Diametric calix[6]arene-based phosphine gold(I) cavitands

• Gabriele Giovanardi,
• Andrea Secchi,
• Arturo Arduini and
• Gianpiero Cera

Beilstein J. Org. Chem. 2022, 18, 190–196, doi:10.3762/bjoc.18.21

• phosphine ligand implanted on the aromatic ring (entry 5, Table 1). Interestingly, this effect was substantially improved with the use of the calix[6]arene-based complex C(AuCl)2 (entry 6, Table 1). Overall, the ortho-substituted macrocycle C(AuCl)2 displayed an enhanced selectivity, with respect to the

• ’, 69%); ii) (Me2S)AuCl in DCM, 0 °C to rt (A’(AuCl), 94%; B’(AuCl), 92%; C’(AuCl), 96%). Ligand effect in gold(I)-catalyzed cycloisomerization of 1a. Supporting Information Supporting Information File 18: Experimental procedures, characterization data of compounds and copies of NMR spectra

Peptide stapling by late-stage Suzuki–Miyaura cross-coupling

• Hendrik Gruß,
• Rebecca C. Feiner,
• Ridhiwan Mseya,
• David C. Schröder,
• Michał Jewgiński,
• Kristian M. Müller,
• Rafał Latajka,
• Antoine Marion and
• Norbert Sewald

Beilstein J. Org. Chem. 2022, 18, 1–12, doi:10.3762/bjoc.18.1

• Pd source together with the water-soluble Buchwald ligand sulfonated SPhos (sSPhos) and potassium fluoride as a base. The reaction was performed in a solvent mixture of dimethoxyethane, ethanol and water (DME/EtOH/H2O 9:9:2) at 120 °C under microwave irradiation for 30 min (Scheme 1) [78]. The

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• diphosphine ligand. Preliminary results demonstrated the chiral iron species moderately controlled the enantioselectivity of the aryl Grignard cross-coupling. This work provided a proof-of-concept towards the use of vinylcyclopropanes as useful 1,5-synthons in asymmetric Fe-catalyzed cross-coupling reactions

• ligand and its appropriate steric properties are thought to be crucial to the success of the reaction [71]. The authors showed the in situ-formed 1,3-dienylmagnesium species 33 can also be trapped by a variety of electrophiles, demonstrating the synthetic utility of the reaction. In 2016, Fürstner and

• to trisubstituted (E)-alkenylboronates 55, acting as a 1,5-synthon, similar to Gutierrez‘s vinylcyclopropanes (Scheme 4) [66]. Based on mechanistic investigations, Koh proposed the catalytically active iron-boryl species 57 is generated through the ligand exchange of 56 with B2pin2 which can undergo

Biological properties and conformational studies of amphiphilic Pd(II) and Ni(II) complexes bearing functionalized aroylaminocarbo-N-thioylpyrrolinate units

• Samet Poyraz,
• Samet Belveren,
• Sabriye Aydınoğlu,
• Mahmut Ulger,
• Abel de Cózar,
• Maria de Gracia Retamosa,
• Jose M. Sansano and
• H. Ali Döndaş

Beilstein J. Org. Chem. 2021, 17, 2812–2821, doi:10.3762/bjoc.17.192

• influence of the strength of the ligand and the metal cation sphere (together with small molecules coordinated in its outer sphere) are crucial points to study the structure–activity relationship (SAR) onto a fixed biological target [10][11][12]. In particular, N-benzoylthiourea derivatives are versatile

• , antitumoral, antimalarial, antifungal, or antiviral activities [14]. In this study, as a continuation of our work related to organometallic compounds with very low/modest amphiphilic character [15][16][17], we propose the incorporation of a 3-indolylmethyl group in the ligand and compare the bioactivity

• ligand rotamers were considered during the optimization process. Only one enantiomer was selected for running the calculations for simplicity. The obtained results are gathered in Figure 1 and Figure 2. These calculations show that for ligands L1 and L3, conformer A and conformer B, resulting from a free

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

• be prepared by asymmetric C–H activation. The C–H activation or functionalization can be achieved by a metal-catalyzed chiral phosphoric acid ligand-assisted method, which offers distinct possibilities to provide various chiral biaryl compounds by changing different directing groups (DGs) [46]. Since

• density functional theory calculations [46]. Recently, Shi, Lin and co-workers reported the atroposelective synthesis of axially chiral biaryls by Pd(II)-catalyzed free amine-directed atroposelective C–H olefination using chiral spirophosphoric acid CPA 5 as an efficient ligand and Ag2CO3 as the oxidant

• interactions with the substrates. Moreover, the SPA ligand loading of 1 mol % is effective for this reaction under mild conditions [50]. Moreover, Shi, Lin and co-workers reported the first Pd(II)-catalyzed directed atroposelective C–H allylation of 2-(naphthalen-1-yl)aniline derivatives 14 with methacrylates

Synthetic strategies toward 1,3-oxathiolane nucleoside analogues

• Umesh P. Aher,
• Dhananjai Srivastava,
• Girij P. Singh and
• Jayashree B. S

Beilstein J. Org. Chem. 2021, 17, 2680–2715, doi:10.3762/bjoc.17.182

Ligand-dependent stereoselective Suzuki–Miyaura cross-coupling reactions of β-enamido triflates

• Tomáš Chvojka,
• Athanasios Markos,
• Svatava Voltrová,
• Radek Pohl and
• Petr Beier

Beilstein J. Org. Chem. 2021, 17, 2657–2662, doi:10.3762/bjoc.17.179

• 43 Prague 2, Czech Republic 10.3762/bjoc.17.179 Abstract The stereoselective Suzuki–Miyaura cross-coupling of (Z)-β-enamido triflates is demonstrated. Depending on the nature of the ligand in the palladium catalyst, either retention or inversion of the configuration during the synthesis of β,β

• (Z)-β-enamido triflates could, during the Suzuki cross-coupling, undergo isomerization of the double bond, similarly to enones, and thus serve as starting materials to either (E) or (Z)-isomers of enamides depending on the conditions used. Here we present a study of the effect of ligand on the

• configuration of the double bond were formed preferably. Both conditions were applied to a range of arylboronic acids and (Z)-β-enamido triflates. A: Synthesis of (Z)-β-enamido triflates and subsequent stereoselective cross-coupling reactions. B: Ligand-controlled stereoselective synthesis of β,β-diaryl

Electrocatalytic C(sp³)–H/C(sp)–H cross-coupling in continuous flow through TEMPO/copper relay catalysis

• Bin Guo and
• Hai-Chao Xu

Beilstein J. Org. Chem. 2021, 17, 2650–2656, doi:10.3762/bjoc.17.178

• reaction of tetrahydroisoquinolines with terminal alkynes (Scheme 1C) [10]. The chiral ligand was found to be critical for the stereoinduction as well as product formation for these electrochemical reactions that are conducted in batch. Continuous-flow electrochemical microreactors offer several advantages

• electrochemical microreactors can be a viable tool for developing efficient transition-metal electrocatalysis. C(sp3)–H alkynylation of tetrahydroisoquinolines. L* = chiral ligand. TEMPO = 2,2,6,6-tetramethylpiperidine 1-oxyl. DDQ = 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. BPO = benzoyl peroxide. Substrate

α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions

• Scott Benz and
• Andrew S. Murkin

Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172

• catalyst containing the chiral bisoxazoline ligand (S,S)-8 led to the α-ketol rearrangement product 7 in 70% yield and 68% ee (Figure 3) [5]. The study further demonstrated the effectiveness of the catalyst for a series of analogues of 6 bearing various replacements for the phenyl group, often proceeding

• (Figure 4). These reactions required small adjustments to ligand 11, with m = 1 and Ar = 2,6-Me2C6H3 working best for 12 and m = 0 and Ar = 2,4,6-iPr3C6H2 best for 14. Sc(III) proved to be superior for rearrangement of α-hydroxyaldimines. Under these conditions, products 13 were obtained in poor-to

• catalyzed by Al(III) or Sc(III) liganded by 11. Ligand 11: for 9, m = 1 and Ar = 2,6-iPr2C6H3; for 12, m = 1 and Ar = 2,6-Me2C6H3; and for 14, m = 0 and Ar = 2,4,6-iPr3C6H2. Asymmetric rearrangement of α,α-dialkyl-α-siloxyaldehydes 16 to α-siloxyketones 17 catalyzed by chiral organoaluminum Lewis acid 18

Visible-light-mediated copper photocatalysis for organic syntheses

• Yajing Zhang,
• Qian Wang,
• Zongsheng Yan,
• Donglai Ma and
• Yuguang Zheng

Beilstein J. Org. Chem. 2021, 17, 2520–2542, doi:10.3762/bjoc.17.169

• the photocatalyst RuII is irradiated by light, an electron is transferred from the frontier metal d orbital (t2g orbital) to the ligand-centered π* orbital (RuII*). A metal-to-ligand charge transfer (MLCT) results in the excited singlet state. Through rapid intersystem crossing (ISC), the singlet

• the homoleptic and heteroleptic CuI complexes [22][31][36]. The introduction of bulky ligand substituents might efficiently prevent the reorganization of the excited state. Thus, changing the nature of the chelating ligand can improve the photostability and lifetime of the excited state to meet the

• . The mechanisms underlying photoredox catalysis of CuI complexes have special features and include ligand exchange and rebound mechanisms [38]. CuII complexes provide new avenues for photoredox catalysis, since CuII can undergo ligand exchange/light accelerated homolysis processes, which accelerates

In-depth characterization of self-healing polymers based on π–π interactions

• Josefine Meurer,
• Julian Hniopek,
• Johannes Ahner,
• Michael Schmitt,
• Jürgen Popp,
• Stefan Zechel,
• Kalina Peneva and
• Martin D. Hager

Beilstein J. Org. Chem. 2021, 17, 2496–2504, doi:10.3762/bjoc.17.166

• previous studies, several of these interactions were already applied such as metal–ligand interactions [13][14], hydrogen bonds [15][16] or halogen bonds [17]. Furthermore, π–π interactions also feature a reversible behavior and were therefore utilized for the design of different self-healing polymers [18

Copper-catalyzed monoselective C–H amination of ferrocenes with alkylamines

• Zhen-Sheng Jia,
• Qiang Yue,
• Ya Li,
• Xue-Tao Xu,
• Kun Zhang and
• Bing-Feng Shi

Beilstein J. Org. Chem. 2021, 17, 2488–2495, doi:10.3762/bjoc.17.165

• groups. Kumar and co-workers developed a Cu-mediated C–H chalcogenation and sulfonation of ferrocenes [27][28][29]. The use of a bidentate 1,10-phenathroline ligand was critical to achieve mono-selectivity in the chacogenation reactions [28]. Meanwhile, Co(III)-catalyzed ortho-C–H amidation of ferrocene

• in 2020, an enantioselective C–H annulation of ferrocenylformamides with alkynes was achieved by the Ye group enabled by Ni-Al bimetallic catalysis and a chiral secondary phosphine oxide (SPO) ligand [35]. Hou et al. also reported the asymmetric C−H alkenylation of quinoline- and pyridine-substituted

Exfoliated black phosphorous-mediated CuAAC chemistry for organic and macromolecular synthesis under white LED and near-IR irradiation

• Azra Kocaarslan,
• Zafer Eroglu,
• Önder Metin and
• Yusuf Yagci

Beilstein J. Org. Chem. 2021, 17, 2477–2487, doi:10.3762/bjoc.17.164

• -hydroxypropan-1-ol) ether (Az-3), and 1-(prop-2-yn-1-yloxy)-2,2-bis((prop-2-yn-1-yloxy)methyl)butane (Alk-5) as multifunctional click components were irradiated in the presence of BPNs and CuII ligand under NIR light. The gelation was completed after 24 h (Scheme 3). The photocuring process was also followed by

Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

• Yi Liu,
• Puying Luo,
• Yang Fu,
• Tianxin Hao,
• Xuan Liu,
• Qiuping Ding and
• Yiyuan Peng

Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163

• or ligand in organic chemistry [6][7][8][9][10]. Therefore, the development of efficient methods for the synthesis of pyridine derivatives has attracted considerable attention [11][12][13][14]. The industrial synthetic methods of pyridines mainly involve: i) extraction from coal tar; ii) condensation

• the bisphosphine ligand DTBM-SEGPHOS (56) was very important to promote the transformation efficiently. The reaction showed a broad substrate scope, with aromatic and aliphatic substrates 54 (R1 = aryl, heterocycle, and alkyl) being good coupling partners, providing the corresponding 2,3-dialkyl-5

Strategies for the synthesis of brevipolides

• Yudhi D. Kurniawan and
• A'liyatur Rosyidah

Beilstein J. Org. Chem. 2021, 17, 2399–2416, doi:10.3762/bjoc.17.157

• prospective possibility to obtain ent-21 from precursor 20 by utilizing an antipode ligand in a Noyori reduction. As the continuation, intermediate 40 was coupled with (E)-p-methoxycinnamic acid (17) under Steglich conditions and treated with a Lewis acid to remove the MOM protection giving ester 41

Post-functionalization of drug-loaded nanoparticles prepared by polymerization-induced self-assembly (PISA) with mitochondria targeting ligands

• Janina-Miriam Noy,
• Fan Chen and
• Martina Stenzel

Beilstein J. Org. Chem. 2021, 17, 2302–2314, doi:10.3762/bjoc.17.148

• observed change in size after ligand attachment, the stability of the particles to disassembly was analysed by measuring the scattering intensity for different polymer concentrations (c = 0–100 µM) and the critical micelle concentration (cmc) values were determined from the intercept point of the linear

• mitochondria binding ligand does not induce any damaging effects to these cell lines. Many studies have reported that attaching targeting ligands on nanoparticle or liposome surfaces play a key role in overcoming biological barriers and reducing targeting effects. Active targeting or retention can increase

• target agent carrying nanoparticle surface, the interaction between ligand and targeting agent is inhibited and resulted consequently in significant lower nanoparticle targeting efficiency [48][49]. This study demonstrates that every small change to nanoparticle design can result in unpredictable

Synthesis of O⁶-alkylated preQ₁ derivatives

• Laurin Flemmich,
• Sarah Moreno and
• Ronald Micura

Beilstein J. Org. Chem. 2021, 17, 2295–2301, doi:10.3762/bjoc.17.147

• thereby regulates genes that are required for queuosine biosynthesis [8][9][10][11][12][13][14][15][16]. The molecular mechanism behind is called riboswitching. For most riboswitches, ligand binding induces a structural change in the untranslated leader sequence of mRNA by formation (or disruption) of a

• terminator stem (transcriptional control) or repressor stem (translational control). This conformational event signals on or off to gene expression and represents a feedback-type mechanism that is dependent on cellular ligand concentration [13]. Natural occurrence of alkylated prequeuosines Evidence for the

(Phenylamino)pyrimidine-1,2,3-triazole derivatives as analogs of imatinib: searching for novel compounds against chronic myeloid leukemia

• Luiz Claudio Ferreira Pimentel,
• Lucas Villas Boas Hoelz,
• Henayle Fernandes Canzian,
• Frederico Silva Castelo Branco,
• Andressa Paula de Oliveira,
• Vinicius Rangel Campos,
• Floriano Paes Silva Júnior,
• Rafael Ferreira Dantas,
• Jackson Antônio Lamounier Camargos Resende,
• Anna Claudia Cunha,
• Nubia Boechat and
• Mônica Macedo Bastos

Beilstein J. Org. Chem. 2021, 17, 2260–2269, doi:10.3762/bjoc.17.144

• ; maximum iteration = 2000; scaling factor = 0.50; offspring scheme = Scheme 1; termination scheme = variance-based; crossover rate = 0.90. Due to the stochastic nature of the algorithm search, ten independent simulations per ligand were performed to predict the binding mode. Consequently, the complexes

• with the lowest interaction energy were evaluated. The interactions between BCR-Abl-1 and each inhibitor were analyzed using the ligand map algorithm, a standard algorithm in the MVD program [50]. The usual threshold values for H-bonds and steric interactions were used. All figures for molecular

Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• transfer (HAT) and nickel catalysis [54]. The catalytic system consisting of iridium photocatalyst Ir[dF(CF3)ppy]2(dtbbpy)PF6, nickel catalyst NiBr2·3H2O, ligand 4,7-dimethoxy-1,10-phenanthroline (4,7-dOMe-phen), and 3-acetoxyquinuclidine was found to be optimal to afford the desired α-amino C–C coupled

• identified as the suitable ligand instead of the commonly used bipyridyl ligand (vide supra). Notably, the use of the chiral (S,S)-Bn-BiOx ligand resulted in a moderate enantioinduction in the C‒H arylation product. The authors proposed a catalytic cycle to account for the photoredox nickel-catalyzed C(sp3

• of aryl chlorides 8 through selective 2-functionalization of 1,3-dioxolane (13) followed by a mild acidic workup (Scheme 9) [61]. Here, the photocatalyst Ir[dF(CF3)ppy]2(dtbbpy)PF6 and nickel catalyst NiCl2·DME with dtbbpy as ligand, along with K3PO4 as base under irradiation with blue LEDs enabled

Chemical syntheses and salient features of azulene-containing homo- and copolymers

• Vijayendra S. Shetti

Beilstein J. Org. Chem. 2021, 17, 2164–2185, doi:10.3762/bjoc.17.139

• by using [Pd(allyl)Cl]2 and JackiePhos as a ligand to obtain the polymer 30 in 52% yield. The deprotection of the N-Boc functionality led to the formation of poly[2,6-aminoazulene] 31 in excellent yields (Scheme 7C). The N-Boc-protected polymer 30 possessed good solubility in organic solvents and its

Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

• Ranadeep Talukdar

Beilstein J. Org. Chem. 2021, 17, 2102–2122, doi:10.3762/bjoc.17.137

• the desired product 101 in 49% yield [82]. Other copper catalysts such as CuCl or CuBr gave low yields, even when used with 2,2’-bipyridyl as the ligand. First, oxidation of copper(I) takes place, which interacts with elemental sulfur to “activate” it. A nucleophilic attack from N-methylindole (1) to

• were taken as partners in a Buchwald coupling (Scheme 22a) [44]. On the other hand, in 2015, Organ’s group performed a phosphine-ligand free Buchwald amination of 5-chloroindole (164) with amine 165 to give the desired product 167, where the use of the Pd-PEPPSI-IPentCl precatalyst 166 in presence of

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• (diphenylphosphino)ethane (DPPE) as ligand improved the yield of the anthraquinones. Representative examples included anthraquinones 179a and 179b obtained from terminal alkynes and 179c and 179d from internal alkynes [75]. Multicomponent reactions In 2009, Singh and co-workers reported a solvent-free methodology to

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

• scandium(III)/Cp* catalyst containing two units of an o-N,N-(dimethylamino)benzyl ligand [Sc-1] was applied, and several examples of cyclic benzimidazole compounds were obtained in excellent yields (Scheme 2C) [37]. Benzimidazole compounds bearing substituents in their C-2 position are present in several

• similar catalyst, [Sc-2], which bears a more electron-rich cyclopentadienyl ligand, in a scandium-catalyzed C–H [3 + 2] cyclization (Scheme 5B) [40]. In this transformation, several aminoindane derivatives were obtained from benzylimines in the presence of the catalyst [Sc-2], alkenes and [Ph3C][B(C6F5)4

• can be formed from I and the Cr(III) salt to start the cycle, thereby providing intermediate VI. The latter then undergoes a ligand exchange with I to give the product and the key intermediate II. It is noteworthy that the secondary amide works both as the substrate and the ligand for the metal center

Sustainable manganese catalysis for late-stage C–H functionalization of bioactive structural motifs

• Jongwoo Son

Beilstein J. Org. Chem. 2021, 17, 1733–1751, doi:10.3762/bjoc.17.122

• protein–ligand binding properties as well as biological activities of small molecules, potentially leading to dramatic increases in potency, and thus has been widely explored in drug discovery [54][55][56]. Late-stage C–H methylation has recently been investigated using iron and cobalt catalysts as

Cerium-photocatalyzed aerobic oxidation of benzylic alcohols to aldehydes and ketones

• Girish Suresh Yedase,
• Sumit Kumar,
• Jessica Stahl,
• Burkhard König and
• Veera Reddy Yatham

Beilstein J. Org. Chem. 2021, 17, 1727–1732, doi:10.3762/bjoc.17.121

• benzylic alcohol selectively to the aldehyde or ketone is still desirable. Recently, cerium photocatalysis was introduced as a robust alternative to generate oxygen or carbon-centered radicals under mild reaction conditions [57][58][59][60][61][62][63][64]. CeCl3 reacts via ligand-to-metal charge transfer

• inhibition of the catalytic cycle upon the addition of TEMPO revealed that the reaction proceeds through radical intermediates. Next, we carried out UV–vis monitoring experiments in order to verify whether the interaction with the substituted benzyl alcohols and CeIV could lead to a ligand-to-metal charge