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

Synthesis of enantiomerically pure N-(2,3-dihydroxypropyl)arylamides via oxidative esterification

• Akula Raghunadh,
• Satish S More,
• T. Krishna Chaitanya,
• Yadla Sateesh Kumar,
• Suresh Babu Meruva,
• L. Vaikunta Rao and
• U. K. Syam Kumar

Beilstein J. Org. Chem. 2013, 9, 2129–2136, doi:10.3762/bjoc.9.250

• carbenes, such as 9a to 9k, with different bases (triethylamine, DBU, and DABCO) and with or without an additive to optimize the reaction conditions (Table 1). When the NHC was used in 0.25 equivalents in THF or THF/butanol (10:1) the major product isolated in the reaction was benzoin, and the desired

An organocatalytic route to 2-heteroarylmethylene decorated N-arylpyrroles

• Alexandre Jean,
• Jérôme Blanchet,
• Jacques Rouden,
• Jacques Maddaluno and
• Michaël De Paolis

Beilstein J. Org. Chem. 2013, 9, 1480–1486, doi:10.3762/bjoc.9.168

• ) delivering 5a (96%) after prolonged reaction time (22 h, conditions c, Scheme 2). Interestingly and despite its strong nucleophilic character, DABCO (1,4-diazabicyclo[2.2.2]octane) was unable to promote the isomerization (conditions d, Scheme 2) and the starting material was recovered. As presented in Scheme

Catalytic asymmetric tandem Friedel–Crafts alkylation/Michael addition reaction for the synthesis of highly functionalized chromans

• Jiahuan Peng and
• Da-Ming Du

Beilstein J. Org. Chem. 2013, 9, 1210–1216, doi:10.3762/bjoc.9.137

• )2 and TMEDA, no desired product was observed (Table 3, entries 3 and 4). DABCO led to no significant increase in yield and stereoselectivity (Table 3, entry 5). A substantial increase in enantioselectivity was observed with the use of LiOt-Bu, but the yield remained moderate (Table 3, entry 7

Selective copper(II) acetate and potassium iodide catalyzed oxidation of aminals to dihydroquinazoline and quinazolinone alkaloids

• Matthew T. Richers,
• Chenfei Zhao and
• Daniel Seidel

Beilstein J. Org. Chem. 2013, 9, 1194–1201, doi:10.3762/bjoc.9.135

• promote the full oxidation of aminal 21 to deoxyvasicinone (4) were met with disappointment, with yields of 4 for these conditions reaching a maximum of around 40% (Table 3). In most cases, peroxide 8 was observed as a major side product. The Cu/TEMPO/DABCO catalyst system employed by Han et al. [35] for

Spectroscopic characterization of photoaccumulated radical anions: a litmus test to evaluate the efficiency of photoinduced electron transfer (PET) processes

• Maurizio Fagnoni,
• Stefano Protti,
• Davide Ravelli and
• Angelo Albini

Beilstein J. Org. Chem. 2013, 9, 800–808, doi:10.3762/bjoc.9.91

• further evolution that precluded back electron transfer and any chemical reaction with the radical anion. In fact, no accumulation occurred with 1,4-diazabicyclo[2.2.2]octane (DABCO), for which this condition is not possible. The radical anions were produced from benzene polyesters too, but decomposition

• ). With N-(methylamino)ethanol (MAE) a lesser amount of TCB•− was formed and the new absorption at 290 nm, as above, was apparent already during the irradiation (not shown). On the other hand, the TCB•− spectrum did not develop in the presence of DABCO. In this case, TCB was only sluggishly consumed, and

• further tertiary amines, iPr3N causes a somewhat slower accumulation (the conformation of the radical cation is known to be less favorable for deprotonation) [48][49][50], and DABCO (for which deprotonation is impossible [51][52]) causes no detectable formation of TCB•−. Indeed, previous laser flash

Synthesis of 2,3-dihydronaphtho[2,3-d][1,3]thiazole-4,9-diones and 2,3-dihydroanthra[2,3-d][1,3]thiazole-4,11-diones and novel ring contraction and fusion reaction of 3H-spiro[1,3-thiazole-2,1'-cyclohexanes] into 2,3,4,5-tetrahydro-1H-carbazole-6,11-diones

• Lidia S. Konstantinova,
• Kirill A. Lysov,
• Ljudmila I. Souvorova and
• Oleg A. Rakitin

Beilstein J. Org. Chem. 2013, 9, 577–584, doi:10.3762/bjoc.9.62

• -anthracene-1,4-diones 4 with S2Cl2 and DABCO in chlorobenzene gave the corresponding 2,3-dihydronaphtho[2,3-d][1,3]thiazole-4,9-diones 1 and 2,3-dihydroanthra[2,3-d][1,3]thiazole-4,11-diones 2 by triethylamine addition, in high to moderate yields. The DABCO replacement for N-ethyldiisopropylamine in the

• -[butyl(methyl)amino]naphthoquinone 3a with sulfur monochloride and tertiary amines [N-ethyldiisopropylamine (Hünig’s base) and 1,4-diazabicyclooctane (DABCO)]. Treatment of naphthoquinone 3a with S2Cl2 (9 equiv) and Hünig’s base (5 equiv) in THF at 0 °C for 72 h with subsequent heating under reflux for 2

• %, respectively). Sulfur monochloride is known as a powerful chlorinating agent for chlorination of aromatic and heteroaromatic compounds [14][15]. In an attempt to increase the sulfurating ability of S2Cl2 the complex 8 obtained from S2Cl2 and 2 equiv of DABCO [16] was used. We have recently shown that this

New simple synthesis of ring-fused 4-alkyl-4H-3,1-benzothiazine-2-thiones: Direct formation from carbon disulfide and (E)-3-(2-aminoaryl)acrylates or (E)-3-(2-aminoaryl)acrylonitriles

• Qiuping Ding,
• Yuqing Lin,
• Guangni Ding,
• Fumin Liao,
• Xiaoyan Sang and
• Yi-Yuan Peng

Beilstein J. Org. Chem. 2013, 9, 460–466, doi:10.3762/bjoc.9.49

• conditions. (E)-Butyl 3-(2-aminophenyl)acrylate (1a) was chosen as a model substrate, and the results are summarized in Table 1. Among the bases screened, DABCO was found to be superior to the other organic or inorganic bases, although DBU, Et3N, and KOH also provided good results (Table 1, entries 1–6

• ). However, no product could be detected in the absence of base (Table 1, entry 7). When a catalytic amount of DABCO (20 mol %) was used, only a 69% yield of product 2a was obtained. Subsequently, the study results showed that the amount of CS2 had a great effect on the reaction (Table 1, entry 1 versus

• , 4.0 equiv, 91.2 mg) and DABCO (0.3 mmol, 1.0 equiv, 33.6 mg) was stirred in DMSO (2 mL) at room temperature. After completion of the reaction as indicated by TLC (about 2 d), the reaction was quenched by water and extracted with ethyl acetate. The organic layers were dried with anhydrous MgSO4, the

Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP

• Martin Goez,
• Isabell Frisch and
• Ingo Sartorius

Beilstein J. Org. Chem. 2013, 9, 437–446, doi:10.3762/bjoc.9.46

• Martin Goez Isabell Frisch Ingo Sartorius Institut für Chemie, Martin–Luther-Universität Halle–Wittenberg, Kurt–Mothes-Str. 2, 06120 Halle/Saale, Germany 10.3762/bjoc.9.46 Abstract The photoreactions of diazabicyclo[2,2,2]octane (DABCO) and triisopropylamine (TIPA) with the sensitizers

• triethylamine, a complete changeover of the polarization source occurs within a narrow (<20 kJ/mol) window of ∆Gdep far in the exergonic range (at around −100 kJ/mol). In this work, we employ time-resolved CIDNP experiments to study two amines with hindered deprotonation of 1,4-diazabicyclo[2.2.2]octane (DABCO

• ) and triisopropylamine (TIPA). The hindrance is due to a stereoelectronic effect with DABCO [21], and due to overcrowding with TIPA [22]. As sensitizers, we have chosen 9,10-anthraquinone (AQ) on one hand and xanthone (XA) or benzophenone (BP) on the other; with triethylamine, these are typical

Reactions of salicylaldehyde and enolates or their equivalents: versatile synthetic routes to chromane derivatives

• Ishmael B. Masesane and
• Zelalem Yibralign Desta

Beilstein J. Org. Chem. 2012, 8, 2166–2175, doi:10.3762/bjoc.8.244

• of 28% (Scheme 18) [38]. Slightly better yields (33–40%) were achieved when 5-bromo-, 5-chloro- and 3,5-dichloro-substituted salicylaldehydes were employed in the reaction. Ravichandran utilized a classical 1,4-diazabicyclo[2.2.2]octane (DABCO)-catalyzed Baylis–Hillman reaction of salicylaldehyde (5

• isolated in this work. The mechanism of the DABCO-catalyzed reaction of salicylaldehyde and α,β-unsaturated compounds in the synthesis 3-substituted chromenes was proved to proceed through the Baylis–Hillman reaction by Kaye and co-workers [40][41] Their work involved the reaction of salicylaldehyde (5

Organocatalytic cascade aza-Michael/hemiacetal reaction between disubstituted hydrazines and α,β-unsaturated aldehydes: Highly diastereo- and enantioselective synthesis of pyrazolidine derivatives

• Zhi-Cong Geng,
• Jian Chen,
• Ning Li,
• Xiao-Fei Huang,
• Yong Zhang,
• Ya-Wen Zhang and
• Xing-Wang Wang

Beilstein J. Org. Chem. 2012, 8, 1710–1720, doi:10.3762/bjoc.8.195

• enantioselectivity and reactivity. Subsequently, several common inorganic and organic bases were investigated [80][81][82][83]. Unfortunately, the catalytic results showed that with LiOAc, DMAP, DABCO, Et3N, TMEDA as additives, the yield and enantioselectivity were only marginally influenced (Table 4, entries 15–19

Reactions of nitroxides XIII: Synthesis of the Morita–Baylis–Hillman adducts bearing a nitroxyl moiety using 4-acryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl as a starting compound, and DABCO and quinuclidine as catalysts

• Jerzy Zakrzewski

Beilstein J. Org. Chem. 2012, 8, 1515–1522, doi:10.3762/bjoc.8.171

• aldehydes. Keywords: 4-acryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl; DABCO; Morita–Baylis–Hillman reaction; nitroxides; quinuclidine; Introduction In the Morita–Baylis–Hillman (MBH) reaction, aldehydes react with a double bond activated by an electron-withdrawing group (EWG). The vinylic carbon

• bearing an EWG undergoes substitution. The reaction is carried out in the presence of either a tertiary amine (e.g., DABCO [2][3][4][5][6], quinuclidine and its derivatives [7][8][9][10][11][12], DBU [13][14], DBN [13], DMAP and its derivatives [4][15][16], urotropine [17], brucine N-oxide [18]) or a

• that the effects on the reaction of aryl, benzyl, alkyl, and functionalized alkyl acrylic esters with benzaldehyde and furfuraldehyde in the presence of DABCO, strongly depend upon the electronic and steric effects of the ester part. The “unreactivity” of acrylates increases with steric hindrance and

A quantitative approach to nucleophilic organocatalysis

• Herbert Mayr,
• Sami Lakhdar,
• Biplab Maji and
• Armin R. Ofial

Beilstein J. Org. Chem. 2012, 8, 1458–1478, doi:10.3762/bjoc.8.166

• settled by studying the reactivities of independently synthesized intermediates. Kinetic investigations of the reactions of N-heterocyclic carbenes (NHCs) with benzhydrylium ions showed that they have similar nucleophilicities to common organocatalysts (e.g., PPh3, DMAP, DABCO) but are much stronger (100

• -diazabicyclo[2.2.2]octane (DABCO, 38) and (4-dimethylamino)pyridine (DMAP, 39). As shown in Figure 22, DABCO (38) reacts approximately 103 times faster with benzhydrylium ions than DMAP (39), i.e., DABCO (38) is considerably more nucleophilic than DMAP (39) [94]. On the other hand, the equilibrium constant for

• the formation of the Lewis acid–Lewis base adduct with 18g is 160 times smaller for DABCO (38) than for DMAP (39), i.e., DABCO (38) is a significantly weaker Lewis base than DMAP (39). We have previously discussed that it is the higher reorganization energy for the reaction of DMAP (39) that is