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

• -carbon precursor for the synthesis. The forward synthesis transformed 2-acetylfuran (20) to its corresponding alcohol 21 through an asymmetric transfer hydrogenation catalyzed by a ruthenium complex (0.5 mol %) in 98% yield with 95% ee (Scheme 2). The azeotropic mixture of HCO2H/Et3N 5:2 was employed as

• followed by addition of TBSOTf at low temperature successfully formed the (Z)-silyl enol ether 54. Application of the Sharpless asymmetric dihydroxylation, promoted by AD-mix-β, gave the expected β-(R)-hydroxy cyclopropyl product 55 in 84% yield with moderate diastereoselectivity (dr = 2). The formation of

• ether 94 (90%) and the PMB ether was cleaved to liberate the primary alcohol. After being oxidized with IBX, the aldehyde 103 was isolated in 68% yield over two steps. Application of the asymmetric Brown’s allylation afforded 104 in 80% yield (dr 95:5) that was readily esterified to its cinnamate ester

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

• corresponding bicyclic dihydropyrans 119 and 121, respectively (Scheme 36). Later, Namba et al. reported the synthesis of racemic vinylindoline derivatives 123 from N-tosylanilinoallylic alcohol derivative 122 by using 1–2 mol % of Hg(OTf)2 in CH2Cl2 at room temperature [90]. An asymmetric synthesis of

• efficiently utilized for the synthesis of highly strained tricyclo[5.2.1.01,6]decene intermediate 214 containing a cyclobutane ring (Scheme 64). Compound 213 is an important precursor for the asymmetric total synthesis of solanoeclepin A. The formation of β-hydroxyketone 213 was achieved by Hg(TFA)2-mediated

Base-free enantioselective S_N2 alkylation of 2-oxindoles via bifunctional phase-transfer catalysis

• Mili Litvajova,
• Emiliano Sorrentino,
• Brendan Twamley and
• Stephen J. Connon

Beilstein J. Org. Chem. 2021, 17, 2287–2294, doi:10.3762/bjoc.17.146

• charged intermediates, could be an excellent methodology for the enantioselective SN2 alkylation of enolates derived from the 2-oxindole core [13][14][15][16][17][18][19][20][21][22][23]. In recent years, several examples regarding the alkylation of 3-subsituted-2-oxindoles, via asymmetric phase-transfer

• report we disclose the outcome of an investigation into the design of an efficient catalytic asymmetric system capable of manipulating this substrate and its application to the enantioselective synthesis of the potent CRTH2 receptor antagonist 6 [32] (Scheme 1C). Results and Discussion We began our

• could be possible to develop an effective catalytic asymmetric protocol. To the best of our knowledge such base-free catalytic systems have never been applied to processes such as the alkylation of enolates generated in situ. These reactions would produce stoichiometric amounts of acid, which can

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

• development of the research area of asymmetric anion-binding organocatalysis. Key early elucidation studies with chloride as counter-anion confirmed this type of alternative activation, which was then exploited in several processes and contributed to the advance and consolidation of anion-binding catalysis as

• 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

• -workers reported in 2004 an asymmetric Pictet–Spengler reaction of tryptamine-derived imines 4 in the presence of acetyl chloride and 2,6-lutidine, where the chiral thiourea catalyst 6 was employed to enable good yields and enantioselectivities (Scheme 2a) [32]. The initial motivation of their first

(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

• docking results were edited using the Visual Molecular Dynamics 1.9.3 (VMD) program (available for download at http://www.ks.uiuc.edu/Research/vmd/vmd-1.9.3/). Proposed structural modifications to obtain triazole derivatives 1a, b and 2a–j. Asymmetric unit representation of the 1,2,3-triazole derivative

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

• asymmetric substitution. Thus, in the first step, the Claisen–Schmidt condensation of 2-chloro-3-(hydroxymethylene)cyclohex-1-ene-1-carbaldehyde on 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (TCF) furnished the intermediate 2-(4-((E)-2-((E)-2-chloro-3-(ethoxymethylene)cyclohex-1-en-1-yl

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

• and asymmetric alkynes with heterocyclic compounds and obtained reasonable to satisfactory results (examples 12h–k) [35]. Cu(OAc)2 proved to be an essential oxidant for the success of both the Miura and the Bao methodologies [34][35]. In 2013, Ye and co-workers reported a concise method to synthesize

• anthracene, tetracene, and naphtho[b]thiophene derivatives via ZnBr2-mediated regioselective annulation of asymmetric 1,2-diarylmethine dipivalates 83a (Scheme 20). On the basis of this methodology, they prepared 37 examples of different types of anthracene derivatives, such as compounds 84a–e, in very good

• yields (89–94%) and mild reaction conditions [53]. In a related approach, in 2015, Mohanakrishnan and his group reported the synthesis of anthracene derivatives and other annulated products via the regioselective cyclization of asymmetric 1,2-diarylmethine diol 83b by using a HBr/AcOH system (Scheme 20

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

• , the advances in asymmetric organocatalyzed synthesis of coumarin derivatives are discussed in this review, according to the mode of activation of the catalyst. Keywords: asymmetric synthesis; green chemistry; 2H-chromen-2-one; organocatalysis; Introduction Coumarins are important naturally occurring

• a specific target, i.e., it gives access to a greater diversity of compounds to be explored [26]. In this work, a compilation of the enantioselective synthesis of coumarin derivatives using asymmetric organocatalysis is presented, highlighting the proposed mechanism pathways for the formation of the

• ammonium salts derived from cinchona alkaloids [28]. Therefore, the asymmetric synthesis of coumarin derivatives is herein presented according to the activation mode, i.e., via covalent or non-covalent bonding. Furthermore, the use of bifunctional catalysts and multicatalysis are discussed as well

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

• compounds to produce the corresponding biaryl products with high enantiopurity using vanadium chelated with chiral ligands, such as tridentate asymmetric imine ligands, have been reported. For instance, (S)-binol derivatives could be successfully prepared from 2-naphthols using a dimeric vanadium complex

• molecules of substrate together. In addition, the high enantiopurity was ascribed to a chiral environment that presents three elements of asymmetry. Other examples of vanadium-mediated oxidative homocouplings of phenolic substrates include regioselective and asymmetric homocoupling of phenols and 2

• -hydroxycarbazoles [103][104]. Notably, Kozlowsky and co-workers were the first who reported a method for the vanadium-based asymmetric coupling of phenols and 2-hydroxycarbazoles [105] that allowed the synthesis of a wide range of chiral biphenols and bicarbazoles. The use of a vanadium complex with less electron

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

• -dichlorocamphorsultam) 17-2 [75] (Scheme 37). The maximum enantioselectivity of enolates of β-ketoesters with (−)-9-1 or (+)-9-2, first prepared by Lang in 1988 (see section 1-9), was 70% ee. The asymmetric fluorination with (+)- or (−)-17-2 afforded up to 75% ee as indicated in Scheme 38. The dichloro reagent 17-2

• reagent 27-2 in good to high yields [90]. In addition, Takeuchi et al. reported that optically active N-fluorosultams, (R)- and (S)-N-fluoro-3-cyclohexyl-3-methyl-2,3-dihydrobenzo[1,2-d]isothiazole 1,1-dioxides 27-6 (Scheme 61) were efficient reagents for the asymmetric fluorination of enolates [91]. To

• 'R)-isomer 28-7a and (2'S,3S,5'R)-isomer 28-7b in 81% and 44% yield, respectively. Figure 9 summarizes the outcomes of asymmetric fluorination reactions of enolates of aryl ketones using 28-7a and -7b. In the event isomer 28-7a yielded much better ees than 28-7b. Although 28-7a gave a maximum 70% ee

2,4-Bis(arylethynyl)-9-chloro-5,6,7,8-tetrahydroacridines: synthesis and photophysical properties

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli,
• Noureddine Chaaben,
• Kamel Alimi,
• Stefan Jopp and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 1629–1640, doi:10.3762/bjoc.17.115

• Najeh Tka Mohamed Adnene Hadj Ayed Mourad Ben Braiek Mahjoub Jabli Noureddine Chaaben Kamel Alimi Stefan Jopp Peter Langer Asymmetric Synthesis and Molecular Engineering Laboratory for Organic Electronic Materials, Faculty of sciences of Monastir, Monastir university, Environment street, 5019

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

• Pezhman Shiri,
• Ali Mohammad Amani and
• Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• (Scheme 8B). An asymmetric version of this reaction was developed in 2014 by the Gandon group [42], who employed the chiral bis(phosphine)digold(I) complex 18 as a pre-catalyst in combination with silver triflate as an activator (Scheme 9). They obtained lactams 17 by cyclization of α-substituted N

Breaking paracyclophane: the unexpected formation of non-symmetric disubstituted nitro[2.2]metaparacyclophanes

• Suraj Patel,
• Tyson N. Dais,
• Paul G. Plieger and
• Gareth J. Rowlands

Beilstein J. Org. Chem. 2021, 17, 1518–1526, doi:10.3762/bjoc.17.109

• archetypal cyclophane, with a strong interaction between the two aromatic rings, but it is readily available, being a ‘dimer’ for the polymer parylene [6][7]. Over the last twenty years, there has been a resurgence in interest in this compound as a scaffold for the synthesis of asymmetric catalysts, energy

A straightforward conversion of 1,4-quinones into polycyclic pyrazoles via [3 + 2]-cycloaddition with fluorinated nitrile imines

• Greta Utecht-Jarzyńska,
• Karolina Nagła,
• Grzegorz Mlostoń,
• Heinz Heimgartner,
• Marcin Palusiak and
• Marcin Jasiński

Beilstein J. Org. Chem. 2021, 17, 1509–1517, doi:10.3762/bjoc.17.108

• of 3-trifluoromethylpyrazole derivative 9d. The labeling scheme of the asymmetric unit is shown. Anisotropic displacement parameters of nonhydrogen atoms are drawn as ellipsoids with a 50% probability level. N atoms in blue, O atoms in red, C atoms in grey, H atoms as small white spheres. Structure

Co-crystallization of an organic solid and a tetraaryladamantane at room temperature

• Fabian Rami,
• Jan Nowak,
• Felix Krupp,
• Wolfgang Frey and
• Clemens Richert

Beilstein J. Org. Chem. 2021, 17, 1476–1480, doi:10.3762/bjoc.17.103

• X-ray crystallography were collected after more than one week. Table 1 lists the details of the structures observed. In case of the TDA/phenol co-crystals (Figure 2a/c), the asymmetric unit is made up of one host and two guest molecules, so the overall stoichiometric ratio is 1:2 (TDA/phenol). One

• monoclinic. The TEO/phenol asymmetric unit consists of three TEO and three phenol molecules, resulting in a molar ratio TEO/phenol of 1:1 (Figure 2b/d). In the crystals, the ethoxy group of one of the TAA molecules is disordered, and one phenol molecule exhibits a 120°-rotational disorder for its hydroxy

• have thus far evaded crystallization by themselves. Structure of TDA and TEO, the crystallization hosts used for co-crystallization. Details of the X-ray crystal structures obtained, shown as ORTEP plots at 50% probability, with van der Waals radii of the phenol molecules set to 60%. a) Asymmetric unit

Synthesis of 1-indolyl-3,5,8-substituted γ-carbolines: one-pot solvent-free protocol and biological evaluation

• Premansh Dudhe,
• Mena Asha Krishnan,
• Kratika Yadav,
• Diptendu Roy,
• Krishnan Venkatasubbaiah,
• Biswarup Pathak and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2021, 17, 1453–1463, doi:10.3762/bjoc.17.101

• , alkyl N-arylideneglycinates have attracted much attention in recent years. For instance, the metal-catalyzed asymmetric [3 + 2] cycloaddition of ethyl N-benzylideneglycinates with electron-deficient alkenes has been reported to yield substituted pyrrolidines [30]. Recently, we reported the synthesis of

Organocatalytic asymmetric Michael/acyl transfer reaction between α-nitroketones and 4-arylidenepyrrolidine-2,3-diones

• Chandrakanta Parida and
• Subhas Chandra Pan

Beilstein J. Org. Chem. 2021, 17, 1447–1452, doi:10.3762/bjoc.17.100

• Chandrakanta Parida Subhas Chandra Pan Department of Chemistry, Indian Institute of Technology Guwahati, North Guwahati, Assam, 781039, India 10.3762/bjoc.17.100 Abstract An organocatalytic asymmetric Michael/acyl transfer reaction between α-nitroketones and 4-arylidenepyrrolidine-2,3-diones is

• development of catalytic asymmetric conjugate addition reactions [3][4][5]. In particular, the conjugate addition of nitroalkanes and their derivatives to enones has drawn the attention of organic chemists as the corresponding products can be chemoselectively converted to a variety of useful structures [6

• -nitroketones have been found to be a popular nucleophilic acyl transfer reagent. In 2011, three research groups namely Wang, Yan and Kwong independently revealed the organocatalytic asymmetric conjugate addition of α-nitroketones to β,γ-unsaturated α-keto esters with the concomitant acyl transfer reaction to

Photoinduced post-modification of graphitic carbon nitride-embedded hydrogels: synthesis of 'hydrophobic hydrogels' and pore substructuring

• Cansu Esen and
• Baris Kumru

Beilstein J. Org. Chem. 2021, 17, 1323–1334, doi:10.3762/bjoc.17.92

• appearing at 1723 cm−1 can be attributed to asymmetric C=O group stretching vibrations of carboxylic acid groups on PAA chains. The polyacrylamide-based (PAAM) pore substructure spectrum is exhibiting the typical –NH stretching vibrations at 3420 cm−1 and the band at 1656 cm−1 is corresponding to the strong

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

• ]. The activity and robustness of the catalyst allowed reaction at room temperature over long times and enabled continuous preparation of the desired product with no need for downstream purification. A similar approach was taken by Ötvös and co-workers in the same year [108]. Asymmetric aldol reactions

Structural effects of meso-halogenation on porphyrins

• Keith J. Flanagan,
• Maximilian Paradiz Dominguez,
• Zoi Melissari,
• Hans-Georg Eckhardt,
• René M. Williams,
• Dáire Gibbons,
• Caroline Prior,
• Gemma M. Locke,
• Alina Meindl,
• Aoife A. Ryan and
• Mathias O. Senge

Beilstein J. Org. Chem. 2021, 17, 1149–1170, doi:10.3762/bjoc.17.88

• S19B) units depending on the residue in the asymmetric unit. Considering the bond lengths and angles (Supporting Information File 2, Table S2), there are almost no differences between compound 6 and 8 suggesting that little effect is caused by increasing the size of the halogen atom. This is also seen

Synthesis of functionalized imidazo[4,5-e]thiazolo[3,2-b]triazines by condensation of imidazo[4,5-e]triazinethiones with DMAD or DEAD and rearrangement to imidazo[4,5-e]thiazolo[2,3-c]triazines

• Alexei N. Izmest’ev,
• Dmitry B. Vinogradov,
• Natalya G. Kolotyrkina,
• Angelina N. Kravchenko and
• Galina A. Gazieva

Beilstein J. Org. Chem. 2021, 17, 1141–1148, doi:10.3762/bjoc.17.87

• with asymmetric substrates is the high regioselectivity of the cyclizations of intermediate Michael adducts at one of several reactive nitrogen atoms. For example, reported by Giannola et al. [21], the reaction of 3-thioxo-1,2,4-triazin-5-ones 1 with dimethyl acetylenedicarboxylate (DMAD) leads to the

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• heterocycles. The present work will comprehensively cover the most pertinent contributions to this research area from 2012 to 2020. We regret in advance that some contributions are excluded in order to maintain a concise format. Keywords: asymmetric synthesis; chiral auxiliary; natural products; nitrogen

• important tool in the asymmetric synthesis of aziridines [25][26], α-amino acids [27][28], β-amino acids [23][29] and branched α-amines [30][31]. The Darzens-type asymmetric synthesis of N-(p-toluenesulfinyl)aziridine 2-carboxylate esters (7 and 8) was described through the addition of lithium α

• -butanesulfonamide and applications in some nucleophilic additions, the next sections will describe the synthesis of several alkaloids according to the size of the heterocycles. We regret in advance that some contributions are excluded in order to maintain a concise format. Review Asymmetric synthesis of aziridines

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

• Sciences, Faculty of Chemical Technology, University of Pardubice, Studentská 573, 532 10 Pardubice, Czech Republic 10.3762/bjoc.17.84 Abstract The transition metal (palladium)-catalysed asymmetric 1,4-addition of arylboronic acids to conjugated enones belong to the most important and emerging strategies

• for the construction of C–C bonds in an asymmetric fashion. This review covers known catalytic systems used for this transformation. For clarity, we are using the type of ligand as a sorting criterion. Finally, we attempted to create a flowchart facilitating the selection of a suitable ligand for a

• given combination of enone and arylboronic acid. Keywords: asymmetric reaction; boronic acid; conjugated enones; chromones; enantioselective catalysis; Michael addition; Pd complexes; Introduction The asymmetric 1,4-addition of arylboronic acids to conjugated cyclic enones and chromones is a very

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• Prins cyclization strategies, covering the literature reports of the last twenty years (from 2000 to 2019), with an aim to give an overview on exciting advancements in this area and designing new strategies for the total synthesis of related natural products. Keywords: asymmetric; natural products

• , followed by silyl-Prins cyclization of the resulting homoallylic alcohol. For illustration, a facile enantioselective strategy for the synthesis of cis-2,6-disubstituted 4-methylenetetrahydropyran 161 (91% yield, dr = 5:1) was reported by Yu et al, utilizing, first, asymmetric allylation of an aldehyde by

• , followed by removal of trimethylsilane (Scheme 50). The authors further explored this strategy for the asymmetric synthesis of 3-vinylidene-substituted tetrahydropyran by taking the chiral propargylsilane. A diastereoselective route to cis-2,6-disubstituted tetrahydropyran-4-one 215 was explored by