Entry to 2-aminoprolines via electrochemical decarboxylative amidation of N‑acetylamino malonic acid monoesters

• Olesja Koleda,
• Janis Sadauskis,
• Darja Antonenko,
• Edvards Janis Treijs,
• Raivis Davis Steberis and
• Edgars Suna

Beilstein J. Org. Chem. 2025, 21, 630–638, doi:10.3762/bjoc.21.50

• addressed. Initially, we hypothesized that 11a may form by a single-electron oxidation/decarboxylation (Kolbe reaction) of 9a to generate carbon-centered radical, followed by hydrogen abstraction from solvent. To verify the hypothesis, an electrolysis of acid 9d was performed under optimized conditions

Additive-controlled chemoselective inter-/intramolecular hydroamination via electrochemical PCET process

• Kazuhiro Okamoto,
• Naoki Shida and
• Mahito Atobe

Beilstein J. Org. Chem. 2024, 20, 264–271, doi:10.3762/bjoc.20.27

• (Figure 2B, blue line). However, in the presence of AcOH, the N-alkylation yield was low (Table 1, entry 6) owing to the competitive Kolbe oxidation of the cathodically generated acetate anion. In fact, the oxidation potential of Bu4NOAc is lower than that of 1 (Figure 2C, orange line). A decrease in the

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• ) radicals. Since the dawn of organic chemistry, several radical decarboxylations have been developed, including the Kolbe electrolysis [33][34], the Hunsdiecker reaction [35], and the Barton decarboxylation [36][37][38]. More recently, photoredox catalysis has appeared as a mild alternative to these

Lectins of Mycobacterium tuberculosis – rarely studied proteins

• Katharina Kolbe,
• Sri Kumar Veleti,
• Norbert Reiling and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2019, 15, 1–15, doi:10.3762/bjoc.15.1

• Katharina Kolbe Sri Kumar Veleti Norbert Reiling Thisbe K. Lindhorst Tuberculosis Research Section, Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, 33 North Drive, Bethesda, 20892, MD, United States Microbial Interface Biology, Research

• was originally published in the thesis of K. Kolbe [12] and has been slightly modified for this article). Structure of FimH CRD with a docked azobenzene mannobioside showing the aromatic aglycon and the tyrosine residues, Y48 and Y137, of the protein in close proximity. The figure is a slightly

• bacterial agglutination have provided initial insights into carbohydrate specificity, sub-cellular location and functions of putative mycobacterial lectins. In the thesis of K. Kolbe various sugar derivatives were immobilized in 96 well microtiter plates via an amino group. Bacterial adhesion was studied

Asymmetric synthesis of propargylamines as amino acid surrogates in peptidomimetics

• Matthias Wünsch,
• David Schröder,
• Tanja Fröhr,
• Lisa Teichmann,
• Sebastian Hedwig,
• Nils Janson,
• Clara Belu,
• Jasmin Simon,
• Shari Heidemeyer,
• Philipp Holtkamp,
• Jens Rudlof,
• Lennard Klemme,
• Alessa Hinzmann,
• Beate Neumann,
• Hans-Georg Stammler and
• Norbert Sewald

Beilstein J. Org. Chem. 2017, 13, 2428–2441, doi:10.3762/bjoc.13.240

• groups (Table 3). The cyano moiety was used as precursor of the carboxamide moiety of glutamine, since the cyano group is stable in the presence of nucleophiles and strong bases. The synthesis started with the Kolbe nitrile synthesis of 4-iodobutan-1-ol with NaCN. Performing this transformation in DMSO

1-Imidoalkylphosphonium salts with modulated C_α–P⁺ bond strength: synthesis and application as new active α-imidoalkylating agents

• Jakub Adamek,
• Roman Mazurkiewicz,
• Anna Węgrzyk and
• Karol Erfurt

Beilstein J. Org. Chem. 2017, 13, 1446–1455, doi:10.3762/bjoc.13.142

• side reactions (for example Kolbe-dimerization), the yields were only poor (10–35%) [33][34]. According to our previously reported procedure for the electrochemical decarboxylative α-methoxylation of N-acyl-α-amino acids [18], amino acid derivatives 6 were converted to N-(1-methoxyalkyl)imides 7. The

Diastereoselective anodic hetero- and homo-coupling of menthol-, 8-methylmenthol- and 8-phenylmenthol-2-alkylmalonates

• Matthias C. Letzel,
• Hans J. Schäfer and
• Roland Fröhlich

Beilstein J. Org. Chem. 2017, 13, 33–42, doi:10.3762/bjoc.13.5

• . Keywords: anodic decarboxylation; diastereoselectivity; Kolbe electrolysis; radical hetero-coupling; radical homo-coupling; Introduction Intermolecular radical additions with high diastereoselectivity have been described for a number of cases [1][2][3][4][5][6][7][8][9]. There are much fewer reports on

• -methylmenthol- (2)-, 8-phenylmenthol- (3)-, and 8-p-anisylmenthol- (4)-2-alkylmalonates (Figure 1). Results and Discussion Anodic hetero- and homo-coupling of carboxylates The carboxylic acids 13a/b–18a/b for the Kolbe electrolyses were synthesized according to Scheme 1. The chiral auxiliary 1–4 is acylated

• literature [25], where the oxidation potential for anisole and toluene was determined to be 1.15 V and 1.35 V (vs Ag/Ag+), respectively. In the Kolbe electrolysis a critical potential of 1.9 to 2.2 V (vs Ag/AgCl) has to be exceeded. At this potential the coverage of the electrode with carboxylate ions

Electrosynthesis and electrochemistry

• Siegfried R. Waldvogel

Beilstein J. Org. Chem. 2015, 11, 949–950, doi:10.3762/bjoc.11.105

• Siegfried R. Waldvogel Institute for Organic Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10–14, 55128 Mainz, Germany 10.3762/bjoc.11.105 Keywords: chemical method; electrochemistry; electrosynthesis; sustainability; Since the pioneering work of Kolbe, electrochemistry and

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

• 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

• azabicylco-N-oxyl was employed to kinetically resolve racemic sec-alcohols (Scheme 9). The preparation of 1-(N-acylamino)alkyl sulfones from the anodic electrooxidation of non-Kolbe or Shono-type precursors affords the expected α-methoxyl products. Treatment with triphenylphosphonium salts and sodium aryl

• popularity with an elegant synthesis of the natural product, kingianin A, recently published by the Moses group, albeit not through a Shono or non-Kolbe mechanism [75]. The Shono-type electrooxidation has been used to prepare spirocyclic compounds using a double silyl electroauxiliary approach (Scheme 13

Recent advances in the electrochemical construction of heterocycles

• Robert Francke

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

• their approach, unsaturated and saturated carboxylic acids were simultaneously subjected to a mixed Kolbe-type oxidation in a KOH/methanol electrolyte using an undivided cell under galvanostatic conditions (Scheme 7). The cyclization reaction is initiated with the generation of radical 17 upon anodic

• ester 12. Preparation of pyrrolidines and tetrahydrofurans via Kolbe-type electrolysis of unsaturated carboxylic acids 16. Anodic cyclization of chalcone oximes 19. Generation of N-acyliminium (23) and alkoxycarbenium species (24) from amides and ethers with and without the use of electroauxiliaries

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

• , like CaCO3, produced by fast reaction with metal hydroxides [12]. Carboxylic acids are an interesting class of products, as important intermediates in the synthesis of polymers and pharmaceuticals. Hydroxybenzoic acids are among the few chemicals that are industrially produced from CO2, via the Kolbe

• like process continuity, atom economy and current efficiency. The shortcomings illustrated in this review emphasize the need for more innovative pathways to invent even more efficient and sustainable electrocarboxylation reactions. Synthesis of salicylic acid and p-hydroxybenzoic acid via Kolbe–Schmidt

A practical synthesis of long-chain iso-fatty acids (iso-C₁₂–C₁₉) and related natural products

• Mark B. Richardson and
• Spencer J. Williams

Beilstein J. Org. Chem. 2013, 9, 1807–1812, doi:10.3762/bjoc.9.210

• approaches have been used: (1) two-component cross-couplings that include α-ketoester alkylation/decarboxylation [32][33], aldehyde–olefin photoaddition [34], acetylide alkylation (sp3–sp) [35][36], Wittig coupling [3][21][37][38][39], Kolbe electrosynthesis [35][40][41][42], organocadmium (sp2–sp3) [43][44

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

• Robert J. Perkins Hai-Chao Xu John M. Campbell Kevin D. Moeller Washington University in Saint Louis, Saint Louis, Missouri 63130, United States 10.3762/bjoc.9.186 Abstract Carboxylic acids have been electro-oxidatively coupled to electron-rich olefins to form lactones. Kolbe decarboxylation does

• 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

• taken because of the well-known Kolbe electrolysis reaction (Scheme 3) [10][11]. In the Kolbe electrolysis (Scheme 3, reaction 1), a carboxylic acid is oxidized. A decarboxylation reaction then leads to the formation of a radical that is subsequently trapped by a second radical formed in solution. The

Synthesis and testing of the first azobenzene mannobioside as photoswitchable ligand for the bacterial lectin FimH

• Vijayanand Chandrasekaran,
• Katharina Kolbe,
• Femke Beiroth and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2013, 9, 223–233, doi:10.3762/bjoc.9.26

• Vijayanand Chandrasekaran Katharina Kolbe Femke Beiroth Thisbe K. Lindhorst Christiana Albertina University of Kiel, Otto Diels Institute of Organic Chemistry, Otto-Hahn-Platz 3/4, D-24098 Kiel, Germany, Fax: +49 431 8807410 10.3762/bjoc.9.26 Abstract In order to allow spatial and temporal

A practical microreactor for electrochemistry in flow

• Kevin Watts,
• William Gattrell and
• Thomas Wirth

Beilstein J. Org. Chem. 2011, 7, 1108–1114, doi:10.3762/bjoc.7.127

• conversion was achieved as established by GC/MS. The reaction shown in Scheme 2 has previously been performed in batch electrolysis leading to product 5 in 78% yield [17]. In addition, Kolbe-type reactions were investigated in flow. 2-Phenylacetic acid (6a) was used as a substrate and yields of up to 40% of

• 1,2-diphenylethane (7a) were obtained with the device depicted in Figure 1; the reactions are shown in Scheme 3. The Kolbe reaction did not seem to be a very suitable reaction for a flow reactor due to the large amount of carbon dioxide and hydrogen that is formed at the anode during the

• the reduction of methanol at the cathode. The Kolbe electrolysis of 6a has also been described as a batch reaction, with a solid base, providing the product 7a in 44% yield [19]. This means that the reaction conditions in the electrochemical microreactor were comparable to batch synthesis. The