A new analog of dihydroxybenzoic acid from Saccharopolyspora sp. KR21-0001

• Rattiya Janthanom,
• Yuta Kikuchi,
• Hiroki Kanto,
• Tomoyasu Hirose,
• Arisu Tahara,
• Takahiro Ishii,
• Arinthip Thamchaipenet and
• Yuki Inahashi

Beilstein J. Org. Chem. 2024, 20, 497–503, doi:10.3762/bjoc.20.44

• sp2 methines, one sp3 methine, one sp3 methylene, and one methyl group. The 13C NMR data showed the resonances of twelve carbons, which were classified into six olefinic carbons (including two oxygenated carbons: δC 151.0 and 145.2), three carbonyl carbons, one sp3 methine carbon, one sp3 methylene

Synthesis of 2,2-difluoro-1,3-diketone and 2,2-difluoro-1,3-ketoester derivatives using fluorine gas

• Alexander S. Hampton,
• David R. W. Hodgson,
• Graham McDougald,
• Linhua Wang and
• Graham Sandford

Beilstein J. Org. Chem. 2024, 20, 460–469, doi:10.3762/bjoc.20.41

• of gem-dihalo groups to corresponding CF2 derivatives using silver tetrafluoroborate [5] or mercury(II) fluoride [6], deoxyfluorination of carbonyl derivatives using diethylaminosulfur trifluoride (DAST) or related Deoxo-Fluor and Xtalfluor reagents [7][8]. Alternatively, oxidative

• fluorodesulfurizations of carbonyl derivatives using a combination of sources of halonium and fluoride ions such as 1,3-dibromo-5,5-dimethylhydantoin (DBH) and tetrabutylammonium dihydrogen trifluoride have been achieved [9][10][11]. The transformation of methylene to difluoromethylene using electrophilic fluorinating

Development of a chemical scaffold for inhibiting nonribosomal peptide synthetases in live bacterial cells

• Fumihiro Ishikawa,
• Sho Konno,
• Hideaki Kakeya and
• Genzoh Tanabe

Beilstein J. Org. Chem. 2024, 20, 445–451, doi:10.3762/bjoc.20.39

• of the enterobactin synthetase EntF with Sal-AMS-BPyne requires carbonyl cyanide m-chlorophenylhydrazone, which collapses the proton motive force used in most efflux pumps [17]. Under the same conditions, the competitive inhibition of labeling using excess Sal-AMS is not observed, suggesting that the

Mono or double Pd-catalyzed C–H bond functionalization for the annulative π-extension of 1,8-dibromonaphthalene: a one pot access to fluoranthene derivatives

• Nahed Ketata,
• Linhao Liu,
• Ridha Ben Salem and
• Henri Doucet

Beilstein J. Org. Chem. 2024, 20, 427–435, doi:10.3762/bjoc.20.37

• , carbonyl or nitrile. Using the appropriate arenes, this synthetic route enables the desired functional groups to be introduced at positions 7 to 10 of fluoranthenes. The second method involves a Suzuki coupling followed by an intramolecular C–H bond activation step, and provides access to specific

Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

• Periklis X. Kolagkis,
• Eirini M. Galathri and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36

• step involves the activation of the carbonyl group by the catalyst. This renders it susceptible to a nucleophilic attack from the indole, leading to the formation of the intermediate product. Subsequently, a second nucleophilic attack occurs by another molecule of indole, yielding the final BIM product

• . The difference between the two mechanistic pathways is the nature of activation of the carbonyl group. Protic acids induce the protonation of the carbonyl group of the aldehyde or ketone, enhancing its electrophilic character. Whereas, Lewis acid catalysts bind to the heteroatom of the carbonyl group

• ion activates the carbonyl group of the aldehyde, enabling a nucleophilic attack by a molecule of indole, producing the azafulvenium salt IV. The azafulvenium salt is formed, only when utilizing aromatic aldehydes, as opposed to aliphatic aldehydes, which cannot produce a stable conjugated system

Facile approach to N,O,S-heteropentacycles via condensation of sterically crowded 3H-phenoxazin-3-one with ortho-substituted anilines

• Eugeny Ivakhnenko,
• Vasily Malay,
• Pavel Knyazev,
• Nikita Merezhko,
• Nadezhda Makarova,
• Oleg Demidov,
• Gennady Borodkin,
• Andrey Starikov and
• Vladimir Minkin

Beilstein J. Org. Chem. 2024, 20, 336–345, doi:10.3762/bjoc.20.34

• ][12]. At the first stage, this reaction follows one of three possible reaction pathways, including Schiff base formation (attack at the C(3) center), Michael addition at C(1), or nucleophilic substitution (SNH) at the C(2) center [13][14][15]. Most readily used is the pathway involving carbonyl–amine

Discovery of unguisin J, a new cyclic peptide from Aspergillus heteromorphus CBS 117.55, and phylogeny-based bioinformatic analysis of UngA NRPS domains

• Sharmila Neupane,
• Marcelo Rodrigues de Amorim and
• Elizabeth Skellam

Beilstein J. Org. Chem. 2024, 20, 321–330, doi:10.3762/bjoc.20.32

• . The 1H and 13C NMR spectra of 1 revealed the presence of seven amide NH signals between δH 7.43 and 8.44 ppm supported by the amide carbonyl signals at δC 173.1, 172.6, 172.6, 172.1, 172.1, 171.1 and 171.0 ppm (Table 1). An additional NH signal at δH 10.82 ppm and four aromatic signals at δH 7.50

Photochromic derivatives of indigo: historical overview of development, challenges and applications

• Gökhan Kaplan,
• Zeynel Seferoğlu and
• Daria V. Berdnikova

Beilstein J. Org. Chem. 2024, 20, 228–242, doi:10.3762/bjoc.20.23

• as Li+, Na+ and tetrabutylammonium (TBA+), which could be coordinated by two carbonyl groups of the indoxyl fragments in the Z-form (Figure 9) [45]. The longest half-life of 21.4 min for Z-18c along with the increase of the E–Z conversion in PSS from 32% to 75% was achieved in the presence of Li

• isomerization of N,N'-diacylindigos were measured for the first time. Based on the previous reports, it was expected that inserting further methylene groups as a bridge between the two carbonyl carbons of the oxalyl group in compound 10 would alleviate the conformational restriction and fix the molecules in the

• zwitterionic resonance structures (Figure 3) increases in the excited state of indigo. This partial redistribution of charges, in turn, increases the electrostatic repulsion between the carbonyl groups in the Z-form (Figure 12) resulting in the larger energy gap between HOMO and LUMO and reduced stability for

Copper-catalyzed multicomponent reaction of β-trifluoromethyl β-diazo esters enabling the synthesis of β-trifluoromethyl N,N-diacyl-β-amino esters

• Youlong Du,
• Haibo Mei,
• Ata Makarem,
• Ramin Javahershenas,
• Vadim A. Soloshonok and
• Jianlin Han

Beilstein J. Org. Chem. 2024, 20, 212–219, doi:10.3762/bjoc.20.21

• efficient way for the synthesis of β-trifluoromethyl β-diacylamino esters. Furthermore, this reaction represents the first example of a Mumm rearrangement of β-trifluoromethyl β-diazo esters. Keywords: β-carbonyl diazo; copper catalyst; fluoroalkyl diazo; Mumm rearrangement; unsymmetrical β-diacylamino

• esters, which enriches the studied content of fluoroalkyl diazo compounds. Results and Discussion Due to the instability of β-carbonyl diazo compounds and the occurrence of possible side reactions [58][59][60][61], screening of reaction conditions to optimize this conversion and inhibit the occurrence of

• ][40][41][58][59], a possible mechanism for this Cu-catalyzed reaction of β-trifluoromethyl β-amino esters was proposed in Scheme 4. Initially, β-trifluoromethyl β-amino ester 1a reacts with tert-butyl nitrite to form trifluoromethylated β-carbonyl diazo intermediate A. Then, the diazo intermediate A

Comparison of glycosyl donors: a supramer approach

• Anna V. Orlova,
• Nelly N. Malysheva,
• Maria V. Panova,
• Nikita M. Podvalnyy,
• Michael G. Medvedev and
• Leonid O. Kononov

Beilstein J. Org. Chem. 2024, 20, 181–192, doi:10.3762/bjoc.20.18

• versus α:β = 13:1 for 2). One could speculate that a more nucleophilic carbonyl oxygen of the chloroacetyl group at O-9 in sialyl donor 2 might participate in a stabilization of the intermediate glycosyl cation from the α-side (as we discussed earlier [52][53]) diminishing the α/β ratio. Conversely, at

Tandem Hock and Friedel–Crafts reactions allowing an expedient synthesis of a cyclolignan-type scaffold

• Viktoria A. Ikonnikova,
• Cristina Cheibas,
• Oscar Gayraud,
• Alexandra E. Bosnidou,
• Nicolas Casaretto,
• Gilles Frison and
• Bastien Nay

Beilstein J. Org. Chem. 2024, 20, 162–169, doi:10.3762/bjoc.20.15

• are excellent substrates for such reactions, affording electrophilic carbonyl derivatives susceptible to react with nucleophiles in the acidic reaction mixture [4][5][6][7][8]. Consequently, the Hock rearrangement is likely to be part of tandem processes involving this carbonyl function [9][10][11

• oxocarbenium 7 and 7’ which exists as a stabilized form including an intramolecular stabilizing interaction between the carbocation and the ester carbonyl group. However, in close agreement with Hess and Baldwin’s values found for the rearrangement of cis-1,3-pentadiene [24], this transition state was high in

Perspectives on push–pull chromophores derived from click-type [2 + 2] cycloaddition–retroelectrocyclization reactions of electron-rich alkynes and electron-deficient alkenes

• Michio Yamada

Beilstein J. Org. Chem. 2024, 20, 125–154, doi:10.3762/bjoc.20.13

• intermediate. Subsequently, following the production of an oxide ion through the ring-opening reaction of the 2,5-dihydrofuran ring, the oxide ion attacks another TCNEO molecule. This sequence culminates in the elimination of the tetracyanodioxetane moiety (either as dioxetane or carbonyl dicyanide molecules

Visible-light-induced radical cascade cyclization: a catalyst-free synthetic approach to trifluoromethylated heterocycles

• Chuan Yang,
• Wei Shi,
• Jian Tian,
• Lin Guo,
• Yating Zhao and
• Wujiong Xia

Beilstein J. Org. Chem. 2024, 20, 118–124, doi:10.3762/bjoc.20.12

• 52% (3p) yields, respectively. If the chains did not involve a carbonyl group, the yields were much lower (3q, 25%; 3s, 29%, and 3t, 29%). When a pyrrole ring was used instead of indole, the reaction proceeded but gave the product in low yield (3r). We did not explore the reaction with a primary

Multi-redox indenofluorene chromophores incorporating dithiafulvene donor and ene/enediyne acceptor units

• Christina Schøttler,
• Kasper Lund-Rasmussen,
• Line Broløs,
• Philip Vinterberg,
• Ema Bazikova,
• Viktor B. R. Pedersen and
• Mogens Brøndsted Nielsen

Beilstein J. Org. Chem. 2024, 20, 59–73, doi:10.3762/bjoc.20.8

• expanded by pyrrolo annelation. The optical and redox properties of these compounds, in some cases carbon-rich, were studied by UV–vis absorption spectroscopy and cyclic voltammetry. Synthetically, the work explores IF diones or fluorenone as central building blocks by subjecting the carbonyl groups to a

Using the phospha-Michael reaction for making phosphonium phenolate zwitterions

• Matthias R. Steiner,
• Max Schmallegger,
• Larissa Donner,
• Johann A. Hlina,
• Christoph Marschner,
• Judith Baumgartner and
• Christian Slugovc

Beilstein J. Org. Chem. 2024, 20, 41–51, doi:10.3762/bjoc.20.6

• stabilize the initially formed carbanion as the rate-determining step. A preorganization of the carbonyl bearing Michael acceptors allowed for reasonable fast direct proton transfer from the phenol in aprotic solvents. In contrast, acrylonitrile, not capable of forming a similar preorganization, is hardly

• with several Michael acceptors [34]. In this work we present the formation of stable zwitterions from the reaction of 2,4-di-tert-butyl-6-(diphenylphosphino)phenol (1) and a variety of different Michael acceptors and disclose kinetic investigations on the zwitterion formation with carbonyl and non

• -carbonyl-based Michael acceptors. Results and Discussion Synthesis During our endeavors to identify potent Lewis-base catalysts for the oxa-Michael reaction [13][14], the triarylphosphine 1 was tested in a model reaction (2 equiv allyl alcohol, 1 equiv acrylonitrile, 0.05 equiv 1). However, no conversion

1-Butyl-3-methylimidazolium tetrafluoroborate as suitable solvent for BF₃: the case of alkyne hydration. Chemistry vs electrochemistry

• Marta David,
• Elisa Galli,
• Richard C. D. Brown,
• Marta Feroci,
• Fabrizio Vetica and
• Martina Bortolami

Beilstein J. Org. Chem. 2023, 19, 1966–1981, doi:10.3762/bjoc.19.147

• well-known and useful reaction in organic chemistry, affording carbonyl compounds based on an atom-economical approach. Indeed, the addition of water to the triple bond of a terminal alkyne leads to the formation of the corresponding methyl ketone or aldehyde, in the case of Markovnikov or anti

• -BF4 towards disubstituted alkynes containing a carbonyl group adjacent to the triple bond. This class of substrates, after water addition, yields 1,3-dicarbonyl compounds, which could yield BF2-chelates under our experimental conditions [109]. In order to study their behaviour, we decided to avoid

• ). Unfortunately, any attempt to hydrate disubstituted alkynes containing a carbonyl group adjacent to the triple bond (1m, 1n) with electrogenerated BF3, according to the procedure adopted for the other alkynes, failed, yielding only starting material. We then tried to electrogenerate BF3 in BMIm-BF4, directly in

N-Boc-α-diazo glutarimide as efficient reagent for assembling N-heterocycle-glutarimide diads via Rh(II)-catalyzed N–H insertion reaction

• Grigory Kantin,
• Pavel Golubev,
• Alexander Sapegin,
• Alexander Bunev and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2023, 19, 1841–1848, doi:10.3762/bjoc.19.136

• N–H bond of tetrazoles and 1,2,4-triazole was realized for the first time. This transformation can serve as a powerful tool to carry out N-modification of these heterocycles. Despite all our efforts, it was not possible to obtain N–H insertion products with N-heterocycles containing an α-carbonyl

• group (Figure 2). We observed formation of complex mixtures in the case of δ-valerolactam, glutarimide and oxindole. This observation can be attributed to the competing direction of the attack of the carbenoid onto the carbonyl oxygen atom resulting in unstable intermediates. In the reaction with 5

• have been obtained. Glutarimide-based immunomodulatory drugs (IMiDs) and CRBN ligands. Examples of α-carbonyl NH-heterocycles for which N–H insertion products could not be obtained. Main literature approaches towards α-hetaryl glutarimides 1 (routes A and B) and new “diazo” methodology based on Rh(II

Trifluoromethylated hydrazones and acylhydrazones as potent nitrogen-containing fluorinated building blocks

• Zhang Dongxu

Beilstein J. Org. Chem. 2023, 19, 1741–1754, doi:10.3762/bjoc.19.127

• ], trifluorinated α-methylene-γ-lactams [99][100], and β-trifluoromethyl-β-acylhydrazonyl carbonyl compounds [101] (Scheme 15). Among these fluorinated products, the trifluoromethylated homoallylic acylhydrazines were easily transformed to CF3-substituted pyrazolines and 1,6-dihydropyridazines via a cascade

Effects of the aldehyde-derived ring substituent on the properties of two new bioinspired trimethoxybenzoylhydrazones: methyl vs nitro groups

• Dayanne Martins,
• Roberta Lamosa,
• Talis Uelisson da Silva,
• Carolina B. P. Ligiero,
• Sérgio de Paula Machado,
• Daphne S. Cukierman and
• Nicolás A. Rey

Beilstein J. Org. Chem. 2023, 19, 1713–1727, doi:10.3762/bjoc.19.125

• -acylhydrazones were synthesized and fully characterized, both in solution and in the solid state. The compounds differ with respect to the carbonyl precursors, i.e., 3-substituted salicylaldehydes with either a methyl or a nitro group. Single crystals of both compounds were isolated from the respective mother

• derived from the same 3,4,5-trimethoxybenzoic acid hydrazide, but differ with respect to the carbonyl precursors: herein, 3-substituted salicylaldehydes (Scheme 1) are used, which assure for a harder donor-atoms set in order to target trivalent metal ions such as aluminum(III), which has been proposed to

• experimental absorptions were performed not only with the aid of DFT calculations, but also checked by comparing them to the vibrations of the respective carbonyl and hydrazide precursors. Although the phenol-related ν(O–H) bands could not be accurately identified due to overlapping with the water stretching

Decarboxylative 1,3-dipolar cycloaddition of amino acids for the synthesis of heterocyclic compounds

• Xiaofeng Zhang,
• Xiaoming Ma and
• Wei Zhang

Beilstein J. Org. Chem. 2023, 19, 1677–1693, doi:10.3762/bjoc.19.123

• ][50][51]. However, to the best of our knowledge, there are only few examples on the reactions of N–H-type semi-stabilized AMYs B3 or B4 which were either derived from special carbonyl compounds (such as isatin) [52][53][54][55] or the AMYs were reacted with uncommon alkenes as the 1,3-dipolarophiles

Sulfur-containing spiroketals from Breynia disticha and evaluations of their anti-inflammatory effect

• Ken-ichi Nakashima,
• Naohito Abe,
• Masayoshi Oyama,
• Hiroko Murata and
• Makoto Inoue

Beilstein J. Org. Chem. 2023, 19, 1604–1614, doi:10.3762/bjoc.19.117

• formula of C45H64O28SNa (calcd 1107.3197). The IR spectrum showed absorption peaks corresponding to hydroxy groups (νmax = 3414 cm−1) and carbonyl groups (νmax = 1782 and 1695 cm−1). The 1H NMR signals (Table 1) were characteristic of a breynogenin moiety, namely, a methyl group [δH 0.92 (d, J = 6.9 Hz

• observed resonances including a carbonyl group [δC 212.3 (C-8)], a spiroketal center [δC 100.6 (C-9)], and a p-hydroxybenzoate [δC 167.6 (C-19), 122.7 (C-20), 133.2 (C-21, 25), 116.7 (C-22, 24), 163.4 (C-23)]. The presence of a breynogenin-α-S-oxide moiety was further evidenced by HSQC, HMBC, and double

• correlations of H-5/C-3, H-16/C-3, and H-17/C-4. The linkage between C-6 and C-7 was supported by the HMBC correlations of H-5/C-6 and H-16/C-5. Furthermore, the presence of a carbonyl group was indicated by the HMBC correlations of both H-5 and H-17 with a carbonyl carbon (δC 177.1). Thus, the structure of

Secondary metabolites of Diaporthe cameroonensis, isolated from the Cameroonian medicinal plant Trema guineensis

• Bel Youssouf G. Mountessou,
• Élodie Gisèle M. Anoumedem,
• Blondelle M. Kemkuignou,
• Yasmina Marin-Felix,
• Frank Surup,
• Marc Stadler and
• Simeon F. Kouam

Beilstein J. Org. Chem. 2023, 19, 1555–1561, doi:10.3762/bjoc.19.112

• overlapping at δH 2.28 due to two acetyl groups, which showed strong HMBC cross peaks with the carbonyl carbon signals at δH 169.0. The structure of 2 was fully assigned by using the 13C NMR spectrum which displayed sixteen carbon signals sorted into three methyl signals of which two overlapping ones at δC

Morpholine-mediated defluorinative cycloaddition of gem-difluoroalkenes and organic azides

• Tzu-Yu Huang,
• Mario Djugovski,
• Sweta Adhikari,
• Destinee L. Manning and
• Sudeshna Roy

Beilstein J. Org. Chem. 2023, 19, 1545–1554, doi:10.3762/bjoc.19.111

• ; gem-difluoroalkenes; organic azides; Introduction gem-Difluoroalkenes and their synthetic preparations soared in the last decade, driven by the high demand for carbonyl mimics in medicinal chemistry and drug discovery [1]. Although a wide array of functionalization strategies for gem-difluoroalkenes

• are typically accessed in two ways: (1) direct synthesis using metal or metal-free catalysis and (2) post-functionalization of disubstituted-1,2,3-triazoles [17][18]. The direct synthesis of fully substituted triazoles entails either metal-free carbonyl-based [19][20][21] or metal-mediated and strain

• regioselective reaction that does not rely on carbonyl- or alkyne-based methods or late-stage modifications to access 1,4,5-trisubstituted-1,2,3-triazoles. However, carbonyl chemistry was utilized to synthesize the gem-difluoroalkene starting material [30]. In fact, our findings offer a straightforward direct

Synthesis of 5-arylidenerhodanines in L-proline-based deep eutectic solvent

• Stéphanie Hesse

Beilstein J. Org. Chem. 2023, 19, 1537–1544, doi:10.3762/bjoc.19.110

• ][22]. On the other hand, Pro/Gly DES may also activate carbonyl groups as suggested by Mohire et al. [23] and Theresa et al. [24]. In any event, the DES structure in Pro/Gly seems to play an important role in promoting the reaction. 5-Methylfurfural was selected as another model substrate and similar

Cyclization of 1-aryl-4,4,4-trichlorobut-2-en-1-ones into 3-trichloromethylindan-1-ones in triflic acid

• Vladislav A. Sokolov,
• Andrei A. Golushko,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2023, 19, 1460–1470, doi:10.3762/bjoc.19.105

• -enones) undergo intramolecular transformation into 3-trichloromethylindan-1-ones (CCl3-indanones) in Brønsted superacid CF3SO3H (triflic acid, TfOH) at 80 °C within 2–10 h in yields up to 92%. Protonation of the carbonyl oxygen of the starting CCl3-enones by TfOH affords the key reactive intermediates

• form of the starting compound [Cl3CCH=CHC(=OH+)Me]. The presence of two strong electron-withdrawing substituents, the trichloromethyl group (CCl3) and a protonated carbonyl (C(OH+)Me), at the carbon–carbon double bond makes this O-protonated species electrophilic enough to react with arenes (Scheme 1a

• atoms H2 and H3 in cations Aa,c,d and their neutral precursors 1a,c,d were 0.59–0.86 and 0.28–0.31 ppm (Table 2). These downfield shifts of the signals point to an inductively induced positive charge on these hydrogens due to the protonation of the oxygens of the carbonyl and hydroxy groups. According