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

• ). Fortunately, the desired product 2a was obtained in 57% yield. No reaction was observed using TEA or DABCO, possibly because the allenic intermediate could not be formed by these comparatively weak bases (Table 1, entries 2 and 3), which was different from the previous work. Other bases, such as TBD, Cs2CO3

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• abstraction by PINO and/or the Co3+–oxygen complex to provide the pyridine derivatives (Scheme 21). One of the other noteworthy examples is a copper chloride/1,4-diazabicyclo[2.2.2]octane (DABCO) and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-catalyzed aerobic oxidative dehydrogenation approach

• yield. The proposed mechanism of this transformation is illustrated in the formation of 73. It involved oxidation of Cu(I)-(DABCO)2 by either oxygen or TEMPO to afford the Cu(II)-(DABCO)2 complex which gets coordinated with the N-atom of the substrate and TEMPO to generate an η2 complex Y. The benzylic

• Hantzch 1,4-DHPs. DABCO and TEMPO-catalyzed aerobic oxidative dehydrogenation of quinazolines and 4H-3,1-benzoxazines. Putative mechanism for Cu(I)–DABCO–TEMPO catalyzed aerobic oxidative dehydrogenation of tetrahydroquinazolines. Potassium triphosphate modified Pd/C catalysts for the oxidative

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

• obtaining mechanistic information on the present reaction, three representative optically active substrates (R,E)-6 were selected and submitted to the identical conditions as above (Table 4). Furthermore, in the case of (R,E)-6a, conditions in entries 6 (6 M NaOH aq in MeOH) and 19 (DABCO in toluene) in

• possessed its conformation as shown in Table 4. Although DABCO attained the same level of CT (Table 4, entry 3) albeit a slower reaction rate, this is not the case for the conditions of 6 M NaOH aq in MeOH and only 21% CT was observed. The latter result would be because of the competing occurrence of

• intermolecular reprotonation by the solvent. The present interesting proton shift reaction was also computationally simulated [7] by employing (R,E)-6h with the substitution pattern of R1 = Ph and R2 = Me as the model substrate. For simplicity, 1,4-diazabicyclo[2.2.2]octane (DABCO) was employed as the

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

• regioselective 5-exo-dig cyclization–proton transfer–isomerization sequential process. They found that the easily available N-(propargylcarbamothioyl)amides 53 in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) as the base in refluxing ethanol, rapidly cyclized and produced the corresponding dihydrothiazol

• -propargylamines 47 with benzotriazolylthiones 48. Mechanism proposed to explain the synthesis of 2,5-disubstituted thiazoles 49 developed by Sasmal. Mo-catalyzed cyclization of N-propargylthiocarbamate 50. (a) DABCO-mediated intramolecular cyclization of N-(propargylcarbamothioyl)amides 53 to the corresponding

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

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

• observed under mild conditions with L11. The activity of catalysts L11 was found to be comparable to the activity of common thiourea-based hydrogen bond donors, and double-charged catalyst DABCO-Me2·2X was found to be one of the most active catalysts. As before [53], the activity of ammonium salts L11 was

A versatile route to polythiophenes with functional pendant groups using alkyne chemistry

• Xiao Huang,
• Li Yang,
• Rikard Emanuelsson,
• Jonas Bergquist,
• Maria Strømme,
• Martin Sjödin and
• Adolf Gogoll

Beilstein J. Org. Chem. 2016, 12, 2682–2688, doi:10.3762/bjoc.12.265

• an sp3 carbon increased the yield of the transetherification reaction significantly. Attempts were also made to attach an alkyne to EDOT via the reaction between hydroxymethyl EDOT and propargyl tosylate using DABCO as catalyst, but it led to a very low yield and this EDOT-propargyl product was very

Economical and scalable synthesis of 6-amino-2-cyanobenzothiazole

• Jacob R. Hauser,
• Hester A. Beard,
• Mary E. Bayana,
• Katherine E. Jolley,
• Stuart L. Warriner and
• Robin S. Bon

Beilstein J. Org. Chem. 2016, 12, 2019–2025, doi:10.3762/bjoc.12.189

• ), which has an amine handle for straight-forward derivatisation. Here we present an economical and scalable synthesis of ACBT based on a cyanation catalysed by 1,4-diazabicyclo[2.2.2]octane (DABCO), and discuss its advantages for scale-up over previously reported routes. Keywords: ACBT; cyanation; 2

• -cyanobenzothiazoles; DABCO; luciferins; organocatalysis; Introduction Functionalised 2-cyanobenzothiazoles (CBTs, 1) are key building blocks for the synthesis of luciferins 3 [1][2][3], substrates of natural and engineered firefly luciferases that are widely used for bioluminescence imaging (BLI) [4][5]. The typical

• (DABCO) as a catalyst for the cyanation of heteroaryl halides [19] inspired us to explore the DABCO-catalysed cyanation of 2-chlorobenzothiazoles. Indeed, the treatment of 2-chloro-6-nitrobenzothiazole (6) with DABCO (15 mol %) and sodium cyanide (NaCN, 1.05 equiv) in DMSO/water 1:1, at room temperature

Ionic liquids as transesterification catalysts: applications for the synthesis of linear and cyclic organic carbonates

• Maurizio Selva,
• Alvise Perosa,
• Sandro Guidi and
• Lisa Cattelan

Beilstein J. Org. Chem. 2016, 12, 1911–1924, doi:10.3762/bjoc.12.181

• carbonate was examined in the presence of the ionic liquid DABCO–DMC obtained in situ by reacting DABCO and DMC (Scheme 13) [65]. DABCO by itself is more basic than the DABCO–DMC IL as indicated by its pH in aqueous solution. Nonetheless the DABCO–DMC IL promoted higher glycerol conversion (77% vs 19% after

• carbonyl moiety (Scheme 14). It must be noted that in these two examples the selectivity of the reaction could be tuned just by changing the catalyst precursor: by switching from the DBU-based IL to the DABCO–DMC IL, the selectivity changed from 82% for glycerol carbonate, to 83% for glycidol. In another

• a valid alternative for the industrial production of DMC [59]. Although ionic liquids can catalyze both reactions, this review will only briefly discuss the second transesterification step. Yang et al. tested many basic ILs derived from DABCO for the synthesis of DMC starting from ethylene carbonate

Synthesis of 2-oxindoles via 'transition-metal-free' intramolecular dehydrogenative coupling (IDC) of sp² C–H and sp³ C–H bonds

• Nivesh Kumar,
• Santanu Ghosh,
• Subhajit Bhunia and
• Alakesh Bisai

Beilstein J. Org. Chem. 2016, 12, 1153–1169, doi:10.3762/bjoc.12.111

• , methallyl, dimethylallyl, and geranyl esters, we were interested for IDC using simple organic bases such as triethylamine, pyridine, and DABCO (Table 2) [64]. It was found that IDC can operate in the presence of organic bases to afford products only in 25–34% yields of 2-oxindoles (Table 2, entries 1, 2 and

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• bisthiourea (cat. 26)-catalyzed asymmetric Morita–Baylis–Hillman reaction of isatins with α,β-unsaturated γ-butyrolactam (Scheme 41) [58]. The reactions were performed in DCM at room temperature with catalytic amounts of DABCO (5 mol %). A variety of isatin derivatives were tested under this catalytic system

Supported bifunctional thioureas as recoverable and reusable catalysts for enantioselective nitro-Michael reactions

• José M. Andrés,
• Miriam Ceballos,
• Alicia Maestro,
• Isabel Sanz and
• Rafael Pedrosa

Beilstein J. Org. Chem. 2016, 12, 628–635, doi:10.3762/bjoc.12.61

• were dried and stored over microwave–activated 4 Å molecular sieves. Supported thioureas II–V and unsupported thioureas I and VI were prepared according to reported procedures [30][31]. Racemic reference samples were prepared by using DABCO (5 mol %) following the same procedure as described below

Cupreines and cupreidines: an established class of bifunctional cinchona organocatalysts

• Laura A. Bryant,
• Rossana Fanelli and
• Alexander J. A. Cobb

Beilstein J. Org. Chem. 2016, 12, 429–443, doi:10.3762/bjoc.12.46

• give the corresponding thietanes 96. In another example of how a different catalyst can lead to a different product, the authors demonstrated that the use of DABCO led instead to the [4 + 2] adduct (Scheme 22) [66]. Domino reaction Although it could be argued that some of the reactions within this

A quadruple cascade protocol for the one-pot synthesis of fully-substituted hexahydroisoindolinones from simple substrates

• Hong-Bo Zhang,
• Yong-Chun Luo,
• Xiu-Qin Hu,
• Yong-Min Liang and
• Peng-Fei Xu

Beilstein J. Org. Chem. 2016, 12, 253–259, doi:10.3762/bjoc.12.27

• easily accessible substrates. Results and Discussion We initiated this study by using 2-benzylidenemalononitrile (1a) and 2-oxo-N,3-diphenylpropanamide (2a) [61][62][63][64] in 0.5 mL of CH3CN in the presence of 10 mol % of DABCO. After 12 h at room temperature, the reaction afforded the expected product

Copper-catalyzed aerobic radical C–C bond cleavage of N–H ketimines

• Ya Lin Tnay,
• Gim Yean Ang and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2015, 11, 1933–1943, doi:10.3762/bjoc.11.209

• additive 1,10-phenanthroline to 40 mol % slightly improved the yield, giving 3a in 40% yield (Table 1, entry 1). The use of 2,2’-bipyridine (bpy) provided a comparable result (Table 1, entry 2), while performing the reaction in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) led to lower yields of

An efficient synthesis of N-substituted 3-nitrothiophen-2-amines

• Sundaravel Vivek Kumar,
• Shanmugam Muthusubramanian,
• J. Carlos Menéndez and
• Subbu Perumal

Beilstein J. Org. Chem. 2015, 11, 1707–1712, doi:10.3762/bjoc.11.185

• with ethanol to give the pure 3-nitro-N-(p-tolyl)thiophen-2-amine (3e) without the need for chromatography. Then the model reaction was further investigated by employing alternative bases such as 1,4-diazabicyclo[2.2.2]octane (DABCO, Table 1, entry 4), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU, Table 1

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

A facile synthesis of functionalized 7,8-diaza[5]helicenes through an oxidative ring-closure of 1,1’-binaphthalene-2,2’-diamines (BINAMs)

• Youhei Takeda,
• Masato Okazaki,
• Yoshiaki Maruoka and
• Satoshi Minakata

Beilstein J. Org. Chem. 2015, 11, 9–15, doi:10.3762/bjoc.11.2

• organic bases like DABCO (pKa 8.93 in DMSO [32]) and DBU (pKa 23.9 in MeCN [33]) gave a lower yield (32%) and no product, respectively (Table 1, entries 14 and 15). As results, the use of the moderately weak organic base 2,6-lutidine (pKa 6.72 in water [34]) successfully afforded 2a in high yield (Table 1

Morita–Baylis–Hillman reaction of acrylamide with isatin derivatives

• Radhey M. Singh,
• Kishor Chandra Bharadwaj and
• Dharmendra Kumar Tiwari

Beilstein J. Org. Chem. 2014, 10, 2975–2980, doi:10.3762/bjoc.10.315

• Abstract The Morita–Baylis–Hillman reaction of acrylamide, as an activated alkene, has seen little development due to its low reactivity. We have developed the reaction using isatin derivatives with acrylamide, DABCO as a promoter and phenol as an additive in acetonitrile. The corresponding aza version

• substrate scope. The reaction between 1a and N-methylisatin (2a) was carried out in the presence of DABCO using acetonitrile as the solvent (Table 1, entry 1). Although the reaction was slow and produced low yield (31%), the formation of the product 3aa with starting material remaining was nevertheless

• , entry 15). Although heating to 55–60 °C did reduce the reaction time, this was accompanied by the generation of impurities along with a reduction in yield (Table 1, entry 16 and entry 17). Finally, using two equivalents of acrylamide, DABCO and phenol each (using acetonitrile as a solvent) at rt was

Preparation of phosphines through C–P bond formation

• Iris Wauters,
• Wouter Debrouwer and
• Christian V. Stevens

Beilstein J. Org. Chem. 2014, 10, 1064–1096, doi:10.3762/bjoc.10.106

Cyclic phosphonium ionic liquids

• Sharon I. Lall-Ramnarine,
• Joshua A. Mukhlall,
• James F. Wishart,
• Robert R. Engel,
• Alicia R. Romeo,
• Masao Gohdo,
• Sharon Ramati,
• Marc Berman and
• Sophia N. Suarez

Beilstein J. Org. Chem. 2014, 10, 271–275, doi:10.3762/bjoc.10.22

• compounds were then treated under nitrogen with 1,4-diazabicyclo[2.2.2]octane (DABCO) at 80 °C to remove the borane, and the resultant mixture was purified in a nitrogen-filled glove box on a short silica-gel column. The pure cyclic phosphines (1-n-butylphospholane and 1-n-butylphosphinane) were allowed to

• -phenylphospholane–borane complex, followed by silica-gel chromatography and then removal of the borane with DABCO, to give the pure 1-phenylphospholane. The six-membered cyclic phosphine, which appears to be less air sensitive than the 1-butylphosphinane species, was purified in open air using a short column of

Organobase-catalyzed three-component reactions for the synthesis of 4H-2-aminopyrans, condensed pyrans and polysubstituted benzenes

• Moustafa Sherief Moustafa,
• Saleh Mohammed Al-Mousawi,
• Maghraby Ali Selim,
• Ahmed Mohamed Mosallam and
• Mohamed Hilmy Elnagdi

Beilstein J. Org. Chem. 2014, 10, 141–149, doi:10.3762/bjoc.10.11

• -3,5-dicyanophthalic acid ester derivatives 37a–c were developed. The synthetic methods utilize one-pot reactions of acetylene carboxylic acid esters, α,β-unsaturated nitriles and/or active methylenenitriles in the presence of L-proline or DABCO. Plausible mechanisms are suggested for the formation of

• -oxo-5-phenyl-3H-isoindole-4-carboxylate (40). Keywords: aminopyranes; arylbenzoic acid; DABCO; L-proline; multicomponent; tetrahydronaphthalene; three-component reaction; Introduction The reaction of arylidenemalononitriles with active methyl and methylene compounds was extensively utilized for the

• in the presence of L-proline or DABCO to yield the 2-amino-4H-pyran 18 whose structure was assigned by X-ray crystallographic methods (Figure 3). We assumed that in this process 14 and 15 undergo an initial condensation to yield dione 16 that reacts with malononitrile to afford adduct 17, which

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

• (14) [11]. In order to reduce the amount of acrylate and to increase the yield of compound (±)-16, the Baylis–Hillman reaction between the aldehyde 14 and ethyl acrylate (15) was tried using different catalysts such as DBU, quinuclidine [12] and n-Bu3P. DABCO was found to be a better catalyst and the

Four-component reaction of cyclic amines, 2-aminobenzothiazole, aromatic aldehydes and acetylenedicarboxylate

• Hong Gao,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2013, 9, 2934–2939, doi:10.3762/bjoc.9.330

• produced. After carefully optimizing the reaction conditions, we were pleased to find that the expected 3-(pyrrolidin-1-yl)-2-pyrrolidinones 1h–1m could be prepared in the satisfactory yields by adding the stronger base DABCO into the reaction as base catalyst (Table 1, entries 8–13). Another common cyclic

• ), acetylenedicarboxylate (2.0 mmol), aromatic aldehyde (2.0 mmol), piperidine (3.0 mmol) (in cases of pyrrolidine or morpholine was used in the reaction, pyrrolidine or morpholine (2.0 mmol), DABCO (0.5 mmol)) in ethanol (10.0 mL) was stirred at room temperature for about twenty minutes and then was heated at about 50–60