Asymmetric organocatalyzed synthesis of coumarin derivatives

• Natália M. Moreira,
• Lorena S. R. Martelli and
• Arlene G. Corrêa

Beilstein J. Org. Chem. 2021, 17, 1952–1980, doi:10.3762/bjoc.17.128

• -hydroxycoumarins 1 [65]. This reaction was catalyzed by a bifunctional squaramide 73 and initially both (Z)- and (E)-isomers were observed, besides the isomer 96 as the major product. After the addition of DABCO, the (Z)-isomer became the major product with good to excellent yields and excellent ee, as shown in

Development of N-F fluorinating agents and their fluorinations: Historical perspective

• Teruo Umemoto,
• Yuhao Yang and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

• ’-difluorobipyridinium salts and N,N’-difluoro-1,4-diazoniabicyclo[2.2.2]octane salts, and their many derivatives and analogs, including chiral N-F reagents such as optically active N-fluoro-sultam derivatives, N-fluoro-alkaloid derivatives, DABCO-based N-F derivatives, and N-F binaphthyldisulfonimides. The synthesis

• -diazoniabicyclo[2.2.2]octane bistriflate (22-1a), bis(hydrogensulfate) 22-1b, hydrogensulfate bishydrogenfluoride fluoride 22-1c, bishexafluoroantimonate 22-1e, and bishexafluorophosphate 22-1f were prepared in a pure form by fluorination of 1,4-diazabicyclo[2.2.2]octane (DABCO) with 10% F2/N2 in

• because an inseparable mixture of 22-1d and the DABCO·2HBF4 salt formed. BisBF4 22-1d was considered to be commercially valuable because of its low preparative cost. Umemoto and co-worker found a clean counteranion replacement reaction of the intermediate (F−)x(HF)y(HSO4−)z salts (x + z = 2) by using BF3

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

• proved to be less active. In 2013, the Knoevenagel reaction between benzaldehyde (17) and malononitrile was performed using a similar flow apparatus, however, using a polystyrene-supported DABCO as catalyst. Wang’s group confirmed the stability of the latter, which provides excellent conversions (95–90

Application of the Meerwein reaction of 1,4-benzoquinone to a metal-free synthesis of benzofuropyridine analogues

• Rashmi Singh,
• Tomas Horsten,
• Rashmi Prakash,
• Swapan Dey and
• Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 977–982, doi:10.3762/bjoc.17.79

• nitrochromenobenzofuropyridine 21 was achieved after treatment of 16 with nitrostyrene in the presence of DABCO applying our previously reported ball milling procedure [40]. The synthesis of 22 was performed using the Perkin reaction [41]. The reaction of 16 with propionic anhydride and the corresponding sodium salt in the

Synthesis of bis(aryloxy)fluoromethanes using a heterodihalocarbene strategy

• Carl Recsei and
• Yaniv Barda

Beilstein J. Org. Chem. 2021, 17, 813–818, doi:10.3762/bjoc.17.70

• reactant ratios, the identity of the base and admixture of potential catalysts such as tetrabutylammonium iodide or DABCO showed no improvement in product ratios. Using superstoichiometric 6 and base with chlorodifluoromethane in a bid to form and react 5 in a one-pot protocol were unsuccessful, even after

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• of N-heterocyclic compounds. In 2017, Wu and colleagues [58] uncovered the use of the bis(sulfur dioxide) adduct of DABCO, 1,4-diazabicyclo[2.2.2]octane·(SO2)2, as sulfone source in the EDA complex formation by 4-methyl-1-(p-tolyl)pentan-1-one O-(2,4-dinitrophenyl)oxime (11) towards the

• reaction mechanism for this transformation is as follows (Scheme 6): Firstly, O-aryloxime 11 forms EDA complex 13 by action of DABCO·(SO2)2 and then undergoes light-promoted single-electron transfer, affording the 2,4-dinitrophenol anion, nitrogen radical 14, and radical 15, respectively. 1,5-HAT (hydrogen

• [32] found a bifunctional group reaction of perfluoroalkylation and β-alkenylation by a perfluoroalkyl radical. Perfluoroalkylation product 93 was synthesized by utilizing (E)-3-methyl-1-phenylhept-1,6-dien-3-ol (92) and perfluorobutyl iodide (28) as substrates and potassium phosphate and DABCO as

Deoxygenative C2-heteroarylation of quinoline N-oxides: facile access to α-triazolylquinolines

• Geetanjali S. Sontakke,
• Rahul K. Shukla and
• Chandra M. R. Volla

Beilstein J. Org. Chem. 2021, 17, 485–493, doi:10.3762/bjoc.17.42

• ), we were pleased to observe the formation of C2-triazolylquinoline 3a selectively in 15% NMR yield (Table 1, entry 1). Replacing DIPEA with DABCO or K2CO3 did not further increase the yield of 3a (Table 1, entries 2 and 3). Interestingly, while doing the control studies to understand the role of the

Progress in the total synthesis of inthomycins

• Bidyut Kumar Senapati

Beilstein J. Org. Chem. 2021, 17, 58–82, doi:10.3762/bjoc.17.7

• [80], compound (Z)-(+)-143a delivered the bromodiene (Z,Z)-(+)-145a in good yield and stereoselectivity. Isomerization of (Z)-(+)-143a to (E)-(+)-143b was carried out successfully using sterically hindered base DBU or DABCO. Treatment of (E)-(+)-143b with 144 using the boron-Wittig reaction [79

Using multiple self-sorting for switching functions in discrete multicomponent systems

• Amit Ghosh and
• Michael Schmittel

Beilstein J. Org. Chem. 2020, 16, 2831–2853, doi:10.3762/bjoc.16.233

• release of DABCO using a double self-sorting protocol [54]. Schmittel and co-workers reported on the three-component rectangle [Cu4(16)2(17)2]4+ (SelfSORT-I) that rearranged into the four-component sandwich complex [Cu2(16)(17)(18)]2+ (Figure 8) upon the addition of DABCO (SelfSORT-II). A full

• reversibility was achieved by the addition of the rhodium porphyrin 19 that reversed the system reviving the state SelfSORT-I. Since both self-sorted states exhibited a distinct fluorescence due to the changes at the zinc porphyrin sites, luminescence was used for the selective detection of DABCO in a mixture

• mimicking the concatenation of biological information relays in activating enzymatic activity (Figure 21) [76]. In detail, the work involved the proper handling and networking of twelve components (two distinct nanoswitches 25 and 78; Zn2+, Hg2+, Cu+ metal ions; stator 79, rotator 80 and DABCO (18) as

Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis

• Shahboz Yakubov and
• Joshua P. Barham

Beilstein J. Org. Chem. 2020, 16, 2151–2192, doi:10.3762/bjoc.16.183

• [192], reliable and commercially available [193]. Selectfluor® is synthesized on a multiton p.a. scale in a simple and efficient method (Scheme 3) [193]. The precursor 24 is prepared by alkylation of DABCO (1,4-diazabicyclo[2.2.2]octane) with DCM. A counterion exchange with NaBF4 causes NaCl

Natural dolomitic limestone-catalyzed synthesis of benzimidazoles, dihydropyrimidinones, and highly substituted pyridines under ultrasound irradiation

• Kumar Godugu,
• Venkata Divya Sri Yadala,
• Mohammad Khaja Mohinuddin Pinjari,
• Trivikram Reddy Gundala,
• Lakshmi Reddy Sanapareddy and
• Chinna Gangi Reddy Nallagondu

Beilstein J. Org. Chem. 2020, 16, 1881–1900, doi:10.3762/bjoc.16.156

• (Table 2, entry 1). To achieve the target compound 3a, the same reaction was repeated by employing various catalysts (2.5 wt %), such as Fe2O3, Al2O3, KF–alumina, dolomitic limestone, triethylamine, pyridine, and DABCO in different solvents, such as water, acetone, iPrOH, EtOH, and EtOH/H2O 1:1 (Table 2

• catalysts, Fe2O3, Al2O3, KF–alumina, triethylamine, pyridine, and DABCO, provided a moderate to low yield of the product 3a (Table 2, entries 2–4 and 6–8). The aforesaid reaction was performed under conventional stirring of the model substrates 1 and 2a in H2O in the absence of catalyst for 180 min at 45–50

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• , isolated in moderate to good yields. A possible gram scale-up synthesis was also accomplished. Within the mechanistic cycle, after initial vinylic C–H bond activation and insertion of CO into the C–Pd bond, the acylpalladium intermediate is converted into its conjugated analog under DABCO assistance

Et₃N/DMSO-supported one-pot synthesis of highly fluorescent β-carboline-linked benzothiophenones via sulfur insertion and estimation of the photophysical properties

• Dharmender Singh,
• Vipin Kumar and
• Virender Singh

Beilstein J. Org. Chem. 2020, 16, 1740–1753, doi:10.3762/bjoc.16.146

• observed (Table 1, entry 2). At this stage, we realized that DMSO was a better choice for this transformation as the reaction required a shorter time and afforded the product 2bA in a better yield. Then, other amines such as NMP, Et3N, DBU, and DABCO were also investigated. The use of NMP as an activator

• combination of DABCO and DMSO also afforded the desired product via a clean reaction within 20 min, although only 60% yield of the product was obtained (Table 1, entry 10). This promising result using DABCO encouraged us to explore other amines like DBU, ʟ-proline, pyridine, DMAP, and pyrrolidine as an

Azidophosphonium salt-directed chemoselective synthesis of (E)/(Z)-cinnamyl-1H-triazoles and regiospecific access to bromomethylcoumarins from Morita–Baylis–Hillman adducts

• Soundararajan Karthikeyan,
• Radha Krishnan Shobana,
• Kamarajapurathu Raju Subimol,
• J. Helen Ratna Monica and
• Ayyanoth Karthik Krishna Kumar

Beilstein J. Org. Chem. 2020, 16, 1579–1587, doi:10.3762/bjoc.16.130

• [52]. A mixture of benzaldehyde (1.1 g, 1.14 mL, 0.01 mol), methyl acrylate (2.05 g, 2.15 mL, 0.023 mol) and DABCO (0.87 g, 0.0077 mol) in chloroform (5 mL) was stirred at room temperature for 7 d. The reaction mixture was quenched with 10% aqueous hydrochloric acid (50 mL) and washed repeatedly with

Mechanochemical green synthesis of hyper-crosslinked cyclodextrin polymers

• Alberto Rubin Pedrazzo,
• Fabrizio Caldera,
• Marco Zanetti,
• Silvia Lucia Appleton,
• Nilesh Kumar Dhakar and
• Francesco Trotta

Beilstein J. Org. Chem. 2020, 16, 1554–1563, doi:10.3762/bjoc.16.127

• extraction) functionalized material, with a less negative ζ potential. Experimental Materials β-Cyclodextrin (β-CD), α-cyclodextrin (α-CD), and γ-cyclodextrin (γ-CD) were kindly provided by Roquette Italia SpA and Wacker Chemie. Carbonyldiimidazole (CDI, ≥97.0% (T)), 1,4-diazabicyclo[2.2.2]octane (DABCO

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

• were synthesized through amine-catalyzed formal [2 + 2] cycloadditions. The DABCO-catalyzed tunable formal [4 + 2] and [2 + 2] cycloadditions of benzyl allenoate (395) and methyl 2-oxoalkanedithioates 394 generated the 5-(methylthio)-2-phenylethylidene-2,3-dihydro-1,4-oxathiines 396 with benzyl

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

Accelerating fragment-based library generation by coupling high-performance photoreactors with benchtop analysis

• Quentin Lefebvre,
• Christophe Salomé and
• Thomas C. Fessard

Beilstein J. Org. Chem. 2020, 16, 982–988, doi:10.3762/bjoc.16.87

• the reaction conditions (see 4a, 4f, 5d and 5f), despite a successful report on their decarboxylative arylation under nickel-photoredox-catalyzed conditions [19]. As this report and MacMillan’s report use more basic, but less nucleophilic bases than DABCO, namely Barton’s base and MTBE, the issue

Rhodium-catalyzed reductive carbonylation of aryl iodides to arylaldehydes with syngas

• Zhenghui Liu,
• Peng Wang,
• Zhenzhong Yan,
• Suqing Chen,
• Dongkun Yu,
• Xinhui Zhao and
• Tiancheng Mu

Beilstein J. Org. Chem. 2020, 16, 645–656, doi:10.3762/bjoc.16.61

• , triphos, dpp-BINAP, dpp-OPh, dppb, dppe, P(PhF5)3, P(4-FPh)3, Cydpp, Bipy, DBU, Im, and PPh3 (their structures are shown in Table 2)), bases (Et3N, 1,4-diaza[2.2.2]bicyclooctane (DABCO), N,N-diisopropylethylamine (DIPEA), N,N,N',N'-tetramethylethylenediamine (TMEDA) and 1,2,2,6,6-pentamethylpiperidine

Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• glycine-containing peptides using an in situ-formed heteroleptic copper complex, [Cu(I)(dmp)(xantphos)]PF6 (Scheme 25) [40]. Under blue light irradiation, glycine esters were readily alkylated using NHP esters in the presence of DABCO as a base. A large panel of NHP esters was introduced to ethyl N

• )(xantphos)]BF4 as the catalyst and DABCO as the base (Scheme 27). The products were obtained in moderate to good yields and moderate diastereoselectivities. The reaction was applied to N-alkoxyphthalimides derived from aliphatic and benzyl alcohols and heteroaromatic ones. To explain the reaction outcome

• from the oxidation of the amine with the formed [Cu(II)] complex, followed by a deprotonation by DABCO. The resulting alkoxide is finally converted into the alcohol by the protonated DABCO. During this study, the authors found that replacement of the base by the Brønsted acid (R)-1,1-binaphtyl-2,2-diyl

Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• major isomer (+)-125 was crystallized from (−)-127 using an isopropanol/hexane mixture and confirmed to have R-configuration. The free ligand was obtained by deprotection of the P-center with 1,4-diazabicyclo[2.2.2]octane (DABCO) under refluxing in chloroform for two days at 50 °C. Duplicating the same

• in excellent yields by reacting the protected ligands 135 with DABCO [111][112]. A diverse library of ligands prepared in a similar manner can be obtained by varying the phosphine and the substituents around the skeleton. Some of the ligands prepared include compounds 137–140 shown in Figure 3 [111

Functionalization of the imidazo[1,2-a]pyridine ring in α-phosphonoacrylates and α-phosphonopropionates via microwave-assisted Mizoroki–Heck reaction

• Damian Kusy,
• Agata Wojciechowska,
• Joanna Małolepsza and
• Katarzyna M. Błażewska

Beilstein J. Org. Chem. 2020, 16, 15–21, doi:10.3762/bjoc.16.3

• reaction, because higher temperatures led to decomposition of the reagents (Table 1, entries 6 and 7), and full conversion into the product was not achieved at lower temperatures (Table 1, entry 2). The use of other ligands resulted in a decreased yield (for tri-tert-butylphosphine, (P(t-Bu)3) or DABCO

Why do thioureas and squaramides slow down the Ireland–Claisen rearrangement?

• Dominika Krištofíková,
• Juraj Filo,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2019, 15, 2948–2957, doi:10.3762/bjoc.15.290

• -N-methylcyclohexanamine (65%, Scheme 2) whereas reactions with trihexylamine and diisopropylethylamine provided the product 3c with lower yields. Rearrangement in the presence of N-methylmorpholine, quinine, and N-methylpyrrolidine afforded only traces of acid 3c and reactions with DBU, DABCO and (S

Synthesis and anion binding properties of phthalimide-containing corona[6]arenes

• Meng-Di Gu,
• Yao Lu and
• Mei-Xiang Wang

Beilstein J. Org. Chem. 2019, 15, 1976–1983, doi:10.3762/bjoc.15.193

• 54% and 35% yields, respectively. Corona[3]arene[3]tetrazine bearing even a urea group (3f) was synthesized analogously from the reaction of 1f with 2 when DABCO was employed as a base instead of DIPEA (Scheme 1). It was worth addressing that a chemical yield of 52% implied roughly a 90% yield for

• , 125.7, 73.2, 67.8, 61.8, 38.6; IR (KBr, cm−1) ν: 3472, 1776, 1716, 1382, 1228, 956; HRMS-APCI: [M + Na]+ calcd for C42H33N15O18, 1058.2020; found, 1058.2029; anal. calcd for C42H33N15O18·H2O: C, 48.87; H, 3.35; N, 19.94; found: C, 48.12; H, 3.01; N, 19.90. Synthesis of 3f: To a solution of DABCO (2.1

Identification of optimal fluorescent probes for G-quadruplex nucleic acids through systematic exploration of mono- and distyryl dye libraries

• Xiao Xie,
• Michela Zuffo,
• Marie-Paule Teulade-Fichou and
• Anton Granzhan

Beilstein J. Org. Chem. 2019, 15, 1872–1889, doi:10.3762/bjoc.15.183

• ) or benzyl substituent (6a) does not significantly improve the performance of the probes, as was already described for the dye 2a [58]. Instead, introduction of a DABCO fragment (bringing two additional positive charges) in 4a and 5a leads to higher fluorimetric response of the probes to G4-DNA (e.g