SOMOphilic alkyne vs radical-polar crossover approaches: The full story of the azido-alkynylation of alkenes

• Julien Borrel and
• Jerome Waser

Beilstein J. Org. Chem. 2024, 20, 701–713, doi:10.3762/bjoc.20.64

• , entry 10). The addition of DABCO [18] or TBAI [50], two additives known to activate azidobenziodoxolone (ABX), afforded complex mixtures with no trace of 4a (Table 1, entry 11). Acids or fluorinated alcohols were tested to activate the different hypervalent iodine reagents. While AcOH, TFA and TFE had

Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

• form is able to bind diamine guests between the two porphyrins in the apical position for each zinc center. However, it has been observed that the closing can also be induced directly by diamine guests such as DABCO. This system exhibits an allosteric response with positive cooperativity as the binding

Synthesis of 2,2-difluoro-1,3-diketone and 2,2-difluoro-1,3-ketoester derivatives using fluorine gas

• Alexander S. Hampton,
• David R. W. Hodgson,
• Graham McDougald,
• Linhua Wang and
• Graham Sandford

Beilstein J. Org. Chem. 2024, 20, 460–469, doi:10.3762/bjoc.20.41

• , electrophilic reagent to be important. Given the structural similarity of 1,4-diazabicyclo[2.2.2]octane (DABCO) to the Selectfluor system, a 10% v/v mixture of fluorine in nitrogen was passed through a solution of 1a in acetonitrile containing one equivalent of DABCO, using a fluorination apparatus and gas flow

• the crude yields of fluorinated products were estimated by 19F NMR integration (monofluoro product 2a, δF −189.9 ppm; difluoro product 3a, δF −102.7 ppm) (Table 1, entry 3). Using excess fluorine or DABCO (entries 5 and 6 in Table 1) led to the formation of tars, while 0.1 equiv of DABCO (entry 7

Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

• Periklis X. Kolagkis,
• Eirini M. Galathri and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36

Nucleophilic functionalization of thianthrenium salts under basic conditions

• Xinting Fan,
• Duo Zhang,
• Xiangchuan Xiu,
• Bin Xu,
• Yu Yuan,
• Feng Chen and
• Pan Gao

Beilstein J. Org. Chem. 2024, 20, 257–263, doi:10.3762/bjoc.20.26

• generation of alkyl radicals [39]. After that, a series of methods for the modification of alkylthianthrenium salts have been developed, including the transition-metal-catalyzed cross-coupling with terminal alkynes [40], sulfonylation with DABCO·(SO2)2 [41][42][43], or alkylation of active alkenes [44][45

Construction of diazepine-containing spiroindolines via annulation reaction of α-halogenated N-acylhydrazones and isatin-derived MBH carbonates

• Xing Liu,
• Wenjing Shi,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2023, 19, 1923–1932, doi:10.3762/bjoc.19.143

• )benzenesulfonamides to give chiral azepane spirooxindoles with excellent stereoselectivity (reaction 2 in Scheme 1) [55][56]. Du and co-workers reported a DABCO-mediated [4 + 3] cycloaddition reaction between o-quinone methides and isatin-derived MBH carbonates to give functionalized benzo[b]oxepine derivatives in

• nitrile of isatin 2a as standard reaction. The main experiments are briefly summarized in Table 1. At first, the reaction in DCM in the presence of common organic bases such as DMAP, DABCO, or DBU gave the expected spiro[indoline-3,5'-[1,2]diazepine] 3a in low to moderate yields (Table 1, entries 1–3

• isatins 4 were also employed in the reaction, but it was found that the reaction proceeded sluggishly in the presence of triethylamine (Scheme 3). However, the expected annulation reaction proceeded smoothly in dichloromethane within 24 hours in the presence of DABCO as base, affording the corresponding

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp³)–H to construct C–C bonds

• Hui Yu and
• Feng Xu

Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94

• alkylation of S,S-functionalized internal olefins was achieved by a C(sp2)–H/C(sp3)–H cross-coupling reaction using DTBP as oxidant and DABCO·6H2O as an additive in the presence of FeCl3 (Scheme 22) [83]. The reaction provides a convenient route to tetrasubstituted alkenes and proceeds via a typical radical

• heterocyclic aromatics with α-C–H bonds of ethers was achieved under the irradiation of a 34 W blue LED using rose bengal (RB) as the organic photoredox catalyst, TBHP as oxidizing agent, and DABCO as the base (Scheme 43c) [125]. The wide scope of substrates, aerobic conditions, and gram-scale suitability are

Metal catalyst-free N-allylation/alkylation of imidazole and benzimidazole with Morita–Baylis–Hillman (MBH) alcohols and acetates

• Olfa Mhasni,
• Jalloul Bouajila and
• Farhat Rezgui

Beilstein J. Org. Chem. 2023, 19, 1251–1258, doi:10.3762/bjoc.19.93

• performed using DABCO as an additive, leading to the corresponding 1,4-adducts in 70–84% yields. Keywords: allylic substitution; aza-Michael addition; imidazole; Morita–Baylis–Hillman; Introduction Morita–Baylis–Hillman (MBH) adducts are multifunctionalized compounds having both a hydroxy moiety and a

• 2a and 2b as nucleophilic reagents without catalysts or activating agents (Scheme 1, reaction 2), or from acyclic MBH alcohols 1 using DABCO as a powerful nucleophilic additive (Scheme 1, reaction 3). Results and Discussion In our first investigations, we selected the reaction of the primary acetate

• , the use of DABCO, commonly used as a powerful catalyst or a nucleophilic additive in the reaction of acyclic MBH adducts with various nucleophiles [21][34][35][36][37], did not afford the SN2/SN2’ products but provided the 1,4-adduct 8a in 84% yield (Table 2, entry 4). Alternatively, we also

Selective construction of dispiro[indoline-3,2'-quinoline-3',3''-indoline] and dispiro[indoline-3,2'-pyrrole-3',3''-indoline] via three-component reaction

• Ziying Xiao,
• Fengshun Xu,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2023, 19, 1234–1242, doi:10.3762/bjoc.19.91

• % (Table 1, entry 7). When DABCO or DBU was employed as base, the yield of 3a decreased to 36% and 29% yield, respectively (Table 1, entries 8 and 9). When the loading of ammonium acetate was increased to 0.8 mmol and 1.0 mmol, the yield of 3a increased to 85% and 82% (Table 1, entries 10 and 11

Sulfate radical anion-induced benzylic oxidation of N-(arylsulfonyl)benzylamines to N-arylsulfonylimines

• Joydev K. Laha,
• Pankaj Gupta and
• Amitava Hazra

Beilstein J. Org. Chem. 2023, 19, 771–777, doi:10.3762/bjoc.19.57

• , entry 5). Lowering the temperature to 60 °C had a deleterious effect (Table 1, entry 6). Likewise, reducing the stoichiometry of pyridine to 1 equiv proved detrimental (Table 1, entry 7). Replacing pyridine with other organic and inorganic bases such as Et3N, DBU, DABCO or K2CO3 also gave product 2a

Synthesis of medium and large phostams, phostones, and phostines

• Jiaxi Xu

Beilstein J. Org. Chem. 2023, 19, 687–699, doi:10.3762/bjoc.19.50

• refluxing acetonitrile for 6 h. It underwent a radical cyclization in refluxing benzene for 20 h to give rise to a nine-membered phostone thieno[2,3-d]pyrimidine-fused 2-hydroxy-1,2-oxaphosphonane 2-oxide 46 as a potential inhibitor after the deprotection of the benzyl group in the presence of DABCO in

Direct C2–H alkylation of indoles driven by the photochemical activity of halogen-bonded complexes

• Martina Mamone,
• Giuseppe Gentile,
• Jacopo Dosso,
• Maurizio Prato and
• Giacomo Filippini

Beilstein J. Org. Chem. 2023, 19, 575–581, doi:10.3762/bjoc.19.42

• , the process is driven by the photochemical activity of halogen-bonded complexes formed upon complexation of a sacrificial donor, namely 1,4-diazabicyclo[2.2.2]octane (DABCO), with α-iodosulfones. The reaction provides a variety of densely functionalized products in good yields (up to 96% yield

• ambient temperature and under visible-light irradiation. Interestingly, this method employs 1,4-diazabicyclo[2.2.2]octane (DABCO) as sacrificial donor in the EDA complex formation with 2. To test the feasibility of our design plan, we focused on the reaction between 3-methylindole (1a, 2 equiv) and α

• mechanism (entries 4 and 5, Table 1) [28]. Afterwards, the effect of the chemical nature of the sacrificial donor on the reaction was investigated (entries 6–9, Table 1). In particular, we employed 2,6-lutidine, 1,1,3,3-tetramethylguanidine (TMG), triethylamine (NEt3), and DABCO. Interestingly, the use of

CuAAC-inspired synthesis of 1,2,3-triazole-bridged porphyrin conjugates: an overview

• Dileep Kumar Singh

Beilstein J. Org. Chem. 2023, 19, 349–379, doi:10.3762/bjoc.19.29

• suggested a weak intramolecular inter-porphyrin communication. Further investigation also revealed that the interaction of the star compound 129 with DABCO and Bipy possibly led to the double star formed by the axial coordination of ligand with zinc centers. The synthesis of supramolecular nanoassemblies

An accelerated Rauhut–Currier dimerization enabled the synthesis of (±)-incarvilleatone and anticancer studies

• Tharun K. Kotammagari,
• Sweta Misra,
• Sayantan Paul,
• Sunita Kunte,
• Rajesh G. Gonnade,
• Manas K. Santra and
• Asish K. Bhattacharya

Beilstein J. Org. Chem. 2023, 19, 204–211, doi:10.3762/bjoc.19.19

• ][13][14][15] such as NaHMDS, DBU, NaH, DABCO, t-BuOK, aq NaOH but none of them gave the desired product. Instead, either a complex mixture was formed, or the starting material was recovered as such (Table 1). However, when we treated compound (±)-4 with a strong base such as KHMDS (2 equiv) in THF at

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• unfavorable (DABCO, quinuclidine) and in the case of triarylamines containing no hydrogen atoms at carbon atoms connected to the cation radical center. Cation radicals of aromatic amines or N-heterocyclic cation radicals are usually involved in electron transfer processes due to their low affinity to hydrogen

• introduction of an electron-withdrawing acetoxy group. The DABCO cation radical is less reactive compared to quinuclidine-derived cation radicals. It was involved in the Ni-catalyzed oxidative C–C cross-coupling involving aldehyde C–H bond cleavage with the formation of acyl radicals according to the proposed

• mechanism [109] (Scheme 19). A novel family of redox-organocatalysts based on the synthetically available DABCO fragment was proposed [110] (Scheme 20). The quaternization of one of the nitrogen atoms of DABCO leads to a dramatically improved hydrogen atom abstracting activity which allowed the authors to

A novel spirocyclic scaffold accessed via tandem Claisen rearrangement/intramolecular oxa-Michael addition

• Anastasia Vepreva,
• Alexander Yanovich,
• Dmitry Dar’in,
• Grigory Kantin,
• Alexander Bunev and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2022, 18, 1649–1655, doi:10.3762/bjoc.18.177

• insertion of carbenes derived from diazo arylidene succinimides (DAS) into the O–H bond of phenols is described. The initial adducts underwent a thermally promoted Claisen rearrangement followed by DABCO-catalyzed intramolecular 5-exo-trig oxa-Michael addition. Keywords: Claisen rearrangement; diazo

• from the data collated in Table 1, to our delight, cyclizations of the phenoxide anion generated on the action of base (except for 2,6-lutidine) proceeded as 5-exo-trig (rather than 6-endo-trig) process and yielded spirocyclic compound 7a as a mixture of syn and anti diastereomers. DABCO in toluene at

• [benzofuran-2,3'-pyrrolidine]-2',5'-diones based on Rh2(esp)2-catalyzed insertion of carbenes derived from α-diazosuccinimides (DAS) into the O–H bond of phenols. The initial adducts underwent a thermally promoted Claisen rearrangement followed by a DABCO-catalyzed intramolecular 5-exo-dig Michael addition

Molecular diversity of the base-promoted reaction of phenacylmalononitriles with dialkyl but-2-ynedioates

• Hui Zheng,
• Ying Han,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2022, 18, 991–998, doi:10.3762/bjoc.18.99

• at room temperature resulted in 3,3-dicyano-5-hydroxy-5-arylcyclopent-1-ene-1,2-dicarboxylates in high yields. More importantly, the DABCO-promoted domino reaction of two molecules of each phenacylmalononitrile and dialkyl but-2-ynedioate in acetonitrile at room temperature afforded unique

• acetonitrile at room temperature gave the unexpected products 4a–k in moderate to good yields in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) as base promoter and the results are summarized in Table 3. It can be seen that the products 4a–k contain two scaffolds of each phenacylmalononitrile and

• the reaction was carried out in weak basic solution (Supporting Information File 1) and its single crystal structure was determined by X-ray diffraction (Figure 4). When DABCO was used as a base, the further addition of the alkoxide ion to the cyano group in cis-position of the cyclopentyl ring

Morita–Baylis–Hillman reaction of 3-formyl-9H-pyrido[3,4-b]indoles and fluorescence studies of the products

• Nisha Devi and
• Virender Singh

Beilstein J. Org. Chem. 2022, 18, 926–934, doi:10.3762/bjoc.18.92

• and substituents was also studied during investigation of fluorescence properties of these derivatives. Keywords: β-carboline; DABCO; fluorescence; MBH reaction; Michael addition; structure–fluorescence activity relationship; Introduction Among the polycyclic alkaloids based on indole, the tricyclic

• functionalization of the β-carboline framework. Accordingly, 3-formyl-9H-β-carbolines 6a–e were subjected to MBH reaction with acrylonitrile A and various acrylates B–E under neat conditions in the presence of DABCO as depicted in Scheme 2. All the products were furnished smoothly in 27–72% yield. During this study

Tri(n-butyl)phosphine-promoted domino reaction for the efficient construction of spiro[cyclohexane-1,3'-indolines] and spiro[indoline-3,2'-furan-3',3''-indolines]

• Hui Zheng,
• Ying Han,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2022, 18, 669–679, doi:10.3762/bjoc.18.68

• functionalized various spiro[cyclohexane-1,3'-indolines] and related reactions. Results and Discussion Initially, the reaction conditions were optimized by using isatylidene malononitrile 1a and bis-chalcone 2a as standard reaction. Tertiary amines such as DMAP and DABCO did not catalyze this reaction (entries 1

Heteroleptic metallosupramolecular aggregates/complexation for supramolecular catalysis

• Prodip Howlader and
• Michael Schmittel

Beilstein J. Org. Chem. 2022, 18, 597–630, doi:10.3762/bjoc.18.62

• ]. Notably, the dissipative conditions were realized by addition of a fuel acid [113][114] that surprisingly ignited a base-catalyzed Knoevenagel addition reaction (Figure 25). As DABCO is a stronger binding ligand (log β = 7.20) [115] towards zinc porphyrin (ZnPor) than pyridine (log K = 4.45) [90] the

• reaction of ligand 111, deck 82, DABCO (60), and [Cu(CH3CN)4](PF6) (4:2:3:2) furnished the supramolecular cage [(82)2(60)3] with 60 = DABCO acting as pillars whereas biped [Cu(111)2]+ remained uncoordinated [112]. In an analogous self-assembly with 83 instead of [Cu(111)2]+, ligand 83 was left

• uncoordinated. When State-I was treated with TFA, then the reshuffling of the components afforded the slider-on-deck [Cu(82)(111)2]+ (or [(82)(83)]) and the monoprotonated DABCO (60-H+). Addition of DBU reversed the process. The bipeds in the slider-on-deck systems [Cu(82)(111)2]+ (k298 = 42.2 kHz) and [(82)(83

Recent developments and trends in the iron- and cobalt-catalyzed Sonogashira reactions

• Surendran Amrutha,
• Sankaran Radhika and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 262–285, doi:10.3762/bjoc.18.31

• conditions [13]. This system is applicable to sterically hindered aryl iodides or substituted aryl iodides with terminal arylalkynes (Scheme 2). K3PO4 was the effective base for the reaction of 4-iodoacetophenone with phenylacetylene. Ligands such as DABCO and trans-1,2-diaminocyclohexane were also tested

DABCO-promoted photocatalytic C–H functionalization of aldehydes

• Bruno Maia da Silva Santos,
• Mariana dos Santos Dupim,
• Cauê Paula de Souza,
• Thiago Messias Cardozo and
• Fernanda Gadini Finelli

Beilstein J. Org. Chem. 2021, 17, 2959–2967, doi:10.3762/bjoc.17.205

• , Universidade Federal do Rio de Janeiro 149, Athos da Silveira Ramos Ave, Rio de Janeiro RJ, 21941-909, Brazil 10.3762/bjoc.17.205 Abstract Herein we present a direct application of DABCO, an inexpensive and broadly accessible organic base, as a hydrogen atom transfer (HAT) abstractor in a photocatalytic

• HAT step energetics and determined an optimized geometry for the transition state, showing that the hydrogen atom transfer between aldehydes and DABCO is a mildly endergonic, yet sufficiently fast step. The same calculations were performed with quinuclidine, for comparison of both catalysts and the

• differences are discussed. Keywords: C–H functionalization; DABCO; HAT; photocatalysis; Introduction The functionalization of inert C–H bonds is a goal pursued by chemists from decades, due to its ubiquity in organic molecules. This strategy also dismisses tiresome protecting groups and functional group

Selective sulfonylation and isonitrilation of para-quinone methides employing TosMIC as a source of sulfonyl group or isonitrile group

• Chuanhua Qu,
• Run Huang,
• Yong Li,
• Tong Liu,
• Yuan Chen and
• Guiting Song

Beilstein J. Org. Chem. 2021, 17, 2822–2831, doi:10.3762/bjoc.17.193

• not proceed (Table 1, entry 9). Then, we investigated the effect of a catalytic amount of DBU on the reaction and found that reaction efficiency did not decrease, indicating that the reaction could also be catalyzed by DBU (Table 1, entry 10). When DABCO (triethylene diamine) was used instead of DBU

N-Sulfinylpyrrolidine-containing ureas and thioureas as bifunctional organocatalysts

• Viera Poláčková,
• Dominika Krištofíková,
• Boglárka Némethová,
• Renata Górová,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2021, 17, 2629–2641, doi:10.3762/bjoc.17.176

• significant influence, neither on yields nor on selectivities. Reactions under ball milling with N-methylpyrrole (NMP), iPr2EtN, DABCO, K3PO4·3H2O, N-methylmorpholine (NMM) (Table 3, entries 3–8) proceeded with yields of 53–82%. The highest value of diastereoselectivity was achieved only with triethylamine as

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