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

Chiral isothiourea-catalyzed kinetic resolution of 4-hydroxy[2.2]paracyclophane

• David Weinzierl and
• Mario Waser

Beilstein J. Org. Chem. 2021, 17, 800–804, doi:10.3762/bjoc.17.68

• polymer chemistry [1][2][7][8][9], these planar chiral molecules have been very successfully used in asymmetric catalysis [3][4][10][11][12]. Accordingly, the development of methods for the asymmetric synthesis of enantiomerically pure, or at least enantiomerically enriched, derivatives that can be

• utilized as building blocks for more demanding ligands and catalysts became a task of high importance. Thus, several strategies to access enantioenriched [2.2]paracyclophanes have been reported, either relying on classical resolution approaches or, more recently, making use of asymmetric catalysis to carry

• decades, it was shown that enantioenriched 2 may serve as a valuable building block to access more advanced chiral cyclophane ligands and catalysts [3][4][19][20][21][22] and therefore its asymmetric synthesis became an important task [3][4][18][19][20][21][22][23][24][25][26][27]. Several strategies to

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

• same time providing effective asymmetric induction in the capture of the resulting radical along with enantioselectivity of the product. In 2016, based on the experimental work in 2015 [27], Yu and colleagues [29] reported a type of EDA complex that could complete the hydrotrifluoromethylation of

Synthesis of β-triazolylenones via metal-free desulfonylative alkylation of N-tosyl-1,2,3-triazoles

• Soumyaranjan Pati,
• Renata G. Almeida,
• Eufrânio N. da Silva Júnior and
• Irishi N. N. Namboothiri

Beilstein J. Org. Chem. 2021, 17, 762–770, doi:10.3762/bjoc.17.66

• compounds as binucleophiles for the construction of various carbocycles, heterocycles as well as in asymmetric catalysis [44][45][46][47][48][49][50]. Our initial objective to trap the aza vinyl rhodium carbenoid using 1,3-dicarbonyl compounds to form pyrazolone was unsuccessful which instead led to the

α,γ-Dioxygenated amides via tandem Brook rearrangement/radical oxygenation reactions and their application to syntheses of γ-lactams

• Mikhail K. Klychnikov,
• Radek Pohl,
• Ivana Císařová and
• Ullrich Jahn

Beilstein J. Org. Chem. 2021, 17, 688–704, doi:10.3762/bjoc.17.58

• results indicate negligible asymmetric inductions from the chiral centers, both at the exocyclic hydroxy substituent in the C3 side chain (Table 3, entry 8) and/or of the 1-arylethyl group during the radical cyclization under the reaction conditions (Table 3, entries 9–11). The size of the arylethyl

Amino- and polyaminophthalazin-1(2H)-ones: synthesis, coordination properties, and biological activity

• Zbigniew Malinowski,
• Emilia Fornal,
• Agata Sumara,
• Renata Kontek,
• Karol Bukowski,
• Beata Pasternak,
• Dariusz Sroczyński,
• Joachim Kusz,
• Magdalena Małecka and
• Monika Nowak

Beilstein J. Org. Chem. 2021, 17, 558–568, doi:10.3762/bjoc.17.50

• data are summarized in Table 1. For full details on the comparison of experimental and calculated bond lengths and bond angles of complex 17 are provided in Supporting Information File 2, Table S1. The complex 17 crystallizes in the monoclinic Pc space group with two molecules A and B in one asymmetric

Menthyl esterification allows chiral resolution for the synthesis of artificial glutamate analogs

• Kenji Morokuma,
• Shuntaro Tsukamoto,
• Kyosuke Mori,
• Kei Miyako,
• Ryuichi Sakai,
• Raku Irie and
• Masato Oikawa

Beilstein J. Org. Chem. 2021, 17, 540–550, doi:10.3762/bjoc.17.48

• studies will straightforwardly focus on the enantioselective synthesis of only the (2R)-isomer. The asymmetric Ugi reaction recently developed [29] is of interest for the selective preparation of (2R)-6 (Scheme 1 and Scheme 5) [6][8]. Studies are in progress to develop an asymmetric Ugi/Diels–Alder

The synthesis of chiral β-naphthyl-β-sulfanyl ketones via enantioselective sulfa-Michael reaction in the presence of a bifunctional cinchona/sulfonamide organocatalyst

• Deniz Tözendemir and
• Cihangir Tanyeli

Beilstein J. Org. Chem. 2021, 17, 494–503, doi:10.3762/bjoc.17.43

• Deniz Tozendemir Cihangir Tanyeli Department of Chemistry, Middle East Technical University, 06800 Ankara, Turkey 10.3762/bjoc.17.43 Abstract Cinchona alkaloid-derived organocatalysts are widely employed in various asymmetric transformations, yielding products with high enantiopurity. In this

• respect, a bifunctional quinine-derived sulfonamide organocatalyst was developed to catalyze the asymmetric sulfa-Michael reaction of naphthalene-1-thiol with trans-chalcone derivatives. The target sulfa-Michael adducts were obtained with up to 96% ee under mild conditions and with a low (1 mol

• %) catalyst loading. Selected enantiomerically enriched sulfa-Michael addition products were subjected to oxidation to obtain the corresponding sulfones. Keywords: asymmetric synthesis; bifunctional catalysis; cinchona alkaloids; organocatalysis; sulfa-Michael reaction; Introduction Derivatives of the

Synthetic strategies of phosphonodepsipeptides

• Jiaxi Xu

Beilstein J. Org. Chem. 2021, 17, 461–484, doi:10.3762/bjoc.17.41

• the P–C bond of the spirophosphoranes 201 readily proceeded at room temperature in the presence of moist solvents to give the corresponding phosphonodepsipeptides 202 in high yields (Scheme 37) [56]. An asymmetric synthesis of this class of phosphonodepsipeptides was realized with enantiopure (S)-α

• -hydroxyisovaleric acid-derived spirophosphoranes as the phosphorus reagents [57]. By using a similar strategy, linker-linked bisphosphonodepsidipeptides were synthesized [10]. The current method is also an interesting synthetic strategy of phosphonodepsipeptides. It can realize an asymmetric synthesis of

• phosphonodepsipeptides in the future. However, highly stereoselective asymmetric synthetic methods of phosphonodepsipeptides are of high demand and need to be developed in the near future. Phosphonopeptides, phosphonodepsipeptides, peptides, and depsipeptides. The diverse strategies for phosphonodepsipeptide synthesis

Mesoionic tetrazolium-5-aminides: Synthesis, molecular and crystal structures, UV–vis spectra, and DFT calculations

• Vladislav A. Budevich,
• Sergei V. Voitekhovich,
• Alexander V. Zuraev,
• Vadim E. Matulis,
• Vitaly E. Matulis,
• Alexander S. Lyakhov,
• Ludmila S. Ivashkevich and
• Oleg A. Ivashkevich

Beilstein J. Org. Chem. 2021, 17, 385–395, doi:10.3762/bjoc.17.34

• , respectively. The asymmetric units of compounds 8a and 11a contain one molecule, whereas the unit of 10 includes a half molecule. In contrast to 8a and 11a, the molecule of 10 shows Ci symmetry, with the inversion center lying in the middle of the bond C10–C10a [symmetry code: (a) –x + 2, −y, −z + 1]. The

• show no hydrogen bonds in their crystal structures and only van der Waals interactions take place between the molecules. The bistetrazolium salt 9 (bromide salt of mesoionic compound 10) crystallizes in the trigonal space group , with 18 formula units in the unit cell. The asymmetric unit includes one

• derivatives. Molecules of compounds 8a, 10, 11a, and the bistetrazolium cation 9, with displacement ellipsoids drawn at the 50% probability level. The hydrogen atoms are shown as spheres of arbitrary radii. The atom numbering is done for the asymmetric unit. Experimental (a) and TD-tHCTHhyb/6-311+G(2d,p

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• generate CF3-substituted iminium ions able to promote Friedel–Crafts alkylations [110][111]. Ma et al. exploited this mode of activation in a Brønsted acid-catalyzed three-component asymmetric reaction [112]. Mixing hemiacetal 175, arylaniline 176, and indole derivatives 149 in the presence of a catalytic

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• the corresponding cyclopropane 76 [77]. Caution is advised in view of a recent report that NaBH4 lowers the onset temperature for the thermal decomposition of DMSO [78]. The asymmetric difluorocyclopropanation has not yet been developed to the extent achieved for the epoxidation. Consequently, the

• [81]. The authors obtained the chiral monoacetate intermediates (R)-78 and (S)-80 by lipase-catalyzed methods. The lipase-catalyzed asymmetric transesterification of prochiral diol 77 and the deacetylation of the prochiral diacetate 79 resulted in the formation of the (R)-monoacetate (R)-78 and (S

• enantioselective hydrocupration of difluorocyclopropenes in the presence of chiral diphosphine ligands using stoichiometric hydride sources that included polymethylhydrosiloxane (PMHS) and organoboranes (Scheme 35) [79]. Cossy and co-workers have achieved the catalytic asymmetric transfer hydrogenation with