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