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

Research progress on the pharmacological activity, biosynthetic pathways, and biosynthesis of crocins

• Zhongwei Hua,
• Nan Liu and
• Xiaohui Yan

Beilstein J. Org. Chem. 2024, 20, 741–752, doi:10.3762/bjoc.20.68

• enzymes in crocin biosynthetic pathways CCDs: Crocin biosynthesis initiates with the catalytic cleavage of the C‒C double bond by CCDs at various sites of the carotenoid skeleton. The cleavage generates a carbonyl group at the end of the formed carotenoid derivatives [88]. The CCD family can be

• CsCCD2 that exhibits broader substrate specificity and higher catalytic efficiency through computational modeling. Heterologous expression of the S323A mutant of CsCCD2 in yeast led to a 4-fold enhancement in the production of 1, with a crocetin (1) titer of 107 mg/L in a 5-liter fed-batch fermentation

• supply, overexpressing PsBCH-CsCCD2, and optimizing the fermentation medium, the yield of crocetin (1) reached 12.43 ± 0.62 mg/L in a 5 L bioreactor [115]. While CCD has a higher catalytic activity at low temperature, the biosynthesis of zeaxanthin (7) is more suited to a higher temperature. As such, Liu

Substrate specificity of a ketosynthase domain involved in bacillaene biosynthesis

• Zhiyong Yin and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2024, 20, 734–740, doi:10.3762/bjoc.20.67

• only for the incorporation of one extender unit [2][3]. Although enzyme domains with various specialised catalytic functions can be found as integral part of polyketide synthases, three domain types are fundamental to their biosynthesis, resembling the same logic as observed for fatty acid biosynthesis

• ester 5 was coupled with the carboxylic acid (S)-8, derived from ʟ-leucine ((S)-6) via hydroxyacid (S)-7, to yield the amide (S)-9. Deprotection through catalytic hydrogenation to (S)-10, saponification of the acetate ester and Steglich esterification with N-acetylcysteamine gave access to the desired

Genome mining of labdane-related diterpenoids: Discovery of the two-enzyme pathway leading to (−)-sandaracopimaradiene in the fungus Arthrinium sacchari

• Fumito Sato,
• Terutaka Sonohara,
• Shunta Fujiki,
• Akihiro Sugawara,
• Yohei Morishita,
• Taro Ozaki and
• Teigo Asai

Beilstein J. Org. Chem. 2024, 20, 714–720, doi:10.3762/bjoc.20.65

• AsCPS synthesized copalyl diphosphate and that AsPS then converted it to (−)-sandaracopimaradiene. Since AsPS and AsCPS have distinct domain organizations from those of known fungal TCs and are likely generated through fusion or loss of catalytic domains, our findings provide insight into the evolution

• gene (AsGGS), suggesting that they are related to the biosynthesis of diterpenes (Figure 2A). AsPS and AsCPS consist of αβ and αβγ domains, respectively. Further sequence analysis revealed that the β domain of AsPS contains a mutation at the catalytic aspartic acid residue, indicating that this enzyme

SOMOphilic alkyne vs radical-polar crossover approaches: The full story of the azido-alkynylation of alkenes

• Julien Borrel and
• Jerome Waser

Beilstein J. Org. Chem. 2024, 20, 701–713, doi:10.3762/bjoc.20.64

• since it is known to be reduced by photocatalysts such as Cu(dap)2Cl [17]. This perfectly fits a catalytic cycle involving the reduction of Ts-ABZ (3) followed by oxidation of the carbon radical to form a carbocation and regenerate the ground state catalyst. Styrene (1a) was used as model substrate

Evaluation of the enantioselectivity of new chiral ligands based on imidazolidin-4-one derivatives

• Jan Bartáček,
• Karel Chlumský,
• Jan Mrkvička,
• Lucie Paloušová,
• Miloš Sedlák and
• Pavel Drabina

Beilstein J. Org. Chem. 2024, 20, 684–691, doi:10.3762/bjoc.20.62

• based on derivatives of imidazolidin-4-one were synthesised and characterised. The catalytic activity and enantioselectivity of their corresponding copper(II) complexes were studied in asymmetric Henry reactions. It was found that the enantioselectivity of these catalysts is overall very high and

• itself constitutes a stereocentre [4]. The specific pairing of a chiral ligand and a metal ion is essential for the catalytic characteristics and its effectiveness of the complex in asymmetric syntheses [1][2][3]. In recent years, our research group has synthesised a series of chiral ligands based on 2

• catalytic arrangements of the most enantioselective catalysts, including anchoring on polystyrene beads [8][9], magnetic nanoparticles [10], or block copolymers composed of PEG-poly(Glu) [11]. These modifications have facilitated the recycling of the catalysts, offering numerous advantages, including

Palladium-catalyzed three-component radical-polar crossover carboamination of 1,3-dienes or allenes with diazo esters and amines

• Geng-Xin Liu,
• Xiao-Ting Jie,
• Ge-Jun Niu,
• Li-Sheng Yang,
• Xing-Lin Li,
• Jian Luo and
• Wen-Hao Hu

Beilstein J. Org. Chem. 2024, 20, 661–671, doi:10.3762/bjoc.20.59

• (PPh3)2Cl as catalyst, the model reaction also afforded the corresponding product 4a in 31% yield, demonstrating the H–Pd(II)–X species could be a possible catalytic species (Scheme 4d). According to the UV–visible spectra, the only absorbing species at 467 nm consists in the pre-catalytic system Pd(OAc

• subsequent attack of amine 3 at the latter stage would afford the unsaturated ε-AA derivative 4 and regenerates the Pd(0)Ln to close the catalytic cycle. Different from the reactive site of 1,3-diene, the hybrid alkylPd radical I selectively adds to the central position of the allenyl group of allene 5a

A laterally-fused N-heterocyclic carbene framework from polysubstituted aminoimidazo[5,1-b]oxazol-6-ium salts

• Andrew D. Gillie,
• Matthew G. Wakeling,
• Bethan L. Greene,
• Louise Male and
• Paul W. Davies

Beilstein J. Org. Chem. 2024, 20, 621–627, doi:10.3762/bjoc.20.54

• sphere, accessing more diverse fused imidazolium frameworks and different peripheral functionality offers significant scope to influence catalytic properties. Few studies into L-shaped imidazolylidines have explored core motifs beyond ImPy, with NHCs derived from two π-rich rings fused together

A myo-inositol dehydrogenase involved in aminocyclitol biosynthesis of hygromycin A

• Michael O. Akintubosun and
• Melanie A. Higgins

Beilstein J. Org. Chem. 2024, 20, 589–596, doi:10.3762/bjoc.20.51

• is relatively high. However, this is similar to other myo-inositol dehydrogenases whose KM values are also in the mM range [12][16]. Hyg17 showed a higher catalytic efficiency of 366.7 ± 46.96 M−1 s−1 with myo-inositol as compared to the 29.6 ± 5.28 M−1 s−1 for scyllo-inositol. This reduced catalytic

• efficiency can be attributed to the reduced kcat and increased KM for scyllo-inositol over myo-inositol. We also found that the catalytic efficiency for NAD+ was 452.4 ± 54.49 M−1 s−1 (Table 1 and Figure 2f). Sequence similarity network We generated a sequence similarity network (SSN) for the protein family