A one-pot electrochemical synthesis of 2-aminothiazoles from active methylene ketones and thioureas mediated by NH₄I

• Shang-Feng Yang,
• Pei Li,
• Zi-Lin Fang,
• Sen Liang,
• Hong-Yu Tian,
• Bao-Guo Sun,
• Kun Xu and
• Cheng-Chu Zeng

Beilstein J. Org. Chem. 2022, 18, 1249–1255, doi:10.3762/bjoc.18.130

•  1b). Alternatively, the oxidation of α-C–H of active methylene ketones generate α-carbon-centered radicals, thus providing another way to obtain thiazoles. Recently, Sun et al. reported a tert-butyl hydroperoxide/azodiisobutyronitrile-mediated synthesis of 2-aminothiazoles from active methylene

• produce α-iodo ketone with the molecular I2 produced by anodic oxidation. Subsequently, the nucleophilic substitution between intermediate 4 and thiourea tautomer gives α-sulfur substituted ketone 5. Intermediate 5 undergoes intramolecular nucleophilic addition to the carbonyl group and followed by

Vicinal ketoesters – key intermediates in the total synthesis of natural products

• Marc Paul Beller and
• Ulrich Koert

Beilstein J. Org. Chem. 2022, 18, 1236–1248, doi:10.3762/bjoc.18.129

• with Davis’ oxaziridine and subsequent oxidation using Dess–Martin periodinane. Initial attempts for the key step (15 → 16) like a Nozaki–Hiyama–Kishi reaction failed, but lithium–halogen exchange using t-BuLi at low temperatures gave the desired vinyllithium intermediate I which successfully added to

• ]. DMP oxidation of α-hydroxyester 21 and subsequent cycloisomerization led to the desired cyclization product 23 via transition state II in a dr of 5:1. Final deprotection gave preussochromone A (24). (−)-Preussochromone D A similar approach was chosen in the synthesis of the structurally related

• natural product preussochromone D (30) reported by Koert et al. [13]. The synthesis commenced with the efficient production of alcohol 26 from 5-hydroxy-4H-chromen-4-one (25, Scheme 5) [14]. The ketoester moiety was build up via oxidation and nucleophilic addition of methyl diazoacetate, yielding alcohol

Mechanochemical bottom-up synthesis of phosphorus-linked, heptazine-based carbon nitrides using sodium phosphide

• Blaine G. Fiss,
• Georgia Douglas,
• Michael Ferguson,
• Jorge Becerra,
• Jesus Valdez,
• Trong-On Do,
• Tomislav Friščić and
• Audrey Moores

Beilstein J. Org. Chem. 2022, 18, 1203–1209, doi:10.3762/bjoc.18.125

• nitrogen environments, centered on 399.0 eV and 400.7 eV, respectively [16][40] (Figure 2b). This suggests that while the majority of the heptazine ring remained pyridinic in nature, partial reduction of the ring structure, due to the reductive nature of Na3P and mild oxidation during ambient workup

• following milling and aging, can also have occurred. Additionally, the phosphorus 2p signal in g-h-PCN showed the majority of phosphorus exists as a mixture of P=O and P–O species, with a major peak centered at 133.6 eV (69%, Figure 2c). These species are formed by oxidation with air and hydrolysis upon

Lewis acid-catalyzed Pudovik reaction–phospha-Brook rearrangement sequence to access phosphoric esters

• Jin Yang,
• Dang-Wei Qian and
• Shang-Dong Yang

Beilstein J. Org. Chem. 2022, 18, 1188–1194, doi:10.3762/bjoc.18.123

• Jin Yang Dang-Wei Qian Shang-Dong Yang State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, P. R. China State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Lanzhou 730000, P. R. China 10.3762/bjoc.18.123 Abstract

Reductive opening of a cyclopropane ring in the Ni(II) coordination environment: a route to functionalized dehydroalanine and cysteine derivatives

• Oleg A. Levitskiy,
• Olga I. Aglamazova,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2022, 18, 1166–1176, doi:10.3762/bjoc.18.121

• moiety may be expected to be more prone to the ring opening, and the irreversibility of the cathodic redox process observed in the voltammograms (Epc = −1.60 V vs Ag/AgCl, KCl(sat.) for 3 and Epc = −1.50 V for 4; Figure 1) supported the suggestion. In the reverse anodic scan, a new oxidation peak (A in

Synthesis of tryptophan-dehydrobutyrine diketopiperazine and biological activity of hangtaimycin and its co-metabolites

• Houchao Xu,
• Anne Wochele,
• Minghe Luo,
• Gregor Schnakenburg,
• Yuhui Sun,
• Heike Brötz-Oesterhelt and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2022, 18, 1159–1165, doi:10.3762/bjoc.18.120

• responsible for the oxidation of deoxyhangtaimycin (3), a compound with antiviral activity, to 1 [8]. The thereby installed hemiaminal function is also the breaking point for 1 into a larger lactone-polyene peptide fragment and a smaller fragment HTM222 (2, named after its molecular mass of 222 Da) [2

Electro-conversion of cumene into acetophenone using boron-doped diamond electrodes

• Mana Kitano,
• Tsuyoshi Saitoh,
• Shigeru Nishiyama,
• Yasuaki Einaga and
• Takashi Yamamoto

Beilstein J. Org. Chem. 2022, 18, 1154–1158, doi:10.3762/bjoc.18.119

• , where the BDD’s wide potential window enables the direct anodic oxidation of cumene into the cumyl cation. Since electricity is directly employed as the oxidizing and reducing reagents, the present protocol is easy to use, suitable for scale-up, and inherently safe. Keywords: aromatic alkyl; boron

• -doped diamond electrode; electrosynthesis; oxidation; Introduction Selective oxidation of aromatic alkyl side chains is an important molecular transformation process to obtain various rubbers, resins, fine chemicals, and other industrial products [1][2]: terephthalic acid from p-xylene, cumene

• hydroperoxide/dicumyl peroxide/phenol from cumene, acetophenone from ethylbenzene, and others. Generally, molecular oxygen has been utilized in the straightforward oxidation of aromatic alkyls. However, since molecular oxygen is highly stable, activation of the molecular oxygen itself is necessary, which

Synthesis of protected precursors of chitin oligosaccharides by electrochemical polyglycosylation of thioglycosides

• Md Azadur Rahman,
• Kana Kuroda,
• Hirofumi Endo,
• Norihiko Sasaki,
• Tomoaki Hamada,
• Hiraku Sakai and
• Toshiki Nokami

Beilstein J. Org. Chem. 2022, 18, 1133–1139, doi:10.3762/bjoc.18.117

• electrochemical polyglycosylation is also discussed, based on the oxidation potential of the monomer and oligosaccharides. Keywords: electrochemical glycosylation; glucosamine; oligosaccharide; oxidation potential; polyglycosylation; Introduction Chitin oligosaccharides are partial structures of chitin, which

• process, which involved anodic oxidation at −80 °C and glycosylation at −50 °C. The crude product of the reaction was purified by gel permeation chromatography (GPC), and the monosaccharides 1a–d and oligosaccharides 2a–d (n = 2)–7a–d (n = 7) were isolated. Only thioglycoside 1a (Ar = 4-FC6H4, Eox = 1.70

• . Contrary, thioglycoside 1c (Ar = 4-MeC6H4, Eox = 1.47 V vs SCE), which had the lowest oxidation potential, showed the lowest conversion (51%) and the lowest yield of tetrasaccharide 4c (2%) [8]. This being the case, lower conversion of the building block 1c and lower yield of oligosaccharides 2c–4c

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

• , single-electron oxidation of an electron-rich dienophile generates its radical cation which is then trapped by the diene (Figure 1). Since the forming cyclohexene remains in the radical cation state as well, one electron reduction is required to complete the net redox neutral transformation. Therefore, a

• electrochemistry in most cases, probably because both single-electron oxidation and reduction are made possible at the same surface [45]. This is especially true for the radical cation Diels–Alder reaction, since non-substituted β-methylstyrene, which was previously reported as an unsuccessful dienophile, was

Scope of tetrazolo[1,5-a]quinoxalines in CuAAC reactions for the synthesis of triazoloquinoxalines, imidazoloquinoxalines, and rhenium complexes thereof

• Laura Holzhauer,
• Chloé Liagre,
• Olaf Fuhr,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2022, 18, 1088–1099, doi:10.3762/bjoc.18.111

• to the triazoloquinoxaline complexes 27a–d. To characterize the electrochemical properties of the obtained complexes, cyclic voltammetry measurements were performed. For complexes 27a–d, irreversible oxidation previously assigned to the Re(I)/Re(II) couple [38][45] can be observed at 1.6 V vs SCE

• (see Table 3 and Figure 2); for complexes 29 and 30, this peak is shifted towards 1.4 V, indicating the stronger electron-donating nature of the ligands [38]. Moreover, an additional oxidation state at 1.91 V is present for complex 30 (see Supporting Information File 1 for full trace). For the other

• compounds, this oxidation state is hardly recognizable as it is almost hidden beneath the increase of the curve related to oxidation of the solvent. Scanning towards negative potentials, two reduction waves can be observed between −0.6 V and −1.5 V for complexes 27a–d that can be assigned to reduction of

Facile and diastereoselective arylation of the privileged 1,4-dihydroisoquinolin-3(2H)-one scaffold

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

Beilstein J. Org. Chem. 2022, 18, 1070–1078, doi:10.3762/bjoc.18.109

• the exclusive isolable product when benzene was eliminated from the reaction mixture (Table 1, entry 6). Interestingly, the formation of byproduct 15 (which could be, in principle, obtained by DDQ oxidation of 11 [25]) via the elimination of a diazo group has not been reported. Having identified the

Electrochemical formal homocoupling of sec-alcohols

• Kosuke Yamamoto,
• Kazuhisa Arita,
• Masashi Shiota,
• Masami Kuriyama and
• Osamu Onomura

Beilstein J. Org. Chem. 2022, 18, 1062–1069, doi:10.3762/bjoc.18.108

• ]. Kim et al. reported the formation of vic-1,2-diols in the sacrificial anode-free electrocarboxylation of 1-phenylethanol and benzyl alcohol which involves tetramethylpiperidine-1-oxyl-mediated alcohol oxidation as an anodic event [46]. However, vic-1,2-diols were obtained only as minor products and

• direct oxidation of sec-alcohol 1 to ketone 3 could also proceed under the present reaction conditions. Conclusion In conclusion, we have developed the sacrificial anode-free electrochemical protocol for the synthesis of vic-1,2-diols from sec-alcohols without external chemical oxidants or reductants

Synthesis, optical and electrochemical properties of (D–π)₂-type and (D–π)₂Ph-type fluorescent dyes

• Kosuke Takemura,
• Kazuki Ohira,
• Taiki Higashino,
• Keiichi Imato and
• Yousuke Ooyama

Beilstein J. Org. Chem. 2022, 18, 1047–1054, doi:10.3762/bjoc.18.106

• properties (Φfl-solid = 0.24 nm), compared with OTK-2 (Φfl-solid = 0.15 nm). CV results demonstrated that OTT-2 and OTK-2 exhibit a reversible oxidation wave. Based on photoabsorption, fluorescence spectroscopy and CV for the two dyes, it was found that the lowest unoccupied molecular orbital (LUMO) energy

• were internally referenced to ferrocene/ferrocenium (Fc/Fc+). The electrochemical data are summarized in Table 3. The cyclic voltammograms of the two dyes show a reversible oxidation wave with the anodic peak potential (Epaox) at 0.32 V for OTK-2 and 0.40 V for OTT-2 (Figure 2), while any obvious

• reduction waves and another oxidation waves did not appear within the potential window (Figure 3a and Figure S2a, Supporting Information File 1). The corresponding cathodic peak potential (Epcox) appeared at 0.24 V for OTK-2 and 0.30 V for OTT-2, and thus the peak separations between the Epaox and Epcox

Electrochemical Friedel–Crafts-type amidomethylation of arenes by a novel electrochemical oxidation system using a quasi-divided cell and trialkylammonium tetrafluoroborate

• Hisanori Senboku,
• Mizuki Hayama and
• Hidetoshi Matsuno

Beilstein J. Org. Chem. 2022, 18, 1040–1046, doi:10.3762/bjoc.18.105

• , Hokkaido 060-8628, Japan 10.3762/bjoc.18.105 Abstract Electrochemical Friedel–Crafts-type amidomethylation was successfully carried out by a novel electrochemical oxidation system using a quasi-divided cell and trialkylammonium tetrafluoroborates, such as iPr2NHEtBF4. Constant current electrolysis of

• amidomethylated products in good to high yields. Keywords: electrochemical oxidation; Friedel–Crafts type amidomethylation; N-acyliminium ion; quasi-divided cell; trialkylammonium salt; Introduction Oxidation of amides generates useful intermediates, N-acyliminium ions, which have been widely used in organic

• necessary in some cases (path b in Scheme 1) [14][15]. On the other hand, N-acyliminium ions can easily be generated by electrochemical oxidation without those reagents. Electrochemical oxidation of amides/carbamates yielding N-acyliminium ions is well known as Shono oxidation (path c in Scheme 1) [16] and

Electrochemical vicinal oxyazidation of α-arylvinyl acetates

• Yi-Lun Li,
• Zhaojiang Shi,
• Tao Shen and
• Ke-Yin Ye

Beilstein J. Org. Chem. 2022, 18, 1026–1031, doi:10.3762/bjoc.18.103

• development of a green, efficient, and sustainable protocol for the synthesis of azidoketones is of great significance [7][8][9]. Retrosynthetically, the nucleophilic substitution of α-bromoketones by sodium azide [10] and oxidation of the azido alcohols [11] are among the most straightforward methods to

• studies showed while there was no obvious oxidation peak for TMSN3, 1-phenylvinyl acetate (1) exhibits two oxidation peaks. The first peak (Ep/2 = 1.51 V vs Fc+/0) was assigned to be the oxidation of the vinyl acetate moiety. The control experiment demonstrated that there was no conversion without an

• oxidation of the isopropylbenzene moiety [31][36], which was consistent with its relative low oxidation potential (Eonset = 1.68 V vs Fc+/0). Other electron-donating substituents, such as the OMe (10–12), OPh (13), and OAc (14) were also well tolerated. However, halogenated substrates, including fluoro (15

New azodyrecins identified by a genome mining-directed reactivity-based screening

• Atina Rizkiya Choirunnisa,
• Kuga Arima,
• Yo Abe,
• Noritaka Kagaya,
• Kei Kudo,
• Hikaru Suenaga,
• Junko Hashimoto,
• Manabu Fujie,
• Noriyuki Satoh,
• Kazuo Shin-ya,
• Kenichi Matsuda and
• Toshiyuki Wakimoto

Beilstein J. Org. Chem. 2022, 18, 1017–1025, doi:10.3762/bjoc.18.102

• enzyme VlmA [18]. This intermediate is hypothesized to be transformed into the azoxy bond-containing intermediate via an intramolecular rearrangement accompanied by a concomitant oxidation [18]. Although the exact mechanisms of azoxy bond formation remain unclear, VlmH and VlmA cooperate to biosynthesize

Isolation and biosynthesis of daturamycins from Streptomyces sp. KIB-H1544

• Yin Chen,
• Jinqiu Ren,
• Ruimin Yang,
• Jie Li,
• Sheng-Xiong Huang and
• Yijun Yan

Beilstein J. Org. Chem. 2022, 18, 1009–1016, doi:10.3762/bjoc.18.101

• -H1544 (Figure 3B). First, two molecules of phenylpyruvic acid (7), which is deaminated from ʟ-phenylalanine, are condensed into the six-membered polyporic acid (8) catalyzed by DatA. Then, 8 converts to compounds 3, 4, 5, and 6 through methylation and oxidation. On the other hand, polyporic acid (8

First example of organocatalysis by cathodic N-heterocyclic carbene generation and accumulation using a divided electrochemical flow cell

• Daniele Rocco,
• Ana A. Folgueiras-Amador,
• Richard C. D. Brown and
• Marta Feroci

Beilstein J. Org. Chem. 2022, 18, 979–990, doi:10.3762/bjoc.18.98

• oxidation/degradation. In this paper we describe the cathodic generation and accumulation of NHC in a divided flow cell and its subsequent use as organocatalyst in the self-annulation of cinnamaldehyde and in the esterification of cinnamaldehyde. Results and Discussion Cathodic NHC generation and

• chamber (Figure 1). The requirement for a divided cell (a more complicated device than the undivided configuration) arises from the need to protect electrogenerated NHC from its anodic oxidation in the absence of a consumable anode. To ensure good sealing of the electrolysis cell, the sandwich-type

• oxidation of BF4− was required as the counter electrode reaction, and 10% of methanol was added to the anolyte solution. In this case (Table 1, entry 2) 13% of thione was obtained and the electrode did not show any signs of consumption. The same yield (13%) was obtained using nickel as cathode material

Understanding the competing pathways leading to hydropyrene and isoelisabethatriene

• Shani Zev,
• Marion Ringel,
• Ronja Driller,
• Bernhard Loll,
• Thomas Brück and
• Dan T. Major

Beilstein J. Org. Chem. 2022, 18, 972–978, doi:10.3762/bjoc.18.97

• isomerization is responsible for a slightly different substrate fold inside the active site, hence shifting the product distribution in favor of the IE products in certain enzyme variants rather than the HP products. Oxidation of IEs A and B by lipases results in the formation of the advanced pseudopterosin (P

Electrochemical and spectroscopic properties of twisted dibenzo[g,p]chrysene derivatives

• Tomoya Imai,
• Ryuhei Akasaka,
• Naruhiro Yoshida,
• Toru Amaya and
• Tetsuo Iwasawa

Beilstein J. Org. Chem. 2022, 18, 963–971, doi:10.3762/bjoc.18.96

• higher oxidation potentials than that for DBC-H, even for compounds that contained an electron-donating group such as DBC-Me and DBC-SMe. DFT calculations clearly indicate that these higher oxidation potentials are due to the ineffective conjugation of the MeO group, which is oriented perpendicular to

• , a strong photoluminescence was observed for DBC-H and DBC-Si. Keywords: DFT calculation; dibenzo[g,p]chrysenes; fluorescent compounds; oxidation; polycyclic aromatic hydrocarbon (PAH); twisted acenes; Introduction Polycyclic aromatic hydrocarbons (PAHs) have attracted interest as potential

• DBCs with MeO groups located at X and/or Y (MeO-DBC-1, MeO-DBC-2, and MeO-DBC-3, Figure 1b) [43]. The first oxidation potential (Eox1) of MeO-DBC-1 was reported to be 0.40 V (based on Fc/Fc+), which is 0.48 V lower than that of DBC. In contrast, when a MeO group is introduced at the X position (MeO-DBC

Introducing a new 7-ring fused diindenone-dithieno[3,2-b:2',3'-d]thiophene unit as a promising component for organic semiconductor materials

• Valentin H. K. Fell,
• Joseph Cameron,
• Alexander L. Kanibolotsky,
• Eman J. Hussien and
• Peter J. Skabara

Beilstein J. Org. Chem. 2022, 18, 944–955, doi:10.3762/bjoc.18.94

• Equation 3) [65][66]: In which Eox is the half-wave potential of the first oxidation signal, and Ered is the half-wave potential of the first reduction signal. Ferrocene was used as the internal standard and its HOMO was taken to be −4.8 eV [67]. With these values, the frontier orbital energy levels of EtH

• more negative. This can be attributed to the presence of the electron-withdrawing keto groups [3][20]. In contrast to compounds 2–4, which showed poor reversibility for oxidation and reduction, EtH-T-DI-DTT shows excellent electrochemical stability. Two sequential reversible oxidations can be seen in

Morita–Baylis–Hillman reaction of 3-formyl-9H-pyrido[3,4-b]indoles and fluorescence studies of the products

• Nisha Devi and
• Virender Singh

Beilstein J. Org. Chem. 2022, 18, 926–934, doi:10.3762/bjoc.18.92

• ʟ-tryptophan (1) was much faster than with the tryptophan ester, taking only 45 minutes to complete. Interestingly, KMnO4 oxidation was selective, with no decarboxylation seen. Within 15 minutes, further treatment of 3a–e with methyl iodide in the presence of K2CO3 provided the corresponding methyl

Anti-inflammatory aromadendrane- and cadinane-type sesquiterpenoids from the South China Sea sponge Acanthella cavernosa

• Shou-Mao Shen,
• Qing Yang,
• Yi Zang,
• Jia Li,
• Xueting Liu and
• Yue-Wei Guo

Beilstein J. Org. Chem. 2022, 18, 916–925, doi:10.3762/bjoc.18.91

• intermediate C. Firstly, deprotonation occurred to form the double bond Δ1,10 and led to the formation of (−)-ledene (D) [29], on which the multiple-step oxidation happened at C-2 and C-9 to generate (+)-1. Secondly, the reaction is quenched by an H2O attach at carbocation C-10 to form (+)-globulol (E) [30

• shifts led to aristolane-type carbocation intermediate G, which was further deprotonated to afford 9-aristolene (H) [29]. Multiple-step oxidation on H furnished the structure of 3. The terpene cyclase catalyzed the cyclization of cadinene-type sesquiterpenes using FPP as the substrate, which is first

• characterized the function of a P450 enzyme CYP76AH1 which was responsible for the formation of the aromatic ring of ferruginol in the biosynthesis pathway of tanshinones [34]. Hence, we proposed that the oxidation occurred on L to furnish the aromatic ring of calamenene (M) [29], followed by the hydroxylation

Synthetic strategies for the preparation of γ-phostams: 1,2-azaphospholidine 2-oxides and 1,2-azaphospholine 2-oxides

• Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 889–915, doi:10.3762/bjoc.18.90

• ]azaphosphole 2-oxides 56 by oxidation with mCPBA, while treatment of 1,3-dihydrobenzo[d][1,2]azaphosphole 2-oxides 56 with phosphorus pentasulfide transformed them back to 1,3-dihydrobenzo[d][1,2]azaphosphole 2-sulfides 60. Heating dimethyl 2-aminobenzylphosphonate (61) generated 1-methyl-2-methoxy-1,3

• derivatives 83 followed by an intramolecular cyclization via the intramolecular Arbuzov reaction under heating generated 1,2-azaphospholidine 2-oxides 89. Compounds 89 were further transformed into N-phosphoryl- and N-thiophosphoryl-1,2-azaphospholidine 2-oxides 90/2-sulfides 91 via oxidation with hydrogen

• )acetates 247 in moderate yields of 53–71% with diastereomeric ratios of 1:1.7 to 1:3. The synthetic strategy is more versatile (Scheme 39) [60]. [3 + 2] Annulation via formations of both C–C and P–N bonds After oxidation with K3Fe(CN)6, diphenyl 3,5-di(tert-butyl)-4-hydroxybenzylphosphonate (248) was

Synthesis and HDAC inhibitory activity of pyrimidine-based hydroxamic acids

• Virginija Jakubkiene,
• Gabrielius Ernis Valiulis,
• Markus Schweipert,
• Asta Zubriene,
• Daumantas Matulis,
• Franz-Josef Meyer-Almes and
• Sigitas Tumkevicius

Beilstein J. Org. Chem. 2022, 18, 837–844, doi:10.3762/bjoc.18.84

• followed by aminolysis of the obtained esters with hydroxylamine. Oxidation of the 2-methylthio group to the methylsulfonyl group and following treatment with amines resulted in the formation of the corresponding 2-amino-substituted derivatives, the ester group of which reacted with hydroxylamine to give

• 50–60 °C in 73% and 70% yields, respectively (Scheme 1). In order to functionalize the 2nd position of the pyrimidine ring, the 2-methylthio group of compound 3 was oxidized to the better leaving 2-methylsulfonyl group. In our previous work [31] we investigated the oxidation of some 2