Preparation of imidazo[1,2-a]-N-heterocyclic derivatives with gem-difluorinated side chains

• Layal Hariss,
• Kamal Bou Hadir,
• Mirvat El-Masri,
• Thierry Roisnel,
• René Grée and
• Ali Hachem

Beilstein J. Org. Chem. 2017, 13, 2115–2121, doi:10.3762/bjoc.13.208

• propargylic derivatives 4 [28] with aromatic aldehydes. Then, the DBU-mediated isomerization afforded the desired enones 6a–e in 21–66% yields (Scheme 2 and Table 1). For the synthesis of the desired nitrogen heterocycles, we started our study by reacting 6a with 2-aminopyridine in the presence of AlCl3 and

• DBU (1,8-diazabicycloundec-7-ene) under the same conditions as mentioned above, the desired imidazopyridine derivative 7a was isolated in 33% yield (Scheme 4). This one-pot process gives an overall yield very close to the two-step reaction (38%). Further, the halogen-substituted substrate 7e appeared

• (4 mL), then DBU (0.42 mL, 2.82 mmol, 1.5 equiv) was added and the reaction mixture was stirred at room temperature. After 2 h, 19F NMR showed 100% conversion and the reaction mixture was neutralized with a saturated solution of NH4Cl. After extraction with ethyl acetate, the organic phases were

Synthesis of benzothiophene and indole derivatives through metal-free propargyl–allene rearrangement and allyl migration

• Jinzhong Yao,
• Yajie Xie,
• Lianpeng Zhang,
• Yujin Li and
• Hongwei Zhou

Beilstein J. Org. Chem. 2017, 13, 1866–1870, doi:10.3762/bjoc.13.181

• , but also provides the useful heterocycles which are not easily achieved through other protocols. Results and Discussion In the initial studies, we treated methyl 4-(3-(2-(allylthio)phenyl)-3-methoxyprop-1-yn-1-yl)benzoate (1a) with DBU (0.1 equiv) in THF at 50 °C under N2 for 12 h (Table 1, entry 1

• temperature was found to be less effective for the reaction (Table 1, entry 13). Without the base, no reaction occurred, implying that the reaction proceeded exclusively through the allenic intermediate (Table 1, entry 14). Thus, the optimal reaction conditions were DBU (0.2 equiv) under nitrogen in THF at 50

• reaction proceeded under mild conditions to produce useful benzothiophene and indole derivatives. Examples of biologically active benzothiophene derivatives. Synthesis of benzothiophenes. Reaction conditions: 1 (0.5 mmol), DBU (0.1 mmol), THF (2.0 mL), 50 °C, 12 h, under N2. Yields are isolated yields

Iodoarene-catalyzed cyclizations of N-propargylamides and β-amidoketones: synthesis of 2-oxazolines

• Somaia Kamouka and
• Wesley J. Moran

Beilstein J. Org. Chem. 2017, 13, 1823–1827, doi:10.3762/bjoc.13.177

• [32][33][34][35][36]. Gao and co-workers described the I2-catalyzed cyclization of β-acylaminoketones using tert-butyl hydroperoxide as the oxidant; notably, adding DBU led to oxazole formation whereas adding K2CO3 generated oxazolines [37][38]. Our proposed new approaches to oxazoline formation

Encaging palladium(0) in layered double hydroxide: A sustainable catalyst for solvent-free and ligand-free Heck reaction in a ball mill

• Wei Shi,
• Jingbo Yu,
• Zhijiang Jiang,
• Qiaoling Shao and
• Weike Su

Beilstein J. Org. Chem. 2017, 13, 1661–1668, doi:10.3762/bjoc.13.160

• our previous researches [4][51], it is found that the bases used have a significant influence on the yields of the reaction. Thus, several bases such as NaOH, KOH, Cs2CO3, K2CO3, t-BuOK, Et3N and DBU were investigated and the results are shown in Table 1. It is notable that both inorganic and organic

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

Base-promoted isomerization of CF₃-containing allylic alcohols to the corresponding saturated ketones under metal-free conditions

• Yoko Hamada,
• Tomoko Kawasaki-Takasuka and
• Takashi Yamazaki

Beilstein J. Org. Chem. 2017, 13, 1507–1512, doi:10.3762/bjoc.13.149

• reported intriguing 1,3-proton shift of 4,4,4-trifluorobut-2-yn-1-ols was successfully extended to the 4,4,4-trifluorobut-2-en-1-ol system under metal-free conditions to afford the corresponding saturated ketones in high to excellent chemical yields using such a convenient and easy-to-handle base as DBU at

• excess amount of CsF, the resultant product (E)-2Fb was further converted in situ to the corresponding saturated ketone (E)-5b (R = Ph). Confirmation of this process was performed by the action of DBU, resulting in 95% conversion of the starting allylic alcohol (E)-2Fb [14]. Quite recently [15], the same

• -less expensive DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), whose results are reported in this article in detail. Results and Discussion Preparation of substrates (E)-6 was carried out by way of our recently reported one-pot procedure [16]: thus, after reaction of an appropriate Grignard reagent and ethyl

Synthesis of alkynyl-substituted camphor derivatives and their use in the preparation of paclitaxel-related compounds

• M. Fernanda N. N. Carvalho,
• Rudolf Herrmann and
• Gabriele Wagner

Beilstein J. Org. Chem. 2017, 13, 1230–1238, doi:10.3762/bjoc.13.122

• the sultam before the second equivalent undergoes the desired nucleophilic addition to the carbonyl group. All attempts to re-oxidise the sultam 15 to the sulfonimide 13, using Cl2/pyridine [37] or N-tert-butylphenylsulfinimidoyl chloride/DBU [38] under literature conditions, were unsuccessful due to

Total syntheses of the archazolids: an emerging class of novel anticancer drugs

• Stephan Scheeff and
• Dirk Menche

Beilstein J. Org. Chem. 2017, 13, 1085–1098, doi:10.3762/bjoc.13.108

• coupling, acetate protection of the newly generated hydroxy group and DBU-mediated elimination. This three-step sequence proceeded as shown in Scheme 6 with excellent yields (94%) giving the triene 33 as a single diastereomer, which demonstrates the usefulness of aldol condensations in complex target

DMAP-assisted sulfonylation as an efficient step for the methylation of primary amine motifs on solid support

• Johnny N. Naoum,
• Koushik Chandra,
• Dorit Shemesh,
• R. Benny Gerber,
• Chaim Gilon and
• Mattan Hurevich

Beilstein J. Org. Chem. 2017, 13, 806–816, doi:10.3762/bjoc.13.81

• challenge our hypothesis collidine was replaced by two SPS compatible bases namely, 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU, pKb ≈ 1.10) which is a stronger base than collidine (pKb ≈ 6.57, Table 1, entry 7) and by DMAP (pKb ≈ 4.48) which is a superior nucleophile (Table 1, entry 8). HPLC analysis of the

• crude demonstrated that replacing collidine with DMAP resulted in a dramatic improvement in the conversion of 1 to 1a (98%) and a significant decrease in the amount of the byproducts (Table 1, entry 8). On the other hand, replacing the collidine by DBU resulted in no conversion of 1 to 1a (Table 1

• , entry 7). To further evaluate the effect of base on the conversion and purity, another study was performed with motif 4 as a model using DBU, DMAP, pyridine, and collidine as additives. HPLC analysis showed that the additive used indeed has an impact on the conversion of 4 to 4a and on the crude purity

N-Propargylamines: versatile building blocks in the construction of thiazole cores

• S. Arshadi,
• E. Vessally,
• L. Edjlali,
• R. Hosseinzadeh-Khanmiri and
• E. Ghorbani-Kalhor

Beilstein J. Org. Chem. 2017, 13, 625–638, doi:10.3762/bjoc.13.61

• converted to the corresponding vinylthiazolines 38 through the treatment with dithioic acids 37 in the presence of EDCI in dichloromethane. This transformation is believed to occur through a tandem coupling–cyclization reaction. The authors showed that the treatment of 38 with DBU at 0 °C provided thiazoles

Transition-metal-catalyzed synthesis of phenols and aryl thiols

• Yajun Liu,
• Shasha Liu and
• Yan Xiao

Beilstein J. Org. Chem. 2017, 13, 589–611, doi:10.3762/bjoc.13.58

• . In 2013, in the study of the synthesis of (Z)-3-arylthioacrylic acids and thiochromenones, Lee and co-workers found that 89% yield of thiophenol could be directly obtained by Pd (PPh3)2Cl2/dppb (L18) catalyzed coupling reaction of iodobenzene and Na2S·5H2O in the presence of DBU (Scheme 61) [104]. In

Pd- and Cu-catalyzed approaches in the syntheses of new cholane aminoanthraquinone pincer-like ligands

• Nikolay V. Lukashev,
• Gennadii A. Grabovyi,
• Dmitry A. Erzunov,
• Alexey V. Kazantsev,
• Gennadij V. Latyshev,
• Alexei D. Averin and
• Irina P. Beletskaya.

Beilstein J. Org. Chem. 2017, 13, 564–570, doi:10.3762/bjoc.13.55

• (6a) is readily aminated by phthalimide using classical Ullmann conditions (15% Cu powder, quinoline, 200 °C in PhNO2) [41]. However, the reaction of 3c with 6a using the same conditions, as well as the addition of stronger bases (DABCO, DIPEA, DBU) afforded extremely low yields (7–12%) of aminated

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• 76% yield. The former 271 was obtained from the trienone 270/270’ which underwent ring closure to give the 6-membered ring [105] (Scheme 76). 2.2 From alkynes DBU and CpRu(PPh3)2Cl dual catalysts enabled a one-pot annulation of aldehyde 273 and cyclopentanone (274) to give the 1-indanone derivative

• rings 3.1 From alkynes The intramolecular, dehydro-Diels–Alder reaction of ketene dithioacetals 302 leading to formation of various benzo[f]-1-indanones 303–305, has been described in 2015 by Bi et al. [117]. Modulation on the reaction parameters such as addition of DBU and the type of atmospheric gas

The reductive decyanation reaction: an overview and recent developments

• Jean-Marc R. Mattalia

Beilstein J. Org. Chem. 2017, 13, 267–284, doi:10.3762/bjoc.13.30

• -withdrawing group. Synthesis of (±)-isoretronecanol 19. DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene [74]. Proposed mechanism with 14a for the NaBH4 induced decyanation reaction (“BH3” = BH3·THF) [74]. Reductive decyanation by a sodium hydride–iodide composite (26 examples) [81]. Proposed mechanism for the

Interactions between photoacidic 3-hydroxynaphtho[1,2-b]quinolizinium and cucurbit[7]uril: Influence on acidity in the ground and excited state

• Jonas Becher,
• Daria V. Berdnikova,
• Darinka Dzubiel,
• Heiko Ihmels and
• Phil M. Pithan

Beilstein J. Org. Chem. 2017, 13, 203–212, doi:10.3762/bjoc.13.23

• absorption band with two local maxima at 381 nm and 400 nm (MeOH) or 379 nm and 398 nm (MeCN) remains. In contrast, the addition of DBU as a base resulted in the strong increase of the broad absorption band at 431 nm in MeOH and at 457 nm in MeCN. The emission spectrum of 2 in MeOH consists of one intense

• band at 457 nm upon excitation at 400 nm, along with a very weak red-shifted signal at 600 nm. Upon addition of DBU, the emission is efficiently quenched. The red-shifted emission band, however, develops into a very intense signal on addition of the base to the expense of the blue-shifted band. In MeCN

• : after addition of DBU. Normalized emission spectra of 2 (c = 10 µM) in MeOH (A, λex = 400 nm) and MeCN (B, λex = 398 nm). Black lines: without additive, red: after addition of CF3COOH, blue: after addition of DBU. Photometric titration of CB[7] (c = 0.45 mM) to 2 (c = 15 µM) in BPE buffer (with 10% v/v

Total synthesis of a Streptococcus pneumoniae serotype 12F CPS repeating unit hexasaccharide

• Peter H. Seeberger,
• Claney L. Pereira and
• Subramanian Govindan

Beilstein J. Org. Chem. 2017, 13, 164–173, doi:10.3762/bjoc.13.19

• glycosylating agent by removal of the anomeric TBDPS silyl ether using HF-pyridine and subsequent treatment with trichloroacetonitrile in the presence of catalytic amounts of DBU to afford glycosyl trichloroacetimidate trisaccharide 2 (Scheme 1). With trisaccharide fragments 2 and 3 in hand, the convergent [3

• % over two steps; (d) (PhSe)2, BAIB, NaN3, CH2Cl2, rt, 24 h; (e) NIS, THF/H2O (1:1), rt, 80% over two steps; (f) CCl3CN, DBU, CH2Cl2, 0 °C to rt, 2 h, 72%; (g) TES, TFA, CH2Cl2, 0 °C, 6 h; (h) benzoyl chloride, pyridine, rt, 18 h, 80% over two steps. Synthesis of the non-reducing end trisaccharide 2

• . Reagents and conditions: (a) TMSOTf, CH2Cl2, −30 °C, 74%; (b) NaOMe (0.5 M in MeOH), MeOH, rt; (c) trimethyl orthoacetate, p-TsOH, toluene; (d) 80% AcOH, rt, 71% over three steps; (e) 9, NIS, TMSOTf, dioxane/toluene (3:1), −10 °C, 54%; (f) HF-pyridine, THF, 0 °C; (g) CCl3CN, DBU, CH2Cl2, 0 °C, 57% over two

The synthesis of α-aryl-α-aminophosphonates and α-aryl-α-aminophosphine oxides by the microwave-assisted Pudovik reaction

• Erika Bálint,
• Ádám Tajti,
• Anna Ádám,
• István Csontos,
• Konstantin Karaghiosoff,
• Mátyás Czugler,
• Péter Ábrányi-Balogh and
• György Keglevich

Beilstein J. Org. Chem. 2017, 13, 76–86, doi:10.3762/bjoc.13.10

• use of many types of catalysts, such as acids (HCOOH) [15] or bases (NaOH [16], 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) [17], tetramethylguanidine (TMG) [18][19]), p-toluenesulfonyl chloride [20], metal salts (MgSO4) [21], CdI2 [22]), metal complexes (BF3·EtO2 [23][24], t-PcAlCl [15]), and phase

Supramolecular frameworks based on [60]fullerene hexakisadducts

• Andreas Kraft,
• Johannes Stangl,
• Ana-Maria Krause,
• Klaus Müller-Buschbaum and
• Florian Beuerle

Beilstein J. Org. Chem. 2017, 13, 1–9, doi:10.3762/bjoc.13.1

• detector using Cu Kα radiation (unsplit Kα1 + Kα2 doublet, mean wavelength λ = 154.19pm), reflection and transmission geometry. Hexakisadduct 2: C60 (565 mg, 785 µmol, 1 equiv), malonate 1 (3.10 g, 7.84 mmol, 10 equiv) and CBr4 (26.0 g, 78.4 mmol, 100 equiv) were dissolved in dry toluene (500 mL). DBU

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

• Pavel Nagorny and
• Zhankui Sun

Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283

• with DBU and initiator (Ph2CHOH) to accomplish C=O activation and to promote the polymerization reactions (Scheme 6). Highly charged tetraalkylbisammonium salts (i.e., DABCO-Me2·2X) were found to be particularly active catalysts. Based on computational studies, the authors proposed that substrate

Electron-transfer-initiated benzoin- and Stetter-like reactions in packed-bed reactors for process intensification

• Anna Zaghi,
• Daniele Ragno,
• Graziano Di Carmine,
• Carmela De Risi,
• Olga Bortolini,
• Pier Paolo Giovannini,
• Giancarlo Fantin and
• Alessandro Massi

Beilstein J. Org. Chem. 2016, 12, 2719–2730, doi:10.3762/bjoc.12.268

• 1a with 2-chlorobenzaldehyde 2a furnishing the benzoylated benzoin 3aa (double aroylation product) was selected as the benchmark (Table 1). Quite surprisingly, the polystyrene-supported 1,8-diazabicyclo [5.4.0]undec-7-ene 4 (PS-DBU) was completely inefficient (DMF, 35 °C, Ar atmosphere) in both

Development of a continuous process for α-thio-β-chloroacrylamide synthesis with enhanced control of a cascade transformation

• Olga C. Dennehy,
• Valérie M. Y. Cacheux,
• Benjamin J. Deadman,
• Denis Lynch,
• Stuart G. Collins,
• Humphrey A. Moynihan and
• Anita R. Maguire

Beilstein J. Org. Chem. 2016, 12, 2511–2522, doi:10.3762/bjoc.12.246

• . Elevating the temperature to 90 °C and employing DBU, as a more basic alternative to triethylamine, did not increase the reactivity. Hence, the focus was instead directed on converting the existing batch process (Scheme 2), with sodium ethoxide as base, into a stand-alone continuous process. Initially

Sydnone C-4 heteroarylation with an indolizine ring via Chichibabin indolizine synthesis

• Florin Albota,
• Mino R. Caira,
• Constantin Draghici,
• Florea Dumitrascu and
• Denisa E. Dumitrescu

Beilstein J. Org. Chem. 2016, 12, 2503–2510, doi:10.3762/bjoc.12.245

• followed by solvent extraction gave the sydnone-indolizines 9 in yields of over 50%. If the dissolution of the quaternary salts was incomplete, a small quantity of ethanol could be added. Alternatively, replacement of sodium bicarbonate with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and the use of

• acetonitrile as solvent gave, in the case of the representative pyridinium bromide 8a, compound 9a in 53% yield. Similarly, 9a could be prepared in 54% yield by heating pyridine 6a under reflux with sydnone derivative 7 for four hours followed by the addition of DBU for cyclization. Although all three

Inhibition of peptide aggregation by means of enzymatic phosphorylation

• Kristin Folmert,
• Malgorzata Broncel,
• Hans v. Berlepsch,
• Christopher H. Ullrich,
• Mary-Ann Siegert and
• Beate Koksch

Beilstein J. Org. Chem. 2016, 12, 2462–2470, doi:10.3762/bjoc.12.240

• ) with respect to the resin and two hour double couplings. A mixture of DBU (1,8-diazabicyclo[5,4,0]undec-7-ene) and piperidine (2% each) in DMF was used for Fmoc-deprotection (3 × 10 min). The resin was washed between each step with DMF and DCM (3 × 6 mL each). Peptides were cleaved from the resin by

Useful access to enantiomerically pure protected inositols from carbohydrates: the aldohexos-5-uloses route

• Felicia D’Andrea,
• Giorgio Catelani,
• Lorenzo Guazzelli and
• Venerando Pistarà

Beilstein J. Org. Chem. 2016, 12, 2343–2350, doi:10.3762/bjoc.12.227

• condensation reactions were performed at room temperature by treating aldohexos-5-ulose derivatives with catalytic amounts of DBU (0.15 equiv) as an organic base promoting agent in toluene, a 1:1 mixture of toluene–CH2Cl2, or CH2Cl2 to circumvent solubility problems (Table 1, see Supporting Information File 1

High performance p-type molecular electron donors for OPV applications via alkylthiophene catenation chromophore extension

• Paul B. Geraghty,
• Calvin Lee,
• Jegadesan Subbiah,
• Wallace W. H. Wong,
• James L. Banal,
• Mohammed A. Jameel,
• Trevor A. Smith and
• David J. Jones

Beilstein J. Org. Chem. 2016, 12, 2298–2314, doi:10.3762/bjoc.12.223

• 11b, cat. Pd2dba3·4t-Bu3P[HBF4], THF, K3PO4 (2M), 80 °C, 16 h, and ii) N-hexylrhodanine (10 equiv), CHCl3, cat DBU. Extracted UV–vis absorption peak positions for the BXxR series. (λmax in bold). Extracted fluorescence emission peak positions for the BXxR materials (λexcit 580 nm). Extracted UV–vis