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

Cation affinity numbers of Lewis bases

• Christoph Lindner,
• Raman Tandon,
• Boris Maryasin,
• Evgeny Larionov and
• Hendrik Zipse

Beilstein J. Org. Chem. 2012, 8, 1406–1442, doi:10.3762/bjoc.8.163

• values are about 70 to 80 kJ/mol smaller than the respective BHCA values (e.g., for pyridine (1) or triphenylphosphane (89)). Moreover, some of the weakest Lewis bases considered here such as DABCO (44) are not sufficently basic to form covalently bound adducts with trityl cations. The TCA values

• calculated for these systems thus represent the reaction enthalpies for the formation of ion-dipole complexes. Aside from DABCO this is the case for 345, 45, and 347. The C–N bond distances of the energetically best conformations of these complexes range from 2.8 Å to 4.0 Å. As a reference bond length the C

• –N distance in pyridine-trityl adduct (1TT), which amounts to 1.57 Å, can be used. A slightly increased C–N bond length can be found for the TCA-adduct of quinuclidine 53 (1.76 Å), which is in distinct contrast to the structurally similar DABCO. It should be added that all other electrophiles

Organocatalytic asymmetric allylic amination of Morita–Baylis–Hillman carbonates of isatins

• Hang Zhang,
• Shan-Jun Zhang,
• Qing-Qing Zhou,
• Lin Dong and
• Ying-Chun Chen

Beilstein J. Org. Chem. 2012, 8, 1241–1245, doi:10.3762/bjoc.8.139

• catalysis of DABCO. No desired reaction occurred for phthalimide [25] or N-allyl p-toluenesulfonamide [27], which has been successfully applied in the asymmetric amination of MBH carbonates derived from aryl aldehydes. Pleasingly, the reaction took place smoothly to afford product 4a when hydroxylamine 3a

Stereoselective, nitro-Mannich/lactamisation cascades for the direct synthesis of heavily decorated 5-nitropiperidin-2-ones and related heterocycles

• Pavol Jakubec,
• Dane M. Cockfield,
• Madeleine Helliwell,
• James Raftery and
• Darren J. Dixon

Beilstein J. Org. Chem. 2012, 8, 567–578, doi:10.3762/bjoc.8.64

• methylene or methine carbon acids with nitro olefins in the presence of DABCO (20–30 mol %) in THF (Scheme 2). Where diastereoisomers were created in the Michael addition step and stereocontrol was poor, the diastereomeric mixtures were recrystallised to afford single diastereomers 6a, b, e. The relative

Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• (after removal of excess acrylic acid) with the aid of an oligomeric alkyl carbodiimide 44 (Scheme 19) [19]. Interestingly, Willis and coworkers have shown that aryl N-aminosulfonamides may be accessed by three-component coupling of aryl iodides, hydrazines, and DABCO·(SO2)2 as a convenient source of

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

The subtle balance of weak supramolecular interactions: The hierarchy of halogen and hydrogen bonds in haloanilinium and halopyridinium salts

• Kari Raatikainen,
• Massimo Cametti and
• Kari Rissanen

Beilstein J. Org. Chem. 2010, 6, No. 4, doi:10.3762/bjoc.6.4

• of iodo- and nitrobenzenes [29][30]. In our recent studies [33], we have shown that 1-iodo-3,5-dinitrobenzene forms surprisingly strong C–I···N halogen bonds (23% shorter than the sum of standard VDW radii [17]) with 1,4-diazabicyclo[2.2.2]octane (DABCO). One of the main challenges in supramolecular

• previous study on co-crystals of 1-iodo-3,5-dinitrobenzene and DABCO (1,4-diazabicyclo[2.2.2]octane) [33]. Thus, we prepared X-ray quality crystals of 13 from an ethyl acetate solution of 3-iodopyridine and 5-nitroisophthalic acid in 2 : 1 molar ratio. Despite the stoichiometry employed in the

Sordarin, an antifungal agent with a unique mode of action

• Huan Liang

Beilstein J. Org. Chem. 2008, 4, No. 31, doi:10.3762/bjoc.4.31

• in MeCN afforded a product of excellent quality that was directly utilized in the next step. Then, treatment of crude 93 in acrylonitrile with a catalytic amount of DABCO gave the Baylis-Hillman product 94. Preparation of the Danishefsky-like diene 95 by treatment of 94 with Hunig’s base and TES

Hydrogen bonding patterns in the cocrystals of 5-nitrouracil with several donor and acceptor molecules

• Reji Thomas,
• R. Srinivasa Gopalan,
• G. U. Kulkarni and
• C. N. R. Rao

Beilstein J. Org. Chem. 2005, 1, No. 15, doi:10.1186/1860-5397-1-15

• evaporation of a solution of I in respective solvents. Cocrystals of I with non-solvent guests – piperazine, N,N'-dimethylpiperazine, 3-aminopyridine and diazabicyclo [2.2.2]octane (DABCO)- were made by solvothermal method. In all the cases, the compound I and the guest molecule were taken in 1:1 ratio in

• example of such stacking has been found in the cocrystal of I with DABCO and water (molar composition, 2:2:5), as shown in Figure 8. The structure contains cyclic dimers of nitrouracil (see inset of Figure 8) formed through N-H...O interactions (H(22A)...O(12), 1.878(3) Å and H(12A)...O(22), 2.189(3) Å

• ), arranged in the form of parallel set of tapes. The nitrouracil tapes are held between sheets of the DABCO molecules, which in turn are covered by layers of water molecules. These supramolecular assemblies get rotated along the a axis by 90° alternately. There is extensive hydrogen bonding between DABCO and