Asymmetric organocatalytic synthesis of chiral homoallylic amines

• Nikolay S. Kondratyev and
• Andrei V. Malkov

Beilstein J. Org. Chem. 2024, 20, 2349–2377, doi:10.3762/bjoc.20.201

• attributed to the chair-like transition state where the organoboron reagent 1 exchanges one isopropoxy group for one of the BINOL 3 oxygen atoms, whereas the free OH group of the BINOL forms a hydrogen bond to the carbonyl of substrate 2. The flanking phenyl groups on the BINOL facilitate recognition between

• method involves squaramide 51-catalysed chloride abstraction from readily accessible N-carbamoyl α-chloroglycinates 48 or 54 (Scheme 11) [35], with a simultaneous nucleophilic attack of allylsilane 49 (Scheme 11A) or allylstannane 55 (Scheme 11B). The reactions are highly sensitive to moisture and oxygen

Hydrogen-bond activation enables aziridination of unactivated olefins with simple iminoiodinanes

• Phong Thai,
• Lauv Patel,
• Diyasha Manna and
• David C. Powers

Beilstein J. Org. Chem. 2024, 20, 2305–2312, doi:10.3762/bjoc.20.197

• center [26][27]. Despite the prevalence of acid-activation in promoting carbon [28], oxygen [29][30], sulfur [31], chlorine [32], and fluorine [33] transfer reactions of hypervalent iodine compounds, these strategies have not been applied to activation of iminoiodinanes for nitrene transfer chemistry. We

Synthesis and reactivity of the di(9-anthryl)methyl radical

• Tomohiko Nishiuchi,
• Kazuma Takahashi,
• Yuta Makihara and
• Takashi Kubo

Beilstein J. Org. Chem. 2024, 20, 2254–2260, doi:10.3762/bjoc.20.193

• radical. The unpaired electron is primarily located at the central sp2 carbon, a highly reactive site. The DAntM radical readily reacts with oxygen, leading to 1,2-dioxetane intermediate and decomposition to give anthryl aldehyde and a stable anthroxyl radical. Results and Discussion The synthetic route

• pathway involving hydrogen abstraction from water yielding 4, and a major pathway involving oxygen addition to the central carbon to afford 1,2-dioxetane (DOT) intermediate. Usually, DOT derivatives are known to readily decompose [38], and this DOT intermediate is also considered to decompose upon C–C and

• the DAntM radical were successfully conducted. Although the DAntM radical exhibits σ-dimerization in solution, it readily dissociates into a monomeric radical due to the presence of two bulky 9-anthryl groups. However, the DAntM radical retains a highly reactive nature with oxygen, resulting in the

Natural resorcylic lactones derived from alternariol

• Joachim Podlech

Beilstein J. Org. Chem. 2024, 20, 2171–2207, doi:10.3762/bjoc.20.187

O,S,Se-containing Biginelli products based on cyclic β-ketosulfone and their postfunctionalization

• Kateryna V. Dil and
• Vitalii A. Palchykov

Beilstein J. Org. Chem. 2024, 20, 2143–2151, doi:10.3762/bjoc.20.184

• signals clearly corresponds to the heterocycles depicted above. Figure S8 (see Supporting Information File 1) shows 1H NMR spectra for Ph-substituted O,S,Se-DHPMs 2a,h,o. It can be seen from them that when going from oxygen to selenium (2h→2a→2o), the signals of both NH groups shift to down field (7.87

Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

• , facilitating their cyclization with intermediary formed hydrazones to yield 5-hydroxypyrazolines. After subsequent interaction with atmospheric oxygen, the product 65 is formed. This method exhibits a high degree of substituent tolerance, and aliphatic compounds generally lead to higher yields. A special

1,2-Difluoroethylene (HFO-1132): synthesis and chemistry

• Liubov V. Sokolenko,
• Taras M. Sokolenko and
• Yurii L. Yagupolskii

Beilstein J. Org. Chem. 2024, 20, 1955–1966, doi:10.3762/bjoc.20.171

• . Photochemical [2 + 2]-cycloaddition with fluorinated aldehydes and ketones gives access to a variety of fluorinated oxygen-containing heterocycles. We hope that this article will help chemists to utilize HFO-1132 and that this olefin will find applications as a useful synthon in organic chemistry. 1,2

Regioselective alkylation of a versatile indazole: Electrophile scope and mechanistic insights from density functional theory calculations

• Pengcheng Lu,
• Luis Juarez,
• Paul A. Wiget,
• Weihe Zhang,
• Krishnan Raman and
• Pravin L. Kotian

Beilstein J. Org. Chem. 2024, 20, 1940–1954, doi:10.3762/bjoc.20.170

• similar to 6. They observed high N1-selectivity using NaH in THF with pentyl bromide and electron-deficient indazoles, postulating a coordination of the indazole N2-atom and an electron-rich oxygen atom in a C-3 substituent with the Na+ cation from NaH. Under anhydrous conditions the yields ranged from 44

• the chelation pathway proposed in Figure 5, we hypothesized that 18 (Figure 9) would provide a model for exploring the mechanism further. If chelation between an electron-rich oxygen atom from a substituent and a Lewis acid (such as Cs+ or P+) were taking place, we would expect regioselectivity for

• indazole and the deprotonated indazole was only −0.2 kcal/mol (Figure 11). Again, no preorganized intermediates were found. The NCIs were consistent with the parent system. The hydrogen bond between the H on the electrophilic methyl group and an ester oxygen was found in the transition state leading to the

A new platform for the synthesis of diketopyrrolopyrrole derivatives via nucleophilic aromatic substitution reactions

• Vitor A. S. Almodovar and
• Augusto C. Tomé

Beilstein J. Org. Chem. 2024, 20, 1933–1939, doi:10.3762/bjoc.20.169

• than the oxygen due to the preferential existence of 4-hydroxypyridine in the pyridin-4-one tautomeric form [37][38][39]. The structures of dyes 3a–f, 4a, 4d and 4f were unambiguously established through their 1H, 13C and 19F NMR and mass spectra. The 1H NMR spectra of the symmetrical compounds

Negishi-coupling-enabled synthesis of α-heteroaryl-α-amino acid building blocks for DNA-encoded chemical library applications

• Matteo Gasparetto,
• Balázs Fődi and
• Gellért Sipos

Beilstein J. Org. Chem. 2024, 20, 1922–1932, doi:10.3762/bjoc.20.168

• underrepresented in the peer-reviewed literature in comparison to phenyl groups or their six-membered counterparts (e.g., pyridines, pyrimidines) [42]. Furthermore, the increasing importance of small heteroaromatic rings containing nitrogen, sulfur and/or oxygen in medicinal chemistry is well depicted by the list

Solvent-dependent chemoselective synthesis of different isoquinolinones mediated by the hypervalent iodine(III) reagent PISA

• Ze-Nan Hu,
• Yan-Hui Wang,
• Jia-Bing Wu,
• Ze Chen,
• Dou Hong and
• Chi Zhang

Beilstein J. Org. Chem. 2024, 20, 1914–1921, doi:10.3762/bjoc.20.167

• deprotonation with sulfamate, gives the 4-substituted isoquinolinone derivative 2a (Scheme 6). Looking into the formation of 2c' from 1c (Scheme 2), two other resonance structures for the initially formed intermediate 1CC, namely 1CC' and 1CC'', are shown in Scheme 7. The oxygen atom in the amide motif of the

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