8) [56]. A solution of the salt was evaporated on a quartz substrate until ≈110 nm

• ([1,3]dithiolo[4,5-b][1,4]dithiinylidene) 52 – DDQ 53. Reaction conditions (i) (EtO)3P, 110 °C, N2, 2 h. Reaction conditions (i) EtOH, reflux, overnight; (ii) diisopropylethylamine in CH2Cl2, room temperature, overnight; (iii) (AcO)2Hg/AcOH, CHCl3, rt, 3h; iv) (EtO)3P, 110 °C, N2, 2 h; (v) sample in THF

A simple and efficient method for the preparation of 5-hydroxy-3-acyltetramic acids

• Johanna Trenner and
• Evgeny V. Prusov

Beilstein J. Org. Chem. 2015, 11, 323–327, doi:10.3762/bjoc.11.37

• DMB group with CAN [17] produced no product either. Successful removal of the DMB-protecting group from hydroxylated tetramic acid 16 and (trimethylsilyl)ethyl hemiaminal 19 was achieved upon treatment with an excess of DDQ in wet DCM. Treatment of the N-allyl-protected compound using catalytic

Photovoltaic-driven organic electrosynthesis and efforts toward more sustainable oxidation reactions

• Bichlien H. Nguyen,
• Robert J. Perkins,
• Jake A. Smith and
• Kevin D. Moeller

Beilstein J. Org. Chem. 2015, 11, 280–287, doi:10.3762/bjoc.11.32

• ][25]. The reaction requires a careful balance between the initial condensation reaction and the oxidative step with either CAN or DDQ serving as the mediator. In the third reaction (Scheme 7), an intramolecular alcohol nucleophile was added to an olefin coupling reaction [26]. When a radical cation

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

• synthesized also from aromatic aldehydes, α,β-unsaturated aldehydes, or allylic alcohols in the presence of the DDQ (2,3-dichloro-5,6-dicyanobenzoquinone)/amberlyst-15 system in a methanol/toluene mixture under microwave irradiation [171]. Methyl, ethyl, and isopropyl benzoates were prepared from benzaldehyde

Articulated rods – a novel class of molecular rods based on oligospiroketals (OSK)

• Pablo Wessig,
• Roswitha Merkel and
• Peter Müller

Beilstein J. Org. Chem. 2015, 11, 74–84, doi:10.3762/bjoc.11.11

• , the PMB group was cleaved by DDQ to give the orthogonally protected trispiro rod 8 (Scheme 1). To demonstrate the capability of the approach outlined in Figure 3 we selectively activated both sides of building block 8 either by introduction of an azide group (9) or liberation of the terminal alkyne by

• –Martin-periodinane. iii: pentaerythritol, pTsOH (cat.). iv: 2-(4-methoxybenzyloxy)acetic acid, DCC, HOBt. v: (COCl)2/DMSO. vi: NaH, TMSCl, TMSOTf, vii DDQ, DCM, buffer pH 7). Synthesis of articulated rod 11 (i: CBr4, PPh3, NaN3. ii: K2CO3/MeOH. iii: Cu/C DCM/MeOH 1:1, cat. Et3N). Sequential deprotection

• of 11 and synthesis of triple articulated rod 14 (i: K2CO3/MeOH. ii: CBr4/PPh3/NaN3.iii: Cu/C, Et3N. iv: CBr4/PPh3/NaN3.). Synthesis of articulated rods 23–25 with increased solubility (i: 4-hydroxypiperidine, DCC, HOBt. ii: (COCl)2/DMSO. iii: 6, NaH, TMSCl, TMSOTf. iv: DDQ. v: K2CO3/MeOH. vi: CBr4

Efficient deprotection of F-BODIPY derivatives: removal of BF₂ using Brønsted acids

• Mingfeng Yu,
• Joseph K.-H. Wong,
• Cyril Tang,
• Peter Turner,
• Matthew H. Todd and
• Peter J. Rutledge

Beilstein J. Org. Chem. 2015, 11, 37–41, doi:10.3762/bjoc.11.6

• and conditions: (a) (i) 2,4-dimethyl-1H-pyrrole (5), TFA, DCM, rt, overnight; (ii) DDQ, rt, 2 h; (iii) Et3N, BF3·OEt2, rt, overnight, 27%; (b) NH2NH2·H2O, 10% Pd/C, EtOH, reflux, 2 h, 90%; (c) (i) 1 M HCl (aq), CH3OH, NaNO2, H2O, 0 °C, 1 h; (ii) NaN3, H2O, rt, 2 h, 71%; (d) propargyl-tri-Boc cyclam 12

• , CuSO4·5H2O, sodium ascorbate, THF/H2O (7:3), 50 °C, 12 h, 100%; (e) trimethylsilylacetylene, CuI, Pd(PPh3)4, Et3N, THF, rt, overnight, 100%; (f) K2CO3, CH3OH, rt, overnight, 71%; (g) (i) 2,4-dimethyl-1H-pyrrole (5), TFA, DCM, rt, overnight; (ii) DDQ, rt, 2 h; (iii) Et3N, BF3·OEt2, rt, overnight, 24%; (h

Recent advances in the electrochemical construction of heterocycles

• Robert Francke

Beilstein J. Org. Chem. 2014, 10, 2858–2873, doi:10.3762/bjoc.10.303

• converted with α- and β-pinene to form euglobal model compounds 55 and 56. The electrolysis was carried out in an undivided cell under potentiostatic conditions with a CH3NO2/Et4NOTs electrolyte. DDQ was employed as a redox mediator, allowing for operation at a relatively low electrode potential of 0.45 V

Solution processable diketopyrrolopyrrole (DPP) cored small molecules with BODIPY end groups as novel donors for organic solar cells

• Diego Cortizo-Lacalle,
• Calvyn T. Howells,
• Upendra K. Pandey,
• Joseph Cameron,
• Neil J. Findlay,
• Anto Regis Inigo,
• Tell Tuttle,
• Peter J. Skabara and
• Ifor D. W. Samuel

Beilstein J. Org. Chem. 2014, 10, 2683–2695, doi:10.3762/bjoc.10.283

• ). Compound 6 was prepared by acid-catalysed condensation of 5-bromothiophene-2-carbaldehyde with 3-ethyl-2,4-dimethylpyrrole, followed by oxidation with DDQ. Deprotonation with triethylamine and subsequent treatment with boron trifluoride diethyl etherate yielded 6. The entire synthesis was carried out as a

• -dimethylformamide, rt, 16 h, 88%; (iii) trifluoroacetic acid, dichloromethane, rt, 16 h; DDQ, rt, 24 h; triethylamine, BF3·OEt2, rt, 24 h, 33% and 12% for 6 and 7, respectively; (iv) DPP 8, Pd2(dba)3, tri-tert-butylphosphonium tetrafluoroborate, THF/water, tripotassium phosphate, reflux, 48 h, 55% and 34% for 9 and

Expanding the scope of cyclopropene reporters for the detection of metabolically engineered glycoproteins by Diels–Alder reactions

• Anne-Katrin Späte,
• Verena F. Schart,
• Julia Häfner,
• Andrea Niederwieser,
• Thomas U. Mayer and
• Valentin Wittmann

Beilstein J. Org. Chem. 2014, 10, 2235–2242, doi:10.3762/bjoc.10.232

• purification of the β-anomer. Retention time β-anomer: 15 min, α-anomer: 16.5 min. β-Anomer: 1H NMR (400 MHz, CDCl3) δ 6.54 (s, 1H, =CH), 5.72 (d, J = 8.7 Hz, 1H, H-1), 5.39 (dd, J = 3.6, 1.1 Hz, 1H, H-4), 5.10 (ddq, J = 11.4, 3.4, 1.4 Hz, 1H, H-3), 4.61–4.48 (m, 1H, NH), 4.14 (qd, J = 11.3, 6.6 Hz, 3H, H-2, H

Synthesis and bioactivity of analogues of the marine antibiotic tropodithietic acid

• Patrick Rabe,
• Tim A. Klapschinski,
• Nelson L. Brock,
• Christian A. Citron,
• Paul D’Alvise,
• Lone Gram and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2014, 10, 1796–1801, doi:10.3762/bjoc.10.188

• . Oxidative cleavage of the glycol with NaIO4 resulted in a β-ketoester aldehyde that upon treatment with silica gel underwent an intramolecular aldol condensation to a mixture of 10a and 11a that were separable by column chromatography. Oxidation with DDQ gave tert-butyl tropone-2-carboxylate (12a) that was

• treated under various oxidation conditions (including DDQ, IBX, SeO2, and MnO2) to install the tropone moiety by dehydrogenation, but unfortunately all these reaction conditions failed. Compound 22 was subsequently converted into the free acid 23 by treatment with TFA, while similar conversions of 20 and

Synthesis of zearalenone-16-β,D-glucoside and zearalenone-16-sulfate: A tale of protecting resorcylic acid lactones for regiocontrolled conjugation

• Hannes Mikula,
• Julia Weber,
• Dennis Svatunek,
• Philipp Skrinjar,
• Gerhard Adam,
• Rudolf Krska,
• Christian Hametner and
• Johannes Fröhlich

Beilstein J. Org. Chem. 2014, 10, 1129–1134, doi:10.3762/bjoc.10.112

• dry DMF after optimization in terms of base and solvent type (Scheme 4A). Königs–Knorr glucosylation of the PMB-protected mimic 15 afforded 16, which was deprotected using 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) for oxidative PMB cleavage and subsequent ester saponification to yield the desired

• glucoside 17 in an overall yield of 30% (Scheme 4B). Applying this procedure to ZEN (1) afforded the glucosylated intermediate 19 after Königs–Knorr glucosylation of 14-PMB-ZEN (18), but subsequent deprotection using DDQ did not afford the desired product. Also an alternative procedure for oxidative PMB

• . Since the DDQ-promoted cleavage of phenolic PMB ethers can be complicated by overoxidation, especially with electron-rich phenolic compounds [35], we assume a significant effect of the conjugated olefinic double bond at C-6’ of the resorcylic acid moiety being responsible for the observed different

Synthesis of complex intermediates for the study of a dehydratase from borrelidin biosynthesis

• Frank Hahn,
• Nadine Kandziora,
• Steffen Friedrich and
• Peter F. Leadlay

Beilstein J. Org. Chem. 2014, 10, 634–640, doi:10.3762/bjoc.10.55

• ]. a) DDQ, CH2Cl2, rt, 30 min (85%); b) DMP, CH2Cl2, rt, 2 h; c) NaOCl, 2-methyl-2-butene, t-BuOH, phosphate buffer, rt, 16 h; d) TMS-CHN2, toluene/MeOH 2:3, rt, 40 min (58% over three steps); e) second generation Grubbs catalyst, crotonaldehyde, CH2Cl2, 40 °C, 120 min (88%); DDQ = 2,3-dichloro-5,6

An oxidative amidation and heterocyclization approach for the synthesis of β-carbolines and dihydroeudistomin Y

• Suresh Babu Meruva,
• Akula Raghunadh,
• Raghavendra Rao Kamaraju,
• U. K. Syam Kumar and
• P. K. Dubey

Beilstein J. Org. Chem. 2014, 10, 471–480, doi:10.3762/bjoc.10.45

• , whereas the OH proton in 8a shows a high nOe (Scheme 6). Dihydro-β-carboline 7 was then subjected to an aromatization reaction to obtain eudistomin Y (6). The aromatization reaction was attempted with oxidizing agents such as DDQ and MnO2 as per the reported conditions in literature. The formation of

Simple two-step synthesis of 2,4-disubstituted pyrroles and 3,5-disubstituted pyrrole-2-carbonitriles from enones

• Murat Kucukdisli,
• Dorota Ferenc,
• Marcel Heinz,
• Christine Wiebe and
• Till Opatz

Beilstein J. Org. Chem. 2014, 10, 466–470, doi:10.3762/bjoc.10.44

• products and 3,5-disubstituted pyrrole-2-carbonitriles 10 are obtained. Tsuge et al. reported the oxidation of pyrroline-3-carboxylates with chloranil [45] while pyrrole-2-carboxylates were obtained from the oxidation of pyrroline-2-carboxylate with chloranil [46][47] or DDQ [48]. Different oxidants were

• screened for the oxidation of cyanopyrroline 6a to pyrrole 10a and the results were judged by TLC. While chloranil, MnO2, NBS/DBU, and iodine/DBU in toluene or chlorobenzene did not give any conversion, bromotrichloromethane/DBU and DDQ gave positive results. The latter was found to be more suitable since

• the use of bromotrichloromethane/DBU resulted in many side reactions. Table 2 summarizes the results of the oxidation of 6a–j with DDQ in toluene under reflux. The reaction worked smoothly with aryl-substituted compounds. The only failure was observed in case of compound 6c which possesses an alkyl

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• in the formation of a bridged tetracycle after initial Heck coupling followed by carbo-palladation and subsequent β-hydride elimination [69][70][71]. Double bond regioisomers (between C7 & C8 or C13 & C14) were obtained. Oxidation with DDQ yielded the 1,6-unsaturated ketone 72. Selective epoxidation

Total synthesis of (+)-grandiamide D, dasyclamide and gigantamide A from a Baylis–Hillman adduct: A unified biomimetic approach

• Andivelu Ilangovan and
• Shanmugasundar Saravanakumar

Beilstein J. Org. Chem. 2014, 10, 127–133, doi:10.3762/bjoc.10.9

• ). Among different reagents such as DDQ, CAN, Yb(OTf)3 and CeCl3–NaI used for deprotection of the PMB group, TFA gave the better result. Even though POCl3 [14] was able to effect complete removal of the PMB group in short time, the yield was only moderate. Thus (±)-grandiamide D ((±)-5) was obtained in

Cyclopamine analogs bearing exocyclic methylenes are highly potent and acid-stable inhibitors of hedgehog signaling

• Johann Moschner,
• Anna Chentsova,
• Nicole Eilert,
• Irene Rovardi,
• Philipp Heretsch and
• Athanassios Giannis

Beilstein J. Org. Chem. 2013, 9, 2328–2335, doi:10.3762/bjoc.9.267

• conditions for the deprotection of the benzyl ether (DDQ, DCE/pH 7 phosphate buffer, 40 °C, 86%) and the benzenesulfonylamine (sodium naphthalenide, DME, −78 °C, 79%) allowed for the isolation of bis-exo-cyclopamine 6 in 18% overall yield from 3. The hydrogenation of intermediate 4 by using Wilkinson’s

• % overall yield from 3. Alternatively, the use of previously devised conditions for benzyl deprotection (DDQ, DCE/pH 7 phosphate buffer, 45 °C, 78%) and then sodium borohydride-mediated reduction of the azide (EtOH, 65 °C, 62%) cleanly furnished primary amine 9, an exo-cyclopamine derivative with no F-ring

• . Deprotetion of the 4-methoxybenzyl ether (DDQ, DCE/pH 7 phosphate buffer, 25 °C, 59%) and cyclization under Mitsunobu conditions (n-Bu3P, DEAD, toluene, 0 °C→25 °C, 93%) yielded piperidine 18. Deprotection of the benzyl ether by using previously devised conditions (DDQ, DCE/pH 7 phosphate buffer, 44 °C, 70

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

The chemistry of isoindole natural products

• Klaus Speck and
• Thomas Magauer

Beilstein J. Org. Chem. 2013, 9, 2048–2078, doi:10.3762/bjoc.9.243

• -benzoquinone (DDQ) gave the dioxocularine yagonine (146). The bioinspired, base-mediated transformation of 146 to 136 obviously proceeds via a benzilic acid rearrangement–oxidation sequence. In 1996, the group of Suau accessed aristocularine 137 along with 149 in one step from acetamide 148. In the presence of

A reductive coupling strategy towards ripostatin A

• Kristin D. Schleicher and
• Timothy F. Jamison

Beilstein J. Org. Chem. 2013, 9, 1533–1550, doi:10.3762/bjoc.9.175

• repeated silica gel chromatography, and the desired syn diol was converted to the bis-silylated compound 54. However, attempted oxidative deprotection of the PMB ether of 54 with DDQ led to destruction of the material. It seems likely that this is again due to the presence of the allylic/benzylic site in

Total synthesis of ochnaflavone

• Monica M. Ndoile and
• Fanie R. van Heerden

Beilstein J. Org. Chem. 2013, 9, 1346–1351, doi:10.3762/bjoc.9.152

• repeated with DDQ in dry dioxane under reflux (101 °C) [27], but the starting material again decomposed, and when the temperature was lowered to 80 °C, a mixture of products was observed. It was clear that the ether-linked dimeric chalcone decomposes at temperatures exceeding 100 °C. Reaction of dimeric