Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

• addition with Grignard reagents Feringa and co-workers realized the tandem conjugate addition of Grignard reagents to 4-chlorocrotonates 46 [42]. The enolate 47, which was formed in this process, underwent an intramolecular nucleophilic substitution to form cyclopropane derivatives. Thioesters, esters as

Direct C2–H alkylation of indoles driven by the photochemical activity of halogen-bonded complexes

• Martina Mamone,
• Giuseppe Gentile,
• Jacopo Dosso,
• Maurizio Prato and
• Giacomo Filippini

Beilstein J. Org. Chem. 2023, 19, 575–581, doi:10.3762/bjoc.19.42

• to photochemically generate electrophilic radicals that can drive the functionalization of suitable electron-rich substrates [23]. Exploiting this strategy, here we report a novel metal-free methodology for the direct homolytic aromatic substitution (HAS) reaction of indoles 1 with α-iodosulfones 2

A new oxidatively stable ligand for the chiral functionalization of amino acids in Ni(II)–Schiff base complexes

• Alena V. Dmitrieva,
• Oleg A. Levitskiy,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2023, 19, 566–574, doi:10.3762/bjoc.19.41

• as the starting platform for the modification of an amino acid moiety by nucleophilic substitution and addition reactions, including electrochemically induced processes [5][16][17][18][31]. The electrochemical behavior of the new complexes was investigated to get an experimental support for their

Access to cyclopropanes with geminal trifluoromethyl and difluoromethylphosphonate groups

• Ita Hajdin,
• Romana Pajkert,
• Mira Keßler,
• Jianlin Han,
• Haibo Mei and
• Gerd-Volker Röschenthaler

Beilstein J. Org. Chem. 2023, 19, 541–549, doi:10.3762/bjoc.19.39

• closely linked to the substitution pattern of the cyclopropane unit [2]. The prevalence of the biologically active cyclopropyl derivatives, either isolated from natural sources or rationally designed as pharmaceutical agents, has inspired chemists to find efficient methods for their preparation. Among

Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

• -trifluoromethyl substituent forming the ketone product in <10% yield. While substitution of the norbornene was tolerated, both EWGs and EDGs hindered the reaction. Upon several mechanistic studies, the authors proposed the catalytic cycle begins with the oxidative addition of the active Ni(0) catalyst to imide 27

• little effect on the reaction (32b) with reactions involving unsymmetrically substituted bicyclic alkenes demonstrating complete regioselectivity for either 1,2,3- or 1,2,4-trisubstitued products (32a, 32f). DFT calculations were used to explain the syn-1,2-substitution experimentally observed rather

• , the authors noted the reaction was stereoselective for the trans-addition product. Mechanistically, the authors proposed the reaction begins with the Cu-mediated substitution reaction of iodobenzene (66a) with KSCN to afford phenyl thiocyanate (70). The Cu complex can then undergo oxidative addition

Transition-metal-catalyzed C–H bond activation as a sustainable strategy for the synthesis of fluorinated molecules: an overview

• Louis Monsigny,
• Floriane Doche and
• Tatiana Besset

Beilstein J. Org. Chem. 2023, 19, 448–473, doi:10.3762/bjoc.19.35

• . The substitution pattern on the aromatic ring did not affect the reaction efficiency, the meta-substituted derivative 2e as well as the ortho-substituted derivative 2f were obtained in high yields (70% and 63% yields, respectively). It should be noted that the presence of ortho-substituents on the

• , from 52 to 91% yields). The substitution pattern of the aromatic ring had no impact on the outcome of the reaction as illustrated with substrates substituted by a methyl group (7b, 7d, and 7f) at the para-, meta- and ortho-positions, which were readily functionalized in 71%, 84% and 78% yields

• yield (63%). The same year, Besset and co-workers reported a palladium-catalyzed C(sp2)–SCF3 bond formation on amides derived from 8-aminoquinoline as a cleavable directing group in the presence of the Munavalli reagent V (Scheme 9, 12 examples, up to 71% yield) [106]. Depending on the substitution

Group 13 exchange and transborylation in catalysis

• Dominic R. Willcox and
• Stephen P. Thomas

Beilstein J. Org. Chem. 2023, 19, 325–348, doi:10.3762/bjoc.19.28

• (Scheme 16) [75]. The reaction was proposed to occur through activation of the alkyl fluoride 68 with H-B-9-BBN, followed by electrophilic substitution of the arene 69 to give a Wheland intermediate and a fluoroborohydride 70 (Scheme 16). Loss of H2 gave the arylated product 71, dihydrogen, and F-B-9-BBN

Synthesis and reactivity of azole-based iodazinium salts

• Thomas J. Kuczmera,
• Annalena Dietz,
• Andreas Boelke and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2023, 19, 317–324, doi:10.3762/bjoc.19.27

• substitution to take place. With 2.5 equivalents of TfOH as the optimum amount of acid the product 5aa was obtained in a yield of 69% (Table 1, entry 3). Similar results were observed with DCM at 40 °C (Table 1, entry 5). A higher amount of mCPBA did not lead to a better yield due to more washing required to

• . Next, the iodonium center was stabilized through an additional N-coordination via ortho-pyrazole substitution, giving the iodonium salts 5ba and 5bb in 88% and 50% yield. When replacing imidazoles by indazoles the oxidation was not as efficient giving the products 5bc and 5bd with only 24% and 44

• center intact. Treatment of the ortho-pyrazole-substituted salt 5bb with MeOTf resulted in a selective benzimidazole N-methylation. A reaction on the pyrazole nitrogen is impeded due to its coordination with the iodane’s σ-hole (Scheme 2a). Besides nitrogen-substitution, the benzimidazole C-2 position of

Continuous flow synthesis of 6-monoamino-6-monodeoxy-β-cyclodextrin

• János Máté Orosz,
• Dóra Ujj,
• Petr Kasal,
• Gábor Benkovics and
• Erika Bálint

Beilstein J. Org. Chem. 2023, 19, 294–302, doi:10.3762/bjoc.19.25

• in 69% yield and 98% purity according to the authors. Many nucleophiles can react with tosylated CDs to give the corresponding C-6-monofunctionalized CDs. However, alkaline bases cannot be used as nucleophiles due to the intramolecular substitution, resulting in a mono-3,6-anhydro product [13]. On

• industrial processes. Batch synthesis of 6A-azido-6A-deoxy-β-CD (N3-β-CD) (3) Substitution of the p-toluenesulfonyl group of Ts-β-CD (2) by azide can be carried out in water [40][41], DMF [14][42], or in their combination [43][44] at elevated temperatures. Water is preferred over DMF due to its lower cost

• the tosyl–azide substitution was optimized (Scheme 2). First, the best solvent was sought. Unfortunately, practically no reaction took place when the same solvent was used as for the tosylation reaction (Table 2, entries 1–4), so we had to evaporate the solution exiting the first flow reaction, and

Synthesis, α-mannosidase inhibition studies and molecular modeling of 1,4-imino-ᴅ-lyxitols and their C-5-altered N-arylalkyl derivatives

• Martin Kalník,
• Sergej Šesták,
• Juraj Kóňa,
• Maroš Bella and
• Monika Poláková

Beilstein J. Org. Chem. 2023, 19, 282–293, doi:10.3762/bjoc.19.24

• endocyclic nitrogen with a benzyl or alkyl unit functionalized either with non-polar hydrocarbons or a polar amine, amidine and guanidine group. The ensuing assay with the model GMIIb enzyme (fruit fly Golgi α-mannosidase II) revealed that N-substitution improved both potency and selectivity, achieving

• than analogues 17–19 toward the GH38 enzymes tested. Thus, it appears that N-substitution of the free iminosugar 20 considerably reduces the inhibitory activity. Among imino-ᴅ-lyxitols 26–29, 6-deoxy-DIM 29 was found to be the most potent derivative (Ki = 0.065 μM and 0.19 μM for GMIIb and AMAN-2

• enzyme. Therefore, the next efforts should be focused on the identification of a novel N-substitution pattern of the DIM skeleton that would have more beneficial effects on the inhibition profile. Natural iminosugars (1,4-dideoxy-1,4-imino-ᴅ-mannitol (DIM) and swainsonine) and selected examples of

Friedel–Crafts acylation of benzene derivatives in tunable aryl alkyl ionic liquids (TAAILs)

• Swantje Lerch,
• Stefan Fritsch and
• Thomas Strassner

Beilstein J. Org. Chem. 2023, 19, 212–216, doi:10.3762/bjoc.19.20

• lithium bis(trifluoromethylsulfonyl)imide (LiNTf2). All reactions are generally tolerant towards different aryl substitutions, substitution patterns, alkyl chain lengths and can be carried out in a multigram scale [57]. The acylation of the electron-rich benzene derivative anisole with acetic anhydride

Sequential hydrozirconation/Pd-catalyzed cross coupling of acyl chlorides towards conjugated (2E,4E)-dienones

• Benedikt Kolb,
• Daniela Silva dos Santos,
• Sanja Krause,
• Anna Zens and
• Sabine Laschat

Beilstein J. Org. Chem. 2023, 19, 176–185, doi:10.3762/bjoc.19.17

• substituents in the one-pot reaction and showed that regardless of the substitution pattern, the reactions lead to the stereoselective formation (≥95% (2E,4E)) of the respective dienones under mild conditions. It was found that enynes with alkyl chains gave higher yields than the corresponding aryl-substituted

• benzoyl chloride (26a). The best results were obtained in the reaction of aliphatic enyne 25e with benzoyl chloride (26a) and acetyl chloride (22) in yields of 34% and 65%, respectively. Methyl substitution on the alkene functionality of enyne 25 did not affect the yield, however, methyl substitution at

Total synthesis of insect sex pheromones: recent improvements based on iron-mediated cross-coupling chemistry

• Eric Gayon,
• Guillaume Lefèvre,
• Olivier Guerret,
• Adrien Tintar and
• Pablo Chourreu

Beilstein J. Org. Chem. 2023, 19, 158–166, doi:10.3762/bjoc.19.15

• constitutes an extremely powerful tool in total synthesis. In order to reach sustainable and economically appealing conditions, the quest for the substitution of palladium by non-noble metals has been investigated for more than four decades. To address this issue, new eco-friendly synthetic routes relying on

1,4-Dithianes: attractive C2-building blocks for the synthesis of complex molecular architectures

• Bram Ryckaert,
• Ellen Demeyere,
• Frederick Degroote,
• Hilde Janssens and
• Johan M. Winne

Beilstein J. Org. Chem. 2023, 19, 115–132, doi:10.3762/bjoc.19.12

• transformations of aryl substrates have also been reported for thiovinyl ethers, and also for dihydrodithiins (Scheme 5), although there are obvious limitations to this point of view. Classical electrophilic aromatic substitution procedures such as the Vilsmeier–Haack reaction or a simple nitration have been

• products (viz 16, Scheme 5b) [37]. Electrophilic aromatic substitution under less forcing reaction conditions of the same substrate 15, using a room temperature nitration procedure, does yield the expected mononitrated dithiin 17 in good yield, without desulfurization [38]. 1,4-Dithiin-2-carbaldehyde (18

Synthesis and characterisation of new antimalarial fluorinated triazolopyrazine compounds

• Kah Yean Lum,
• Jonathan M. White,
• Daniel J. G. Johnson,
• Vicky M. Avery and
• Rohan A. Davis

Beilstein J. Org. Chem. 2023, 19, 107–114, doi:10.3762/bjoc.19.11

• [14], we had undertaken some preliminary investigations into the use of commercially available Diversinate™ reagents and showed the bicyclic nitrogen-rich core of Series 4 was amenable to this chemistry, with radical sulfinate substitution occurring with high-selectivity at C-8 and in respectable

• triazolopyrazines were all evaluated in vitro for antimalarial activity and cytotoxicity. Results and Discussion Previous structure–activity relationship (SAR) studies reported that any substitution at the C8 position of Series 4 triazolopyrazines can lower the potency for P. falciparum [14][15][16]. However, a

• recent preliminary SAR study identified that substitution at the C8 position with trifluoromethane and difluoroethane moieties using Diversinate™ chemistry increased the potency of the parent scaffold (compound 2), suggesting the potential of these fluoroalkyl groups for improving the potency of other

Revisiting the bromination of 3β-hydroxycholest-5-ene with CBr₄/PPh₃ and the subsequent azidolysis of the resulting bromide, disparity in stereochemical behavior

• Christian Schumacher,
• Jas S. Ward,
• Kari Rissanen,
• Carsten Bolm and
• Mohamed Ramadan El Sayed Aly

Beilstein J. Org. Chem. 2023, 19, 91–99, doi:10.3762/bjoc.19.9

• of Science, Port Said University, 42522-Port Said, Egypt 10.3762/bjoc.19.9 Abstract Cholesterol reacts under Appel conditions (CBr4/PPh3) to give 3,5-cholestadiene (elimination) and 3β-bromocholest-5-ene (substitution with retention of configuration). Thus, the bromination of cholesterol deviates

• inversion. For note, the 1H NMR spectrum of 5 revealed the presence of ca. 15% of the β-epimer 6, which could result from an incomplete stereospecificity of the substitution opening an alternative reaction path. Also in this case, the NMR data are then in agreement with the reported ones [18]. In light of

NaI/PPh₃-catalyzed visible-light-mediated decarboxylative radical cascade cyclization of N-arylacrylamides for the efficient synthesis of quaternary oxindoles

• Dan Liu,
• Yue Zhao and
• Frederic W. Patureau

Beilstein J. Org. Chem. 2023, 19, 57–65, doi:10.3762/bjoc.19.5

• , good yields of the corresponding oxindoles (3da–ga) were achieved. A trifluoromethyl-substituted acrylamide afforded the product 3fa in very high 85% yield. In addition, ortho-substitution at the N-aryl moiety was also well tolerated, albeit with slightly decreased yields (3ha–ka, 50–63

Improving the accuracy of ³¹P NMR chemical shift calculations by use of scaling methods

• William H. Hersh and
• Tsz-Yeung Chan

Beilstein J. Org. Chem. 2023, 19, 36–56, doi:10.3762/bjoc.19.4

• in our hands, in some cases giving widely divergent chemical shifts for the two chemically equivalent phosphorus atoms, which could potentially exacerbate any deviations from the experimental chemical shifts. Since derivatives with methyl (1a) and butyl substitution on PA were reported and had

• method using the Latypov training set is superior for this collection of compounds; the substitution of 1a – which still exhibited two conformations – for 1 actually gave better results for the Latypov method than for the others, and gave a much better fit than had 1. Inspection of the deviations showed

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• their synthesis (Scheme 2). The synthetic variant of 3 was designed as the common scaffold 16, bearing the appropriate substitution for sequential revelation of carboxylic acid moieties. The highly congested decalin core of common scaffold 16 was obtained by a modified electrochemical polycyclization of

• presence of appropriate additives (Scheme 18). According to the postulated mechanism, the reaction is initiated by an SET of the dicinnamyl ether substrate to Fukuzumi’s salt 233, leading to radical cation 216. Earlier findings of the same group [107] revealed that substitution on the aryl groups is the

• to the intermediate trans-218. In the presence of external nucleophiles (e.g., MeOH), the cation can be trapped, leading to substitution in the 7-position, while the radical is postulated to be oxidized to a cation, followed by a Friedel–Crafts reaction to the final product 222. When an excess of

A novel spirocyclic scaffold accessed via tandem Claisen rearrangement/intramolecular oxa-Michael addition

• Anastasia Vepreva,
• Alexander Yanovich,
• Dmitry Dar’in,
• Grigory Kantin,
• Alexander Bunev and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2022, 18, 1649–1655, doi:10.3762/bjoc.18.177

• crystallography. In all other cases, only the pure syn diastereomer was isolated and characterized. The yields of spirocyclic products were generally modest to good over two steps. An electron-accepting group in the benzylidene portion (5j) or an N-benzyl substitution in the starting material (5g) lowered the

A novel bis-triazole scaffold accessed via two tandem [3 + 2] cycloaddition events including an uncatalyzed, room temperature azide–alkyne click reaction

• Ksenia Malkova,
• Andrey Bubyrev,
• Vasilisa Krivovicheva,
• Dmitry Dar’in,
• Alexander Bunev and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2022, 18, 1636–1641, doi:10.3762/bjoc.18.175

• transformation. Introduction of an α-methyl substitution in propargylamine (compound 16) was tolerated and the respective reaction gave product 17 in a yield comparable to (and somewhat better than) that of unsubstituted compound 5a. Homologation of propargylamine made a significant impact on the course of the

Synthetic study toward the diterpenoid aberrarone

• Liang Shi,
• Zhiyu Gao,
• Yiqing Li,
• Yuanhao Dai,
• Yu Liu,
• Lili Shi and
• Hong-Dong Hao

Beilstein J. Org. Chem. 2022, 18, 1625–1628, doi:10.3762/bjoc.18.173

• for this facile transformation might proceed with first hydrogenation followed by the substitution of the labile triflate ester (for details, see Supporting Information File 1). Moving forward, compound 17 was further converted into alkynone 9 through DIBAL-H reduction, nucleophilic addition and Dess

Formal total synthesis of macarpine via a Au(I)-catalyzed 6-endo-dig cycloisomerization strategy

• Jiayue Fu,
• Bingbing Li,
• Zefang Zhou,
• Maosheng Cheng,
• Lu Yang and
• Yongxiang Liu

Beilstein J. Org. Chem. 2022, 18, 1589–1595, doi:10.3762/bjoc.18.169

• ring smoothly, leading to the exclusive formation of biaryl intermediate 11 in a yield of 82%. It is worth noting that the methoxy substitution in the substrate played a crucial role in controlling the selectivity of the cycloisomerization according to our previous study [15]. It was rationalized that

Functionalization of imidazole N-oxide: a recent discovery in organic transformations

• Koustav Singha,
• Imran Habib and
• Mossaraf Hossain

Beilstein J. Org. Chem. 2022, 18, 1575–1588, doi:10.3762/bjoc.18.168

• summarized so that the chemists, researchers, and pharmaceutical industries find its effectiveness in near future for the synthesis of potent, novel, and non-toxic drug molecules. Keywords: functionalization; imidazole N-oxide; mechanistic insights; multicomponent reaction; nucleophilic substitution

• substitution reactions Metal-free coupling reaction through nucleophilic substitution of H-atom (SNH) In 2020, a C–H/C–Li coupling reaction between 2H-imidazole 1-oxides and pentafluorophenyllithium under transition metal-free conditions was reported by Timofey D. Moseev and co-workers [17]. The reaction

• proceeds through the nucleophilic substitution of a H-atom (SNH) at the C-5 position of the imidazole N-oxides. This reaction methodology can be considered as suitable process for the syntheses of bioactive imidazole compounds containing (poly)fluoroaryl moieties. Interestingly, in some of the

Efficient synthesis of aziridinecyclooctanediol and 3-aminocyclooctanetriol

• Emine Salamci and
• Ayse Kilic Lafzi

Beilstein J. Org. Chem. 2022, 18, 1539–1543, doi:10.3762/bjoc.18.163

• group in compound 10 was converted to the corresponding alcohol 11 as the sole isomer via SN2 substitution by hydrolysis. In the azidolysis reaction of compound 8, we propose that because the azide group is bulkier than the water molecule, it could not substitute the second mesylate group, and therefore

• have achieved the synthesis of 3-aminocyclooctanetriol 13 and aziridinecyclooctanediol 16 starting from cis,cis-1,3-cyclooctadiene. The nitrogen functionalities were introduced by the substitution with NaN3 of the corresponding mesylate. Reduction of the azido functionalities gave monoaminocyclitol and