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

• oxidized to the corresponding imine 94 by oxygen in the air (as the cyclization did not proceed when the reaction was conducted under nitrogen atmosphere). The activation of the triple bond by tetrabutylammonium bromide regioselectively induced the 6-endo-dig cyclization to furnish 95 in moderate yields

Hetero-polycyclic aromatic systems: A data-driven investigation of structure–property relationships

• Sabyasachi Chakraborty,
• Eduardo Mayo Yanes and
• Renana Gershoni-Poranne

Beilstein J. Org. Chem. 2024, 20, 1817–1830, doi:10.3762/bjoc.20.160

• heteroatoms boron, nitrogen, oxygen, and sulfur and ranging in size from four-membered to six-membered rings. Compared to the parent polycyclic aromatic hydrocarbons (PAHs), PASs containing heterocycles offer greater structural diversity as well as a much broader range of optoelectronic properties. Such

• , and contain nitrogen, boron, oxygen, and sulfur atoms. Using these building blocks, we generated a chemical library of cata-condensed hetero-PASs (cc-hPASs) ranging in size from 3- to 10-ring systems, by combining the rings according to the annulation types shown in Figure 1B. The number, type, and

• oxygen raise the HOMO level [41][42], while boron lowers the LUMO level [43]. COMPAS-2 provides, for the first time, the possibility to substantiate these observations in a data-driven manner and, perhaps, to extract quantitative assessments of these effects. In this section, we study the effects of the

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

• , spanning the period from 2000 to 2023, for the preparation of spiro heterocyclic steroids. The compounds surveyed encompass four-, five-, six-, and seven-membered heterocycles appended to various positions of steroidal backbones, with spirocycles containing oxygen, nitrogen, and sulfur atoms being

• size and type of targeted cycle, ranging from four- to seven-membered rings, and encompasses heterocycles containing oxygen, nitrogen, sulfur, and/or phosphorus atoms. In instances where the stereochemistry of the new spiro centre remains undetermined, it is omitted. Additionally, the review excludes

• sodium hydride, yielding moderate yields (ranging from 23% to 68%). The cyclization initially formed the non-isolated intermediate i, which was oxidized by molecular oxygen from air, introducing the hydroxy group at the α-position of the cyano group. The protocol utilised mild conditions and short

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

• dearomatization of 33 via enantioselective hydroxylation using molecular oxygen and generates cyclohexadienone 34. As demonstrated by Corey [36] and Nicolaou [37], highly reactive intermediate 34 likely dimerizes non-enzymatically through stepwise reactions involving (1) an initial intermolecular Michael addition

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

• easily overoxidized to carboxylic acids. Over the past decades a variety of methods have been developed, utilizing toxic heavy metals such as pyridinium dichromate (PDC) [3][4][5] or manganese dioxide (Figure 1) [6][7]. Molecular oxygen [8] and peroxides [9][10] can also be used as inexpensive terminal

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

• by Norrish–Yang cyclization, which employs easily accessible α-aminoacetophenones as starting materials [11][12][13][14][15]. Furthermore, ring-opening reactions of azetidines have been recently achieved using sulfur and oxygen nucleophiles [16][17][18][19][20][21][22][23][24][25]. However, methods

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

• pathways Methyltransferases can be classified based on various factors, such as their substrates (small molecule MTs, protein MTs, or RNA/DNA MTs), the atom that accepts the methyl group (oxygen = O-MTs, nitrogen = N-MTs, carbon = C-MTs, sulphur = S-MTs, or halide = H-MTs), metal or cofactor dependence

• perform oxygen-directed methylation [59]. A range of natural products are known to undergo O-methylation [61], improving membrane permeability, absorption, and oral bioavailability [61][62]. The most extensively studied O-MTs are those that methylate catecholic hydroxy groups [63]. Several O-methylation

• ]. Further O-MTs can be classified based on a common acceptor group of modification, namely C-terminal carboxy-MTs and peptide/protein ʟ-aspartyl O-MTs (PAMTs). C-terminal carboxymethyltransferases Carboxy-MTs catalyse the formation of a methyl ester by methylating the oxygen atom within the hydroxy group 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

• membranes to ensure a high proton conduction or leading to an efficient reaction production of hydrogen and oxygen gases, with no risk of electrolyte leakage and restricted gas-crossover [15][16][17]. Also, besides their conductivity and their low permeability to fuel and oxidant, the chemical and

• triazine moiety, giving the membrane more structural flexibility; ii) nitrogen and oxygen atoms of these groups can also participate in the proton conduction of the membranes. The new membranes were prepared by casting incorporation of the synthesized 1,3,5-triazinephosphonate (TPs) derivatives. Proton

• atom occurred by several substitution degrees by both the oxygen atom of hydroxyphenyl or the hydroxymethyl group of compound 11, giving a complex mixture. The use of DIPEA as base, under the previous conditions, gave the desired trisubstituted compound TP7 (crude, 47%) (Scheme 6). However

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

• –AlCl2 complex yields the final product 1-chloro-2-naphthol (P–Cl). The calculated mechanism for the chlorination reaction starts with coordination of a PIFA oxygen atom to aluminum chloride. This generates a highly exergonic PIFA–AlCl3 adduct. In Figure 1, the Gibbs free energy of this adduct is set as

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

• difluorinated iodotoluene B. Then, LiBF4 can perform a salt metathesis with B to produce LiF along with the active hypervalent iodoarene catalyst C. The activated hypervalent iodine catalyst C can coordinate to the alkene to form complex D. The nucleophilic oxygen of the amide will attack in the internal

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

• simple oxygen atmosphere (Scheme 1a) [30][31][32]. Most recently, we also showed that phenotellurazines could catalyze the oxidative dimerization of indoles, likewise under a simple oxygen atmosphere. 2-Methoxyphenotellurazine PTeZ2 proved to be the optimal catalyst in the latter case (Scheme 1b) [33

Synthesis of indano[60]fullerene thioketone and its application in organic solar cells

• Yong-Chang Zhai,
• Shimon Oiwa,
• Shinobu Aoyagi,
• Shohei Ohno,
• Tsubasa Mikie,
• Jun-Zhuo Wang,
• Hirofumi Amada,
• Koki Yamanaka,
• Kazuhira Miwa,
• Naoyuki Imai,
• Takeshi Igarashi,
• Itaru Osaka and
• Yutaka Matsuo

Beilstein J. Org. Chem. 2024, 20, 1270–1277, doi:10.3762/bjoc.20.109

• -butyl groups, which disrupted the π–π stacking between the fullerene cages. The slight difference in sublimation temperature between t-Bu-FIDO and t-Bu-FIDS might be due to the slightly higher electron density of the sulfur atom compared with the oxygen atom. Additionally, data on the degradation

Domino reactions of chromones with activated carbonyl compounds

• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 1256–1269, doi:10.3762/bjoc.20.108

• phosphoranes were less studied in my group. Chromones are oxygen heterocycles which are of pharmacological interest and represent versatile synthetic building blocks which can undergo various types of domino reactions [24][25][26][27][28]. In 2001, Nehad N. R. Saleh in my group developed a new synthesis of

• , because the electron-withdrawing character of the CF3 group which destabilizes the formation of a cation at the neighboring position. In addition, the carbon–sulfur bond was not cleaved, due to the lower leaving group ability of sulfur as compared to oxygen. The yields of the two products were moderate. 3

• -Halochromones Dimethyl acetone-1,3-dicarboxylate The reaction of dimethyl acetone-1,3-dicarboxylate (3) with 3-bromochromone (15a) afforded product 33 (Scheme 17) [32]. The first step is again a 1,4-addition to give intermediate P. Subsequent cyclization by intramolecular nucleophilic attack of the oxygen atom

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

• under otherwise identical conditions gave a completely different spectrum (Figure 1B, red) and we assume that the triplet state of Aza-H is almost fully quenched by oxygen at the selected delay, which is supported by additional kinetic measurements (see below). The second transient species is identified

• transient species in Ar-saturated/air-saturated solution is also reflected in the kinetic traces at 440 nm and 640 nm (Figure 1B, inset). Following the decay of the transient triplet species (³Aza-H), essentially the same signal is reached irrespective of the presence of oxygen or argon in the solution. The

• solution of Aza-H with a lower concentration of TsNa (200 µM). We presumed this would enable us to exclusively monitor Aza-H•+ quenching by TsNa, since any triplet Aza-H would be deactivated by oxygen (see above). The ionization efficiency of Aza-H exhibits a quadratic dependence on the laser intensity

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

• a monoclinic crystal system in the space group P21/c. The structure was similar to the structure of oxamide 3 (Figure 2). The hydrogen of the NH unit was concealed by the oxygen atoms of the C=O and OMe units. Consequently, it did not engage in intermolecular hydrogen bonding. Due to the planar

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

• -Orf6, the substrates were able to reductively activate molecular oxygen, thereby enabling subsequent oxidation reactions [21][22][23][24]. However, in the documented reactions of AlpJ-family oxygenases, the substrate 1 appeared insufficient in providing the requisite reducing power, considering the

• conditions [25]. This observation not only affirmed 8 as an intermediate in jadomycin biosynthesis but also suggested a role as a more electron-rich substrate with the potential for direct activation of molecular oxygen. We first confirmed the generation of 8 in the biosynthetic pathway of kinamycin. The

Kinetically stabilized 1,3-diarylisobenzofurans and the possibility of preparing large, persistent isoacenofurans with unusually small HOMO–LUMO gaps

• Qian Liu and
• Glen P. Miller

Beilstein J. Org. Chem. 2024, 20, 1099–1110, doi:10.3762/bjoc.20.97

• ]. Large acenes are prone to photooxidation, especially when dissolved in solution while exposed to ambient light and air. They sensitize singlet oxygen formation, and the same is expected from large isoacenofurans. Indeed, the endoperoxides observed by Hamura and co-workers [3] confirm this expectation

• . We previously studied substituent effects in acenes and reported that several substituents promote photooxidative resistance in pentacenes [5] and larger acenes including heptacene [6] and nonacene [7]. One or more substituents that promote photooxidative resistance by quenching singlet oxygen could

• be utilized on isoacenofurans, too. Additionally, the 1,3-carbons of the furan ring in isoacenofurans are highly reactive towards dienophiles, including singlet oxygen. Thus, we believe that the design of large, persistent isoaceneofurans should include multiple substituents that provide

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

• process, the residual halogen (if any) can decompose hydrogen peroxide into molecular oxygen (Equation 4) [45]. Over the years, various peroxide-bromide processes have been developed based on this chemistry. In particular, significant attention has been given to the preparation of benzyl (mono)bromides

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

• . We focused on the modification of the central heterocyclic core and on the simplification and truncation of the relatively large molecule 1 (Figure 1). In this work, replacing the sulfur atom with a (bio)isosteric oxygen atom yielded two novel structural analogues, whilst our effort towards more

• activity, while the ring-opened derivative 16 showed inhibition with IC50 = 114.2 μM. It seemed that the significantly smaller size of the oxygen atom in the benzoxazole derivative compared to sulfur in HeE1-2Tyr (1) led to an unfavorable molecular shape, while the analogue with the open ring was able to

Auxiliary strategy for the general and practical synthesis of diaryliodonium(III) salts with diverse organocarboxylate counterions

• Naoki Miyamoto,
• Daichi Koseki,
• Kohei Sumida,
• Elghareeb E. Elboray,
• Naoko Takenaga,
• Ravi Kumar and
• Toshifumi Dohi

Beilstein J. Org. Chem. 2024, 20, 1020–1028, doi:10.3762/bjoc.20.90

• attractive class of reagents due to their stability, accessibility, and diverse chemical reactivity [1]. Diaryliodonium(III) salts, in particular, have been widely recognized as efficient arylating reagents for a range of carbon, nitrogen, oxygen, sulfur, and other nucleophiles, and can be employed in the

• 1,3,5-trimethoxybenzene are highly recommended for chemoselective arylation processes. Aryl(TMP)iodonium(III) salts have been successfully used as transition metal-free arylating reagents for various nucleophiles such as nitrogen- [23][24][25][26], oxygen- [13][27][28][29], sulfur- [30], and carbon- [31

Spin and charge interactions between nanographene host and ferrocene

• Akira Suzuki,
• Yuya Miyake,
• Ryoga Shibata and
• Kazuyuki Takai

Beilstein J. Org. Chem. 2024, 20, 1011–1019, doi:10.3762/bjoc.20.89

• with localized spins of unpaired electrons [6]. Thus, it is interesting to introduce a magnetic guest molecule into a magnetic nanographene host regarding the development of a new class of magnetic materials. Oxygen [7][8][9][10][11], nitrogen monoxide molecules [12][13], and potassium clusters having

• . The amount of the cationized FeCp2 (FeCp2+) is obtained as 0.15 mmol/g of FeCp2-ACFs-150 according to the intensity ratio of satellite peaks to the main peaks. The O1s peaks mainly come from oxygen-containing functional groups bonded to nanographene because of oxidization by ambient gaseous species

• C324H36. Thus, oxygen-containing functional groups in ACFs are mainly attached to the edge part of nanographene, being consistent with the higher chemical activity of the edges of graphene [2][6]. Furthermore, the almost same elemental abundance ratio O/C between ACFs and FeCp2-ACFs-150 indicates no

A Diels–Alder probe for discovery of natural products containing furan moieties

• Alyssa S. Eggly,
• Namuunzul Otgontseren,
• Carson B. Roberts,
• Amir Y. Alwali,
• Haylie E. Hennigan and
• Elizabeth I. Parkinson

Beilstein J. Org. Chem. 2024, 20, 1001–1010, doi:10.3762/bjoc.20.88

• oxygen atom in the ring destabilizing the diene HOMO. Thus, when it comes to substituents on a furan ring, it is better to place electron-withdrawing groups in the three and/or five positions of the furan to aid in the natural flow of the electrons [19]. Due to this reactivity, we expected that a Diels

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

• ., in two different periods, reported two paradigmatic examples for indole syntheses. In 2010, they developed the synthesis of 1-(alkoxyarylmethyl)indole-3-carboxylic esters from 2-alkynylaniline imines by using PdI2/KI as catalyst system and oxygen as oxidant [15]. In particular, the reaction was

• reductive elimination and the generated Pd(0) species gets oxidated by the oxygen to the active Pd(II) species (Scheme 7). Synthesis of indoles by metal-catalyzed reductive cyclization reaction of organic nitro compounds with carbon monoxide as reductant In the last 60 years, the metal-catalyzed

• the other hand, Chandrasekhar and Sankararaman reported the same process starting from secondary amines instead of tertiary amines [61]. In this case, the catalyst system was Pd(OCOCF3)2 (10 mol %) and the oxidant Cu(OAc)2 (2 equiv) and oxygen. The reaction was carried out in toluene at 80 °C for 24 h

Synthesis and properties of 6-alkynyl-5-aryluracils

• Ruben Manuel Figueira de Abreu,
• Till Brockmann,
• Alexander Villinger,
• Peter Ehlers and
• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 898–911, doi:10.3762/bjoc.20.80

• molecules within and between a layer with two molecules at the top and the bottom of the unit cell. b) Determined from X-ray structural analysis at 123 K. Element color: carbon (grey), hydrogen (white), oxygen (red) and nitrogen (blue). The thermal ellipsoids are drawn at the 50% probability level. UV–vis

Three-component N-alkenylation of azoles with alkynes and iodine(III) electrophile: synthesis of multisubstituted N-vinylazoles

• Jun Kikuchi,
• Roi Nakajima and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2024, 20, 891–897, doi:10.3762/bjoc.20.79

• difunctionalization of alkynes with various heteroatom and carbon nucleophiles [27][28][29][30][31][32][33][34]. Specifically, intermolecular trans-iodo(III)functionalization of alkynes has been achieved using oxygen nucleophiles such as alcohols [28][32], ethers [33], carboxylic acids [31], phosphate esters [31