Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• excellent yields and enantioselectivities (30 examples, up to 99:1 er). Ion pair Ion pair catalysis has interesting potential in combination with photoredox catalysis considering that the catalytic intermediates are often radical cations or anions. Despite this, there are relatively few examples of this

Styryl-based new organic chromophores bearing free amino and azomethine groups: synthesis, photophysical, NLO, and thermal properties

• Anka Utama Putra,
• Deniz Çakmaz,
• Nurgül Seferoğlu,
• Alberto Barsella and
• Zeynel Seferoğlu

Beilstein J. Org. Chem. 2020, 16, 2282–2296, doi:10.3762/bjoc.16.189

• The dyes 8–12 could have the ability to detect hydroxide anions due to the presence of an OH substituent at the salicylidene moiety. Therefore, the OH− sensing activity of compounds 8–12 was investigated by the addition of hydroxide anions in the form of the corresponding tetrabutylammonium (TBA) salt

• the UV–vis absorption spectrum. Moreover, dyes 8–12 showed an enhancement in fluorescence intensity upon the incremental addition of hydroxide anions to their solutions in DMSO. As shown in Figure 5 and Figure 6, dye 12 showed the highest increase in fluorescence (approx. a 20-fold fluorescence

• classes [28]. Therefore, we investigated dye 8 as a prospect for a fluorescent pH sensor in a basic environment. After having determined the solubility of dye 8 in aqueous solution, the sensing capability of 8 toward hydroxide anions was tested. Several Britton–Robinson buffer solutions, with different pH

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• to the trimethylsumanene synthesis, Sakurai and his co-workers selectively generated mono-, di- and trianions (29–31) using t-BuLi as a base and the formation of these sequential anions were confirmed by 1H and 13C NMR spectroscopy (Scheme 4) [32]. Next, the in situ generated trianion 31 was quenched

• later to this report, in a really dazzling manner, the groups of Rogachev, Hirao, and Petrukhina reported a novel organometallic sandwich supramolecular complex [Na+(18-crown-6)(THF)2][Cs(C21H11‒)2]‒ (138) encapsulating the cesium cation between the sumanenyl anions in a concave manner [69]. To this

Reactions of 3-aryl-1-(trifluoromethyl)prop-2-yn-1-iminium salts with 1,3-dienes and styrenes

• Thomas Schneider,
• Michael Keim,
• Bianca Seitz and
• Gerhard Maas

Beilstein J. Org. Chem. 2020, 16, 2064–2072, doi:10.3762/bjoc.16.173

• non-nucleophilic anions can be isolated [14][15], but in organic synthesis, they are most often generated in situ from suitable precursors and are directly exposed to diverse nucleophiles. Such transformations have been achieved using CH2(CF3)NR2 as the iminium ion precursors [15

Isolation and structure determination of a tetrameric sulfonyl dilithio methandiide in solution based on crystal structure analysis and ⁶Li/¹³C NMR spectroscopic data

• Jürgen Vollhardt,
• Hans Jörg Lindner and
• Hans-Joachim Gais

Beilstein J. Org. Chem. 2020, 16, 2057–2063, doi:10.3762/bjoc.16.172

• , electrostatic interaction with and charge polarization by the positively charged sulfur atom [56] and silicon atom [57], and negative nC–σ*SPh hyperconjugation [56][58]. The anions of (2a)4·(THF)6 and (2a)6·Li2O·(THF)6 adopt conformations around the carbon sulfur bond, which would allow for stabilization by

Automated high-content imaging for cellular uptake, from the Schmuck cation to the latest cyclic oligochalcogenides

• Rémi Martinent,
• Javier López-Andarias,
• Dimitri Moreau,
• Yangyang Cheng,
• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2020, 16, 2007–2016, doi:10.3762/bjoc.16.167

• attractive approach to tackle this central challenge [1][2][3][11][12][13][14]. The noncovalent interaction between the guanidinium cations from CPPs and cell membrane-associated anions, such as phospholipids, proteoglycans, or sialic acids, is considered to enhance the cell surface accumulation of

• substrates, and thus fulfilling the first prerequisite of all internalization (Figure 1) [12][16][17][20][21]. However, this ion-pair interaction weakens significantly in polar solvents. The presence of competing anions in physiological solutions often disturbs the binding, and thus restricting the

• )pyrrole (GCP) cation 1 as a synthetic analogue of the guanidinium cations, somehow a “super-guanidinium” conceived to drive “arginine magic” [20][21] to the extreme (Figure 1) [23]. The power of the Schmuck cation to bind carboxylate and phosphate anions in competitive water has several origins [22

Metal-free synthesis of phosphinoylchroman-4-ones via a radical phosphinoylation–cyclization cascade mediated by K₂S₂O₈

• Qiang Liu,
• Weibang Lu,
• Guanqun Xie and
• Xiaoxia Wang

Beilstein J. Org. Chem. 2020, 16, 1974–1982, doi:10.3762/bjoc.16.164

• phosphonate-functionalized chroman-4-ones [28]. Initially, K2S2O8 thermally decomposes to form sulfate radical anions (SO4•−) [29][30], which react with diphenylphosphine oxide (DPPO, 2) to give the phosphorus-centered radical I [42][43][44]. Then, the phosphorus centered radical I added to the C–C double

Design, synthesis and application of carbazole macrocycles in anion sensors

• Alo Rüütel,
• Ville Yrjänä,
• Sandip A. Kadam,
• Indrek Saar,
• Mihkel Ilisson,
• Astrid Darnell,
• Kristjan Haav,
• Tõiv Haljasorg,
• Lauri Toom,
• Johan Bobacka and
• Ivo Leito

Beilstein J. Org. Chem. 2020, 16, 1901–1914, doi:10.3762/bjoc.16.157

• hydrogen bonding. The primary site of interaction is the X-COO− group. The geometry of the carboxylate group (and to a large extent also its charge distribution) is the same for all carboxylate anions. Therefore, high affinity towards carboxylates is easily achievable, but selectivity towards a specific

• example, a carbazole-urea macrocycle was reported previously [10], however, the binding of anions occurred outside the receptor due to modest dimensions of the macrocyclic cavity. Using click-chemistry, a carbazole-triazole macrocycle, “tricarb”, was prepared that showed the ability to form non-covalent

• superstructures [11]. The rings should be of remarkable size for accommodating even small anions, such as acetate. In many cases the receptor is formally a macrocycle, but the anion is bound on its “surface”, not inside the ring [10][12]. A well-known example is the calix[4]pyrrole family, which emerged as an

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• the rate of recombination [91]. The abrupt termination of an ordered lattice continuity at a surface leads to chemical and structural differences from the bulk material. TiO2, for example, has surface hydroxides, oxygen anions, and Ti3+ cations, which produce high energy states from incomplete bonding

Recent synthesis of thietanes

• Jiaxi Xu

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

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• cations and radical anions) Recently, the exploitation of alkenyl and aryl radical ions has emerged as a platform for the functionalization of small molecules. They appear as attractive intermediates for a direct alkene difunctionalization or arene C–H functionalization. In particular, radical cations are

• strong electrophiles and undergo nucleophilic additions with two-electron donors (Scheme 21a) [93][94]. In contrast, radical anions can act as very strong single-electron nucleophiles and are often subject to fragmentation to give a neutral free radical and a charged species (Scheme 21b) [77][95]. When a

• fragmentation is not favored, these charged radicals can be intercepted and lead to different selectivities when compared to a traditional two-electron chemistry (e.g., anti-Markovnikov vs Markovnikov or ipso-SNAr reactions). Heteroatom-containing radical anions, such as ketyl radicals, constitute a special

The charge-assisted hydrogen-bonded organic framework (CAHOF) self-assembled from the conjugated acid of tetrakis(4-aminophenyl)methane and 2,6-naphthalenedisulfonate as a new class of recyclable Brønsted acid catalysts

• Svetlana A. Kuznetsova,
• Alexander S. Gak,
• Yulia V. Nelyubina,
• Vladimir A. Larionov,
• Han Li,
• Michael North,
• Vladimir P. Zhereb,
• Alexander F. Smol'yakov,
• Artem O. Dmitrienko,
• Michael G. Medvedev,
• Igor S. Gerasimov,
• Ashot S. Saghyan and
• Yuri N. Belokon

Beilstein J. Org. Chem. 2020, 16, 1124–1134, doi:10.3762/bjoc.16.99

• , elemental analysis, and 1H NMR spectroscopy. The framework was supported by hydrogen bonds between the sulfonate anions and the ammonium cations of NDS and protonated TAPM moieties, respectively. The CAHOF material functioned as a new type of catalytically active Brønsted acid in a series of reactions

• parameters a = 20.6034(8) Å, b = 20.1330(8) Å, c = 22.4357(8) Å, β = 91.989(1)°, and cell volume = 9300.9(6) Å3 at 120 K. An asymmetric part of the unit cell contained two ammonium cations, four sulfonate anions, and nine water molecules, held together by numerous hydrogen bonds (Table S2, Supporting

• material F-1 was prepared and characterized by X-ray diffraction, TGA-DSC, elemental analysis, and 1H NMR spectroscopy. One important role played by NDS was that the crystalline three-dimensional CAHOF F-1 was supported by hydrogen bonds between the sulfonate anions and the ammonium cations of NDS and TAPM

Bipyrrole boomerangs via Pd-mediated tandem cyclization–oxygenation. Controlling reaction selectivity and electronic properties

• Liliia Moshniaha,
• Marika Żyła-Karwowska,
• Joanna Cybińska,
• Piotr J. Chmielewski,
• Ludovic Favereau and
• Marcin Stępień

Beilstein J. Org. Chem. 2020, 16, 895–903, doi:10.3762/bjoc.16.81

• starting 1,n-dipyrrolylalkane precursors (RnH, n = 2 or 3) were synthesized by reacting the appropriate pyrrolyl anions with either ethylene ditosylate or 1,3-dibromopropane (Scheme S1, Supporting Information File 1). In our initial coupling experiments, 1,2-dipyrrolylethanes (NDA2H, NMI2H) and 1,3

• performed in more dilute solutions (Table 1, entries 14 and 20). Following our previous experimental and computational findings [32][33], we also checked whether the yields of dilactam products might be improved by increasing the concentration of acetate anions in the reaction mixture. Indeed, annulations

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

• %) (Table 1, entries 1, 18 and 20). Interestingly, RhCl3·3H2O and RhI3 performed well, whereas RhCl3 and RhBr2·2H2O afforded the product in very low yield (Table 1, entries 17–20). This strongly implied that not only the valence state of Rh and the species of anions were crucial for the conversion (even if

• all with halogen anions), but also structural differences (e.g., crystal water, RhCl3 vs RhCl3·3H2O) of analogous Rh salts played an important role in the catalytic synthesis of benzaldehyde. Among all tested rhodium salts, RhCl3·3H2O afforded benzaldehyde in the highest yield and was chosen as the

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

• charge of the final molecule if the cyanine comprises no additional substituent exhibiting a negative charge at the molecular skeleton. Furthermore, it requires to combine this cation with appropriate anions to achieve a good compatibility with the surrounding matrix. Compatibility in these examples

• available in some geographic areas where these materials have been used in practice. Such anions can be either bis(trifluoromethyl)sulfonylimides [5], aluminates [6] or sulfonates comprising long alkyl chains [5]. Alternatively, a barbiturate group positioned at the meso-position of the cyanine can also

• sometimes lead to unexpectedly high solubility in aprotic polar surroundings [5]. Nevertheless, a variation between the cation of the cyanine with distinct anions may move such materials to applications where either an aqueous surrounding being available in biological applications [7][8][9] or a dipolar

Oligomeric ricinoleic acid preparation promoted by an efficient and recoverable Brønsted acidic ionic liquid

• Fei You,
• Xing He,
• Song Gao,
• Hong-Ru Li and
• Liang-Nian He

Beilstein J. Org. Chem. 2020, 16, 351–361, doi:10.3762/bjoc.16.34

• depicted in Scheme 1. Results and Discussion Considering protic acids have catalytic effects on the esterification reaction, we designed and synthesized a series of ILs containing protic anions as shown in Scheme 2. With the synthesized ILs as catalyst, the ricinoleic acid esterification was performed and

• showed that the protic anion is necessary for the intermolecular esterification as no catalytic activity can be observed for the IL with aprotic anion (Table 1, entries 1 and 2). For the ILs containing protic anions, the ILs containing polyprotic anions are more conducive to esterification (Table 1

Copper-promoted/copper-catalyzed trifluoromethylselenolation reactions

• Clément Ghiazza and
• Anis Tlili

Beilstein J. Org. Chem. 2020, 16, 305–316, doi:10.3762/bjoc.16.30

• , which is in line with an SN2 mechanism. The authors proposed a mechanism where difluorocarbene is first generated upon thermal decomposition of the starting difluorophosphobetaine. The carbene then reacts with elemental selenium to yield difluoroselenophosgene, and in the presence of fluoride anions

Allylic cross-coupling using aromatic aldehydes as α-alkoxyalkyl anions

• Akihiro Yuasa,
• Kazunori Nagao and
• Hirohisa Ohmiya

Beilstein J. Org. Chem. 2020, 16, 185–189, doi:10.3762/bjoc.16.21

• Akihiro Yuasa Kazunori Nagao Hirohisa Ohmiya Division of Pharmaceutical Sciences, Graduate School of Medical Sciences, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan 10.3762/bjoc.16.21 Abstract The allylic cross-coupling using aromatic aldehydes as α-alkoxyalkyl anions is described

• -catalyzed allylic substitution. Keywords: aldehyde; copper; copper catalysis; cross-coupling; palladium; synthetic method; Introduction α-Alkoxy-substituted carbanions (α-alkoxyalkyl anions) are useful C(sp3) nucleophiles for the construction of alcohol units found in a majority of pharmaceuticals

• , agrochemicals and bioactive natural products. Generally, α-alkoxyalkyl anions are presynthesized as stoichiometric organometallic reagents such as organolithium, organozinc, organocuprate, organostannane, organosilane and organoboron compounds [1][2][3][4][5][6]. Alternatively, we showed that easily available

The reaction of arylmethyl isocyanides and arylmethylamines with xanthate esters: a facile and unexpected synthesis of carbamothioates

• Narasimhamurthy Rajeev,
• Toreshettahally R. Swaroop,
• Ahmad I. Alrawashdeh,
• Shofiur Rahman,
• Abdullah Alodhayb,
• Seegehalli M. Anil,
• Kuppalli R. Kiran,
• Chandra,
• Paris E. Georghiou,
• Kanchugarakoppal S. Rangappa and
• Maralinganadoddi P. Sadashiva

Beilstein J. Org. Chem. 2020, 16, 159–167, doi:10.3762/bjoc.16.18

• that could be supported by quantum chemical calculations. Of course, other alternative mechanisms that can be envisioned include one in which the thiolate anions, which were generated, could also either a) regenerate dimethylamide anions from the surrounding DMF solvent; and/or b) possibly add to the

Halogen-bonding-induced diverse aggregation of 4,5-diiodo-1,2,3-triazolium salts with different anions

• Xingyu Xu,
• Shiqing Huang,
• Zengyu Zhang,
• Lei Cao and
• Xiaoyu Yan

Beilstein J. Org. Chem. 2020, 16, 78–87, doi:10.3762/bjoc.16.10

• Xingyu Xu Shiqing Huang Zengyu Zhang Lei Cao Xiaoyu Yan Department of Chemistry, Renmin University of China, Beijing 100872, People’s Republic of China 10.3762/bjoc.16.10 Abstract The synthesis of 4,5-diiodo-1,3-dimesityl-1,2,3-triazolium salts with different anions have been developed. These

• triazolium salts show diverse aggregation via halogen bonding between C–I bonds and anions. Triazolium with halide anions exists as a tetramer with saddle conformation. Triazolium tetrafluoroborate exists as a trimer with Chinese lantern shape conformation. Triazolium trifluoroacetate and acetate exist as

• aldehydes [44]. Despite a variety of XB donors based on 1,2,3-triazole have been reported, no 4,5-diido-1,2,3-triazolium salts have been reported for an XB interaction. Herein, we report the synthesis and characterization of 4,5-diido-1,2,3-triazolium D with different anions. The crystal structures of these

A green, economical synthesis of β-ketonitriles and trifunctionalized building blocks from esters and lactones

• Daniel P. Pienaar,
• Kamogelo R. Butsi,
• Amanda L. Rousseau and
• Dean Brady

Beilstein J. Org. Chem. 2019, 15, 2930–2935, doi:10.3762/bjoc.15.287

• environmentally unfriendly transition-metal-based reactions. Acylations of in situ-generated nitrile anions with esters to produce β-ketonitriles were first reported long ago, for example by using sodium methoxide [2], sodium ethoxide [3] or sodium amide [4][5]. The reaction was found to proceed more efficiently

• -pentoxide or potassium tert-butoxide) acylation of substituted nitrile anions with esters under ambient conditions, as published by Ji et al. (2006) [9] and Kim et al. (2013) [10]. The large excess of ester and expensive base (potassium tert-pentoxide) required in the former method, in our opinion rendered

• alkoxide anions. This reduces the occurrence of undesirable side-reactions, e.g., intermolecular aldol reaction, lactone/ketonitrile product dimerization and ring-opening polymerization. The application of this method to produce the analogous hemiketal 6 from γ-butyrolactone was not as efficient. Although

Preparation of anthracene-based tetraperimidine hexafluorophosphate and selective recognition of chromium(III) ions

• Qing-Xiang Liu,
• Feng Yang,
• Zhi-Xiang Zhao,
• Shao-Cong Yu and
• Yue Ding

Beilstein J. Org. Chem. 2019, 15, 2847–2855, doi:10.3762/bjoc.15.278

• Cr3+ selectively while neglecting other cations, with no remarkable interference being caused in the presence of the latter. In order to probe whether the anions of the chromium(III) salts had effects on the binding of 3 and Cr3+, other chromium(III) salts, CrCl3, CrBr3, Cr2(SO4)3, Cr(NO3)3, and Cr

A chiral self-sorting photoresponsive coordination cage based on overcrowded alkenes

• Constantin Stuckhardt,
• Diederik Roke,
• Wojciech Danowski,
• Edwin Otten,
• Sander J. Wezenberg and
• Ben L. Feringa

Beilstein J. Org. Chem. 2019, 15, 2767–2773, doi:10.3762/bjoc.15.268

• structure determination [13][14] and stabilization of reactive species [15][16][17]. The use of reversible metal–ligand coordination bonds gives rise to systems that allow for adaption to external stimuli such as pH, anions, electric potential, concentration and light [4][8][18][19][20][21]. Using light to

• dynamically control the shape and function of SCCs is a very promising strategy as it is a noninvasive stimulus that can be easily applied with high spatiotemporal control, without producing any waste. Systems have been reported where photoisomerization of azobenzene-derived anions encapsulated in

• amounts of HCl. The additional anions required to balance the charge of the tetracationic Pd2L4 cage could not be unambiguously located in the difference Fourier map (see Supporting Information File 1 for details). The structure belongs to the P4/n space group and the unit cell is occupied by a pair of

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• 79. The complex 79 consisting of diols and a chiral copper catalyst Cu–L* easily gets deprotonated by cathodically generated MeO− to afford alkoxide anions 80, which reacts with anodically generated Br+ to form O-brominated intermediates 81. Finally, MeO− removed HBr from 81 to afford products 75/78

Arylisoquinoline-derived organoboron dyes with a triaryl skeleton show dual fluorescence

• Vânia F. Pais,
• Tristan Neumann,
• Ignacio Vayá,
• M. Consuelo Jiménez,
• Abel Ros and
• Uwe Pischel

Beilstein J. Org. Chem. 2019, 15, 2612–2622, doi:10.3762/bjoc.15.254

• of 0.2–0.4, reaching in some cases values as high as 0.5–0.6. Laser-flash photolysis provided evidence for the existence of excited triplet states. The dyes form fluoroboronate complexes with fluoride anions, leading to the observation of the quenching of the long-wavelength emission band and

• ratiometric response by the build-up of a hypsochromically shifted emission signal. Keywords: anions; dyes; fluorescence; laser-flash photolysis; organoboron; Introduction Boron-containing tri- and tetra-coordinated chromophores have attracted considerable interest due to their often peculiar and highly

• dye 18 is insensitive to oxygen and was tentatively attributed to the formation of a pyrene-based radical cation, resulting from photoionization [46]. Interaction with fluoride anions The presence of the boronic acid ester moiety does not only contribute to significant changes in the fluorescence