2-Heteroarylethylamines in medicinal chemistry: a review of 2-phenethylamine satellite chemical space

• Carlos Nieto,
• Alejandro Manchado,
• Ángel García-González,
• David Díez and
• Narciso M. Garrido

Beilstein J. Org. Chem. 2024, 20, 1880–1893, doi:10.3762/bjoc.20.163

• improvement through inverse agonism at histamine receptor 3 (H3) using recombinant isoforms. This finding corrects their previous assumption of betahistidine acting as an antagonist. Inhibition of cAMP formation and [3H]arachidonic acid release concluded the inverse agonist role. Five-membered heteroaromatic

• -heteroarylethylamine chemical space is constituted by the biogenic amine histamine (43). In a similar fashion as dopamine and epinephrine produced from ʟ-phenylalanine along the catecholamine pathway, histamine is generated from the amino acid ʟ-histidine (42) via enzymatic decarboxylation promoted by ʟ-histidine

• decarboxylase (Scheme 8) [45][46][47]. Histamine is commonly degradated by two enzymes: diamine oxidase (DAO) to produce (imidazol-4-yl)acetic acid (44), or histamine N-methyltransferase (HMT) to N-methylhistamine 45. Monoamine oxidase B (MAO-B) transforms N-methylhistamine into (N-methylimidazol-4-yl)acetic

The Groebke–Blackburn–Bienaymé reaction in its maturity: innovation and improvements since its 21st birthday (2019–2023)

• Cristina Martini,
• Muhammad Idham Darussalam Mardjan and
• Andrea Basso

Beilstein J. Org. Chem. 2024, 20, 1839–1879, doi:10.3762/bjoc.20.162

• that time, along with some 30 solvents. The most widely used conditions, however, remained those originally discovered by Groebke, Blackburn and Bienaymé, namely the use of Sc(OTf)3, perchloric acid or p-toluenesulfonic acid as catalysts, and methanol, ethanol or toluene as solvents, or under solvent

• -free conditions. Although some new metal or Brønsted acid catalysts have been reported in the last few years, the main innovations can be found in the use of organic catalysts, enzymes, and compartmentations. A few reports on the in situ generation of reactants and on the reaction conducted under flow

• conditions can also be found. 1.1 Metal and Brønsted acid catalysts As previously mentioned, Sc triflate is the most widely used Lewis acid for the GBB reaction, generally exhibiting higher catalytic activity compared to other metal triflates, such as Yb, In or Bi. No extensive work had been done on rare

A facile three-component route to powerful 5-aryldeazaalloxazine photocatalysts

• Ivana Weisheitelová,
• Radek Cibulka,
• Marek Sikorski and
• Tetiana Pavlovska

Beilstein J. Org. Chem. 2024, 20, 1831–1838, doi:10.3762/bjoc.20.161

• have been successfully synthesised through a one-pot, three-component reaction involving N,N-dimethylbarbituric acid, an aromatic aldehyde and aniline. By utilizing readily available reagents, this approach opens up the opportunity for the efficient formation of a variety of 5-aryldeazaalloxazines

• -dimethyldichloromethyleniminium chloride and the Vilsmeier reagent, or condensations between o-aminobenzaldehydes and barbituric acid [20][21][23][24][25][26][27]. Neither of these methods allows for the introduction of an aryl substituent into C(5), which confers unique chemical and physical properties on 5-aryldeazaalloxazines

• aldehydes and N-methylbarbituric acid in AcOH/PPA (polyphosphoric acid). However, this method was not successful for the synthesis of 5-aryldeazaalloxazines 2, and we never observed the formation of 5,10-dihydropyrimido[4,5-b]quinolinediones either. We noticed that the chemical nature of the solvent was

Discovery of antimicrobial peptides clostrisin and cellulosin from Clostridium: insights into their structures, co-localized biosynthetic gene clusters, and antibiotic activity

• Moisés Alejandro Alejo Hernandez,
• Katia Pamela Villavicencio Sánchez,
• Rosendo Sánchez Morales,
• Karla Georgina Hernández-Magro Gil,
• David Silverio Moreno-Gutiérrez,
• Eddie Guillermo Sanchez-Rueda,
• Yanet Teresa-Cruz,
• Brian Choi,
• Armando Hernández Garcia,
• Alba Romero-Rodríguez,
• Oscar Juárez,
• Siseth Martínez-Caballero,
• Mario Figueroa and
• Corina-Diana Ceapă

Beilstein J. Org. Chem. 2024, 20, 1800–1816, doi:10.3762/bjoc.20.159

• resulting peptides exhibit unique structural features due to thioether bridges between dehydrated serine or threonine (Dha/Dhb) and cysteine (Cys). These thioether bridges lead to cyclic peptides with the modified amino acid lanthionine (Dha-Cys) or methyllanthionine (Dhb-Cys). The strong antimicrobial

• localize novel evolutive clades This study used 28 amino acid sequences of LanM enzymes from MIBiG [38] whose activity has been experimentally proven [24] to identify homologous sequences using BLASTP [39] (in BV-BRC [40]). They are considered our reference sequences. Two of these reference sequences are

• enzymes amino acid sequences from MIBiG and the homologs identified in our study. The taxonomy of the bacteria to which they belong is indicated in the figure. The selected superclade highlighted in Figure 1, containing sequences that mainly belong to Bacilli and Clostridia, was of particular interest

Chiral bifunctional sulfide-catalyzed enantioselective bromolactonizations of α- and β-substituted 5-hexenoic acids

• Sao Sumida,
• Ken Okuno,
• Taiki Mori,
• Yasuaki Furuya and
• Seiji Shirakawa

Beilstein J. Org. Chem. 2024, 20, 1794–1799, doi:10.3762/bjoc.20.158

• Sao Sumida Ken Okuno Taiki Mori Yasuaki Furuya Seiji Shirakawa Institute of Integrated Science and Technology, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan 10.3762/bjoc.20.158 Abstract Enantioselective halolactonizations of sterically less hindered alkenoic acid substrates

• without substituents on the carbon–carbon double bond have remained a formidable challenge. To address this limitation, we report herein the asymmetric bromolactonization of 5-hexenoic acid derivatives catalyzed by a BINOL-derived chiral bifunctional sulfide. Keywords: asymmetric catalysis

• to asymmetric halolactonizations, especially for the synthesis of chiral γ-butyrolactones and δ-valerolactones via the reaction of 4-pentenoic acid and 5-hexenoic acid derivatives (Scheme 1). Notably, however, substituents on the carbon–carbon double bond of alkenoic acid substrates are generally

Oxidative fluorination with Selectfluor: A convenient procedure for preparing hypervalent iodine(V) fluorides

• Samuel M. G. Dearman,
• Xiang Li,
• Yang Li,
• Kuldip Singh and
• Alison M. Stuart

Beilstein J. Org. Chem. 2024, 20, 1785–1793, doi:10.3762/bjoc.20.157

• such as 5 (Scheme 2D) using large excesses of trichloroisocyanuric acid (TCCA) and potassium fluoride [24]. The iodine(V) fluorides were formed in good spectroscopic yields (79–94%), but only one product, tetrafluoro(4-fluorophenyl)-λ5-iodane 5, was isolated from the reaction mixture by performing

• iodine(I) precursor 8 (Table 1). Reacting 8 with 4 equivalents of trichloroisocyanuric acid (TCCA) and 6 equivalents of potassium fluoride in dry acetonitrile at 40 °C for 48 hours formed difluoroiodane 6 in a 90% spectroscopic yield (Table 1, entry 1). An iodosyl decomposition product 9 was also formed

Ugi bisamides based on pyrrolyl-β-chlorovinylaldehyde and their unusual transformations

• Alexander V. Tsygankov,
• Vladyslav O. Vereshchak,
• Tetiana O. Savluk,
• Serhiy M. Desenko,
• Valeriia V. Ananieva,
• Oleksandr V. Buravov,
• Yana I. Sakhno,
• Svitlana V. Shishkina and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2024, 20, 1773–1784, doi:10.3762/bjoc.20.156

• prepared and characterized. Surprisingly, a well-documented approach to obtain peptide-containing carboxylic acids through acid hydrolysis of the convertible isocyanide moiety in the Ugi bisamides proceeded in an unexpected manner in our case, leading to the formation of derivatives of amides of

• heterylidenepyruvic acid. An optimized synthetic protocol for this transformation was elaborated and a plausible sequence involving the elimination of the 2-chloroacetamide moiety and the conversion of the β-chlorovinyl fragment into a vinyl one is provided. Keywords: convertible isocyanides; multicomponent reaction

• used as acid components in tandem combinations of various multicomponent processes such as Ugi and Ugi, azido-Ugi and Ugi, Ugi and Passerini, Groebke–Blackburn–Bienaymé and Ugi, etc. [15][17][37][38]. The creation of hybrid molecules by using primary and post-modified Ugi products in combination with

Synthesis and characterization of 1,2,3,4-naphthalene and anthracene diimides

• Adam D. Bass,
• Daniela Castellanos,
• Xavier A. Calicdan and
• Dennis D. Cao

Beilstein J. Org. Chem. 2024, 20, 1767–1772, doi:10.3762/bjoc.20.155

• . Heating 5 with hexylamine or aniline in refluxing acetic acid successfully led to the formation of the targeted aromatic diimides bearing either N-hexyl (7-Hex) or N-phenyl (7-Ph) substitutions in good yields. The same strategy was employed to create the imide-capped anthracenes 8-Hex and 8-Ph

Harnessing unprotected deactivated amines and arylglyoxals in the Ugi reaction for the synthesis of fused complex nitrogen heterocycles

• Javier Gómez-Ayuso,
• Pablo Pertejo,
• Tomás Hermosilla,
• Israel Carreira-Barral,
• Roberto Quesada and
• María García-Valverde

Beilstein J. Org. Chem. 2024, 20, 1758–1766, doi:10.3762/bjoc.20.154

• acid, indole-2-carboxylic acid, pyrrole-2-carboxylic acid or N-phenylglycine has allowed the use of these compounds in the Ugi reaction without triggering competitive reactions. The additional functional group present in the resulting Ugi adduct can be leveraged in different post-condensation

• methodology has several drawbacks, as the need to synthesise the 2-azidobenzoic acid from anthranilic acid and sodium azide, the requirement of anhydrous conditions to perform the Staudinger/aza-Wittig sequence or the generation of large quantities of triphenylphosphine oxide which needs to be removed by

• protecting groups, as the reduced nucleophilic character of the amino group of the anthranilic acid would prevent its participation in the Ugi reaction. In this way, the Ugi reaction was performed using arylglyoxals 1, anthranilic acid derivatives 2, amines 3 and isocyanides 4 following the most common

Synthesis of polycyclic aromatic quinones by continuous flow electrochemical oxidation: anodic methoxylation of polycyclic aromatic phenols (PAPs)

• Hiwot M. Tiruye,
• Solon Economopoulos and
• Kåre B. Jørgensen

Beilstein J. Org. Chem. 2024, 20, 1746–1757, doi:10.3762/bjoc.20.153

• blocked like in 2-naphthol (1a) [17]. Oxidation with iodoxybenzoic acid (IBX) [17] or stabilised IBX (SIBX) [18] form o-quinones selectively, even when the p-quinones are structurally feasible. However, all these methods constitute toxic hazards and/or produce stoichiometric amounts of waste products

• flowrate of 100 µL/min. The current was increased from 1 mA to 13 mA to increase the electron equivalents from 1 F/mol to 8 F/mol at a potential of 1.7–3.0 V. The crudes, after evaporation of the solvents, were further hydrolysed with a mixture of HCl, acetic acid, and water to release the quinones before

• phenanthren-4-ol (6b) provided the p-dimethoxylated product 8b in 66% yield (87 mg), consuming 8 F/mol over a duration of 12.7 h (Table 3, entry 5). Next, quinone acetal 8b was hydrolysed to phenanthrene-1,4-dione (9b) using aq acetic acid and HCl in 93% yield. The hydrolysis step went smoothly for all

Syntheses and medicinal chemistry of spiro heterocyclic steroids

• Laura L. Romero-Hernández,
• Ana Isabel Ahuja-Casarín,
• Penélope Merino-Montiel,
• Sara Montiel-Smith,
• José Luis Vega-Báez and
• Jesús Sandoval-Ramírez

Beilstein J. Org. Chem. 2024, 20, 1713–1745, doi:10.3762/bjoc.20.152

• diazo precursor. To achieve this, cholesterol was first esterificated using 2-(4-methoxyphenyl)acetic acid and DCC. The resulting arylacetic ester 12 was then reacted with 4-acetamidobenzenesulfonyl azide (p-ABSA) and DBU in anhydrous acetonitrile to yield the diazo compound 13 in 22% yield. The carbene

• of 10% Pd/C and 5% Pd/CaCO3 yielded reduced compound 19. Cleavage of the THP group with Amberlist-15® resin and a final Jones oxidation of the primary alcohol to the carboxylic acid, led to cyclization with the 17β-OH group affording the lactone 20 in a moderate overall yield (Scheme 6). Biological

• -toluenesulfonic acid-mediated hydrolysis led to the cyclization reaction yielding the steroidal 17-spiro derivatives. The procedure was applied to synthesize drospirenone (Figure 1) and extended to build the spirolactone 23 from DHEA, a key intermediate toward the popular diuretic spironolactone (Scheme 7). 17

Chemo-enzymatic total synthesis: current approaches toward the integration of chemical and enzymatic transformations

• Ryo Tanifuji and
• Hiroki Oguri

Beilstein J. Org. Chem. 2024, 20, 1693–1712, doi:10.3762/bjoc.20.151

• approach, they used a chiral boron catalyst as a Lewis acid and achieved at best an endo/exo selectivity of 1.9:1 in a similar DA reaction. The use of Diels–Alderase in their recent work significantly improved the endo/exo selectivity under mild conditions in water, thereby highlighting the strengths of

• acid 76 in a 4:1 diastereomeric ratio. Thioesterification and removal of the TBS group furnished the desired thioester 77 as a mimic of biosynthetic intermediate 64. With synthetic substrate 77 for enzymatic conversions in hand, Sherman and co-workers attempted to overexpress TylGIV and TylGV, however

• the successive condensation of myristic acid, ʟ-alanine, and glycine to furnish thioester 87 on the peptidyl carrier protein (PCP) domain of SfmB [94][97]. The downstream NRPS module, SfmC, then catalyzes sequential reactions with 86 and 87 to assemble pentacyclic scaffold 93 in a single stroke [97

Oxidation of benzylic alcohols to carbonyls using N-heterocyclic stabilized λ³-iodanes

• Thomas J. Kuczmera,
• Pim Puylaert and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2024, 20, 1677–1683, doi:10.3762/bjoc.20.149

• established in several oxidative transformations including the synthesis of complex molecules and drugs [12][13]. The most prominent examples are the pentavalent derivatives 2-iodoxybenzoic acid (IBX) and Dess–Martin periodinane (DMP) [14][15]. Although mild and selective oxidants, these highly oxidized λ5

• showing no reaction with iodane 1a. Utilizing the tetrazine 1c, p-methylbenzaldehyde (4a) was observed as a new species at 9.94 ppm (Figure 3b). The reaction reached 31% conversion after 72 h, however, p-methylbenzoic acid (4a’) was formed in 35% as well, showing an undesired overreaction. In this

• experiment no formation of an alkoxyiodane was observed, indicating that the formation of this ligand-exchanged intermediate is slower than the dehydrogenation. As a consequence, we attempted to accelerate the ligand exchange through the addition of a Lewis acid and the performance of the NHIs was compared

Ring opening of photogenerated azetidinols as a strategy for the synthesis of aminodioxolanes

• Henning Maag,
• Daniel J. Lemcke and
• Johannes M. Wahl

Beilstein J. Org. Chem. 2024, 20, 1671–1676, doi:10.3762/bjoc.20.148

• . Dioxolanes 11 and 16 are inherently stable and we were unable to cleave the ketal after reaction. Thus, we investigated the feasibility to use boronic acids in the ring-opening reaction (Scheme 3c). Phenylboronic acid 17 is known to exhibit a similar acidity as the corresponding hemiketals providing a

Methyltransferases from RiPP pathways: shaping the landscape of natural product chemistry

• Maria-Paula Schröder,
• Isabel P.-M. Pfeiffer and
• Silja Mordhorst

Beilstein J. Org. Chem. 2024, 20, 1652–1670, doi:10.3762/bjoc.20.147

• the specialised metabolism of bacteria and fungi. Each NRPS module is minimally composed of a condensation (C) domain, an adenylation (A) domain, and a peptidyl carrier protein (PCP or thiolation/T domain), and one module typically incorporates one amino acid into the final natural product. In

• [34]. In reductive amination, the substrate is usually an aldehyde or amine. After the formation of the iminium ion, it is reduced with the appropriate reagent to form the N-methylated amino acid. Different methods have been established using for example benzaldehyde as a protection group, sodium

• intermediate is then reduced with H2 [37]. When synthesising via a reductive ring opening, typically, an N-Fmoc-protected amino acid is condensed with formaldehyde in the presence of p-toluic acid in refluxing toluene to yield the 5-oxazolidinone. Reductive ring opening can be achieved by using an excess of

Polymer degrading marine Microbulbifer bacteria: an un(der)utilized source of chemical and biocatalytic novelty

• Weimao Zhong and
• Vinayak Agarwal

Beilstein J. Org. Chem. 2024, 20, 1635–1651, doi:10.3762/bjoc.20.146

• classes of natural products isolated from Microbulbifer to date include alkaloids [15], fatty acid and polyketides [16][17], and non-ribosomally synthesized peptides [3][4][7]. These findings validate the potential for secondary metabolite discovery from Microbulbifer genus. This review will cover the

• the characterization of a purified agarase belonging to the family GH-86 from Microbulbifer bacteria. Alginate lyases The polysaccharide alginate is produced by various seaweeds and bacteria [44]. Two building blocks, β-ᴅ-mannuronic acid (M) and α-ʟ-guluronic acid (G), are used to assemble alginate in

• a polyM-specific alginate lyase. AlgL17 was an exotype alginate lyase based on its ability of producing 4-deoxy-ʟ-erythro-5-hexoseulose uronic acid (DEH) from sodium alginate [62]. AlgL6 degraded polyM, polyG, and sodium alginate in an exolytic manner. It exhibited good stability in the presence of

New triazinephosphonate dopants for Nafion proton exchange membranes (PEM)

• Fátima C. Teixeira,
• António P. S. Teixeira and
• C. M. Rangel

Beilstein J. Org. Chem. 2024, 20, 1623–1634, doi:10.3762/bjoc.20.145

• acid groups [22]. These membranes have an excellent chemical stability, but their high proton conduction is dependent of the water content of the membranes which limits their operating temperature range to 80 °C [23]. The importance of the membranes for the new sustainable energy sources fostered the

• efforts and investments in the research and development of new membranes that might be able to surpass the actual limitations. Our studies started with the synthesis of phosphonate and phosphonic acid compounds to be used as membrane dopants [24][25]. These studies were followed by the incorporation of

• nucleophilic substitution using hydrobromic acid, as a 33% solution in acetic acid, to afford the corresponding bromide derivative 9 [54] (Scheme 2). Subsequently 1-(benzyloxy)-4-(bromomethyl)benzene (9) underwent Michaelis–Arbuzov reaction with triethyl phosphite to afford diethyl [4-(benzyloxy)phenyl

Supramolecular assemblies of amphiphilic donor–acceptor Stenhouse adducts as macroscopic soft scaffolds

• Ka-Lung Hung,
• Leong-Hung Cheung,
• Yikun Ren,
• Ming-Hin Chau,
• Yan-Yi Lam,
• Takashi Kajitani and
• Franco King-Chi Leung

Beilstein J. Org. Chem. 2024, 20, 1590–1603, doi:10.3762/bjoc.20.142

• design of the reported DAs, we designed and synthesized a series of DAs featuring a second-generation DASA switching motif and different chain lengths of the alkyl linker (i.e., DAn) that connects the DASA indoline motif with the hydrophilic part (i.e., the carboxylic acid motif, Scheme 1). The alkyl

• cellular compatibility was good. These DAn biocompatibility results are the first example showing the intrinsic cytocompatibility of macroscopic soft DA scaffolds. Conclusion Amphiphilic DASAs with alkyl linkers of different length connecting to a carboxylic acid were prepared. Photochemical properties of

• specified. All reactions were performed under nitrogen unless otherwise specified. Analytical thin-layer chromatography (TLC) was performed with Macherey-Nagel silica gel 60 UV254 aluminum plates, and visualization was accomplished by UV light (254 nm or 365 nm) or by staining with phosphomolybdic acid and

Divergent role of PIDA and PIFA in the AlX₃ (X = Cl, Br) halogenation of 2-naphthol: a mechanistic study

• Kevin A. Juárez-Ornelas,
• Manuel Solís-Hernández,
• Pedro Navarro-Santos,
• J. Oscar C. Jiménez-Halla and
• César R. Solorio-Alvarado

Beilstein J. Org. Chem. 2024, 20, 1580–1589, doi:10.3762/bjoc.20.141

• generated in situ simply by mixing PIFA with a Lewis acid, in this case AlCl3. The importance of this protocol arises from the oxidation of an AlCl3-based chlorine atom, which is an available and cheap reagent. Then it is used as an electrophile source in the chlorination process with an umpolung reactivity

• energy between both states indicates the importance of the spontaneous interconversion of both species, which is observed only in the presence of two equivalents of the Lewis acid. After the addition of 2-naphthol, the chlorine atom is introduced barrier-free into the phenolic ring, producing the

Electrocatalytic hydrogenation of cyanoarenes, nitroarenes, quinolines, and pyridines under mild conditions with a proton-exchange membrane reactor

• Koichi Mitsudo,
• Atsushi Osaki,
• Haruka Inoue,
• Eisuke Sato,
• Naoki Shida,
• Mahito Atobe and
• Seiji Suga

Beilstein J. Org. Chem. 2024, 20, 1560–1571, doi:10.3762/bjoc.20.139

• anilines were obtained. The quinoline reduction was efficiently promoted by adding a catalytic amount of p-toluenesulfonic acid (PTSA) or pyridinium p-toluenesulfonate (PPTS). Pyridine was also reduced to piperidine in the presence of PTSA. Keywords: cyanoarene; nitroarene; PEM reactor; pyridine

• of 3a. Based on this hypothesis, we examined the reduction of 1a in the presence of several acids (Table 2). First, electrochemical reduction was performed with 0.2 or 1.0 equiv of acetic acid, but the yield of 3a did not decrease, suggesting that 2a could not be trapped by acetic acid (pKa = 4.75

• ). To ensure the capture of 2a, we performed reduction with phosphoric acid (pKa = 2.12). Although the generation of 3a was suppressed, only a trace amount of 2a was obtained, and almost 1a was recovered (Table 2, entry 4). This was probably because the presence of water inhibited the reaction

Mining raw plant transcriptomic data for new cyclopeptide alkaloids

• Draco Kriger,
• Michael A. Pasquale,
• Brigitte G. Ampolini and
• Jonathan R. Chekan

Beilstein J. Org. Chem. 2024, 20, 1548–1559, doi:10.3762/bjoc.20.138

• biosynthetic enzymes. Ultimately proteolysis releases the modified core peptide as the mature RiPP natural product [5][6]. In the case of the newly described burpitide family of RiPPs, the defining feature is the presence of amino acid side-chain crosslinks installed by a copper-dependent burpitide cyclase [4

• ]. These RiPP natural products encompass a wide range of structural scaffolds including cyclopeptide alkaloids that contain a phenolic ether-linkage and the lyciumin-type peptides that are composed of a crosslink between the Trp-indole-N and the carbon in another amino acid side chain or peptide backbone

• tryptophan at the position for cyclization, indicating they may correspond to the stephanotic acid-type burpitides like moroidin (Trp-indole-C to carbon crosslink, Figure 3) [4]. Amaranthaceae family The Amaranthaceae family is home to the known moroidin producer, Celosia argentea var. cristata (Cockscomb

Benzylic C(sp³)–H fluorination

• Alexander P. Atkins,
• Alice C. Dean and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 1527–1547, doi:10.3762/bjoc.20.137

• FAT with Selectfluor to produce the desired benzyl fluoride. Increasing amino acid and Selectfluor loadings achieved difluorination of the benzylic substrates. This procedure was demonstrated predominately on primary benzylic substrates, but could be used to effect the fluorination of several

• positions was observed when both positions were present, as highlighted by the formation of 19 and 20 in equal yields from the same substrate. In the same year, Yoneda and co-workers reported the electrochemical benzylic fluorination of four phenylacetic acid esters and 1-tetralone (Figure 38) [96]. Et4N

• radical benzylic C(sp3)–H fluorination using Selectfluor. Silver and amino acid-mediated benzylic fluorination. Copper-catalysed radical benzylic C(sp3)–H fluorination using NFSI. Copper-catalysed C(sp3)–H fluorination of benzylic substrates with electrochemical catalyst regeneration. Yields are NMR

Primary amine-catalyzed enantioselective 1,4-Michael addition reaction of pyrazolin-5-ones to α,β-unsaturated ketones

• Pooja Goyal,
• Akhil K. Dubey,
• Raghunath Chowdhury and
• Amey Wadawale

Beilstein J. Org. Chem. 2024, 20, 1518–1526, doi:10.3762/bjoc.20.136

• 10.3762/bjoc.20.136 Abstract The enantioselective 1,4-addition reaction of pyrazolin-5-ones to α,β-unsaturated ketones catalyzed by a cinchona alkaloid-derived primary amine–Brønsted acid composite is reported. Both enantiomers of the anticipated pyrazole derivatives were obtained in good to excellent

• marked increase in both the yield and enantioselectivity of the product 3aa were observed. Among the screened Brønsted acids A1–6, the combination of 15 mol % of the catalyst I and 30 mol % of (±)-mandelic acid (A5) was found to be superior in terms of enantioselectivity (92% ee) of the product 3aa

• presence of one equivalent Brønsted acid additive A5, the catalyst II generates the monoprotonated diamine II-A5. The condensation of the primary amine moiety in II-A5 with the carbonyl group of the α,β-unsaturated ketone 1b in presence of the Brønsted acid leads to the formation of the iminium ion

Towards an asymmetric β-selective addition of azlactones to allenoates

• Behzad Nasiri,
• Ghaffar Pasdar,
• Paul Zebrowski,
• Katharina Röser,
• David Naderer and
• Mario Waser

Beilstein J. Org. Chem. 2024, 20, 1504–1509, doi:10.3762/bjoc.20.134

• -selective manner with moderate levels of enantioselectivities (up to 83:17 er). Furthermore, the obtained products can be successfully engaged in nucleophilic ring opening reactions, thus giving highly functionalized α-amino acid derivatives. Keywords: allenoates; amino acids; azlactones; organocatalysis

• -functionalizations by reacting them with suited C- or heteroatom electrophiles. α-Amino acid-derived azlactones 1 are amongst the most commonly utilized starting materials to access more diverse chiral α,α-disubstituted amino acids (Scheme 1A) [20][21][22]. More specifically, these compounds can be engaged in a

• thus wondering if we could extend this ammonium salt-catalyzed β-selective allenoate functionalization strategy to other amino acid classes. Azlactones 1 have previously been used for γ-selective additions to allenoates under chiral phosphine catalysis [28]. In addition, glycine Schiff base derivatives

Electrophotochemical metal-catalyzed synthesis of alkylnitriles from simple aliphatic carboxylic acids

• Yukang Wang,
• Yan Yao and
• Niankai Fu

Beilstein J. Org. Chem. 2024, 20, 1497–1503, doi:10.3762/bjoc.20.133

• system [48]. To probe the radical intermediate in the reaction, a radical rearrangement experiment with cyclopropane-derived acid 31 was subjected to the standard conditions, leading to the expected ring opening, alkene-containing nitrile product 32 in 62% isolated yield (Figure 3A). Moreover