Functionalization of N-arylglycine esters: electrocatalytic access to C–C bonds mediated by n-Bu₄NI

• Mi-Hai Luo,
• Yang-Ye Jiang,
• Kun Xu,
• Yong-Guo Liu,
• Bao-Guo Sun and
• Cheng-Chu Zeng

Beilstein J. Org. Chem. 2018, 14, 499–505, doi:10.3762/bjoc.14.35

• generated from anodic oxidation of 1a, followed by additional oxidation [32][33][34][35][36]. To prove the practicability of the protocol, a scaled-up reaction was also carried out. As illustrated in Scheme 4, when 6 mmol of ethyl p-tolylglycinate (1a) was allowed to react with 1,3,5-trimethoxybenzene (2a

• ) under the standard conditions, adduct 3aa was isolated in a 75% yield, without obvious losing of yield. To better understand the reaction mechanism, control experiments were performed. As shown in Scheme 5, the anodic oxidation of 1a in the absence of a C–H nucleophile under the standard conditions

• experiments described above, as well as related references [4], a plausible mechanism for the electrocatalytic cross dehydrogenative coupling of N-arylglycine esters 1 with C–H nucleophiles 2 is outlined in Scheme 6. The anodic oxidation of iodide generates the active species I2 or I+. Followed by a

The selective electrochemical fluorination of S-alkyl benzothioate and its derivatives

• Shunsuke Kuribayashi,
• Tomoyuki Kurioka,
• Shinsuke Inagi,
• Ho-Jung Lu,
• Biing-Jiun Uang and
• Toshio Fuchigami

Beilstein J. Org. Chem. 2018, 14, 389–396, doi:10.3762/bjoc.14.27

• electrochemical fluorination, we have studied the anodic fluorination of S-alkyl benzothioate and its derivatives as well as its cyclic analogues such as benzothiophenone. Results and Discussion Oxidation potentials of S-butyl benzothioates At first, the anodic oxidation potentials of S-butyl benzothioate (1a), S

• cleavage nor benzene ring fluorination took place at all. Finally, the anodic fluorination of benzothioates having a γ and δ-carboxyl group, 1m and 1n, was examined. The anodic oxidation of 1m and 1n proceeded; however, α-fluorination did not occur. In both cases, an anodic intramolecular cyclization took

• the other hand, a minor pathway involves a C–S bond cleavage to form benzoyl fluoride as is observed in the case of the anodic oxidation of S-aryl benzothioates [23]. In the case of S-alkyl benzothioates bearing a carboxyl group at the γ and δ-position with respect to the sulfur atom, after generation

Preactivation-based chemoselective glycosylations: A powerful strategy for oligosaccharide assembly

• Weizhun Yang,
• Bo Yang,
• Sherif Ramadan and
• Xuefei Huang

Beilstein J. Org. Chem. 2017, 13, 2094–2114, doi:10.3762/bjoc.13.207

• thioglycoside donor 136 was preactivated through anodic oxidation, followed by the addition of the acceptor 137 to afford disaccharide 138 (Scheme 20). Repeating this process, a series of oligo-glucosamine ranging from tri- to hexa-saccharides 139–142 was successfully prepared. 2-Deoxy and 2,6-dideoxyglycosides

Total synthesis of TMG-chitotriomycin based on an automated electrochemical assembly of a disaccharide building block

• Yuta Isoda,
• Norihiko Sasaki,
• Kei Kitamura,
• Shuji Takahashi,
• Sujit Manmode,
• Naoko Takeda-Okuda,
• Jun-ichi Tamura,
• Toshiki Nokami and
• Toshiyuki Itoh

Beilstein J. Org. Chem. 2017, 13, 919–924, doi:10.3762/bjoc.13.93

• potential precursor 7 of TMG-chitotriomycin (1) using disaccharide 5bβ as a building block as illustrated in Figure 3. The automated electrochemical assembly of building blocks was initiated by the anodic oxidation of 5bβ and the subsequent coupling with thioglycoside 4 afforded the corresponding

• Bu4NOTf (1.7 mmol, 676 mg) and anhydrous dichloromethane (16 mL) was placed with TfOH (1 mmol, 90 μL). The automated synthesis was started immediately after the cooling bath temperature reached −80 °C. The anodic oxidation (1.05 F/mol, 10 mA) takes 73 minutes and then a dichloromethane solution containing

Opportunities and challenges for direct C–H functionalization of piperazines

• Zhishi Ye,
• Kristen E. Gettys and
• Mingji Dai

Beilstein J. Org. Chem. 2016, 12, 702–715, doi:10.3762/bjoc.12.70

• -amine radical followed by trapping with acrylate, to functionalize the α-position of amines [68]. The strategy works for morpholine and piperazine substrates, but the yields for the latter are generally low, ranging from 12% to 41% (Figure 17). Anodic oxidation strategy Another uncommon way to perform α

• -position functionalization is using electroorganic chemistry [69]. As shown in Figure 18, bisformyl protected piperazine 106 could be converted to 107 in 91% yield under anodic oxidation conditions at 500 g scale [70]. While this method is limited and only allows for functionalization with alkoxy groups

• , et al. in 2013 [67]. Free radical approach by Undheim et al. in 1994 [68]. Anodic oxidation approach by Nyberg et al. in 1976 [70]. Acknowledgements We thank the Purdue University for financial support.

Interactions between tetrathiafulvalene units in dimeric structures – the influence of cyclic cores

• Huixin Jiang,
• Virginia Mazzanti,
• Christian R. Parker,
• Søren Lindbæk Broman,
• Jens Heide Wallberg,
• Karol Lušpai,
• Adam Brincko,
• Henrik G. Kjaergaard,
• Anders Kadziola,
• Peter Rapta,
• Ole Hammerich and
• Mogens Brøndsted Nielsen

Beilstein J. Org. Chem. 2015, 11, 930–948, doi:10.3762/bjoc.11.104

• radical species monitored upon oxidation); (c) time dependence of the current (red line) and the double-integrated EPR intensity (black solid squares). Vis–NIR spectral changes observed during anodic oxidation of each TTF unit to cation radical within the first voltammetric double peak: TTF–TTF → TTF

Electrochemical oxidation of cholesterol

• Jacek W. Morzycki and
• Andrzej Sobkowiak

Beilstein J. Org. Chem. 2015, 11, 392–402, doi:10.3762/bjoc.11.45

• byproducts was diminished with this system. The presented system proved suitable for the electrochemical glycosylation of 3β-hydroxy-Δ5-steroids [43]. In this case, 2,3,4,6-tetra-O-acetyl-D-glucopyranose was used as a nucleophile (Scheme 10). The anodic oxidation of cholesterol (1) carried out in

• electrochemical acetoxylation of cholesterol at the allylic position. Direct anodic oxidation of cholesterol in dichloromethane. A plausible mechanism of the electrochemical oxidation of cholesterol in dichloromethane. The electrochemical formation of glycosides and glycoconjugates. Efficient electrochemical

Cathodic reductive coupling of methyl cinnamate on boron-doped diamond electrodes and synthesis of new neolignan-type products

• Taiki Kojima,
• Rika Obata,
• Tsuyoshi Saito,
• Yasuaki Einaga and
• Shigeru Nishiyama

Beilstein J. Org. Chem. 2015, 11, 200–203, doi:10.3762/bjoc.11.21

• window against evolution of both hydrogen and oxygen and for their high stability which is derived from their diamond carbon structure [6]. Although anodic oxidation reactions mediated by BDD electrodes have been exploited in organic synthesis, there have been only few reports regarding their application

• . As shown in Figure 1, the radical intermediate derived from phenylacrylate through a one-electron reduction (right) differs from that obtained by anodic oxidation of 4-hydroxyphenyl-1-propene (left). Therefore, the reductive dimerization of cinnamic acid derivatives was expected to provide access to

3α,5α-Cyclocholestan-6β-yl ethers as donors of the cholesterol moiety for the electrochemical synthesis of cholesterol glycoconjugates

• Aneta M. Tomkiel,
• Adam Biedrzycki,
• Jolanta Płoszyńska,
• Dorota Naróg,
• Andrzej Sobkowiak and
• Jacek W. Morzycki

Beilstein J. Org. Chem. 2015, 11, 162–168, doi:10.3762/bjoc.11.16

• leads to sterol glycoconjugates. Initially, the reaction of cholesterol (1) with various sugars was studied. During anodic oxidation of cholesterol in dichloromethane (the choice of solvent is crucial as the reaction course may be different in other solvents) [1], splitting of the carbon–oxygen bond in

• chromatography performed on a 70–230 mesh silica gel (J. T. Baker). Typical electrochemical experiment. Anodic oxidation of 6β-phenyloxy-3α,5α-cyclocholestane (6f) in the presence of 1,2:3,4-di-O-isopropylidene-D-galactopyranose (7): 6β-Phenyloxy-3α,5α-cyclocholestane (138 mg, 0.30 mmol) and 1,2:3,4-di-O

Highly selective electrochemical fluorination of dithioacetal derivatives bearing electron-withdrawing substituents at the position α to the sulfur atom using poly(HF) salts

• Bin Yin,
• Shinsuke Inagi and
• Toshio Fuchigami

Beilstein J. Org. Chem. 2015, 11, 85–91, doi:10.3762/bjoc.11.12

• was achieved by direct and indirect anodic oxidation in the presence of the poly(HF) salts [12][13][14][15][16][23][24][25] or alkali-metal fluorides like KF and CsF with PEG 200 [17]. The anodic fluorination of a dithioacetal derived from an aliphatic aldehyde provided the fluorodesulfurization

• % yield (Figure 1a). Previously, we obtained 3b in 75% yield by constant potential anodic oxidation of ethyl α-(phenylthio)acetate in a similar electrolytic solution [22]. A comparable dependency of product selectivity on supporting poly(HF) salts was also observed in a series of Et4NF·nHF (n = 3–5

The Shono-type electroorganic oxidation of unfunctionalised amides. Carbon–carbon bond formation via electrogenerated N-acyliminium ions

• Alan M. Jones and
• Craig E. Banks

Beilstein J. Org. Chem. 2014, 10, 3056–3072, doi:10.3762/bjoc.10.323

• are useful reactive synthetic intermediates in a variety of important carbon–carbon bond forming and cyclisation strategies in organic chemistry. The advent of an electrochemical anodic oxidation of unfunctionalised amides, more commonly known as the Shono oxidation, has provided a complementary route

• electroorganic techniques and future directions. Keywords: anodic oxidation; electrochemistry; electroorganic, electrosynthesis, N-acyliminium ions; natural products; non-Kolbe oxidation; peptidomimetics; Shono oxidation; synthesis; Review N-Acyliminium ions are synthetically versatile N-Acyliminium ions [1][2

• electrochemical anodic oxidation of an α-methylene group to an amide (or carbamate) to generate a new carbon–carbon bond via an anodic methoxylation step and Lewis acid mediated generation of an N-acyliminium ion reactive intermediate; Scheme 1 overviews such a process [11]. Although the anodic oxidation

Recent advances in the electrochemical construction of heterocycles

• Robert Francke

Beilstein J. Org. Chem. 2014, 10, 2858–2873, doi:10.3762/bjoc.10.303

• anodic oxidation of electron-rich olefins such as enol ethers 1 in methanolic solution generates radical cation 2 which can be used for a number of cyclization reactions (Scheme 2) [32][33]. Moeller et al. demonstrated that by intramolecular trapping of this highly reactive intermediate with a tethered

• approach, the anodic oxidation of olefins was combined with a sequential chemical oxidation in a one-pot fashion (Scheme 3) [39]. By using DMSO instead of methanol as nucleophilic co-solvent for electrolysis, a pool of alkoxysulfonium ions 7 is generated from tosylamine 5. The generation of the cation pool

• oxidation into the anodic cyclization of olefins was extended to intramolecular coupling of 1,6-dienes 9 (Scheme 4) [39]. In this version of the combined cyclization/oxidation, the second carbon–carbon double bond acts as the nucleophile after anodic oxidation, leading to bisalkoxysulfonium species 10. When

Detonation nanodiamonds biofunctionalization and immobilization to titanium alloy surfaces as first steps towards medical application

• Juliana P. L. Gonçalves,
• Afnan Q. Shaikh,
• Manuela Reitzig,
• Daria A. Kovalenko,
• Jan Michael,
• René Beutner,
• Gianaurelio Cuniberti,
• Dieter Scharnweber and
• Jörg Opitz

Beilstein J. Org. Chem. 2014, 10, 2765–2773, doi:10.3762/bjoc.10.293

• deposition during the electrochemical immobilization. We applied an electrochemical technique of anodic oxidation to get a stable immobilization of the particles during anodic oxide layer growth. A FIB-STEM tool was used to characterize the topology and layer system of titanium based alloy after

Electrocarboxylation: towards sustainable and efficient synthesis of valuable carboxylic acids

• Roman Matthessen,
• Jan Fransaer,
• Koen Binnemans and
• Dirk E. De Vos

Beilstein J. Org. Chem. 2014, 10, 2484–2500, doi:10.3762/bjoc.10.260

• difficulty operating in organic solvents and under high pressure conditions, limiting operational conditions [44]. The anodic oxidation of more reduction stable tetraalkylammonium salts is another approach compatible with non-sacrificial anodes (Scheme 6c). Here, the released tetraalkylammonium cations

• implementation in a continuous process. The anodic oxidation of formate generates one CO2 molecule and one proton, giving a controlled supply of protons to the cathode (Scheme 8). Conducting the electrocarboxylation with tetraethylammonium oxalate, without formate salts, increases the amount of C6 compared to C5

• anode can also be used for CO2 fixation in other aliphatic halides. The anodic oxidation of tetraethylammonium oxalate is used in the electrocarboxylation of 1-bromo-2-methylpentane, which is almost quantitatively converted into 3-methylhexanoic acid [52]. The electrocarboxylation of 1,4-dibromo-2

Anodic coupling of carboxylic acids to electron-rich double bonds: A surprising non-Kolbe pathway to lactones

• Robert J. Perkins,
• Hai-Chao Xu,
• John M. Campbell and
• Kevin D. Moeller

Beilstein J. Org. Chem. 2013, 9, 1630–1636, doi:10.3762/bjoc.9.186

• appear to proceed through an olefinic radical cation intermediate. Results and Discussion Initial cyclization studies The compatibility of the carboxylic acid with the anodic cyclization was initially studied by examining the anodic oxidation of substrates 14a–c (Table 1). The oxidation of 14a nicely

• readily as radical 21a. Indeed, the anodic oxidation of 19g gave low yields and poor current efficiency, mirroring the results obtained from the oxidation of unsubstituted styrene 19a. As with other substrates, the oxidation potential of 19g was lower than that of its seven-membered ring counterpart 19h

Efficient electroorganic synthesis of 2,3,6,7,10,11-hexahydroxytriphenylene derivatives

• Carolin Regenbrecht and
• Siegfried R. Waldvogel

Beilstein J. Org. Chem. 2012, 8, 1721–1724, doi:10.3762/bjoc.8.196

• [11][12]. Furthermore, no transition metal cations, which promote the cleavage of the ketal moiety [11], are involved. The anodic oxidation of catechol derivatives was first demonstrated by Parker et al. [13]. Applying this methodology in a specific electrolysis cell, Simonet et al. established a

• Anodic oxidation of catechol ketals We report a simple protocol for the anodic oxidation of catechol ketals forming triphenylene ketals (Scheme 1). Best results were obtained in PC and TMABF4 (method A) or TBABF4 (method B) as electrolytes. Performing the reaction in PC is beneficial for several reasons

• . However, our method provides easy access to pure 3 which can easily be separated and purified by simple filtration. Conclusion Triphenylene ketals are easily available by anodic oxidation using a simple galvanostatic protocol. Best results are obtained when the synthesized dehydrotrimers are almost

Conjugated polymers containing diketopyrrolopyrrole units in the main chain

• Bernd Tieke,
• A. Raman Rabindranath,
• Kai Zhang and
• Yu Zhu

Beilstein J. Org. Chem. 2010, 6, 830–845, doi:10.3762/bjoc.6.92

• easily electropolymerized by anodic oxidation. An insoluble, non-luminescent polymer film formed at the electrode that exhibited reversible electrochromic properties (Table 4). The film could be switched from blue in the neutral state via transparent grey to purple red in the oxidized state. The

Generation of pyridyl coordinated organosilicon cation pool by oxidative Si-Si bond dissociation

• Toshiki Nokami,
• Ryoji Soma,
• Yoshimasa Yamamoto,
• Toshiyuki Kamei,
• Kenichiro Itami and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2007, 3, No. 7, doi:10.1186/1860-5397-3-7

• ]. The coordination also stabilizes the thus-generated radical cation and weakens the C-Sn bond. A similar effect of intramolecular coordination was observed in the case of silicon [23]. Another important point is that pyridyl group is rather inactive toward the anodic oxidation. Thus, we chose to use a