Front Cover: Electrochemical Hydroxylation of Electron‐Rich Arenes in Continuous Flow (Eur. J. Org. Chem. 20/2022)

Abstract

The Front Cover demonstrates that electrochemistry in continuous flow is so convenient and reliable that even kids could do it. Electrochemical hydroxylation of sensitive electron‐rich arenes was achieved by the implementation of a flow setup. Our goal is to motivate organic chemists, who tend to be quite conservative, to apply the modern techniques in their everyday research and explore new reaction pathways. Cover artwork by Alina Andreyenka. More information can be found in the Research Article by M. Ošeka et al.

Continuous Flow Electrochemistry Enables Practical and Site‐Selective C−H Oxidation

“…The electrochemical oxygenation reaction was compatible with sensitive functional groups such as amino ester (29), alkyl bromide (30), and alkyl sulfonate (31). Moreover, diphenyl methane (32) and methylarenes such as 4-methoxyanisole (33), 4-tert-butyltoluene (34), 4-bromotoluene (35) were successfully converted to the corresponding benzyl alcohols despite that they were prone to overoxidation. [16] The more electron-deficient methyl 4-methylbenzoate reacted primary on the benzene ring to give phenol products.…”

“…We have been interested in the development of electrooxidative synthetic methods with continuous flow electrochemistry [31][32][33][34] and have achieved arene C(sp 2 )À H hydroxylation to produce phenols. [34,35] Herein, we report a practical electrochemical method for the highly selective monooxidation of benzylic C(sp 3 )À H bonds in continuous flow (Figure 1c). This electrochemical method offers several advantages, including an exceptionally broad scope (compatible with alkylarenes of a wide range of electronic properties and applicable to 1°, 2°, and 3°benzylic C(sp 3 )À H bonds), high site selectivity, excellent scalability, and the absence of any catalysts or chemical oxidants, enabling not only the efficient and cost-effective conversion of feedstock chemicals to value-added benzyl alcohols but also the late-stage oxygenation of drug molecules and natural products.…”

Distinctive Arbutin‐Containing Markers: Chemotaxonomic Significance and Insights into the Evolution of Proteaceae Phytochemistry

“…The ensuing solids were loaded onto silica gel pug and eluted to provide 5 fractions: fraction 1 (16 mg; 50 % AcOEt/hexanes elution, 100 mL), fraction 2 (9 mg; 75 % AcOEt/hexanes elution, 100 mL), fraction 3 (10 mg; 100 % AcOEt elution, 100 mL), fraction 4 (134 mg; 10 % MeOH/AcOEt elution, 100 mL), fraction 5 (218 mg; 25 % MeOH/AcOEt elution, 100 mL). Fraction 1 (16 mg) and extract A (60 mg) were combined following TLC analysis, and analyzed by GCMS which indicated the presence of eugenol (3 d), [39] acetyleugenol (3 e), [39] dihydroactinidiolide (3 f), [40] and previously reported compound 3 g. [41] Fraction 4 (134 mg) was subjected to automated flash column chromatography (4 g silica cartridge, 0-100 % AcOEt/ hexanes, 10 min; then 0-40 % MeOH/AcOEt, 6 min), which provided arbutin (1 a) [9] (10 mg), and shikimic acid (3 a) (19 mg). [33a] LCMS analysis of fractions 4 and 5 also supported the presence of previously reported glycosides 1 f and 1 g.…”

Electrochemical Rearrangement of Indoles to Spirooxindoles in Continuous Flow

“…While most of the organic electrosynthesis is conducted with batch reactors, continuous flow electrochemical microreactors facilitate conversion, allow easy scale‐up and automation, and reduce the use of supporting electrolyte because of their unique features such as small interelectrode distance, short residence time and large surface to volume ratio [20–28] . Importantly, continuous flow electrochemical microreactors has been shown to enable reactions that are difficult in batch [29–37] . Despite these advantages, continuous flow electrochemical microreactors are underutilized in electrochemical organic synthesis.…”

“…[20][21][22][23][24][25][26][27][28] Importantly, continuous flow electrochemical microreactors has been shown to enable reactions that are difficult in batch. [29][30][31][32][33][34][35][36][37] Despite these advantages, continuous flow electrochemical microreactors are underutilized in electrochemical organic synthesis. During the preparation of this manuscript, Tong and coworkers reported electrochemical oxidative rearrangement of tetrahydro-β-carbolines employing a zero-gap divided flow cell with solution recycle.…”