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

Metal-free aerobic oxidations mediated by N-hydroxyphthalimide. A concise review

• Lucio Melone and
• Carlo Punta

Beilstein J. Org. Chem. 2013, 9, 1296–1310, doi:10.3762/bjoc.9.146

• -dicyanobenzoquinone (DDQ) [37]. Xu et al. also reported a similar one-electron-transfer activation of NHPI promoted by nonmetal xanthone and tetramethylammonium chloride (TMAC), for the selective oxidation of hydrocarbons (Scheme 14) [38]. In the proposed mechanism, TMAC has the unique role of decomposing the

Expeditious, mechanochemical synthesis of BODIPY dyes

• Laramie P. Jameson and
• Sergei V. Dzyuba

Beilstein J. Org. Chem. 2013, 9, 786–790, doi:10.3762/bjoc.9.89

• different one-pot procedures (Scheme 1) [1][2]: (a) Lewis acid (usually trifluoroacetic acid, TFA) catalyzed condensation between a 2-substituted pyrrole and an aldehyde, followed by oxidation with DDQ or p-chloranil, and subsequent treatment with base (Et3N or Hunig’s base are typically used) and BF3·OEt2

• , several oxidizing agents were tried, including the typically used DDQ as well as Ce(NH4)2(NO3)6. However, p-chloranil afforded the highest isolated yield (Table 1, entries 1–3). We also found that adding small amounts of CH2Cl2 (1–2 mL) prior to the addition of p-chloranil allowed for a more efficient

Asymmetric synthesis of a highly functionalized bicyclo[3.2.2]nonene derivative

• Toshiki Tabuchi,
• Daisuke Urabe and
• Masayuki Inoue

Beilstein J. Org. Chem. 2013, 9, 655–663, doi:10.3762/bjoc.9.74

• heptenone 12 [17][18][19][20][21]. The more thermodynamically stable silyl enol ether 13 was regioselectively formed from 12 under Holton’s conditions [22], and DDQ-mediated oxidation of 13 resulted in the formation of α,β-unsaturated ketone 14. Asymmetric reduction of ketone 14 was in turn realized by

• = 6.4, 5.5 Hz, H3), 5.49 (1H, br ddq, J = 7.3, 7.3, 1.4 Hz, H15). Diene 14: DDQ (7.1 g, 31 mmol) was added to a solution of 13 (3.3 g 16 mmol) and 2,6-lutidine (5.4 mL, 46 mmol) in benzene (30 mL) at 0 °C. The reaction mixture was stirred at room temperature for 20 min and filtered through a short

NHC-catalysed highly selective aerobic oxidation of nonactivated aldehydes

• Lennart Möhlmann,
• Stefan Ludwig and
• Siegfried Blechert

Beilstein J. Org. Chem. 2013, 9, 602–607, doi:10.3762/bjoc.9.65

• mpg-C3N4 and oxygen. NHC-catalysts derived from the corresponding salts are known to react with aldehydes to provide I and lead after oxidation to acyl cation intermediate II. Subsequent reactions with nucleophiles give esters, amides or acids. Reagents such as MnO2 [5][6][7], DDQ, TEMPO and

De novo synthesis of D- and L-fucosamine containing disaccharides

• Daniele Leonori and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2013, 9, 332–341, doi:10.3762/bjoc.9.38

• hydrolysis and hydrogenation. Monosaccharide D-13 was obtained in 85% yield (the β-linkage further confirmed by 1JC1–H1 164.1 Hz, Scheme 6A). Direct glycosylation after DDQ-deprotection was possible and the use of differentially protected glucose building block 15 [68] yielded the desired β-disaccharide 16

• data as above. D-Fucosamine monosaccharide D-13 A solution of D-12 (56 mg, 80.0 mmol, 1.0 equiv) in CH2Cl2 (0.9 mL) and H2O (90 mL) was treated with DDQ (21 mg, 94.0 mmol, 1.2 equiv) and stirred in the dark at rt for 2 h. Saturated NaHCO3 (2 mL) and CH2Cl2 (5 mL) were added and the layers were

• -13, D-12 (24 mg, 34.0 mmol, 1.0 equiv), DDQ (21 mg, 41.0 mmol, 1.2 equiv), KOH (1.8 mg, 34.0 mmol, 1.0 equiv) and Pd/C (10 mg), gave L-13 (9 mg, 75%) as an amorphous solid; [α]D20 −111.1 (c 1.0, H2O), other data as above. D-Fucosamine disaccharide 17 A solution of 16 (21 mg, 19.0 mmol, 1.0 equiv) in

On the proposed structures and stereocontrolled synthesis of the cephalosporolides

• Sami F. Tlais and
• Gregory B. Dudley

Beilstein J. Org. Chem. 2012, 8, 1287–1292, doi:10.3762/bjoc.8.146

• ]. DDQ oxidation of PMB ether produced 1,3-dioxane 15 [37]. Protecting group manipulation led to the formation of primary alcohol 17 [38], which was converted into homopropargyl silyl ether 19 over two steps, i.e., DMP oxidation and subsequent Ohira–Bestmann ethynylation [39]. Coupling of the propargyl

Synthesis of 4” manipulated Lewis X trisaccharide analogues

• Christopher J. Moore and
• France-Isabelle Auzanneau

Beilstein J. Org. Chem. 2012, 8, 1134–1143, doi:10.3762/bjoc.8.126

• desired protected Lex analogues. One-step global deprotection (Na/NH3) of the protected 4”-methoxy analogue, and two-step deprotections (removal of a p-methoxybenzyl with DDQ, then Zemplén deacylation) of the 4”-deoxychloro and 4”-deoxyfluoro protected Lex analogues gave the desired compounds in good

• p-methoxybenzyl group with DDQ in CH2Cl2/H2O (15:1 v/v) was followed by Zemplén deacylation, giving the target Lex analogues 4 and 5 in 78% and 75%, respectively, over the two steps. The structures of the final deprotected trisaccharides 3–5 were confirmed by HR–ESI mass spectrometry and NMR

• -fucopyranosyl)-β-D-glucopyranoside (4). A solution of the protected trisaccharide 27 (39 mg, 0.0347 mmol) and DDQ (12 mg, 1.5 equiv) in CH2Cl2 (350 μL) and H2O (20 μL, 6% v/v) was stirred at room temperature for 2 h. The mixture was filtered over Celite and the solids were washed with CH2Cl2 (5 mL). The

Algicidal lactones from the marine Roseobacter clade bacterium Ruegeria pomeroyi

• Ramona Riclea,
• Julia Gleitzmann,
• Hilke Bruns,
• Corina Junker,
• Barbara Schulz and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2012, 8, 941–950, doi:10.3762/bjoc.8.106

• chromatography on silica gel (pentane/diethyl ether 3:1) to yield the butanolides as colourless oils. cis-2-Methylpentan-4-olide (7): Yield: 0.38 g (3.28 mmol, 97%). TLC (hexane/ethyl acetate 2:1): Rf 0.48; GC (BPX-5): I = 1005; 1H NMR (400 MHz, CDCl3) δ 4.40 (ddq, 3JH,H = 5.4, 11.5, 6.1 Hz, 1H, CH), 2.66 (ddq

• (m, 1H, CH), 2.65 (ddq, 3JH,H = 8.5, 12.0, 7.0 Hz, 1H, CH), 2.47 (ddd, 3JH,H = 5.4, 8.6 Hz, 2JH,H = 12.4 Hz, 1H, CH2), 1.77 (dquin, 2JH,H = 14.4 Hz, 3JH,H = 7.2 Hz, 1H, CH2), 1.68–1.57 (m, 1H, CH2), 1.48 (dt, 2JH,H = 3JH,H = 12.2 Hz, 3JH,H = 10.4 Hz, 1H, CH2), 1.25 (d, 3JH,H = 7.1 Hz, 1JC,H = 128.3

• chromatographic means. trans-2-Methylpentan-4-olide (8): Yield: 0.30 g (2.63 mmol, 59%, dr = 77:23, cis/trans), TLC (hexane/ethyl acetate 2:1): Rf 0.48; GC (BPX-5): GC: I = 1006; 1H NMR (400 MHz, CDCl3) δ 4.63 (ddq, 3JH,H = 5.0, 7.0, 6.4 Hz, 1H, CH), 2.74–2.62 (m, 1H, CH), 2.08–1.96 (m, 2H, CH2), 1.33 (d, 3JH,H

Identification and isolation of insecticidal oxazoles from Pseudomonas spp.

• Florian Grundmann,
• Veronika Dill,
• Andrea Dowling,
• Aunchalee Thanwisai,
• Edna Bode,
• Narisara Chantratita,
• Richard ffrench-Constant and
• Helge B. Bode

Beilstein J. Org. Chem. 2012, 8, 749–752, doi:10.3762/bjoc.8.85

• and 8 were synthesized. Briefly, the respective tryptamine derivatives were formed, which were then oxidized at the alpha-position with the help of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and cyclized to give the oxazoles by using phosphorylchloride as described [9]. Additionally, three

Photochemical and thermal intramolecular 1,3-dipolar cycloaddition reactions of new o-stilbene-methylene-3-sydnones and their synthesis

• Kristina Butković,
• Željko Marinić,
• Krešimir Molčanov,
• Biserka Kojić-Prodić and
• Marija Šindler-Kulyk

Beilstein J. Org. Chem. 2011, 7, 1663–1670, doi:10.3762/bjoc.7.196

• spectra. Nevertheless, the proton H-5 of the fused benzene ring in structure 12 is in the multiplet together with other aromatic protons, which is in accordance with the proposed structure. The structure of the photoproducts was confirmed by an additional experiment on the crude reaction mixture with DDQ

• pathway of sydnone ring (N–CH) and trans- and cis-stilbene (α–β). Thermal and photochemical intermolecular [3 + 2] cycloadditions. Synthesis of the target molecules 3a and 3b. Photolysis of cis- or trans-3. Aromatization with DDQ. Possible mechanism for the formation of the photoproducts. Thermal reaction

Synthesis of fluoranthenes by hydroarylation of alkynes catalyzed by gold(I) or gallium trichloride

• Sergio Pascual,
• Christophe Bour,
• Paula de Mendoza and
• Antonio M. Echavarren

Beilstein J. Org. Chem. 2011, 7, 1520–1525, doi:10.3762/bjoc.7.178

• -tetrahydrofluoranthene, and 8a, the crude mixtures were treated with excess DDQ in toluene under reflux to provide pure 8a. No reaction or decomposition was observed when the reaction was carried out with gold(I) complex 5 (Table 2, entries 1 and 2). In contrast, the more electrophilic gold(I) complex 6 with phosphite

• triaryl substituted diacenaphtho[1,2-j:1',2'-l]fluoranthenes (decacyclenes) 2a and 2b in very good overall yields after aromatization of the crude products with DDQ. Remarkably, this triple hydroarylation occurs efficiently with an average yield per C–C bond formation that is greater than 90%. Conclusion

Efficient syntheses of 25,26-dihydrodictyostatin and 25,26-dihydro-6-epi-dictyostatin, two potent new microtubule-stabilizing agents

• María Jiménez,
• Wei Zhu,
• Andreas Vogt,
• Billy W. Day and
• Dennis P. Curran

Beilstein J. Org. Chem. 2011, 7, 1372–1378, doi:10.3762/bjoc.7.161

• reduce the conjugated alkene, followed directly by removal of the PMB group with DDQ. This sequence afforded alcohol 23 in 76% yield over two steps. A stereoselective 1,3-syn reduction was then performed under Prasad conditions [44] to give the target diol (90%) as a single isomer. The stereochemistry at

Multicomponent reaction access to complex quinolines via oxidation of the Povarov adducts

• Esther Vicente-García,
• Rosario Ramón,
• Sara Preciado and
• Rodolfo Lavilla

Beilstein J. Org. Chem. 2011, 7, 980–987, doi:10.3762/bjoc.7.110

• aromatic species. The literature contains scattered reports of the use of oxidants for this transformation: 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), ceric ammonium nitrate (CAN), nitrobenzene, elemental sulfur, palladium and manganese dioxide among others, all of them far from being ideally suited

• for these substrates. One of the most commonly used is DDQ, which affords quinolines in acceptable yields. The main advantages of this oxidizing agent lie in its chemoselectivity and a requirement for relatively mild conditions, allowing it to be used in the presence of a wide range of substituents of

• and amine moieties, leading to dihydroquinoline intermediates that, after spontaneous oxidation in air, provide the final fragmented quinolines. The ability of DDQ to act as a Lewis acid and promote this alternative pathway has some precedent in the literature [19]. Furthermore, TFA treatment of

High chemoselectivity in the phenol synthesis

• Matthias Rudolph,
• Melissa Q. McCreery,
• Wolfgang Frey and
• A. Stephen K. Hashmi

Beilstein J. Org. Chem. 2011, 7, 794–801, doi:10.3762/bjoc.7.90

• PMB-protected aldehyde 43 (Scheme 11) [45]. The resulting furfuryl alcohol 44 was then propargylated to give 45. The deprotection was however, problematic. Treatment of the latter with cerium ammonium nitrate led to decomposition. Only with DDQ was the desired alcohol 39 obtained in moderate yield

Studies on polynuclear furoquinones. Part 1: Synthesis of tri- and tetra- cyclic furoquinones simulating BCD/ABCD ring system of furoquinone diterpenoids

• Faruk H. Shaik and
• Gandhi K. Kar

Beilstein J. Org. Chem. 2009, 5, No. 47, doi:10.3762/bjoc.5.47

• aromatized with DDQ in refluxing benzene, 2-bromo-1-naphthaldehyde (2) was produced in excellent yield. Reduction (NaBH4/EtOH) of the aldehyde 2 produced the alcohol 3 as a colorless solid, in 94% yield, which on reaction with PBr3/CCl4 produced the bromide 4 as a light yellow solid. The bromide was then

• in due course. Experimental Furan-2-boronic acid, 2-tetralone and tetrakis(triphenylphosphine)palladium(0) and DDQ were purchased from Sigma-Aldrich (U.S.A). Trifluoroacetic anhydride was purchased from Alfa Aesar (Lancaster). 2-Bromo-3,4-dihydronaphthalene-1-carbaldehyde was prepared from 2

• furoquinone 13. Assignment of chemical shifts (1H NMR and 13C NMR) of compound 13. Reagents and conditions: i) DDQ (1.5 equiv), dry benzene, reflux, argon atmosphere, 37 h, 83%. ii) NaBH4, EtOH, room temperature, 2 h, 94%. iii) PBr3, CCl4, 60 °C, 1 h, 82%. iv) KCN, DMF, room temperature, overnight then 1 h at

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• concave face of the molecule, anti to the exo-disposed benzyloxymethyl group. The standard methodology involving azide displacement gave the aziridine 84. The benzyl groups were removed using a Birch reduction and subsequent oxidation with DDQ furnished the aziridinomitosane 85 in good overall yield

A short stereoselective synthesis of (+)-(6R,2′S)-cryptocaryalactone via ring- closing metathesis

• Palakodety Radha Krishna,
• Krishnarao Lopinti and
• K. L. N. Reddy

Beilstein J. Org. Chem. 2009, 5, No. 14, doi:10.3762/bjoc.5.14

• THF at 0 °C to give cinnamyl alcohol derivative 14 (87%, Scheme 3). Alcohol 14 was protected as its acetate under conventional reaction conditions. The PMB (p-methoxybenzyl protecting group) in compound 15 was selectively removed with DDQ in CH2Cl2/H2O (19:1) to afford homoallylic alcohol 16 (89