Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• from the indoline to B(C6F5)3. The resultant iminium ion is deprotonated by a second indoline molecule with the formation of an ammonium ion and the final indole. The ammonium ion reacts with a HB(C6F5)3 anion with the release of a H2 molecule and the regeneration of B(C6F5)3 for the next catalytic

• -hydroxylation of lactams under phase-transfer organocatalysis conditions employing a chiral quaternary ammonium ion salt. Selective CH-oxidation of methylarenes to aldehydes or carboxylic acids. An example of the regioselective CH-amination by a sterically hindered imide-N-oxyl radical precursor. CH-amination

Thermodynamic and electrochemical study of tailor-made crown ethers for redox-switchable (pseudo)rotaxanes

• Henrik Hupatz,
• Marius Gaedke,
• Hendrik V. Schröder,
• Julia Beerhues,
• Arto Valkonen,
• Fabian Klautzsch,
• Sebastian Müller,
• Felix Witte,
• Kari Rissanen,
• Biprajit Sarkar and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2020, 16, 2576–2588, doi:10.3762/bjoc.16.209

• synthesis of crown ether-based rotaxanes in 1995, crown ethers played a crucial role in the development of mechanically interlocked molecules (MIMs) [22][23]. This rotaxane synthesis was facilitated by the formation of a threaded complex (pseudorotaxane) between a secondary ammonium ion and dibenzo-24-crown

• between the catechol ring of the crown ether and aromatic moieties of the secondary ammonium ion contribute to the complex formation [22][23][24][25]. Over the last 25 years, a detailed understanding of the thermodynamic and kinetic properties of crown ether/ammonium complexes has developed enabling the

• ammonium axles were employed: On the one hand, A1·PF6 can only form a threaded complex with crown-8 ether derivatives due to the two bulky benzyl substituents on the ammonium ion. On the other hand, A2·PF6 possesses one narrow alkyl substituent allowing both crown-8 and crown-7 ethers to form threaded

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

• ]. Aziridines tolerate nucleophiles because chain growth requests the ammonium ion [93][94][95][96]. On the other hand, chain propagation includes the carbocation in the case of oxiranes and oxetanes [92]. More of interest can be seen absorbers, which do not follow such reaction routes. Scheme 7 depicts a

A toolbox of molecular photoswitches to modulate the CXCR3 chemokine receptor with light

• Xavier Gómez-Santacana,
• Sabrina M. de Munnik,
• Tamara A. M. Mocking,
• Niels J. Hauwert,
• Shanliang Sun,
• Prashanna Vijayachandran,
• Iwan J. P. de Esch,
• Henry F. Vischer,
• Maikel Wijtmans and
• Rob Leurs

Beilstein J. Org. Chem. 2019, 15, 2509–2523, doi:10.3762/bjoc.15.244

• CXCR3 agonists are scarce and are mostly limited to peptidomimetics [25], which makes our published biaryl series a notable exception [24]. The general scaffold of these biaryl ligands consists of a polycycloaliphatic anchor and a biaryl moiety both linked to an ammonium ion. Depending on the

Metal-free mechanochemical oxidations in Ertalyte^® jars

• Andrea Porcheddu,
• Francesco Delogu,
• Lidia De Luca,
• Claudia Fattuoni and
• Evelina Colacino

Beilstein J. Org. Chem. 2019, 15, 1786–1794, doi:10.3762/bjoc.15.172

• co-oxidant agent, and in the catalytic cycle reacts with KBr generating in situ −OBr, a stronger oxidizing species. Subsequently, a catalytic amount of −OBr oxidizes the TEMPO radical to the N-oxo-ammonium ion A. The latter in turn rapidly oxidizes the alcohol to the corresponding carbonyl compound

Discrete multiporphyrin pseudorotaxane assemblies from di- and tetravalent porphyrin building blocks

• Mirko Lohse,
• Larissa K. S. von Krbek,
• Sebastian Radunz,
• Suresh Moorthy,
• Christoph A. Schalley and
• Stefan Hecht

Beilstein J. Org. Chem. 2015, 11, 748–762, doi:10.3762/bjoc.11.85

• Universität Berlin, Takustraße 3, 14195 Berlin, Germany. Fax: +49(0)308385-5366; Tel: +49(0)308385-2639 10.3762/bjoc.11.85 Abstract Two pairs of divalent and tetravalent porphyrin building blocks carrying the complementary supramolecular crown ether/secondary ammonium ion binding motif have been synthesized

• . The crown ether/secondary ammonium ion binding motif [34] is a powerful tool to create well-defined pseudorotaxane structures [35][36][37][38][39], which have also served as precursors in rotaxane syntheses [40][41][42] thus providing access to interlocked, mechanically bound molecules. Based on these

• these building blocks is based on force-field calculations, which suggest a good geometric fit between the crown ether hosts and the ammonium ion guests. The two monovalent building blocks A1 and C1 serve as control compounds. Based on this “toolbox”, which can be expanded in the future with other

Supramolecular chemistry II

• Christoph A. Schalley

Beilstein J. Org. Chem. 2011, 7, 1541–1542, doi:10.3762/bjoc.7.181

• Beilstein Journal of Organic Chemistry [1]. This first series of articles had quite a broad scope ranging from encapsulation and carbohydrate, peptide, anion and ammonium ion binding, through chiral recognition, the formation of pseudorotaxanes and template effects, all the way to allosteric binding to

When gold can do what iodine cannot do: A critical comparison

• Sara Hummel and
• Stefan F. Kirsch

Beilstein J. Org. Chem. 2011, 7, 847–859, doi:10.3762/bjoc.7.97

• reaction does not occur via electrophilic activation. Instead, due to the iodide ion still present in the reaction mixture, the ammonium ion intermediate undergoes SN1 or SN2 substitution, or even E2 elimination of an alkyl group. This system yields products in up to quantitative yields, and successfully

Pyridinium based amphiphilic hydrogelators as potential antibacterial agents

• Sayanti Brahmachari,
• Sisir Debnath,
• Sounak Dutta and
• Prasanta Kumar Das

Beilstein J. Org. Chem. 2010, 6, 859–868, doi:10.3762/bjoc.6.101

• , 1H), 9.85 (s, 1H), 10.79 (br, 1H) ppm; ESI-MS: m/z calcd for C24H43N2O (the quaternary ammonium ion, 100%) 375.3370; found 375.3335 [M]+; Elemental analysis calcd (%) for C24H43N2OCl: C, 70.12 H, 10.54; N, 6.81; found: C, 69.86; H, 10.31; N, 6.53. Data for 2: 1H NMR (300 MHz, CDCl3, 25 °C): δ = 0.87

• (t, 3H), 1.25 (br, 24H), 1.65–1.74 (m, 2H), 2.67 (t, 2H), 4.44 (s, 3H), 7.88–7.93 (m, 1H), 8.44–8.46 (d, 1H), 9.24–9.27 (d, 1H), 9.85 (s, 1H), 10.80 (br, 1H) ppm; ESI-MS: m/z calcd for C22H39N2O (the quaternary ammonium ion, 100%) 347.3057, found 347.2011 [M]+; Elemental analysis calcd (%) for

• for C20H35N2O (the quaternary ammonium ion, 100%) 319.2744; found 319.1093 [M]+; Elemental analysis calcd (%) for C20H35N2OCl: C, 67.67; H, 9.94; N, 7.89; found: C, 67.49; H, 10.02; N, 8.07. Data for 4: 1H NMR (300 MHz, CDCl3, 25 °C): δ = 0.87 (t, 3H), 1.26 (br, 24H), 1.59 (br, 2H), 2.29 (t, 2H), 7.53

Aromatic and heterocyclic perfluoroalkyl sulfides. Methods of preparation

• Vladimir N. Boiko

Beilstein J. Org. Chem. 2010, 6, 880–921, doi:10.3762/bjoc.6.88

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

• develop synthetic receptors for their selective molecular recognition. The type of host compounds for organic ammonium ion binding span a wide range from crown ethers to calixarenes to metal complexes. Typical intermolecular interactions are hydrogen bonds, electrostatic and cation–π interactions

• , hydrophobic interactions or reversible covalent bond formation. In this review we discuss the different classes of synthetic receptors for organic ammonium ion recognition and illustrate the scope and limitations of each class with selected examples from the recent literature. The molecular recognition of

• ammonium ions in amino acids is included and the enantioselective binding of chiral ammonium ions by synthetic receptors is also covered. In our conclusion we compare the strengths and weaknesses of the different types of ammonium ion receptors which may help to select the best approach for specific

Comparison of zwitterionic N-alkylaminomethanesulfonic acids to related compounds in the Good buffer series

• Robert D. Long,
• Newton P. Hilliard Jr,
• Suneel A. Chhatre,
• Tatiana V. Timofeeva,
• Andrey A. Yakovenko,
• Daniel K. Dei and
• Enoch A. Mensah

Beilstein J. Org. Chem. 2010, 6, No. 31, doi:10.3762/bjoc.6.31

• between amine and sulfonic acid groups as originally described by Norman Good, and in common use as biological buffers). Our hypothesis was that a shorter carbon chain (one carbon) between the amino and sulfonic acid groups should lower the ammonium ion pKa values. The alkylaminomethanesulfonate compounds

• point (Figure 3). Since the ionization of the sulfonic acid functional group is essentially complete in aqueous solution, for purposes of creating buffers we are primarily interested in the pKa of the ammonium ion proton dissociation (1a to 1c). The pKa of this dissociation is observed to be influenced

• likely explanation for the observed ammonium ion acidity, the possibility of a through space intramolecular interaction (i.e. hydrogen-bonding or similar stabilization) of the proton with the sulfonate moiety cannot be discounted as a contributing factor. Results and Discussion Synthetic methodology

Synthesis of phosphorothioates using thiophosphate salts

• Babak Kaboudin and
• Fatemeh Farjadian

Beilstein J. Org. Chem. 2006, 2, No. 4, doi:10.1186/1860-5397-2-4

• benzamide. All efforts for solving this problem failed and in all cases benzamide was obtained as the major product. We decided to replace this ammonium ion with a triethyl ammonium ion and then to study the reaction of new salt with benzoyl chloride. Triethylammonium O,O'-diethyl thiophosphate was obtained