Bioinformatic prediction of the stereoselectivity of modular polyketide synthase: an update of the sequence motifs in ketoreductase domain

• Changjun Xiang,
• Shunyu Yao,
• Ruoyu Wang and
• Lihan Zhang

Beilstein J. Org. Chem. 2024, 20, 1476–1485, doi:10.3762/bjoc.20.131

• from 17 modular cis-AT PKSs [8]. In addition, Keatinge–Clay reported a conserved “H” motif in the sequence of A2-type KRs and a “P” motif in B2-type KRs as markers to distinguish them from the non-epimerizing A1/B1-type KRs [9]. The presence of the catalytic "Y" motif and the absence of the NADPH

• domain. Among actinobacterial KRs from β-modules, A-type KRs (52%) are the most abundant, followed by B-type KRs (36%), and C-type KRs (12%). Comparison between KRS and KRC subdomains KR domains are structurally divided into two subdomains: a catalytic subdomain (KRC) with an intact Rossmann fold where

• stereoselectivity of KR is controlled solely by KRC, and KRS does not influence its catalytic selectivity. Moreover, A2- and B2-type KRCs formed a separatable clade from A1- and B1-type KRC, respectively, suggesting that phylogenetic analysis can be used for stereochemical prediction. It is noteworthy that A0- (0

Synthesis of 2-benzyl N-substituted anilines via imine condensation–isoaromatization of (E)-2-arylidene-3-cyclohexenones and primary amines

• Lu Li,
• Na Li,
• Xiao-Tian Mo,
• Ming-Wei Yuan,
• Lin Jiang and
• Ming-Long Yuan

Beilstein J. Org. Chem. 2024, 20, 1468–1475, doi:10.3762/bjoc.20.130

• could be easily carried out by catalytic hydrogenation to produce 6 (Scheme 6a). On the other hand, 4ax could smoothly undergo N-methylation with MeI to give product 7 in quantitative yield (Scheme 6b). Conclusion In conclusion, we have developed an efficient method to rapidly synthesize 2-benzyl-N

Challenge N- versus O-six-membered annulation: FeCl₃-catalyzed synthesis of heterocyclic N,O-aminals

• Giacomo Mari,
• Lucia De Crescentini,
• Gianfranco Favi,
• Fabio Mantellini,
• Diego Olivieri and
• Stefania Santeusanio

Beilstein J. Org. Chem. 2024, 20, 1412–1420, doi:10.3762/bjoc.20.123

• content of the reaction environment during the time. Then, to explain the related formation of 5 and 6, we hypothesized a plausible reaction mechanism in which iron is involved in two concomitant catalytic cycles (Scheme 4). Initially, FeCl3 forms an acid–base complex with one of the alkoxy groups of 4

• providing intermediate A. The latter, by loss of a trichloro(alkoxy)ferrate(III) anion, generates a strong electrophile such as the oxocarbenium cation intermediate B. The released trichloro(alkoxy)ferrate(III) splits into FeCl3, which enters the catalytic cycle, and a free alkoxide, which acts as a base

• catalytic cycle. Similar to what was previously observed, the elimination of the trichloro(alkoxy)ferrate(III) anion from intermediate C provides the iminium ion D, susceptible to nucleophilic attack by a water molecule present in the reaction medium, leading to the carbinolamines 6. This latter synthesis

Hypervalent iodine-catalyzed amide and alkene coupling enabled by lithium salt activation

• Akanksha Chhikara,
• Fan Wu,
• Navdeep Kaur,
• Prabagar Baskaran,
• Alex M. Nguyen,
• Zhichang Yin,
• Anthony H. Pham and
• Wei Li

Beilstein J. Org. Chem. 2024, 20, 1405–1411, doi:10.3762/bjoc.20.122

• catalysis, which often involves the catalytic use of an iodoarene with stoichiometric oxidants such as MCPBA, Selectfluor, etc. [18][19][20]. Earlier and recent hypervalent iodine-catalyzed olefin halofunctionalizations by several groups have predicated on the use of intramolecular olefin substrates

• α-phenylstyrene produced the respective oxazoline products with high regioselectivity and reasonable yields using iodoanisole as the catalyst precursor (Figure 3, products 24 and 25). The proposed catalytic cycle (Figure 4) begins with iodotoluene A which is oxidized by Selectfluor salt into the

• , 16 h. b) Iodoanisole (20 mol %). Alkene substrate scope studies. a) Standard conditions: alkene (0.25 mmol), iodotoluene (20 mol %), LiBF4 (100 mol %), Selectfluor (150 mol %), 3,4-dimethylbenzamide (400 mol %), MeNO2 (0.25 M), rt, 16 h. b) Iodoanisole (20 mol %), MeCN (0.25 M). Proposed catalytic

Synthetic applications of the Cannizzaro reaction

• Bhaskar Chatterjee,
• Dhananjoy Mondal and
• Smritilekha Bera

Beilstein J. Org. Chem. 2024, 20, 1376–1395, doi:10.3762/bjoc.20.120

• synthesized via the Cannizzaro reaction. Proposed catalytic cycle for the dehydrogenation of alcohols. Intramolecular Cannizzaro reaction of aryl glyoxal hydrates using TOX catalysts. Intramolecular Cannizzaro reaction of aryl methyl ketones using ytterbium triflate/selenium dioxide. Intramolecular Cannizzaro

Generation of alkyl and acyl radicals by visible-light photoredox catalysis: direct activation of C–O bonds in organic transformations

• Mithu Roy,
• Bitan Sardar,
• Itu Mallick and
• Dipankar Srimani

Beilstein J. Org. Chem. 2024, 20, 1348–1375, doi:10.3762/bjoc.20.119

• . Different photocatalysts, such as transition metal complexes [23][24], organic dyes [25], and semiconductors [26], can be employed for visible-light-induced chemical processes. The choice of photocatalyst depends on the specific requirements of the catalytic process, including the type of reaction, the

• thiocarbonyl derivatives were prepared by reaction of thiocarbonyldiimidazole (TCDI, 15) with alcohols in the presence of a catalytic amount of DMAP (0.4 equiv). TCDI is a very popular substrate for such reaction types and was first introduced by Barton and McCombie (Scheme 6) [20]. In this process, the

• final reductive elimination gives the desired alkene and Ni(I). The two catalytic cycles are finally completed by single-electron reduction of [Ni(I)] by [Ir(II)], which regenerates [Ni(0)] and ground-state [Ir(III)]. Cyclic oxalates readily form the corresponding alkyl radicals under iridium

Synthesis of 1,2,3-triazoles containing an allomaltol moiety from substituted pyrano[2,3-d]isoxazolones via base-promoted Boulton–Katritzky rearrangement

• Constantine V. Milyutin,
• Andrey N. Komogortsev and
• Boris V. Lichitsky

Beilstein J. Org. Chem. 2024, 20, 1334–1340, doi:10.3762/bjoc.20.117

• obtained in three steps from allomaltol by a previously described method [27][28] Earlier, we have shown that hydrazone 3a can be synthesized by reaction of compound 1a with phenylhydrazine (5) in ethanol using a catalytic amount of p-TsOH (Scheme 2). Next, we supposed that hydrochlorides of arylhydrazines

Transition-metal-catalyst-free electroreductive alkene hydroarylation with aryl halides under visible-light irradiation

• Kosuke Yamamoto,
• Kazuhisa Arita,
• Masami Kuriyama and
• Osamu Onomura

Beilstein J. Org. Chem. 2024, 20, 1327–1333, doi:10.3762/bjoc.20.116

• -light-mediated alkene hydroarylation commonly requires external reductants and/or hydrogen atom sources to complete the catalytic cycle [21][22][23][24][25]. Over the past few decades, electrochemistry has proven to be an environmentally benign and convenient approach for accessing open-shell

Phenotellurazine redox catalysts: elements of design for radical cross-dehydrogenative coupling reactions

• Alina Paffen,
• Christopher Cremer and
• Frederic W. Patureau

Beilstein J. Org. Chem. 2024, 20, 1292–1297, doi:10.3762/bjoc.20.112

• substitution patterns on the redox catalytic activity. Keywords: cross-dehydrogenative coupling; O2 activation; phenotellurazine; redox catalysis; Te catalysis; Introduction Tellurium catalysis has become increasingly important in recent years. This is due to its unique chalcogen bonding ability, thus

• reaction [6][7], and Gabbaï yet another in a different cyclization reaction [8][9], among other catalytic chalcogen bonding activation examples [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. In contrast, we have reported recently some redox-active Te-based catalysts

• ]. In the present study, we decided to revisit the design of the phenotellurazine redox catalyst, in the hope of improving it as well as enabling new catalytic reactivity. In particular, we wished to investigate and optimize the level of electronic cooperativity between the Te- and N-centers, the effect

Oxidative hydrolysis of aliphatic bromoalkenes: scope study and reactivity insights

• Amol P. Jadhav and
• Claude Y. Legault

Beilstein J. Org. Chem. 2024, 20, 1286–1291, doi:10.3762/bjoc.20.111

• utilizing a hypervalent iodine-catalyzed oxidative hydrolysis reaction. This catalytic process provides both symmetrical and unsymmetrical dialkyl bromoketones with moderate yields across a broad range of bromoalkene substrates. Our studies also reveal the formation of Ritter-type side products by an

• ). We then explored catalytic conditions for the generation of the iodine(III) reagent. Remarkably, when catalytic PhI (0.2 equiv) was employed for in situ generation of Koser’s reagent by using m-CPBA (1.2 equiv) as an oxidant, almost similar results were obtained (Table 2, entry 1) with those obtained

• by stoichiometric use of HTIB. Attempt to perform the reaction using a catalytic amount of 2-iodobenzoic acid (0.2) under similar oxidizing conditions resulted in slightly diminished yield for the desired α-bromoketone (Table 2, entry 2). Notably, the direct use of HTIB as the catalyst, with a

Mechanistic investigations of polyaza[7]helicene in photoredox and energy transfer catalysis

• Johannes Rocker,
• Till J. B. Zähringer,
• Matthias Schmitz,
• Till Opatz and
• Christoph Kerzig

Beilstein J. Org. Chem. 2024, 20, 1236–1245, doi:10.3762/bjoc.20.106

• increased when the triplet efficiently reacts in a catalytic cycle such that turnover numbers exceeding 4400 are achievable with this organocatalyst. Keywords: energy transfer; laser spectroscopy; organocatalyst; photoredox; time-resolved spectroscopy; Introduction The emergence of photoredox chemistry in

• 0.34, is essentially non-reactive under our conditions. Cyanopyridine- and sulfinate-derived radicals are produced in equal concentrations in the catalytic cycle, suggesting that radical coupling is indeed the final reaction step to give the stable sulfonylation/arylation product. The triplet of Aza-H

• chromophores and their roles in catalytic cycles have been extensively studied leading to numerous findings and novel reaction pathways [55][58][59][60][61]. Lately, polyazahelicenes have gained some attention by synthetic groups [62][63][64][65][66]. However, this chromophore class is underexplored concerning

Competing electrophilic substitution and oxidative polymerization of arylamines with selenium dioxide

• Vishnu Selladurai and
• Selvakumar Karuthapandi

Beilstein J. Org. Chem. 2024, 20, 1221–1235, doi:10.3762/bjoc.20.105

• , regioselective aromatic electrophilic substitution is often difficult. Various synthetic strategies have evolved to address such problems and expand the scope of SeO2 beyond the oxidizing capability. Ren et al. adopted potassium-iodide-mediated catalytic selenation of aromatic compounds using SeO2 (Scheme 1) [33

• derivatives was almost exclusively promoted via aromatic electrophilic substitution. All of these reactions reveal the importance of using catalytic processes, preactivated substrates, or of blocking ortho or para sites to obtain the desired arylchalcogen compounds in good yield. To our surprise, Bhat et al

Cofactor-independent C–C bond cleavage reactions catalyzed by the AlpJ family of oxygenases in atypical angucycline biosynthesis

• Jinmin Gao,
• Liyuan Li,
• Shijie Shen,
• Guomin Ai,
• Bin Wang,
• Fang Guo,
• Tongjian Yang,
• Hui Han,
• Zhengren Xu,
• Guohui Pan and
• Keqiang Fan

Beilstein J. Org. Chem. 2024, 20, 1198–1206, doi:10.3762/bjoc.20.102

• -dependent reactions of AlpJ-family oxygenases. Furthermore, the AlpJ- and JadG-catalyzed reactions of CR1 could be quenched by superoxide dismutase, supporting a catalytic mechanism wherein the substrate CR1 reductively activates molecular oxygen, generating a substrate radical and the superoxide anion O2

• •−. Our findings illuminate a substrate-controlled catalytic mechanism of AlpJ-family oxygenases, expanding the realm of cofactor-independent oxygenases. Notably, AlpJ-family oxygenases stand as a pioneering example of enzymes capable of catalyzing oxidative reactions in either an FADH2/FMNH2-dependent or

• contraction reactions, yielding a benzofluorene intermediate 4 and the dimer 5, both featuring a kinamycin skeleton (Scheme 1) [11][12]. Recent investigations unveiled the catalytic activity of the O-methyltransferase-like protein AlpH, which catalyzes a unique SAM-independent coupling of ʟ-glutamylhydrazine

Bismuth(III) triflate: an economical and environmentally friendly catalyst for the Nazarov reaction

• Manoel T. Rodrigues Jr.,
• Aline S. B. de Oliveira,
• Ralph C. Gomes,
• Amanda Soares Hirata,
• Lucas A. Zeoly,
• Hugo Santos,
• João Arantes,
• Catarina Sofia Mateus Reis-Silva,
• João Agostinho Machado-Neto,
• Leticia Veras Costa-Lotufo and
• Fernando Coelho

Beilstein J. Org. Chem. 2024, 20, 1167–1178, doi:10.3762/bjoc.20.99

• , Dhoro and Tius demonstrated that weak acids could also be used as efficient catalysts for the Nazarov reaction [24]. In this context, some research groups developed methodologies that allowed the use of a catalytic amount of Lewis acid. By using more reactive divinyl ketone derivatives, the

• electrocyclization reaction could be mediated by weaker Lewis acids, and consequently a catalytic amount of them could be used. The first example of a catalytic version of the Nazarov cyclization was reported by Denmark and Jones [25][26][27][28][29][30][31]. They found that a substoichiometric amount of FeCl3 (40

• –50 mol %) promoted the cyclization of silylated derivatives efficiently. However, when 10 mol % was used, the conversion was poor. Denmark’s and Jones’s pioneering work was used as inspiration for the development of catalytic methodologies for this reaction. In 2004, Lang and Trauner described the

Manganese-catalyzed C–C and C–N bond formation with alcohols via borrowing hydrogen or hydrogen auto-transfer

• Mohd Farhan Ansari,
• Atul Kumar Maurya,
• Abhishek Kumar and
• Saravanakumar Elangovan

Beilstein J. Org. Chem. 2024, 20, 1111–1166, doi:10.3762/bjoc.20.98

• Milstein [17] in hydrogenation and dehydrogenation reactions with pincer-decorated manganese complexes, significant progress has been made in manganese catalysis [18][19][20]. Notably, well-defined low-valent diamagnetic manganese(I) complexes have been studied in many catalytic transformations, and

• methanol was achieved at 100 °C with one equivalent of t-BuOK. In all the cases, the catalytic system selectively yielded mono-N-alkylated and N-methylated products under mild conditions. Noteworthy, high functional group tolerance, such as alkenes, halogens, thioethers, and benzodioxane derivatives was

• -methylation of amines with methanol was achieved with lower catalyst and base loading. Sortais et al. reported an elegant example of a manganese-catalyzed N-methylation of primary amines with methanol using catalytic amounts of base. They synthesized a novel Mn(I) complex bearing a bis(diaminopyridine

Synthesis of 1,4-azaphosphinine nucleosides and evaluation as inhibitors of human cytidine deaminase and APOBEC3A

• Maksim V. Kvach,
• Stefan Harjes,
• Harikrishnan M. Kurup,
• Geoffrey B. Jameson,
• Elena Harjes and
• Vyacheslav V. Filichev

Beilstein J. Org. Chem. 2024, 20, 1088–1098, doi:10.3762/bjoc.20.96

• bacteria and fungi but not in mammalian cells, acts only on cytosine. Cytidine deaminase (CDA) as a key enzyme in the pyrimidine salvage pathway in mammals deaminates both cytidine and 2'-deoxycytidine. Members of the apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like (APOBEC) family, such as

• partially localised in the nucleus of cells and, in cancer cells, become genotoxic [24]. A3A and A3H are single-domain enzymes, whereas A3B is a double-domain enzyme, in which only the C-terminal domain (CTD) has catalytic activity, and the N-terminal domain (NTD) is responsible for binding of DNA and for

• ]. Scheme 1 shows the synthesis of the target nucleobases. N-Boc-vinylamine (3) was synthesised from commercially available N-vinylformamide (1) as a stable source of vinylamine by treatment of 1 with Boc2O in THF in the presence of a catalytic amount of DMAP, followed by cleavage of the formyl moiety under

Light on the sustainable preparation of aryl-cored dibromides

• Fabrizio Roncaglia,
• Alberto Ughetti,
• Nicola Porcelli,
• Biagio Anderlini,
• Andrea Severini and
• Luca Rigamonti

Beilstein J. Org. Chem. 2024, 20, 1076–1087, doi:10.3762/bjoc.20.95

• follows a different mechanism, producing the ortho and para-bromoarenes through Ar-SE, that involves cationic intermediates. In this case, a catalytic amount of iodine [21][22] or FeCl3 [23] is added to enhance the electrophilicity of bromine. While widely employed and capable of producing reliable

• ]. This method found prevalent application in the bromination of side-chain positions (right side of Figure 2) [26][27]. However, the addition of molecular iodine in catalytic amounts makes it suitable for aromatic bromination “in the dark” (left side of Figure 2). This gives rise to a radical-initiated

• byproducts, that were still detected in small amounts through 1H NMR (see the image in the Supporting Information File 1). Ring bromination of xylenes is commonly carried out using molecular bromine in the absence of light, along with the aforementioned catalytic promoters (FeBr3 or I2) [59][60]. Some

Novel analogues of a nonnucleoside SARS-CoV-2 RdRp inhibitor as potential antivirotics

• Luca Julianna Tóth,
• Kateřina Krejčová,
• Milan Dejmek,
• Eva Žilecká,
• Blanka Klepetářová,
• Lenka Poštová Slavětínská,
• Evžen Bouřa and
• Radim Nencka

Beilstein J. Org. Chem. 2024, 20, 1029–1036, doi:10.3762/bjoc.20.91

• viruses and plays a crucial role in viral RNA replication. In the proteome of SARS-CoV-2, the catalytic subunit nsp12, expressed together with the cofactors nsp7 and nsp8, constitutes the RdRp [8]. RdRp is usually targeted by nucleotide analogue inhibitors (NAIs) [9]. This class of antivirals can inhibit

Carbonylative synthesis and functionalization of indoles

• Alex De Salvo,
• Raffaella Mancuso and
• Xiao-Feng Wu

Beilstein J. Org. Chem. 2024, 20, 973–1000, doi:10.3762/bjoc.20.87

• years later, they performed, using the same catalytic and oxidative conditions, another oxidative heterocyclization/alkoxycarbonylation process for the synthesis of N-substituted indole-3-carboxylic esters and N–H free indole-3-carboxylic esters from N-substituted 2-alkynylanilines and 2-alkynylanilines

• , Davies et al. published a paper presenting a new method for the synthesis of indoles from o-nitrostyrenes by using a different catalyst system and performing the reaction under mild conditions [27]. At first they decided to change the catalytic system applied by Söderberg using 1,10-phen instead of PPh3

• as ligand, because it was already known that catalysts derived from palladium(II) salts and bidentate nitrogen ligands were highly reactive systems for the reduction of o-nitrostyrenes [28][29][30]. The catalytic system Pd(OAc)2/1,10-phen worked better than Söderberg´s one (Pd(OAc)2/PPh3) under mild

Enhancing structural diversity of terpenoids by multisubstrate terpene synthases

• Min Li and
• Hui Tao

Beilstein J. Org. Chem. 2024, 20, 959–972, doi:10.3762/bjoc.20.86

• , that bind trinuclear magnesium clusters for diphosphate abstraction, whereas class II TSs have a DXDD motif that acts as the catalytic acid. Recently, several novel unconventional TSs that share low sequence and structural similarities with classical TSs have been discovered and comprehensively

• cyclization reactions to form pre-sodorifen (103, Figure 8b), which was subsequently converted to 102 by TS [57]. Key residues lining the catalytic cavity of SpSodMT, Q57, F58, N219, V273, and L302, were found to affect product outcomes, and mutagenesis of these residues resulted in new C16-prenyl substrates

Enantioselective synthesis of β-aryl-γ-lactam derivatives via Heck–Matsuda desymmetrization of N-protected 2,5-dihydro-1H-pyrroles

• Arnaldo G. de Oliveira Jr.,
• Martí F. Wang,
• Rafaela C. Carmona,
• Danilo M. Lustosa,
• Sergei A. Gorbatov and
• Carlos R. D. Correia

Beilstein J. Org. Chem. 2024, 20, 940–949, doi:10.3762/bjoc.20.84

• conditions: b) 4de (0.105 mmol, 1.0 equiv), PhSH (0.16 mmol, 1.5 equiv), K2CO3 (0.21 mmol, 2 equiv), MeCN (1 mL), DMSO (0.4 mL), 25 °C, 2 h. Enantiomeric ratio (er) determined by high-performance liquid chromatography (HPLC) analysis of the purified compounds. A rationale for the catalytic cycle for the Heck

(Bio)isosteres of ortho- and meta-substituted benzenes

• H. Erik Diepers and
• Johannes C. L. Walker

Beilstein J. Org. Chem. 2024, 20, 859–890, doi:10.3762/bjoc.20.78

• catalytic system of B2cat2 and 4-phenylpyridine to form pyridine-boryl radicals which initiated ring expansion. The method was shown to be similarly tolerable of functional groups as Procter’s synthesis. Intramolecular crossed [2 + 2] cycloadditions offer an alternative approach to 1,2-disubstituted BCHs

Activity assays of NnlA homologs suggest the natural product N-nitroglycine is degraded by diverse bacteria

• Kara A. Strickland,
• Brenda Martinez Rodriguez,
• Ashley A. Holland,
• Shelby Wagner,
• Michelle Luna-Alva,
• David E. Graham and
• Jonathan D. Caranto

Beilstein J. Org. Chem. 2024, 20, 830–840, doi:10.3762/bjoc.20.75

• and kinetic experiments or crystallization of the active homodimer will be required to resolve the catalytic mechanism. If NnlA is specific for NNG as suggested by these results, it is worth speculating about potential functions of NNG and other nitramine natural products. Bacterial natural products

Skeletal rearrangement of 6,8-dioxabicyclo[3.2.1]octan-4-ols promoted by thionyl chloride or Appel conditions

• Martyn Jevric,
• Julian Klepp,
• Johannes Puschnig,
• Oscar Lamb,
• Christopher J. Sumby and
• Ben W. Greatrex

Beilstein J. Org. Chem. 2024, 20, 823–829, doi:10.3762/bjoc.20.74

• the byproduct triphenylphosphine oxide, necessitating chromatography which resulted in some hydrolysis. There are a number of catalytic activation strategies for Appel or Mitsunobu reactions such as those described by the Denton group [30], and Rutjes and co-workers [31], and while these may prove

Advancements in hydrochlorination of alkenes

• Daniel S. Müller

Beilstein J. Org. Chem. 2024, 20, 787–814, doi:10.3762/bjoc.20.72

• ]. It is important to note that we are not aware of any catalytic enantioselective hydrochlorination reactions of alkenes. Conjugate additions of HCl to a complex of α,β-unsaturated acids, incorporated in an α-cyclodextrin, which corresponds to a formal hydrochlorination was reported by Tanaka and co

• only 10–25% of the primary chloride for the reaction of tert-butylethylene with HCl in the presence of benzoyl peroxide [33]. c) Several metal halides such as AlCl3, SnCl4, FeCl3, and CuCl exhibit catalytic activities for the hydrochlorination of alkenes. The enthalpy of formation for the hydrogen

• Syntheses [83]. The proposed catalytic cycle is shown in Figure 7 and involves the following steps. First, a cobalt hydride complex A is formed in situ from Co(II) complex and the silane. Then, regioselective alkene hydrocobaltation takes place. This step is highly regioselective, placing the cobalt atom on