First synthesis of acylated nitrocyclopropanes

• Kento Iwai,
• Rikiya Kamidate,
• Khimiya Wada,
• Haruyasu Asahara and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2023, 19, 892–900, doi:10.3762/bjoc.19.67

• reaction with dinucleophiles such as 2-aminopyridines, which affords pyrido[1,2-a]pyrimidinones through ring opening (Scheme 1, reaction a) [1]. Chemical transformations that take advantage of polyfunctionality are also possible. A six-membered ring forms between the aryl group and ester functionality

Cassane diterpenoids with α-glucosidase inhibitory activity from the fruits of Pterolobium macropterum

• Sarot Cheenpracha,
• Ratchanaporn Chokchaisiri,
• Lucksagoon Ganranoo,
• Sareeya Bureekaew,
• Thunwadee Limtharakul and
• Surat Laphookhieo

Beilstein J. Org. Chem. 2023, 19, 658–665, doi:10.3762/bjoc.19.47

• unsaturation required the presence of two heterocyclic rings in the molecule. The presence of an ester carbonyl signal (δC 167.0) and a deshielded oxygenated carbon resonance at C-12′ (δC 104.1) implied the formation of six-membered ring via an ester bond between C-16 and C-12′. In addition, an epoxide moiety

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

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

• -membered ring structure 3ra could be successfully isolated with a good yield (66%). A number of alkyl radical precursors were then synthesized and evaluated in the reaction (Scheme 3). We found that redox-active esters derived from primary, secondary, and tertiary aliphatic carboxylic acids were all

• synthesis of (±)-physovenine and (±)-physostigmine alkyl analogues exhibiting inhibitory activity against acetylcholinesterase and butyrylcholinesterase [30][78][79][80][81][82][83][84]. Subsequently, we expanded the scope of this protocol to include a benzamide derived acrylamide 1r. The expected six

Synthesis of (−)-halichonic acid and (−)-halichonic acid B

• Keith P. Reber and
• Emma L. Niner

Beilstein J. Org. Chem. 2022, 18, 1629–1635, doi:10.3762/bjoc.18.174

• -equatorial position, and the trisubstituted alkene within the six-membered ring serves as the nucleophile. It is important to note that in this chair-like conformer, the ethyl ester group at C2 assumes a pseudo-equatorial position. Although an alternative boat-like conformer is also possible (which would

1,4,6,10-Tetraazaadamantanes (TAADs) with N-amino groups: synthesis and formation of boron chelates and host–guest complexes

• Artem N. Semakin,
• Ivan S. Golovanov,
• Yulia V. Nelyubina and
• Alexey Yu. Sukhorukov

Beilstein J. Org. Chem. 2022, 18, 1424–1434, doi:10.3762/bjoc.18.148

• ]. In tripodal molecules, three functional arms are bound to a central trivalent scaffold, which can be a single atom (e.g., carbon, nitrogen, or phosphorus), a small ring (usually aromatic or saturated six-membered ring), or a macrocycle (Figure 1a). The functional properties of tripodal molecules are

Radical cation Diels–Alder reactions of arylidene cycloalkanes

• Kaii Nakayama,
• Hidehiro Kamiya and
• Yohei Okada

Beilstein J. Org. Chem. 2022, 18, 1100–1106, doi:10.3762/bjoc.18.112

• reaction is a typical example of this activation mode since both the original diene and dienophile are electron-rich and thus not an effective combination of reactants [1][2][3][4][5][6][7][8][9][10][11]. Single-electron transfer makes the construction of six-membered ring systems possible. In general

Chemistry of polyhalogenated nitrobutadienes, 17: Efficient synthesis of persubstituted chloroquinolinyl-1H-pyrazoles and evaluation of their antimalarial, anti-SARS-CoV-2, antibacterial, and cytotoxic activities

• Viktor A. Zapol’skii,
• Isabell Berneburg,
• Ursula Bilitewski,
• Melissa Dillenberger,
• Katja Becker,
• Stefan Jungwirth,
• Aditya Shekhar,
• Bastian Krueger and
• Dieter E. Kaufmann

Beilstein J. Org. Chem. 2022, 18, 524–532, doi:10.3762/bjoc.18.54

• group forming a six-membered ring system that upon reaction with 7-chloro-4-hydrazinylquinoline formed 5-aminopyrazoles 5a,l–o. Here, a nucleophilic attack of the NH2 group of the arylhydrazine on the C3 position of the butadiene chain is observed due to the sterically hindered rigidized six-membered

• ring system in the dienes 4a,l–o (Scheme 4). The obtained 5-aminopyrazoles 5a,l–o show the following 13C NMR shifts of the pyrazole ring and the dichloromethyl group: 149.5–149.9 ppm (C-NHR), 114.7–116.1 ppm (C-NO2), 147.0–147.2 ppm (C=N), and 62.2–62.3 ppm (CHCl2). On the other hand, the dienes 4b–k

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

• in a diastereomeric pair of cyclized products 69 and 71, respectively. It was observed that the cis-isomer was predominant in the case of the five-membered ring while the trans-isomer was predominant in the case of the six-membered ring formation (Scheme 24) [72]. Cyclization involving alkynes (-C≡C

Nomimicins B–D, new tetronate-class polyketides from a marine-derived actinomycete of the genus Actinomadura

• Zhiwei Zhang,
• Tao Zhou,
• Taehui Yang,
• Keisuke Fukaya,
• Enjuro Harunari,
• Shun Saito,
• Katsuhisa Yamada,
• Chiaki Imada,
• Daisuke Urabe and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2021, 17, 2194–2202, doi:10.3762/bjoc.17.141

• ring was fused with another six-membered ring to give a dehydrodecalin core by the correlations from a singlet methyl hydrogen atom H25 to C4, C5, and C13. A series of HMBC correlations from two methyl singlets H27 and H28 elucidated the carbon connectivity of C23–C18–C19–C20–C21 (Figure 2), which was

• ). Placement of the oxygenated carbon atom C8 between C7 and C9 and the attachment of the oxygenated methylene carbon atom C26 to C8 were deduced from the HMBC correlations from H7 and H9 to C8 and C26 and from H26 to C7, C8, and C9, thereby establishing a highly oxygenated cyclohexane ring. This six-membered

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

• of this kind of reaction is the catalytic use of the hydride donor, in this case phenylsilane (PhSiH3), due to the regeneration of the active metal hydride species in the cycloisomerization mechanism pathway (Scheme 18). The lower cyclization constant for the six-membered ring formation, in

• good yields. Five- and six-membered rings were synthesized by this method, and the tetracyclic compounds 69i–l were obtained when isopregol halide derivatives were employed. No diastereoselectivity was observed in the five-membered cyclizations (Scheme 26A, 69e–g), whereas the six-membered ring 69h was

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

• , and diverse transformations are known to create new C–C bonds and/or to extend the (poly)cyclic system. In this context, cycloadditions are of special importance, and Diels–Alder reactions have successfully been explored in conversions aimed at the construction of a new, six-membered ring [5]. However

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

• were performed and they predicted correctly the observed experimental results considering a six-membered ring cyclic transition state. The addition took place to the Si-face of the imines with (RS)-configuration. Compounds 97 were also evaluated in a preliminary study in leukemia strains (Scheme 29

• number of classical methodologies have been used for their synthesis, in which the key step is the generation of the six-membered ring, including the aldol reaction, the reductive amination, Mannich reaction, ring closing metathesis, Diels–Alder reaction with imines as dienophiles, aza-Prins cyclization

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

• rearrangement [102] in an analogous heterocyclic system. 8 Pyridines/fused pyridines 8.1 Pyridines Pyridines are six-membered ring systems consisting of five carbon atoms and one nitrogen atom. Highly substituted pyridines are known to show various pharmacological activities and are also found in various

A chromatography-free and aqueous waste-free process for thioamide preparation with Lawesson’s reagent

• Ke Wu,
• Yichen Ling,
• An Ding,
• Liqun Jin,
• Nan Sun,
• Baoxiang Hu,
• Zhenlu Shen and
• Xinquan Hu

Beilstein J. Org. Chem. 2021, 17, 805–812, doi:10.3762/bjoc.17.69

• effective in the decomposition of the inherent stoichiometric six-membered-ring byproduct from the Lawesson’s reagent to a highly polarized diethyl thiophosphonate. The treatment significantly simplified the following chromatography purification of the desired thioamide in a small scale preparation. As

• compounds [2][3][4][5]. Although LR is a powerful, mild and versatile thionation reagent, the workup procedures of reactions involving this reagent have received quite a few negative comments [6][7][8][9][10]. The reason for this is that an inherent six-membered ring structure A (Figure 1) is formed from

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

• , cyanides, esters, ethers, halides, and heterocycles, and various α-aminoketones (32 examples) can be yielded in 90% isolated yield. According to the author, the EDA complex had a six-membered-ring transient state, and the imine also acted as an organic base (abstracting proton from α-keto acid), proving

Annulation of a 1,3-dithiole ring to a sterically hindered o-quinone core. Novel ditopic redox-active ligands

• Sergey V. Norkov,
• Anton V. Cherkasov,
• Andrey S. Shavyrin,
• Maxim V. Arsenyev,
• Viacheslav A. Kuropatov and
• Vladimir K. Cherkasov

Beilstein J. Org. Chem. 2021, 17, 273–282, doi:10.3762/bjoc.17.26

• mixture. X-ray diffraction data revealed that the bond lengths distribution in the six-membered ring of 6b is typical of sterically hindered o-quinones. The annulated fragment including the 1,3-dithiole cycle and the malononitrile unit is almost flat. The six-membered o-quinone ring is distorted due to

• structural data. The reaction of 4 with gem-dithiolate 5c resulted in o-quinone 6c in a good yield (Scheme 1, route 2). TLC control indicated that 6c was the only colored product in this synthesis. In o-quinone 6c the six-membered ring at the attached fragment exists in p-quinonoid form. According to the X

Synthesis of purines and adenines containing the hexafluoroisopropyl group

• Viacheslav Petrov,
• Rebecca J. Dooley,
• Alexander A. Marchione,
• Elizabeth L. Diaz,
• Brittany S. Clem and
• William Marshall

Beilstein J. Org. Chem. 2020, 16, 2739–2748, doi:10.3762/bjoc.16.224

• that with the CF3 moieties nearer the five-membered ring of the azabenzimidazole unit, and the rotamer of higher energy was that with the CF3 moieties near the six-membered ring (see Figure 4). Density functional theory calculations predict an enthalpy difference of 0.48 kcal⋅mol−1 between the two

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

Natural dolomitic limestone-catalyzed synthesis of benzimidazoles, dihydropyrimidinones, and highly substituted pyridines under ultrasound irradiation

• Kumar Godugu,
• Venkata Divya Sri Yadala,
• Mohammad Khaja Mohinuddin Pinjari,
• Trivikram Reddy Gundala,
• Lakshmi Reddy Sanapareddy and
• Chinna Gangi Reddy Nallagondu

Beilstein J. Org. Chem. 2020, 16, 1881–1900, doi:10.3762/bjoc.16.156

• confirmed that the reaction stopped at the bisimine I stage. This was due to the intramolecular hydrogen bonding between the hydrogen atom of the ortho-hydroxy group and the nitrogen atom of the imine group in a six-membered ring transition state [87]. Similarly, the reaction between 3-ethoxysalicylaldehyde

A cyclopeptide and three oligomycin-class polyketides produced by an underexplored actinomycete of the genus Pseudosporangium

• Shun Saito,
• Kota Atsumi,
• Tao Zhou,
• Keisuke Fukaya,
• Daisuke Urabe,
• Naoya Oku,
• Md. Rokon Ul Karim,
• Hisayuki Komaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 1100–1110, doi:10.3762/bjoc.16.97

• six-membered ring and the axial orientations of H-31 and the H-41 methyl group. Therefore, the relative configuration of the spiroacetal ring was established to be (23S*,24R*,25S*,27R*,30S*,31S*) (Figure 7). The molecular formula of pseudosporamicin B (3) was determined to be C41H70O9 based on a

One-pot synthesis of dicyclopenta-fused peropyrene via a fourfold alkyne annulation

• Ji Ma,
• Yubin Fu,
• Junzhi Liu and
• Xinliang Feng

Beilstein J. Org. Chem. 2020, 16, 791–797, doi:10.3762/bjoc.16.72

• -membered ring B. The large difference between the LUMO and HOMO leads to an intramolecular charge transfer, resulting in broad absorption bands in the UV–vis spectrum (Figure 3a) [36]. In addition, the LUMO energy of 1 (−2.98 eV) is significantly lower than that of 6 (−2.38 eV), which is responsible for

• aromatic core. In contrast to 6, compound 1 presents a significant difference in the shape of its molecular orbitals. The LUMO of 1 is mainly localized on the core, whereas the HOMO keeps a line of high electron density along the fused five-membered rings (rings A and C in Figure 2d) and the central six

Regio- and stereoselective synthesis of new ensembles of diversely functionalized 1,3-thiaselenol-2-ylmethyl selenides by a double rearrangement reaction

• Svetlana V. Amosova,
• Andrey A. Filippov,
• Nataliya A. Makhaeva,
• Alexander I. Albanov and
• Vladimir A. Potapov

Beilstein J. Org. Chem. 2020, 16, 515–523, doi:10.3762/bjoc.16.47

• group in the six-membered ring 5 are not equivalent. As consequence they are observed in the 1H NMR spectrum as two doublets of doublets with geminal and vicinal coupling constants with the SCH-proton in the same ring (3.79 ppm, 2JН,Н = 12.4 Hz, 3JН,Н = 2.1 Hz; 3.33 ppm, 2JН,Н = 12.4 Hz, 3JН,Н = 6.6 Hz

Combination of multicomponent KA² and Pauson–Khand reactions: short synthesis of spirocyclic pyrrolocyclopentenones

• Riccardo Innocenti,
• Elena Lenci,
• Gloria Menchi and
• Andrea Trabocchi

Beilstein J. Org. Chem. 2020, 16, 200–211, doi:10.3762/bjoc.16.23

• imposed by the adjacent phenyl and cyclohexyl rings [59]. The treatment of compound 5 under Schmidt reaction conditions with sodium azide in TFA [60] resulted in the conversion to the corresponding six-membered ring lactam 39 in 41% yield, demonstrating the reactivity of the enone 5 at the carbonyl group

Functionalization of the imidazo[1,2-a]pyridine ring in α-phosphonoacrylates and α-phosphonopropionates via microwave-assisted Mizoroki–Heck reaction

• Damian Kusy,
• Agata Wojciechowska,
• Joanna Małolepsza and
• Katarzyna M. Błażewska

Beilstein J. Org. Chem. 2020, 16, 15–21, doi:10.3762/bjoc.16.3

• halogen substituent in the imidazo[1,2-a]pyridine ring on its reactivity in the Mizoroki–Heck reaction. We confined our studies to the analogs bearing substituents at positions 6, 7, and 8 of the six-membered ring of the imidazo[1,2-a]pyridine (1a–f, in Figure 1) [24]. We found that the reaction occurred