Mild and efficient synthesis and base-promoted rearrangement of novel isoxazolo[4,5-b]pyridines

• Vladislav V. Nikol’skiy,
• Mikhail E. Minyaev,
• Maxim A. Bastrakov and
• Alexey M. Starosotnikov

Beilstein J. Org. Chem. 2024, 20, 1069–1075, doi:10.3762/bjoc.20.94

• -b]pyridine took place, followed by a base-promoted decarbonylation/isoxazole ring opening. Such transformations have been previously reported for benzo[d]isoxazoles with a carbonyl or carboxyl group in position 3 or 3-unsubstituted benzo[d]isoxazoles [25][26][27][28][29]. This means that the formyl

Novel route to enhance the thermo-optical performance of bicyclic diene photoswitches for solar thermal batteries

• Akanksha Ashok Sangolkar,
• Rama Krishna Kadiyam and
• Ravinder Pawar

Beilstein J. Org. Chem. 2024, 20, 1053–1068, doi:10.3762/bjoc.20.93

• back isomerization of the photoproduct of type-Id photoswitch to the corresponding diene have resulted in a TS that is associated with undesired thermal degradation (Figure 3). The obtained TS follows a conventional, synchronous and concerted dissociation mechanism to produce the undesired carbonyl

• pathway, however the energetic stability of the parent diene favours the reversible photoswitching. Extending the unsaturated bridge of the bicyclic diene with an –O– unit promotes the thermal degradation of the photoproduct to the carbonyl compounds. Among the studied systems, the bicyclic diene

Structure–property relationships in dicyanopyrazinoquinoxalines and their hydrogen-bonding-capable dihydropyrazinoquinoxalinedione derivatives

• Tural N. Akhmedov,
• Ajeet Kumar,
• Daken J. Starkenburg,
• Kyle J. Chesney,
• Khalil A. Abboud,
• Novruz G. Akhmedov,
• Jiangeng Xue and
• Ronald K. Castellano

Beilstein J. Org. Chem. 2024, 20, 1037–1052, doi:10.3762/bjoc.20.92

• Information File 1). The double substitution did not proceed presumably due to the strong electron-donating effect of -NH2, diminishing the electrophilicity of the π-system. However, the mono-aminated product 16f has the potential to serve as a useful building block for condensation with carbonyl

• -crystal X-ray analysis of 2b, and its important structural parameters were compared with that of 2a (#CCDC 227464) reported in the literature [25]. An improved 2D nanostructure through highly ordered organization facilitated by H-bonding is revealed. Notably, the C–C distance between two carbonyl groups

• respect to the carbonyl groups (Figure 6b) and 5.25° concerning peripheral rings 1 and 3 (Figure 6c). The unit cell is composed of a dimer of 2b held together by intermolecular N–H∙∙∙N and C–H∙∙∙O=C H-bonds with average distances of 2.30 Å and 2.28 Å, respectively (Figure 6d and 6e). The herringbone

Carbonylative synthesis and functionalization of indoles

• Alex De Salvo,
• Raffaella Mancuso and
• Xiao-Feng Wu

Beilstein J. Org. Chem. 2024, 20, 973–1000, doi:10.3762/bjoc.20.87

• , the metal-catalyzed direct C–H carbonylation of indoles is an effective and straightforward approach to synthesize indole derivatives containing a carbonyl function in position 3. On the other hand, only a few examples to synthesize indole-2-carbonyl derivatives have been realized. One example is the

Enantioselective synthesis of β-aryl-γ-lactam derivatives via Heck–Matsuda desymmetrization of N-protected 2,5-dihydro-1H-pyrroles

• Arnaldo G. de Oliveira Jr.,
• Martí F. Wang,
• Rafaela C. Carmona,
• Danilo M. Lustosa,
• Sergei A. Gorbatov and
• Carlos R. D. Correia

Beilstein J. Org. Chem. 2024, 20, 940–949, doi:10.3762/bjoc.20.84

• very little influence in the enantiomeric ratios, although electron-donating groups performed slightly better in terms of yield, as observed before for the N-Boc-protected pyrrolines. Weak electron-donating groups such as the methyl group furnished compound 4bj in a higher yield and good er. Carbonyl

Direct synthesis of acyl fluorides from carboxylic acids using benzothiazolium reagents

• Lilian M. Maas,
• Alex Haswell,
• Rory Hughes and
• Matthew N. Hopkinson

Beilstein J. Org. Chem. 2024, 20, 921–930, doi:10.3762/bjoc.20.82

• fluoride 2, carbonyl sulfide and another fluoride ion. As a result of this pathway, each molecule of the BT-SCF3 reagent can in principle lead to the formation of two molecules of acyl fluoride 2. Indeed, a yield of 2a above 50% was observed during the optimisation studies using 0.5 equiv of BT-SCF3 (Table

Synthesis and properties of 6-alkynyl-5-aryluracils

• Ruben Manuel Figueira de Abreu,
• Till Brockmann,
• Alexander Villinger,
• Peter Ehlers and
• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 898–911, doi:10.3762/bjoc.20.80

• intermediate. A second effect appears to play a more important role and could be related to the structure of the starting material. The 6-position is part of an enamine and an α,β-unsaturated carbonyl structure, as depicted in Scheme 3. According to the mesomeric structure of the enamine, the 6-position could

(Bio)isosteres of ortho- and meta-substituted benzenes

• H. Erik Diepers and
• Johannes C. L. Walker

Beilstein J. Org. Chem. 2024, 20, 859–890, doi:10.3762/bjoc.20.78

• . Fessard, Salomé and co-workers used this approach to synthesise a small collection of 2-oxo-BCHs including 42 and 44 (Scheme 4A) [40]. These could then be used as precursors for ortho-benzene isosteric 1,2-BCHs (Scheme 4B) [40]. Carbonyl reduction of 42a yielded alcohol (±)-45a. From 42b, Wittig

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

• that the only difference between compounds 3 and 2 is the position of the hydroxy group [28]. Analyses of the NMR data of compound 4 concluded that it is an analogue of 2. In comparison with 2, compound 4 has a ketone carbonyl signal at δC 219.1 and we finally confirmed its structure by comparing it

Research progress on the pharmacological activity, biosynthetic pathways, and biosynthesis of crocins

• Zhongwei Hua,
• Nan Liu and
• Xiaohui Yan

Beilstein J. Org. Chem. 2024, 20, 741–752, doi:10.3762/bjoc.20.68

• enzymes in crocin biosynthetic pathways CCDs: Crocin biosynthesis initiates with the catalytic cleavage of the C‒C double bond by CCDs at various sites of the carotenoid skeleton. The cleavage generates a carbonyl group at the end of the formed carotenoid derivatives [88]. The CCD family can be

Substrate specificity of a ketosynthase domain involved in bacillaene biosynthesis

• Zhiyong Yin and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2024, 20, 734–740, doi:10.3762/bjoc.20.67

• performed to eliminate any unreacted free 11 in the reaction mixture. The resulting protein preparations were subsequently analysed by 13C NMR spectroscopy. While the signal for the thioester carbonyl group of free 11 dissolved in incubation buffer was observed at δ = 203.33 ppm (Figure 1A), for both

• sample was subsequently subjected to another round of centrifugation using an ultrafiltration centrifugal tube, resulting in the detection of a signal for a thioester carbonyl group in the filtrate for both samples derived from (S)- and (R)-11 at δ = 203.35 ppm (Figure 1E). This observation supports

• incubation buffer as described above was applied. No signal corresponding to a thioester carbonyl group was detected in the protein preparations (Figure 1F), while signals at δ = 203.33 ppm for free 11 were observed in the filtrates obtained after the first step (Figure 1G). Conclusion Taken together, we

Isolation and structure determination of a new analog of polycavernosides from marine Okeania sp. cyanobacterium

• Kairi Umeda,
• Naoaki Kurisawa,
• Ghulam Jeelani,
• Tomoyoshi Nozaki,
• Kiyotake Suenaga and
• Arihiro Iwasaki

Beilstein J. Org. Chem. 2024, 20, 645–652, doi:10.3762/bjoc.20.57

• )/δC 206.9 (C-9) connected C-11 and C-8 through a ketone carbonyl carbon at C-9 and hemiacetal carbon at C-10, revealing the 16-membered macrolide structure of 1. The HMBC, δH 4.27 (H-1’)/δC 85.3 (C-5), revealed that the disaccharide moiety was connected to C-5. Finally, considering the molecular

Production of non-natural 5-methylorsellinate-derived meroterpenoids in Aspergillus oryzae

• Jia Tang,
• Yixiang Zhang and
• Yudai Matsuda

Beilstein J. Org. Chem. 2024, 20, 638–644, doi:10.3762/bjoc.20.56

• instead of the C-4′ carbonyl group (Figure 2C). It is unlikely that 8 is the direct product of InsA7; thus, we hypothesized that an endogenous enzyme in A. oryzae is responsible for the reduction, with an enoylreductase first reducing the C-2′/C-3′ double bond of 7 and the resulting product undergoing

HPW-Catalyzed environmentally benign approach to imidazo[1,2-a]pyridines

• Luan A. Martinho and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2024, 20, 628–637, doi:10.3762/bjoc.20.55

• report from the literature [24] a plausible reaction mechanism is shown in Scheme 6. It involves the nucleophilic attack of the aminopyridine 1 to the HPW-activated carbonyl compound 2, followed by iminium ion formation (iii) and [4 + 1] cycloaddition with the isocyanide. A 1,3-hydrogen shift yields the

Chemical and biosynthetic potential of Penicillium shentong XL-F41

• Ran Zou,
• Xin Li,
• Xiaochen Chen,
• Yue-Wei Guo and
• Baofu Xu

Beilstein J. Org. Chem. 2024, 20, 597–606, doi:10.3762/bjoc.20.52

• enzymatic ring-expansion process in their respective fungi. Both shentonins A (1) and B (2) also feature a reduction of a carbonyl to a hydroxy group within the succinimide ring. All isolated compounds were subjected to antimicrobial evaluations, and compound 12 was found to have moderate inhibitory

• m/z 341.1862 [M − H]− (calcd for C20H25N2O3, 341.1870). Spectroscopic analysis, including 1H NMR, 13C NMR (Table 1), and DEPT, revealed that compound 1 contains three methyl groups, one of which is oxygenated, four methines, three saturated non-protonated carbons, and two ketone carbonyl carbons (δC

• carbonyl carbon (δC 174.6). Its NMR profile is similar to brocaeloid C [24], with the distinction of an added succinimide substructure at N-15, where the ketone carbonyl carbon at C-16 is replaced by a hydroxy carbon. The isoprene group is consistent with that in compound 1. HMBC cross-peaks from H-10 to C

Synthesis of photo- and ionochromic N-acylated 2-(aminomethylene)benzo[b]thiophene-3(2Н)-ones with a terminal phenanthroline group

• Vladimir P. Rybalkin,
• Sofiya Yu. Zmeeva,
• Lidiya L. Popova,
• Irina V. Dubonosova,
• Olga Yu. Karlutova,
• Oleg P. Demidov,
• Alexander D. Dubonosov and
• Vladimir A. Bren

Beilstein J. Org. Chem. 2024, 20, 552–560, doi:10.3762/bjoc.20.47

• vibrations of the thiophene and amide carbonyl groups were observed at 1663–1678 and 1705–1713 cm−1, respectively. The 1H NMR spectra contained signals of methine protons (=CH–) in the region 7.92–9.02 ppm, which corresponded to the Z-configuration of the C=C bond. According to data previously obtained [14

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

Ligand effects, solvent cooperation, and large kinetic solvent deuterium isotope effects in gold(I)-catalyzed intramolecular alkene hydroamination

• Ruichen Lan,
• Brock Yager,
• Yoonsun Jee,
• Cynthia S. Day and
• Amanda C. Jones

Beilstein J. Org. Chem. 2024, 20, 479–496, doi:10.3762/bjoc.20.43

• localized due to the strong competitive carbonyl resonance donation of the non-attacking nitrogen. Weaker competitive donation from the more electronegative oxygen, and the less electron-donating phenyl, would lead to decreasing nucleophilicity, respectively, for the carbamate and benzamide attacking

• nitrogen. Thus, the rate of intramolecular hydroamination is enhanced by a more nucleophilic nitrogen. Another qualitative interpretation is that rates are enhanced by carbonyl basicity. Gas-phase basicity measurements indicate that ureas are more basic than amides [47][50], and here the most Lewis base

• with alkene but also the urea carbonyl. The Bronsted acidity of the urea would be increased by coordination to gold, and if such coordination is key to enabling reactivity, this would confirm the higher reactivity of urea 1a. The divergent behavior of sulfonamide 1d does not find an easy explanation

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