p-Nitrophenyl carbonate promoted ring-opening reactions of DBU and DBN affording lactam carbamates

• Madhuri Vangala and
• Ganesh P Shinde

Beilstein J. Org. Chem. 2016, 12, 2086–2092, doi:10.3762/bjoc.12.197

• with a large substrate scope. Keywords: carbonates; DBN; DBU; lactams; p-nitrophenyl; Introduction Among various organic bases, amidines such as DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) and DBN (1,5-diazabicyclo[4.3.0]non-5-ene) having an imino group attached to the α-carbon of the amine are

Scope and limitations of a DMF bio-alternative within Sonogashira cross-coupling and Cacchi-type annulation

• Kirsty L. Wilson,
• Alan R. Kennedy,
• Jane Murray,
• Ben Greatrex,
• Craig Jamieson and
• Allan J. B. Watson

Beilstein J. Org. Chem. 2016, 12, 2005–2011, doi:10.3762/bjoc.12.187

• concentrations (Table 1, entries 2 and 3) allowing for a reduction in solvent volume, commensurate with the principles of green chemistry [46][47]. In attempts to further limit waste, we scanned a series of bases (see Supporting Information File 1); organic bases consistently performed more effectively and

• . Organic bases such as pyridine (Table 2, entry 2), DIPEA (Table 2, entry 4), and Et3N (Table 2, entry 6) were tolerated at 25 °C with DIPEA and Et3N also tolerated at 50 °C. DBU, however, was not tolerated at any temperature (Table 2, entry 8). With the exception of KOAc (Table 2, entry 1), all inorganic

• -used organic transformations. For example, the majority of many other standard cross-coupling processes employ inorganic or organic bases and heat (e.g., Suzuki–Miyaura, Heck). Accordingly, Cyrene may be projected to be incompatible with standard conditions for these reactions and its use would

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

• than iodine (conditions A). Although our iodine-mediated IDC is successful in most of the cases, however, in few cases we have seen moderate yields of products. Thus, we decided to carry out IDC in the presence of organic bases as well. Thus, for an alternative approach to 2-oxindoles bearing allyl

• , 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

• intramolecular-dehydrogenative-coupling (IDC)a. IDC in the presence of organic bases. Reproduced from [46]. Supporting Information Supporting Information File 166: Copies of 1H, and13C NMR spectra for all new compounds. Acknowledgements Financial support from the Department of Science and Technology (DST

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

Synthesis of 2-trifluoromethylpyrazolo[5,1-a]isoquinolines via silver triflate-catalyzed or electrophile-mediated one-pot tandem reaction

• Xiaoli Zhou,
• Meiling Liu,
• Puying Luo,
• Yingjun Lai,
• Tangtao Yang and
• Qiuping Ding

Beilstein J. Org. Chem. 2014, 10, 2286–2292, doi:10.3762/bjoc.10.238

• organic bases were examined, and the results showed that CsF was the best choice (91% yield, Table 1, entry 8). The control experiment also showed that the base was important for the reaction to proceed (8% yield, Table 1, entry 13). Subsequently, a range of solvents, such as acetonitrile, toluene, THF

Efficient CO₂ capture by tertiary amine-functionalized ionic liquids through Li⁺-stabilized zwitterionic adduct formation

• Zhen-Zhen Yang and
• Liang-Nian He

Beilstein J. Org. Chem. 2014, 10, 1959–1966, doi:10.3762/bjoc.10.204

• through formation of zwitterionic adducts, combining synthetic strategies to ionic liquids (ILs) and coordination. The essence of our strategy is to make use of multidentate cation coordination between Li+ and an organic base. Also PEG-functionalized organic bases were employed to enhance the CO2

• method combining the formation of ILs and coordination to achieve equimolar CO2 capture through zwitterionic adduct formation. The essence of our strategy is to make use of the multisite coordination interaction between Li+ and organic bases or PEG-functionalized organic bases. The readily prepared ILs

• process is thermodynamically favourable. Conclusion In summary, efficient CO2 capture was achieved through formation of zwitterionic adducts with readily synthesized chelated ILs. Multisite coordination interaction between the Li+ cation and organic bases or PEG-functionalized organic bases is thought to

One-pot stereoselective synthesis of α,β-differentiated diamino esters via the sequence of aminochlorination, aziridination and intermolecular S_N2 reaction

• Yiwen Xiong,
• Ping Qian,
• Chenhui Cao,
• Haibo Mei,
• Jianlin Han,
• Guigen Li and
• Yi Pan

Beilstein J. Org. Chem. 2014, 10, 1802–1807, doi:10.3762/bjoc.10.189

• to the previous reports on the derivatization of aminohalogenation reactions, the vicinal haloamines usually underwent elimination or aziridination reactions when they were treated with organic bases (Scheme 2) [33][34][35]. However, when benzylamine was added to haloamine 1a in acetonitrile, 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

• grinding to take place. Next, we examined several different bases for the deprotonation of the dipyrrolium species. Organic bases such as Et3N and DBU (Table 1, entries 1 and 5), proved to be most effective. Although DBU gave comparable results to Et3N, variations in yields were observed, likely due to the

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

• ). Soluble organic bases were also tested and failed to increase the yields (Table 1, entries 11 and 12). When benzoic acid (5a) was used as an additive, the yield was slightly improved to 77% (Table 1, entry 13). With the increase of the acidity, the yield was noticeably decreased (Table 1, entry 13 versus

• 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

Translation of microwave methodology to continuous flow for the efficient synthesis of diaryl ethers via a base-mediated S_NAr reaction

• Charlotte Wiles and
• Paul Watts

Beilstein J. Org. Chem. 2011, 7, 1360–1371, doi:10.3762/bjoc.7.160

• substitution; organic bases; Introduction Diaryl ethers are a synthetically interesting subunit [1], with examples found in a series of medicinally significant natural products, such as (−)-K-13 (1) [2], riccardin C (2) [3] and combretastatins [4], along with synthetic herbicides, such as RH6201 (3) [5

• alternative to DMA. Screening of organic bases: With one of the salient features of microreaction technology being the speed of reaction optimisation, due to the low system hold-up volume, we subsequently investigated the effect of base type and stoichiometry on the reaction in MeCN. Whilst this would

• the diaryl ether 7 in high purity. Using this approach, we investigated stoichiometries from 0.01 to 2.00 equiv for 10 additional organic bases (Table 1), with 1.0 M stock solutions prepared owing to the variable miscibility of the selected bases with the reaction solvent, MeCN. In order to gauge the

Au(I)/Au(III)-catalyzed Sonogashira-type reactions of functionalized terminal alkynes with arylboronic acids under mild conditions

• Deyun Qian and
• Junliang Zhang

Beilstein J. Org. Chem. 2011, 7, 808–812, doi:10.3762/bjoc.7.92

• inorganic and organic bases was also investigated: K2CO3, K3PO4, K3PO4·3H2O, NaHCO3, NaOAc were substantially less effective, whilst organic bases such as iPr2NH, Et2NH, TMEDA, Bu3N, PhNMe2 were not effective bases in this catalytic system (see Supporting Information File 1). These results indicated that

CuCl-catalyzed aerobic oxidation of 2,3-allenols to 1,2-allenic ketones with 1:1 combination of phenanthroline and bipyridine as ligands

• Shuxu Gao,
• Yu Liu and
• Shengming Ma

Beilstein J. Org. Chem. 2011, 7, 396–403, doi:10.3762/bjoc.7.51

• then screened for the oxidation of 1a. The results are summarized in Table 1 and Table 2. We found that (1) K2CO3 is the most effective base (Table 1, entry 1) and that organic bases such as NEt3 and DBU are generally ineffective (Table 1, entries 6 and 7); (2) toluene is the best solvent (Table 2). In

Studies on Pd/NiFe₂O₄ catalyzed ligand-free Suzuki reaction in aqueous phase: synthesis of biaryls, terphenyls and polyaryls

• Sanjay R. Borhade and
• Suresh B. Waghmode

Beilstein J. Org. Chem. 2011, 7, 310–319, doi:10.3762/bjoc.7.41

• after 5 and 10 min when the ratio of DMF and water was 1:1 and 3:2, respectively (Table 1, entries 13–18). The results suggested that, the ratio of water to DMF played an important role in the Pd/NiFe2O4 catalyzed Suzuki reaction. Among the various bases studied, inorganic bases were superior to organic

• bases such as triethylamine (TEA) and tributylamine (TBA) which may be due to partial inhomogenity in the aqueous phase. As the basicity of alkali carbonate increases, the time for completion of the reaction increases (Table 2, entries 4–6). Na2CO3 was found to be the best base (Table 2, entry 4

Michael-type addition of azoles of broad-scale acidity to methyl acrylate

• Sławomir Boncel,
• Kinga Saletra,
• Barbara Hefczyc and
• Krzysztof Z. Walczak

Beilstein J. Org. Chem. 2011, 7, 173–178, doi:10.3762/bjoc.7.24

• -centred organic bases expressed by the equation: pKa (DMF) = 0.9463 pKa (water) + 1.4154 [32][33]. This semi-empirical relationship enables an initial selection of a base required for a sufficient level of deprotonation of N–H azole acids. 1a and 1b as weak N–H acids required an equimolar amount of a

Synthesis of indolo[3,2-b]carbazole-based new colorimetric receptor for anions: A unique color change for fluoride ions

• Ajit Kumar Mahapatra,
• Giridhari Hazra and
• Prithidipa Sahoo

Beilstein J. Org. Chem. 2010, 6, No. 12, doi:10.3762/bjoc.6.12

• absorbance in UV–vis studies. This is presumably because the presence of a relatively high amount of protic solvent disfavors the formation of the deprotonated receptor. However, in the water–acetonitrile system, no color changes were observed upon addition of organic bases such as triethylamine whilst the

Solvent-free and time-efficient Suzuki–Miyaura reaction in a ball mill: the solid reagent system KF–Al₂O₃ under inspection

• Franziska Bernhardt,
• Ronald Trotzki,
• Tony Szuppa,
• Achim Stolle and
• Bernd Ondruschka

Beilstein J. Org. Chem. 2010, 6, No. 7, doi:10.3762/bjoc.6.7

• Ando et al. as a useful agent for inducing alkylation reactions [21]. Additional benefits have been derived by taking advantage of the strongly basic nature of KF–Al2O3, which can replace organic bases in a number of reactions including, but not limited to, alkylations or epoxidations [18][19][20][22