Electrochemical formal homocoupling of sec-alcohols

• Kosuke Yamamoto,
• Kazuhisa Arita,
• Masashi Shiota,
• Masami Kuriyama and
• Osamu Onomura

Beilstein J. Org. Chem. 2022, 18, 1062–1069, doi:10.3762/bjoc.18.108

• improve the yield of 2a (Table 1, entries 2–4). The present reaction proceeded in the presence of quaternary ammonium salts with different counter anions including the BF4 anion, and Et4NBr was found to be the preferable electrolyte among them (Table 1, entry 1 vs entries 5–7). Next, we examined the

First example of organocatalysis by cathodic N-heterocyclic carbene generation and accumulation using a divided electrochemical flow cell

• Daniele Rocco,
• Ana A. Folgueiras-Amador,
• Richard C. D. Brown and
• Marta Feroci

Beilstein J. Org. Chem. 2022, 18, 979–990, doi:10.3762/bjoc.18.98

• known salts, at present used in a wide variety of chemical fields. The first definition of ionic liquids was given by Paul Walden in 1914: “they are materials composed of cations and anions, that melt around 100 °C or below as an arbitrary temperature limit” [1]. ILs are salts formed by non or weakly

• coordinated cations and anions, usually bulky organic cations and inorganic or organic anions such as −BF4, −PF6, −N(CF3SO2)2, etc. [2][3]. The physicochemical properties of RTILs (room temperature ionic liquids) are reported in the literature and include very low vapor pressure, and thus the possibility to

Electroreductive coupling of 2-acylbenzoates with α,β-unsaturated carbonyl compounds: density functional theory study on product selectivity

• Naoki Kise and
• Toshihiko Sakurai

Beilstein J. Org. Chem. 2022, 18, 956–962, doi:10.3762/bjoc.18.95

• -oxobutyl)phthalides 5 were produced as the sole products by the reaction of 1 with methyl vinyl ketone (2b). It was found by DFT calculations for the cyclization step of the intermediate enolate anions that the product selectivity was in good agreement with the free energy differences (∆G) in the

• Information Supporting Information File 215: Characterization data for compounds, copies of 1H and 13C NMR spectra, X-ray crystallographic data (ORTEP) of 3b, CV data of compounds 1a–h, and DFT calculation data for cyclization of enolate anions. Supporting Information File 216: Cif for 3b. Acknowledgements

Cathodic generation of reactive (phenylthio)difluoromethyl species and its reactions: mechanistic aspects and synthetic applications

• Sadanobu Iwase,
• Shinsuke Inagi and
• Toshio Fuchigami

Beilstein J. Org. Chem. 2022, 18, 872–880, doi:10.3762/bjoc.18.88

• dithiocarbonate. Cathodic reduction of 1. Indirect cathodic reduction of 1 using o-phthalonitrile as mediator. Mechanism for the formation of product 3. Reaction of compound 1 with PhS anions. Cathodic reduction of compound 1 in the presence of α-methylstyrene at a high current density. Indirect cathodic

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

• a result, the polymerization of ε-caprolactone (123) was switched OFF. Addition of chloride anions from n-Bu4NCl led to the substitution of the tertiary amine ligand at both rhodium centers generating the semi-open form [125(Cl)2]. Since the aluminum(III) salen center became now exposed, the

BINOL as a chiral element in mechanically interlocked molecules

• Matthias Krajnc and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2022, 18, 508–523, doi:10.3762/bjoc.18.53

• the thread (see Figure 16). The stereoselective binding of chiral anions by rotaxanes 64a/b was studied by 1H NMR titration experiments, using the dicationic macrocycle (S)-61-Me22+ (obtained by methylation of the triazole units in (S)-61) as a reference system. As guest molecules, the Boc-protected

• to slightly better stereodiscrimation of the guest molecules (see Figure 17). Subsequently, Beer and co-workers reported the first example of a chiral halogen-bonding [3]rotaxane for the recognition and sensing of dicarboxylate anions [64]. The [3]rotaxane (S)-68 was prepared in a two-fold clipping

• reaction, namely reaction of bis-amine 66 and bis-acid chloride 67 in the presence of the dicationic axle (S)-65. The resulting rotaxane (S)-68 (37% yield, see Figure 18) features a central chiral BINOL unit with two adjacent binding sites for anions, each made of two iodotriazole-XB donors (on the thread

Synthesis of piperidine and pyrrolidine derivatives by electroreductive cyclization of imine with terminal dihaloalkanes in a flow microreactor

• Yuki Naito,
• Naoki Shida and
• Mahito Atobe

Beilstein J. Org. Chem. 2022, 18, 350–359, doi:10.3762/bjoc.18.39

• selectivity toward 3a/4 decreased (Table 3, entry 3). As mentioned above, this is probably because the protons generated by the oxidation of the THF solvent at anode could easily meet the radical anions of imine 1 generated at cathode due to the very short interelectrode distance. In the electrochemical

• formation of 4 by the reaction between protons and the radical anions of 1. As shown in Table 4, entry 6, the yield of 3a decreased when the electricity was fixed at 2 F mol−1 by increasing the flow rate over the conditions in Table 4, entry 2. On the other hand, as shown in Table 4, entry 7, the yield of

• anions of imine 1 with the terminal dihaloalkane is also considered to be an important factor in the formation of the desired product 3a. Therefore, a model reaction was conducted using dihaloalkanes with different types of terminal halogens (Cl, Br, and I) (Table 7). When the terminal halogen of the

New advances in asymmetric organocatalysis

• Radovan Šebesta

Beilstein J. Org. Chem. 2022, 18, 240–242, doi:10.3762/bjoc.18.28

• by a review article devoted to aza-Michael reactions of amines and amides [17]. The evolution of the understanding of noncovalent activation modes led to the realization that anion-binding is a critical feature in many transformations. Halide anions are highly relevant and widely occurring within

Regioselective synthesis of methyl 5-(N-Boc-cycloaminyl)-1,2-oxazole-4-carboxylates as new amino acid-like building blocks

• Jolita Bruzgulienė,
• Greta Račkauskienė,
• Aurimas Bieliauskas,
• Vaida Milišiūnaitė,
• Miglė Dagilienė,
• Gita Matulevičiūtė,
• Vytas Martynaitis,
• Sonata Krikštolaitytė,
• Frank A. Sløk and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2022, 18, 102–109, doi:10.3762/bjoc.18.11

• asymmetric unit of the crystal of 6b consists of two (2S)-2-[4-(methoxycarbonyl)-1,2-oxazol-5-yl]piperidin-1-ium cations and two 2,2,2-trifluoroacetate anions (2C10H15N2O3+·2C2F3O2−) (Figure 5; Table 1, Supporting Information File 1 in Tables S1–S3). The substituted piperidinium moieties are in chair

• 1.44 ppm. ORTEP diagram of the asymmetric unit consisting of two cations 6b(A) and 6b(B) and triflate anions. Conversion of cyclic amino acids to 1,2-oxazole derivatives. Plausible mechanisms for the formation of 1,2-oxazoles 4a–h and VII from β-enamino ketoesters 3a–h with hydroxylamine. Synthesis of

1,2-Naphthoquinone-4-sulfonic acid salts in organic synthesis

• Ruan Carlos B. Ribeiro,
• Patricia G. Ferreira,
• Amanda de A. Borges,
• Luana da S. M. Forezi,
• Fernando de Carvalho da Silva and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 53–69, doi:10.3762/bjoc.18.5

• electrons through a redox cycle promoted by the 1,2- or 1,4-naphthoquinone system. In this cycle, transient reactive oxygen (ROS) and nitrogen (RNS) species are formed as free radicals, peroxides, superoxide anions, radical anions, or dianions. These species generated inside cells accelerate hypoxia and

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

• and co-workers demonstrated the generation of highly reductant CO2 radical anions through potassium formate hydrogen atom abstraction promoted by DABCO [25] (Figure 2c). This species was then used for reduction of (hetero)aryl and alkyl halides, and subsequent carboarylation of several styrenes

Synthesis of a novel aminobenzene-containing hemicucurbituril and its fluorescence spectral properties with ions

• Qingkai Zeng,
• Qiumeng Long,
• Jihong Lu,
• Li Wang,
• Yuting You,
• Xiaoting Yuan,
• Qianjun Zhang,
• Qingmei Ge,
• Hang Cong and
• Mao Liu

Beilstein J. Org. Chem. 2021, 17, 2840–2847, doi:10.3762/bjoc.17.195

• association constant up to (2.1 ± 0.3) × 104 M−1. Meanwhile, this macrocycle showed no obvious or only slight enhancement of the fluorescence intensity with selected anions. Keywords: amidobenzene-containing macrocycle; hemicucurbituril; host–guest interaction; macrocycle; modification; Introduction

• ) × 104 M−1, which was contrary to those of hemicucurbiturils. As observed by fluorescence titration experiments, macrocycle 4 showed weak interactions with selected anions. Results and Discussion Because of the relatively strong nucleophilicity of the amino group in aniline, the synthesis could become

• nm, and found to be Ka = (2.1 ± 0.3) × 104 M−1, while the association constant of compound 4 binding to Cu2+ was Ka = (2.8 ± 0.1) × 103 M−1. The macrocycle binds Fe3+ much more strongly than Cu2+. The host–guest interactions between 4 and selected anions, including Cl−, Br−, I−, PF6−, BF4−, HSO4

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

• substitution process. For example, compound 3b reacted with difluoroenolate to form the difluoroalkylated diarylmethane 5 in 83% yield via a Cu(OAc)2-catalyzed hydrodifluoroalkylation reaction [52]. Two other examples were the use of photoredox catalysis to generate acyl anions in situ from aromatic carboxylic

Photophysical, photostability, and ROS generation properties of new trifluoromethylated quinoline-phenol Schiff bases

• Inaiá O. Rocha,
• Yuri G. Kappenberg,
• Wilian C. Rosa,
• Clarissa P. Frizzo,
• Nilo Zanatta,
• Marcos A. P. Martins,
• Isadora Tisoco,
• Bernardo A. Iglesias and
• Helio G. Bonacorso

Beilstein J. Org. Chem. 2021, 17, 2799–2811, doi:10.3762/bjoc.17.191

• damage caused by oxidative stress, especially by eliminating reactive oxygen species (ROS) such as hydroxyl radicals (•OH), superoxide anions (O2•‒), and singlet oxygen (1O2) [3][22][23]. Therefore, research in recent years has focused on new compounds obtained from natural sources or by synthetic

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• excellent enantioselectivity [31]. The widespread use of phosphoric acids and phosphates as chiral acids, chiral anions, and ligands is one of the most important achievements of modern enantioselective catalysis. The atropochiral BINOL, H8-BINOL and SPINOL [32] derived phosphoric acids (Figure 4) [33][34

• (Brønsted acidity/basicity, hydrogen-bonding units, and counter-anions toward metals) [48][49]. In 2019, Shi, Lin, and co-workers achieved an enantioselective synthesis of axially chiral quinoline-derived biaryl atropisomers via Pd-catalyzed C–H olefination of 8-phenylquinoline (11) using a novel chiral

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• the selective formation of diastereomeric products. They also observed that changes in Hg(II) salts result in different ratios of the cis- and trans-isomer in the cyclized products [47]. The differences in cis and trans ratios were primarily due to the basicity of anions associated with Hg(II) salts

Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• Lukas Schifferer Martin Stinglhamer Kirandeep Kaur Olga Garcia Macheno Organic Chemistry Institute, Westfälische-Wilhelms University Münster, Correnstraße 36, 48149 Münster, Germany 10.3762/bjoc.17.145 Abstract This review intends to provide an overview on the role of halide anions in the

• the cationic reactive species. Keywords: anion binding; asymmetric catalysis; halide anions; hydrogen donors; noncovalent interactions; Introduction Halogens and the respective anionic halides occupy an essential role in natural and chemical processes [1][2][3][4]. While in chemical syntheses

• halogens are often regarded as surrogates for further functionalization, their role in natural and physiological processes is much more diverse. One of these processes is the ability of large complex molecules and enzymes to recognize halide anions via hydrogen bonds in aqueous media [5]. Amongst others

Constrained thermoresponsive polymers – new insights into fundamentals and applications

• Patricia Flemming,
• Alexander S. Münch,
• Andreas Fery and
• Petra Uhlmann

Beilstein J. Org. Chem. 2021, 17, 2123–2163, doi:10.3762/bjoc.17.138

• the halide anions Cl−, Br−, and I−-, respectively, UCST behavior can also be induced in polymeric ionic liquids by the addition of a suitable hydrophobic counterion, such as tetrafluoroborate BF4− [288][289]. In both cases, the critical phase transition temperature is strongly affected by the

Towards new NIR dyes for free radical photopolymerization processes

• Haifaa Mokbel,
• Guillaume Noirbent,
• Didier Gigmes,
• Frédéric Dumur and
• Jacques Lalevée

Beilstein J. Org. Chem. 2021, 17, 2067–2076, doi:10.3762/bjoc.17.133

• , 11 of them were never synthesized before. Markedly, noncharged structures, negatively charged cyanine bearing Na+ as counter cation, and positively charged cyanines bearing (B(Ph)4−) or (I−) as counter anions were examined as promising NIR light photoinitiating systems. Excellent photoinitiating

• of counter anions and counter cations as well as cyanine structures are discussed. Results and Discussion Synthesis of the different dyes Two different families of cyanines were prepared, differing by the way how the structure is formed. Notably, dyes Ca and Cb differ from the other cyanines by the

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

• reagents, a match process which minimizes side reactions. Thus, these N-fluoropyridinium salts made possible the fluorination of a diversity of nucleophilic organic compounds with different reactivities ranging across aromatics, carbanions (Grignard reagents, enolate anions), active methylene compounds

• no α-proton to the N-F site proved to be a good choice for fluorinating enolate anions (Scheme 24). The side reaction, involving HF elimination, and which was a problem in reactions with the Barnette’s reagents 4-1 having the α-proton(s) except for 4-1b [26], was avoided here. The HF elimination is a

•  30). NFSI is a stable and non-hygroscopic crystalline solid with a mp of 114–116 °C. NFSI was shown to fluorinate a variety of nucleophiles. As seen in Scheme 31, trimethylsilyl enol ethers, enolate anions of ketones and esters, and aryl- and vinyllithiums were fluorinated with NFSI in moderate to

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

• and restless leg syndrome [53]. Guareschi imides exist in solution predominantly as dicarbonyl tautomers with a cis arrangement of the cyano groups. Conversely, the corresponding anions exist as a mixture of mono- and dienolized tautomers, with a strong preference (≈9:1) for the monoenolized form [8

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• substitution in the 3-position were also tested. The products were usually obtained with a high degree of enantioselectivity in good yields (up to 96%; up to 93% ee; Table 18) [47][49]. An interesting finding was the effect of non-coordinating hexafluorophosphate anions. The addition of 30 mol % NH4PF6

• increased the catalytic activity and allowed to run the reaction at a lower temperature [48]. This can be very useful for substrates that can react with traces of Pd(0) that are formed by minor side reactions. The authors suspected that hexafluorophosphate anions stabilize the cationic Pd species and result

Metal-free glycosylation with glycosyl fluorides in liquid SO₂

• Krista Gulbe,
• Jevgeņija Lugiņina,
• Edijs Jansons,
• Artis Kinens and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 964–976, doi:10.3762/bjoc.17.78

• anomeric ratio observed initially for mannoside 3c (α/β = 82:18, Scheme 1). Finally, we proved the formation of the fluorosulfite species by employing 19F NMR spectroscopy (Figure 1). Glycosylation of the reaction mixture was treated with Et3N to stabilize the possibly formed fluorosulfite anions in form

Beyond ribose and phosphate: Selected nucleic acid modifications for structure–function investigations and therapeutic applications

• Christopher Liczner,
• Kieran Duke,
• Gabrielle Juneau,
• Martin Egli and
• Christopher J. Wilds

Beilstein J. Org. Chem. 2021, 17, 908–931, doi:10.3762/bjoc.17.76

• hydrogen atom to orient towards anions (chloride) in the vicinity and the 3'-nitrogen lone pair engages in a lp → σ* anomeric effect with the antibonding orbital from the adjacent P–O5' bond (Figure 2A). This conjugation is surmised to cause considerably increased rigidity of the phosphoramidate sugar

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

• -poor N-aryloxyamides 160, indole derivative 161, and carbonate or other multicharge anions in CH3CN (Scheme 56). The corresponding products can be given in good yield by modifying substituents on the amide moiety in 160 or N-substituted indoles. Inorganic-base electron donors formed transient complexes