Synthesis, structure, ionochromic and cytotoxic properties of new 2-(indolin-2-yl)-1,3-tropolones

• Yurii A. Sayapin,
• Eugeny A. Gusakov,
• Inna O. Tupaeva,
• Alexander D. Dubonosov,
• Igor V. Dorogan,
• Valery V. Tkachev,
• Anna S. Goncharova,
• Gennady V. Shilov,
• Natalia S. Kuznetsova,
• Svetlana Y. Filippova,
• Tatyana A. Krasnikova,
• Yanis A. Boumber,
• Alexey Y. Maksimov,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2025, 21, 358–368, doi:10.3762/bjoc.21.26

• spectrum of 7a, a correlation of the NH proton with the bridging carbon atoms C(3a'), C(9b'), and the quaternary carbon atom C(1') of the indolenine fragment is observed with δH 136.6 ppm, 134.0 ppm, and 53.6 ppm, respectively (Supporting Information File 2, Figure S20). The most important HMBC

Dioxazolones as electrophilic amide sources in copper-catalyzed and -mediated transformations

• Seungmin Lee,
• Minsuk Kim,
• Hyewon Han and
• Jongwoo Son

Beilstein J. Org. Chem. 2025, 21, 200–216, doi:10.3762/bjoc.21.12

• enantioselectivity. Furthermore, a lactam containing a quaternary carbon center (2g) was prepared. However, a lower enantioselectivity was observed for product 2h due to the similar steric environment of the two alkyl substituents. As shown in Figure 1, a catalytic cycle was proposed for the intramolecular C–H

Non-covalent organocatalyzed enantioselective cyclization reactions of α,β-unsaturated imines

• Sergio Torres-Oya and
• Mercedes Zurro

Beilstein J. Org. Chem. 2024, 20, 3221–3255, doi:10.3762/bjoc.20.268

• , Mei and co-workers reported a chiral phosphoric acid-catalyzed asymmetric intermolecular formal (3 + 2) cycloaddition of azoalkenes 53 with azlactones 15 (Scheme 28). This methodology provides fully substituted 4-pyrrolin-2-ones 78 bearing a quaternary carbon atom in high yields (72–95%) and

A review of recent advances in electrochemical and photoelectrochemical late-stage functionalization classified by anodic oxidation, cathodic reduction, and paired electrolysis

• Nian Li,
• Ruzal Sitdikov,
• Ajit Prabhakar Kale,
• Joost Steverlynck,
• Bo Li and
• Magnus Rueping

Beilstein J. Org. Chem. 2024, 20, 2500–2566, doi:10.3762/bjoc.20.214

Electrophotochemical metal-catalyzed synthesis of alkylnitriles from simple aliphatic carboxylic acids

• Yukang Wang,
• Yan Yao and
• Niankai Fu

Beilstein J. Org. Chem. 2024, 20, 1497–1503, doi:10.3762/bjoc.20.133

• functional handles for further elaboration. Notably, tertiary arylacetic acids can also be well tolerated to yield nitriles with quaternary carbon centers in good yields (17 and 18). Simple carboxylic acids without functional groups at the alpha position to stabilize the corresponding carbon centered

Domino reactions of chromones with activated carbonyl compounds

• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 1256–1269, doi:10.3762/bjoc.20.108

• minor products as well (7–20% yields). The formation of biphenyls 44 can be explained by 1,4-addition and ring-cleavage to give intermediate AH, aldol reaction (intermediate AI), migration of the ester group from the quaternary carbon to the phenolic oxygen atom (intermediate AJ) and aromatization. The

Discovery and biosynthesis of bacterial drimane-type sesquiterpenoids from Streptomyces clavuligerus

• Dongxu Zhang,
• Wenyu Du,
• Xingming Pan,
• Xiaoxu Lin,
• Fang-Ru Li,
• Qingling Wang,
• Qian Yang,
• Hui-Min Xu and
• Liao-Bin Dong

Beilstein J. Org. Chem. 2024, 20, 815–822, doi:10.3762/bjoc.20.73

• methyl groups at δH (0.83, 0.87, 0.98 and 1.77). Its 13C and DEPT NMR spectra showed 15 carbon resonances, including four methyl groups, four methylenes, four methines, and three quaternary carbon atoms. This information suggests that it may be a drimenol congener and the structure was further supported

Aldiminium and 1,2,3-triazolium dithiocarboxylate zwitterions derived from cyclic (alkyl)(amino) and mesoionic carbenes

• Nedra Touj,
• François Mazars,
• Guillermo Zaragoza and
• Lionel Delaude

Beilstein J. Org. Chem. 2023, 19, 1947–1956, doi:10.3762/bjoc.19.145

• the orange plates of compound 4c belonged to the monoclinic P21/c group. Due to the asymmetry of the quaternary carbon atom adjacent to the carbene center, the latter compound crystallized as a racemic mixture. Solutions of MIC·CS2 zwitterions 6a–f in CD2Cl2 or CDCl3 employed for NMR analyses were

• contrast with the most common cyclization processes leading to imidazol(in)ium derivatives, which afford symmetrical products with identical substituents on both nitrogen atoms [82]. Although cyclic aldiminium salts are less readily available, they feature a quaternary carbon atom next to the carbenoid

Recent advancements in iodide/phosphine-mediated photoredox radical reactions

• Tinglan Liu,
• Yu Zhou,
• Junhong Tang and
• Chengming Wang

Beilstein J. Org. Chem. 2023, 19, 1785–1803, doi:10.3762/bjoc.19.131

• ]. Importantly, these methodologies could also be smoothly extended to the synthesis of isoquinolinediones, which borne a quaternary carbon center. Furthermore, Yatham and his colleagues unveiled the first NaI/PPh3-mediated photocatalytic decarboxylative cascade cyclization of 2-isocyanobiaryls 44 with alkyl N

Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• -workers [61] extended the application of NHC–copper catalysts to the conjugate addition of boronates to acyclic α,β-unsaturated carboxylic esters, ketones, and thioesters leading to the enantioselective formation of boron-substituted quaternary carbon stereogenic centers (Scheme 43). All transformations

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

• compound 8b revealed only a single signal of a carbonyl carbon at 193.2 ppm, and a signal of a quaternary carbon at 167.0 ppm, which could not be assigned. These spectral data prompted us to reconsider the structure of compound 8b. The reaction of chlorinated nitrostyrene 2b with acetylacetone (3b) was in

Eschenmoser coupling reactions starting from primary thioamides. When do they work and when not?

• Lukáš Marek,
• Jiří Váňa,
• Jan Svoboda and
• Jiří Hanusek

Beilstein J. Org. Chem. 2023, 19, 808–819, doi:10.3762/bjoc.19.61

• lactam 2 structure involving the replacement of a quaternary carbon carrying two electron-donating methyl groups with an electron-withdrawing carbonyl group (2b → 3). The starting isoquinoline-1,3(2H,4H)-dione was prepared [31] from homophthalic acid and then brominated with NBS to give 4

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

• can operate as an efficient photoredox catalyst, providing an economical access to construct important oxindole scaffolds containing a quaternary carbon center. This synthetic method features a broad substrate scope, good functional group tolerance and operational simplicity. Mechanistic

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

• consecutive all-carbon quaternary carbon atoms [54][55][56]. Preliminary biological screening of this family revealed notable antibacterial and anticancer activities due to the α-methylene lactone moiety they bear [57]. Recently, in order to synthesize the common core present in crinipellins, Xie and Ding’s

Synthetic study toward tridachiapyrone B

• Morgan Cormier,
• Florian Hernvann and
• Michaël De Paolis

Beilstein J. Org. Chem. 2022, 18, 1741–1748, doi:10.3762/bjoc.18.183

• ’-methoxy-γ-pyrone in one step. To construct the quaternary carbon of the 2,5-cyclohexadienone of the target, a strategy based on the Robinson-type annulation of an aldehyde derived from α-crotyl-α’-methoxy-γ-pyrone was applied. The grafting of the simplified target’s side chain was demonstrated through an

• oxidative anionic oxy-Cope rearrangement of the tertiary alcohol arising from the 1,2-addition of a 1,3-dimethylallyl reagent to 2,5-cyclohexadienone connected to the α’-methoxy-γ-pyrone motif. Keywords: α’-methoxy-γ-pyrone; 2,5-cyclohexadienone; oxy-Cope; quaternary carbon; Robinson-type annulation

• ; Introduction The α’-methoxy-γ-pyrone motif is present in natural products and bioactive molecules [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Amidst these targets, a number contains a quaternary carbon vicinal to the scaffold, such as crispatene and photodeoxytridachione (Scheme 1a) [15]. These molecules

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

• one quaternary carbon stereocenter and 1,2-dikeone moiety, Nazarov cyclization [33] of 7 was proposed for synthesizing this challenging moiety. The corresponding precursor cyclopentenone 8 may be prepared from alkynone 9 through a gold-catalyzed C–H insertion [34]. Alkynone 9 could be achieved through

Terpenoids from Glechoma hederacea var. longituba and their biological activities

• Dong Hyun Kim,
• Song Lim Ham,
• Zahra Khan,
• Sun Yeou Kim,
• Sang Un Choi,
• Chung Sub Kim and
• Kang Ro Lee

Beilstein J. Org. Chem. 2022, 18, 555–566, doi:10.3762/bjoc.18.58

• displayed 26 carbon signals including two oxygenated carbons (δC 85.8 and 72.4), an oxygenated quaternary carbon (δC 79.5), and a glucopyranosyl unit (δC 101.9, 78.3, 77.7, 75.2, 71.9, and 63.0) (Table 3). These 1H and 13C NMR spectra of 4 were similar to those of ent-kauran-3α,12α,16α-triol except for an

• = 11.8, 5.7 Hz), 3.54 (1H, t, J = 9.3 Hz), 3.39 (1H, t, J = 9.3 Hz), and 3.28 (1H, ddd, J = 9.7, 5.7, 2.2 Hz)]. The 13C NMR spectrum of 5 displayed 28 carbon signals including two oxygenated carbons (δC 85.5 and 72.4), an oxygenated quaternary carbon (δC 79.6), a glucopyranosyl unit (δC 99.5, 75.7, 76.3

Four bioactive new steroids from the soft coral Lobophytum pauciflorum collected in South China Sea

• Di Zhang,
• Zhe Wang,
• Xiao Han,
• Xiao-Lei Li,
• Zhong-Yu Lu,
• Bei-Bei Dou,
• Wen-Ze Zhang,
• Xu-Li Tang,
• Ping-Lin Li and
• Guo-Qiang Li

Beilstein J. Org. Chem. 2022, 18, 374–380, doi:10.3762/bjoc.18.42

• oxygenated sp3 secondary carbon (δC 76.3) and one oxygenated sp3 quaternary carbon (δC 74.2). As two of the six degrees of unsaturation were occupied by the double bond and carbonyl group, the remaining four unsaturations of 1 corresponded to a tetracyclic skeleton. The 1H,1H-COSY experiment (Figure 2

Amamistatins isolated from Nocardia altamirensis

• Till Steinmetz,
• Wolf Hiller and
• Markus Nett

Beilstein J. Org. Chem. 2022, 18, 360–367, doi:10.3762/bjoc.18.40

• the basis of 2D NMR data. In the HMBC spectrum, the singlet methyl protons H3-17 and H3-18 show correlations to C-7, a quaternary carbon at 47.4 ppm (C-8), and an oxymethine carbon at 80.3 ppm (C-9). COSY and HMBC data established the alkyl chain from CH-9 to CH3-16. A correlation between H-9 and C-19

Organocatalytic asymmetric nitroso aldol reaction of α-substituted malonamates

• Ekta Gupta,
• Narendra Kumar Vaishanv,
• Sandeep Kumar,
• Raja Krishnan Purshottam,
• Ruchir Kant and
• Kishor Mohanan

Beilstein J. Org. Chem. 2022, 18, 217–224, doi:10.3762/bjoc.18.25

• with nitrosoarene which provides facile access to chiral hydroxyamino malonamates having a quaternary carbon stereocenter (Scheme 1). Results and Discussion Initially, we chose the Takemoto catalyst to promote the model reaction between methyl N-bromophenyl-α-methylmalonamate (1a) and nitrosobenzene

Regioselective synthesis of methyl 5-(N-Boc-cycloaminyl)-1,2-oxazole-4-carboxylates as new amino acid-like building blocks

• Jolita Bruzgulienė,
• Greta Račkauskienė,
• Aurimas Bieliauskas,
• Vaida Milišiūnaitė,
• Miglė Dagilienė,
• Gita Matulevičiūtė,
• Vytas Martynaitis,
• Sonata Krikštolaitytė,
• Frank A. Sløk and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2022, 18, 102–109, doi:10.3762/bjoc.18.11

• . The 1H,13C-HMBC spectrum of compound 4a revealed that the methylene protons from the azetidine moiety and the 1,2-oxazole methine proton H-3, exhibited long-range correlations with quaternary carbon C-5 (Figure 2c). The aforementioned protonated carbons C-3 and C-3’ showed correlations in the 1,1

Unsaturated fatty acids and a prenylated tryptophan derivative from a rare actinomycete of the genus Couchioplanes

• Shun Saito,
• Kanji Indo,
• Naoya Oku,
• Hisayuki Komaki,
• Masashi Kawasaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2021, 17, 2939–2949, doi:10.3762/bjoc.17.203

• former two fragments were intervened by an sp2 quaternary carbon (C-4) substituted by an allylic methyl group (H-11) based on HMBC correlations from H-11 to C-3, C-4, and C-5. Another intervention by a methylene unit (C-8) to connect the second and third fragments was supported by HMBC correlations from

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• regio- and stereoselective γ-addition reaction of isoxazol-5(4H)-ones 103 to β,γ-alkynyl-α-imino esters 102 for the synthesis of axially chiral tetrasubstituted α-amino allenoates 104 containing an adjacent quaternary carbon stereocenter and an axially chiral tetrasubstituted allene scaffold [104

Isolation and characterization of new phenolic siderophores with antimicrobial properties from Pseudomonas sp. UIAU-6B

• Emmanuel T. Oluwabusola,
• Olusoji O. Adebisi,
• Fernando Reyes,
• Kojo S. Acquah,
• Mercedes De La Cruz,
• Larry L. Mweetwa,
• Joy E. Rajakulendran,
• Digby F. Warner,
• Deng Hai,
• Rainer Ebel and
• Marcel Jaspars

Beilstein J. Org. Chem. 2021, 17, 2390–2398, doi:10.3762/bjoc.17.156

• acid unit, confirmed by long-range correlations observed in the HMBC spectrum from H-2, H-4 to C-6 (δC 113.2), and H-5 to the quaternary carbon C-7 (δC 170.0). On the other hand, the COSY spectrum confirmed the presence of a CH3–CH–CH spin system (H3-12, H-11, and H-9) reminiscent of a threonine unit

• carboxamide C-10 (δC 172.9) and the quaternary carbon C-16 (δC 140.2), between H2-15 and H-18/20 to the quaternary carbon C-16, and a strong correlation from H-15 and H-19 to C-17/20 (δC 129.9). The new oxazoline derivative 5 was named pseudomonbactin B. The absolute configuration of the threonine residue in

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

• for the synthesis of 1,4-dihydroquinoline 129 possessing a quaternary carbon center from 128 [93]. The reaction was reported via a seven-membered bicyclic hemiaminal as mentioned in the mechanism. This catalytic rearrangement protocol was successfully applied for the construction of complex carbon

• Yamamoto et al [116]. The catalytic pathway was proved to involve the direct H-transfer to the vinylmercury complex from the aromatic ring. It involved Hg(OTf)2-catalyzed cyclization of aryl 1,1-disubstituted allenes with the formation of a quaternary carbon center followed by the formation of a cationic