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

Selective detection of DABCO using a supramolecular interconversion as fluorescence reporter

• Indrajit Paul,
• Debabrata Samanta,
• Sudhakar Gaikwad and
• Michael Schmittel

Beilstein J. Org. Chem. 2019, 15, 1371–1378, doi:10.3762/bjoc.15.137

• -component rectangle [Cu4(1)2(2)2]4+ and the four-component sandwich complex [Cu2(1)(2)(4)]2+ is triggered by inclusion and release of DABCO (4). The fully reversible and clean switching between two multicomponent supramolecular architectures can be monitored by fluorescence changes at the zinc porphyrin

• sites. The structural changes are accompanied by a huge spatial contraction/expansion of the zinc porphyrin–zinc porphyrin distances that change from 31.2/38.8 Å to 6.6 Å and back. The supramolecular interconversion was used for the highly selective detection of DABCO in a mixture of other similar

• dual-state supramolecular transformation driven by addition/removal of DABCO (4) and it requires a transition between completive vs incomplete self-sorting [27][28]. The fact that DABCO (4) exclusively drives the supramolecular interconversion was further developed into a fluorescent reporter system

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• , 2-bromobenzaldehydes 62 and carbon monoxide (23) at atmospheric pressure, with the assistance of DABCO as base and tri(tert-butyl)phosphonium tetrafluoroborate as ligand (Scheme 19) [100]. A variety of substituents in the benzene rings (R1, R3) are compatible with the reaction conditions, but

• -component reaction with aryldiazonium tetrafluoroborates 68, DABCO·(SO2)2 (69) and nitriles 70 under Ru(IV) photocatalysis with visible light and in the presence of a Lewis acid (Scheme 21) [101]. Up to 24 isoindolinone derivatives were obtained, bearing a wide variety of aryl moieties at the sulfonyl group

• . Nevertheless, most of the known multicomponent methods for the preparation of 2-oxindoles are based on the use of N-aryl amides as the main partner of the reagent pool. Wu et al. reacted N-(2-iodoaryl)acrylamides 113, DABCO·(SO2)2 (69, also known as DABSO) as a surrogate of sulfur dioxide and hydrazine 114 in

New α- and β-cyclodextrin derivatives with cinchona alkaloids used in asymmetric organocatalytic reactions

• Iveta Chena Tichá,
• Simona Hybelbauerová and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2019, 15, 830–839, doi:10.3762/bjoc.15.80

• solvent, 40 °C, and 168 hours), the solvent of the reaction had to be changed in the case of non-methylated CDs due to their lower solubility in organic solvents. The reaction conditions and results are summed up in Table 3. First, the racemic version of this reaction with DABCO gave 89% yield of the

Mn-mediated sequential three-component domino Knoevenagel/cyclization/Michael addition/oxidative cyclization reaction towards annulated imidazo[1,2-a]pyridines

• Olga A. Storozhenko,
• Alexey A. Festa,
• Delphine R. Bella Ndoutoume,
• Alexander V. Aksenov,
• Alexey V. Varlamov and
• Leonid G. Voskressensky

Beilstein J. Org. Chem. 2018, 14, 3078–3087, doi:10.3762/bjoc.14.287

• ), DABCO (Table 1, entry 17) or K2CO3 (Table 1, entry 18) did not increase the yield of 5a. Increasing the amount of Et3N to 3.8 equiv at the second step allowed to suppress the formation of byproduct 22 (Scheme 6, reaction 2, IV) and simplified the isolation of 5a (Table 1, entry 19, further referred to

DABCO- and DBU-promoted one-pot reaction of N-sulfonyl ketimines with Morita–Baylis–Hillman carbonates: a sequential approach to (2-hydroxyaryl)nicotinate derivatives

• Soumitra Guin,
• Raman Gupta,
• Debashis Majee and
• Sampak Samanta

Beilstein J. Org. Chem. 2018, 14, 2771–2778, doi:10.3762/bjoc.14.254

• Soumitra Guin Raman Gupta Debashis Majee Sampak Samanta Discipline of Chemistry, Indian Institute of Technology Indore, Simrol, Indore, 453552, Madhya Pradesh, India 10.3762/bjoc.14.254 Abstract An intriguing DABCO-catalyzed and DBU-promoted one-pot synthesis of an important class of (2

• -Michael reaction between MBH carbonates derived from an acrylate/acrylonitrile and N-sulfonyl ketimines as C,N-binucleophiles catalyzed by DABCO, followed by elimination of SO2 under the influence of base and subsequent aromatization in an open atmosphere. Keywords: MBH carbonates; metal-free; N-sulfonyl

• cyclic sulfamidate imines and MBH acetates of acrylate as coupling partners [68]. Herein, we further present a DABCO-catalyzed and DBU-promoted sequential one-pot procedure for the access to the interesting class of (2-hydroxyaryl)nicotinates/nicotinonitriles from N-sulfonyl ketimines and MBH adducts as

An overview on recent advances in the synthesis of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials and their catalytic applications in chemical processes

• Hashem Sharghi,
• Pezhman Shiri and
• Mahdi Aberi

Beilstein J. Org. Chem. 2018, 14, 2745–2770, doi:10.3762/bjoc.14.253

• -sulfo-1,4-diazabicyclo[2.2.2]octane-1,4-diium) chloride (C4(DABCO-SO3H)2·4Cl, 31) and its applications in the synthesis of spiro-oxindole derivatives 36 and 37 was described. C4(DABCO-SO3H)2·4Cl 31 acted as an efficient, cheap, and reusable nanocatalyst for synthesis of 2-amino-4H-pyran derivatives 36

• . The catalytic applications of (C4(DABCO-SO3H)2·4Cl) IL for the synthesis of spiro-isatin derivatives and spiro-acenaphthenequinone derivatives. The catalytic applications of (C4(DABCO-SO3H)2·4Cl) IL for the synthesis of bis 2-amino-4H-pyran derivatives. The synthetic route of N,N-disulfo-1,1,3,3

Assembly of fully substituted triazolochromenes via a novel multicomponent reaction or mechanochemical synthesis

• Robby Vroemans,
• Yenthel Verhaegen,
• My Tran Thi Dieu and
• Wim Dehaen

Beilstein J. Org. Chem. 2018, 14, 2689–2697, doi:10.3762/bjoc.14.246

• equivalent nitroalkene, 1.2 equivalents of salicylaldehyde and 0.1 equivalents of DABCO as catalyst in the first step at 40 °C, and 2 equivalents of benzyl azide, 2 equivalents of acetic acid, 0.3 equivalents of BHT as antioxidant, 4 Å MS and DMF under argon atmosphere at 120 °C in the second step. Crude NMR

• 4a–g. aReaction conditions for two-step one-pot procedure: 1. 1 (1.2 equiv), 2 (1 equiv), DABCO (0.1 equiv), 1.5 h, 40 °C; 2. 4 (2 equiv), acetic acid (2 equiv), BHT (0.3 equiv), 4 Å MS (50 mg), DMF (0.1 mL), 24 h, 120 °C. bReaction conditions for two-step one-pot procedure with solid

• reaction vial: 1. 1 (1.2 equiv), 2a (1 equiv), DABCO (0.1 equiv), 15 min, 30 Hz; 2. 4a (2 equiv), acetic acid (2 equiv), BHT (0.3 equiv), 4 Å MS (50 mg), DMF (2 mL), 24 h, 120 °C. bReaction time for the first step: 2 h. The overall isolated yields are given for 2 steps. Two-step reaction towards

Atom-economical group-transfer reactions with hypervalent iodine compounds

• Andreas Boelke,
• Peter Finkbeiner and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2018, 14, 1263–1280, doi:10.3762/bjoc.14.108

• is subsequently desilylated with TBAF in the presence of CuCl and DABCO to obtain the alkynylcopper species D. In the meantime oxidative addition of the previously released iodoarene 2 to the Pd(0) species occurs and the resulting palladium(II) complex E then undergoes transmetallation with the

Mechanochemistry of nucleosides, nucleotides and related materials

• Olga Eguaogie,
• Joseph S. Vyle,
• Patrick F. Conlon,
• Manuela A. Gîlea and
• Yipei Liang

Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81

• -, monomethoxytrityl- or dimethoxytrityl chloride (Scheme 1) [39]. A variety of temperatures and either inorganic or low-melting organic bases were surveyed. Optimal yields were achieved at 140 °C using DABCO by hand-grinding the reaction mixture in molten tetra-n-butylammonium bromide (TBAB) for five minutes. In the

• isolated. Subsequently, Patil and Kartha described the gram-scale preparation of 5′-tritylated uridine derivatives in a planetary ball mill (using a steel vessel and balls) in the absence of TBAB [40]. Following extended grinding (600 rpm for 15 hours) of the nucleoside in the presence of excess DABCO and

Bromide-assisted chemoselective Heck reaction of 3-bromoindazoles under high-speed ball-milling conditions: synthesis of axitinib

• Jingbo Yu,
• Zikun Hong,
• Xinjie Yang,
• Yu Jiang,
• Zhijiang Jiang and
• Weike Su

Beilstein J. Org. Chem. 2018, 14, 786–795, doi:10.3762/bjoc.14.66

• replacing TEA by 1,4-diazabicyclo[2.2.2]octane (DABCO) (Table 1, entry 11). Besides, other organic or inorganic bases gave poor results (Table 1, entries 12–18). Next, the additives were investigated in the coupling reactions (Figure 1, see detailed results in Supporting Information File 1, Table S1

Fluorescent nucleobase analogues for base–base FRET in nucleic acids: synthesis, photophysics and applications

• Mattias Bood,
• Sangamesh Sarangamath,
• Moa S. Wranne,
• Morten Grøtli and
• L. Marcus Wilhelmsson

Beilstein J. Org. Chem. 2018, 14, 114–129, doi:10.3762/bjoc.14.7

• -iodoaniline 32 in 68% yield after isolation [52]. The cyclization was performed via nucleophilic aromatic substitution with DBU and DABCO. Presumably DABCO activates the chlorine and modifies it into a better leaving group allowing the sterically hindered base DBU to abstract a proton from the protected

• a more straightforward and versatile synthetic route. The Stille coupling was changed to a Suzuki–Miyaura coupling and the cyclization was performed directly starting from the free aniline nitrogen, as we found that Boc protection was required only for cyclization when using DBU and DABCO. To faster

• °C, 68%; b) DABCO, DBU, DMF, 21 h, 75 °C; c) 25% TFA in CH2Cl2, 3 h, rt, 96% over two steps; d) NaOMe, MeOH, rt, 64%; e) DMTr-Cl, pyridine, 65%; f) 2-chloro-4H-1,3,2-benzodioxaphosphorin-4-one, pyridine, CH2Cl2, 30 min, 0 °C to rt; g) aq triethylammonium bicarbonate, 52% over two steps. Synthesis of

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• ) compared to the conventional method that generally takes days to a week for completion. The reaction of methyl acrylate with different para-substituted aryl aldehydes in the presence of 20 mol % 1,4-diazabicyclo[2.2.2]octane (DABCO) catalyst at 0.5–45 h yielded the MBH products in 28–98% yield [53]. Wittig

• palladium salts (Pd(OAc)2 or Pd(PPh3)4) and DABCO (1,4-diazabicyclo[2.2.2]octane) various acetylenes and aryl halides were coupled to obtain the Sonogashira coupling products in excellent yields (near quantitative, Scheme 10a). The reactions were reported for aliphatic alkynes as well. In Scheme 10b, an