Harnessing the versatility of hydrazones through electrosynthetic oxidative transformations

• Aurélie Claraz

Beilstein J. Org. Chem. 2024, 20, 1988–2004, doi:10.3762/bjoc.20.175

• conducted in a divided cell under potentiostatic conditions at 1.2–1.65 V vs SCE in acetonitrile. In 1976, the same group reported the anodic cyclization of chalcone-derived N-phenylhydrazone 3 to pyrazole 4 in a divided cell at constant current (Scheme 2) [37]. The obtained poor yield was explained by the

• point of view, the authors proposed the formation of N-pyridyl radical 18 through the anodic oxidation of in situ-generated anion 17. Subsequent radical cyclization, second anodic cyclization and deprotonation yielded the fused heterocycle 16. Similarly, Youssef and Alajimi disclosed the electrochemical

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• . Recent advances in anodic cyclization reactions along with their detailed mechanistic rationale have been studied in details in an article published by Moeller’s group [45]. Herein, we present a systematic description of electrooxidation reactions where asymmetry has been induced by means of chiral

Oxidative and reductive cyclization in stiff dithienylethenes

• Michael Kleinwächter,
• Ellen Teichmann,
• Lutz Grubert,
• Martin Herder and
• Stefan Hecht

Beilstein J. Org. Chem. 2018, 14, 2812–2821, doi:10.3762/bjoc.14.259

• case of modified thiazoles [5] or using the strongly donating -PhNMe2 substituent [40]. In these compounds, the first oxidation wave is fully reversible and anodic cyclization occurs only after the second step, forming the open dication (EEC mechanism). By combining strongly electron-donating and

• electron-withdrawing substituents within one molecule (Me2NPh-DTE-PhCN), we could access an open isomer showing two separated one-electron waves upon both oxidation and reduction (Figure 6). As in the examples above, the first oxidation wave of O-Me2NPh-DTE-PhCN is fully reversible and anodic cyclization

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

• be the most suitable combination as electrolytic solvent and supporting salt as well as fluorine source for the anodic fluorination. The electrochemical fluorination of cyclic benzothioates such as benzothiophenone was also achieved. Keywords: anodic cyclization; diastereoselective fluorination

• of an α-cationic intermediate, the intramolecular cyclization seems to take place faster than combination with a fluoride ion as shown in Scheme 6. In support of this, we have reported a fluoride ion-promoted anodic cyclization of α-(phenylthio)-N-phenyl- and α-(phenylthio)-N-benzylacetamides [28] as

Recent advances in the electrochemical construction of heterocycles

• Robert Francke

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

• reactions is presented and discussed in this review. Keywords: anodic cyclization; electrosynthesis; heterocycle; olefin coupling; organic electrochemistry; radical cyclization; Introduction The construction of heterocyclic cores undoubtedly represents a highly important discipline of organic synthesis

• 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

• . Principle of indirect electrolysis. Anodic intramolecular cyclization of olefines in methanol. Anodic cyclization of olefines in CH2Cl2/DMSO. Intramolecular coupling of 1,6-dienes in CH2Cl2/DMSO. Cyclization of bromopropargyloxy ester 12. Proposed mechanism for the radical cyclization of bromopropargyloxy

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

• . Radical cation stabilization by an o-methoxy substituent. General scheme for anodic cyclization reactions. Anodic cyclization competition study. Kolbe electrolysis reactions. Oxidative coupling between a carboxylic acid and electron-rich olefin. Predicted relative rates of single-electron oxidation based

• not appear to be a significant competing pathway. Experimental results indicate that oxidation occurs at the olefin and that the reaction proceeds through a radical cation intermediate. Keywords: carboxylic acid; cyclization; electrolysis; free radical; kolbe; radical cation; Introduction Anodic