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

• and mild Mitsunobu conditions for the preparation of N2-substituted indazole analogs 16a–q. By directly reacting compound 6 with alcohols 13a–q (2 equiv), diethyl azodicarboxylate (DEAD, 2 equiv), and triphenylphosphine (TPP, 2 equiv) in THF at 50 °C (conditions B), the corresponding N2-substituted

• found in Supporting Information File 1. General procedure for the N1-alkylation using alkyltosylates Preparation of methyl 5-bromo-1-methy-1H-indazole-3-carboxylate (15a) To a solution of methyl 5-bromo-1H-indazole-3-carboxylate (300 mg, 1.176 mmol) in dioxane (10 mL) at room temperature was added

• , 268.9902. General procedure for the N2-alkylation using Mitsunobu conditions Preparation of methyl 5-bromo-2-methyl-2H-indazole-3-carboxylate (16a) To a solution of methyl 5-bromo-1H-indazole-3-carboxylate (1.384 g, 5.43 mmol) in THF (15 mL) was added triphenylphosphine (2.85 g, 10.85 mmol) and methanol

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

• crucial function in many biological processes. Due to their bifunctional character, they have been also used for combinatorial chemistry purposes, such as the preparation of DNA-encoded chemical libraries. We developed a practical synthesis for α-heteroaryl-α-amino acids starting from an array of small

• ][28]. However, the selectivity of these photoredox reactions is driven by the structural properties of the heteroaromatic ring. During the preparation of this article, the Meggers group published an outstanding enantioselective iron-catalyzed α-amination pathway (Scheme 1b) [29]. The method is widely

• amino group by reduction. We reasoned that increasing the sp2 fraction and the rigidity of the whole structure will lead to increased stability of these derivatives. The first exploratory attempts demonstrated the easy preparation and the high bench stability of the oxime derivatives, therefore we opted

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

• option for the preparation of isoquinolinone derivatives. In 2020, two reports have been published on the conversion of alkyne-tethered N-alkoxybenzamides to isoquinolinones by intramolecular oxidative annulation, either electrochemically or using the hypervalent iodine reagent phenyliodine(III

Access to 2-oxoazetidine-3-carboxylic acid derivatives via thermal microwave-assisted Wolff rearrangement of 3-diazotetramic acids in the presence of nucleophiles

• Ivan Lyutin,
• Vasilisa Krivovicheva,
• Grigory Kantin and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2024, 20, 1894–1899, doi:10.3762/bjoc.20.164

• versatile methods for the preparation of structurally diverse β-lactam derivatives is of great importance and relevance. Continuing the investigation of the reactivity and synthetic potential of diazotetramic acids (1), we have recently shown that these diazo reagents can act as precursors of β-lactam

• ; reaction scale – 0.25 mmol; ascaled-up (1.5 mmol) yield. Negative results with several N-, O-, and C-nucleophiles and with diazo reagent 1m. Preparation of acids 4 by hydrogenolysis of benzyl esters and examples of acid 4a amidation. Supporting Information Deposition Number CCDC 2323689 (for 3t) contains

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

• . Brunschweiger et al. employed the compartmentation strategy to overcome synthetic problems related to the preparation of a DNA-encoded GBB library [17]. DNA-encoded libraries (DELs) are widely used in screening projects, allowing the synthesis of a huge number of compounds as pools, and the identification of

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

• -type syntheses, MCRs have become helpful tools for more efficient preparation of chemical libraries with higher molecular diversity and complexity in fewer steps and less time [28][29]. Considering the limitations of existing methods, as well as the applications of 5-aryldeazaalloxazines 2, and in the

• (1H,3H)-dione) by refluxing with thionyl chloride [20][23]. However, the preparation of partially hydrogenated 5,10-dihydropyrimido[4,5-b]quinolinediones has been repeatedly reported by one-pot condensation of substituted anilines, aldehydes and barbituric acids, usually in protic solvents (alcohols

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

• ; enantioselectivity; halogenation; lactones; organocatalysis; Introduction Catalytic asymmetric halolactonizations of alkenoic acids are powerful methods for the preparation of important chiral lactones in enantioenriched forms [1][2][3][4][5][6][7][8][9][10][11]. A wide variety of chiral catalysts have been applied

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

• investigate hypervalent iodine(V) fluorides has been limited primarily by their difficult preparation traditionally using harsh fluorinating reagents such as trifluoromethyl hypofluorite and bromine trifluoride. Here, we report a mild and efficient route using Selectfluor to deliver hypervalent iodine(V

• ) fluorides by reacting iodine(III) precursors with commercially available Selectfluor. The method avoids large excesses of reagents and pure iodine(V) fluorides are isolated after a simple work-up. Results and Discussion Preparation of bicyclic difluoro(aryl)-λ5-iodanes Two different types of bicyclic

• protocol using TCCA (4 equivalents) and KF (6 equivalents) was then applied to both bicyclic iodine(III) amides 11a and 11b, but these reactions also failed to form either difluoroiodane 7a or 7b. Following the successful preparation and isolation of difluoroiodane 6, we investigated its ability to

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

• bisamides based on the same aldehydes and amines may also demonstrate biological activity. In view of these facts, we decided to develop a new approach for the synthesis of hybrid molecules containing substituted heterocyclic and peptidomimetic moieties. The first stage of this approach was the preparation

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

• organic thin-film transistors from heteroacenes. Inspired by these results, we sought to demonstrate the preparation of all-carbon scaffolds, i.e., acenes, that are cata-annulated with cyclic imides. Here, we communicate the successful synthesis of 1,2,3,4-NDIs and -ADIs and the characterization of their

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

• substituents of the new heterocycle rather than functionalization on C-3 (Scheme 22). Spirothiazolidine steroids Horiuchi et al. introduced a novel synthetic approach for the preparation of steroidal spiro 1,3-thiazolidines from 2α-bromo-3-oxo steroids, exemplified by compound 76 [46]. Initially, treatment of

• 2α-bromo-3-oxo-, 2β-bromo-3-oxo-, and 4β-bromo-3-oxo-steroids. In 2012, Shamsuzzaman et al. presented a synthetic route for the preparation of novel steroidal spiro derivatives incorporating three heterocyclic moieties [47]. Initially, thiosemicarbazone 80 served as the starting material, undergoing

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

• biosynthetic intermediate 8 to its analogs 21, enabling the chemo-enzymatic total synthesis of 1. The chemical synthesis commenced with the preparation of two fragments and their subsequent coupling to assemble the core 5/8/5 tricyclic scaffold (Scheme 3A). The left-half fragment, aldehyde 14, was synthesized

A fiber-optic spectroscopic setup for isomerization quantum yield determination

• Anouk Volker,
• Jorn D. Steen and
• Stefano Crespi

Beilstein J. Org. Chem. 2024, 20, 1684–1692, doi:10.3762/bjoc.20.150

• . [17], the spectrum of trans-azobenzene can be easily obtained by careful preparation of the sample in the dark. The absorption spectrum of cis-azobenzene, however, is challenging to obtain via direct measurement, due to its intrinsic thermal instability and sensitivity to ambient light. The authors

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

• strain; Introduction Identifying efficient methods for the preparation of densely functionalized molecules is one of the central goals of modern organic chemistry. In this context, application of strained molecules has garnered increasing attention due to their intrinsic reactivity [1][2]. However

• , accessing strained molecules continues to pose a synthetic challenge because many reported methods require harsh conditions for the preparation. An attractive alternative to traditional synthesis can be found in photochemical methods, bypassing energetic constraints by the utilization of photon energy. Thus

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

• report the synthesis of a new series of triazinephosphonate derivatives and their use as dopants in the preparation of new modified Nafion membranes. The triazinephosphonate derivatives were prepared by substitution of chlorine atoms in cyanuric chloride. Diverse conditions were used to obtain the

• , in the same experimental conditions. Results and Discussion Preparation of triazine derivatives The synthesis of 1,3,5-triazinephosphonate (TP) derivatives, to be used as dopants on new membranes, were carried out from the commercially available cyanuric chloride (1), through the substitution of

• to chlorine, and the singlet signal of the phosphorus atom at the 31P NMR spectrum. The synthesis of the corresponding 4-hydroxyphenylphosphonate derivatives followed the same strategy of the amino counterparts’ preparation (Scheme 6). The initial reaction between cyanuric acid (1) and diethyl 4

pKalculator: A pK_a predictor for C–H bonds

• Rasmus M. Borup,
• Nicolai Ree and
• Jan H. Jensen

Beilstein J. Org. Chem. 2024, 20, 1614–1622, doi:10.3762/bjoc.20.144

• string. Furthermore, we adjust the shell radius from 5 to 6, improving the performance of the ML model to predict pKa values as detailed in Supporting Information File 1, section “The descriptor”. Data preparation and hyperparameter optimization Building on the procedure outlined by Ree et al. [14], we

• preparation and hyperparameter optimization”, the QM-computed pKa values are translated into binary values, with ‘1’ representing the lowest QM-computed pKa value and ‘0’ representing other QM-computed pKa values. The performance metrics for the test set demonstrate that the regression model (MCC of 0.97

Generation of multimillion chemical space based on the parallel Groebke–Blackburn–Bienaymé reaction

• Evgen V. Govor,
• Vasyl Naumchyk,
• Ihor Nestorak,
• Dmytro S. Radchenko,
• Dmytro Dudenko,
• Yurii S. Moroz,
• Olexiy D. Kachkovsky and
• Oleksandr O. Grygorenko

Beilstein J. Org. Chem. 2024, 20, 1604–1613, doi:10.3762/bjoc.20.143

• country. The authors thank Mr. Oleksandr Liashuk and Dr. Anastasiia Hurieva for their help with manuscript preparation, Prof. Dr. Anrdiy A. Tolmachev for his encouragement and support, and all the brave people of Ukraine for making this publication possible. Funding The work was funded by Enamine Ltd. and

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

• source (380–800 nm, 300 W) positioned at a distance of 1 cm from the sample. Preparation of aqueous samples All aqueous solutions of DAn were prepared according to the following general procedure: DAn (5.0 wt %) was mixed with 1.0 equivalent NaOH in Milli-Q water. The obtained aqueous solution was

• microscope. The preparation of soft scaffolds composed of DA6, DA7, and DA11, respectively, on a glass substrate was done as follows: Aqueous solutions of DA6 (5.0 wt %, 92.9 mM), DA7 (5.0 wt %, 90.5 mM), and DA11 (5.0 wt %, 82.2 mM) were manually added to an aqueous solution of CaCl2 (150 mM) by pipette

• wavelength of the X-ray beam (Cu Kα irradiation, 1.54 Å). The sample-to-detector distance was ≈100 mm. The obtained diffraction patterns were integrated along the Debye–Scherrer ring to afford 1D intensity data using the Rigaku 2DP software. Attachment of hBM-MSCs onto DAn scaffold surface The preparation of

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

• -methylquinoline derivatives could be fluorinated in yields of up to 70%. In 2013, Groves and co-workers reported the use of manganese salen and manganese porphyrin catalysts in the preparation of a range of secondary benzyl fluorides via C–H fluorination (Figure 31) [80]. Substrates bearing electron-withdrawing

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

• by harsh reaction conditions, which reduces functional group compatibility and product diversity. As such, the development of practical methods for the preparation of alkylnitriles from readily available starting materials are particularly valuable in synthetic and medicinal applications [15][16][17

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

• , deepening our understanding of the stereocontrol of PKSs. Results and Discussion Preparation of KR sequence dataset We first curated the amino acid sequences of KR domains from characterized bacterial cis-AT PKSs recorded in MIBiG database [20] and by manual literature review. In total, 1,762 KRs whose

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

• Lu Li Na Li Xiao-Tian Mo Ming-Wei Yuan Lin Jiang Ming-Long Yuan National and Local Joint Engineering Research Center for Green Preparation Technology of Biobased Materials; School of Chemistry and Environment, Yunnan Minzu University, Kunming, China 10.3762/bjoc.20.130 Abstract A catalyst- and

• are not always readily accessible. Typically, the preparation methods involve SNAr reactions with N-centered nucleophiles [5], nitroarene reduction [6] and transition metal (e.g., Pd, Cu)-catalyzed C–N cross coupling of aryl halides, aryl sulfonates or arylboronic acid reagents with ammonia or NH

• anilines [19] (Scheme 1, (3)). To date, although plentiful amination–aromatization approaches for the preparation of anilines have been well-established, to develop novel and efficient synthetic methods still remains highly desirable. In continuation of our recent studies on synthetic applications of

Synthesis of cyclic β-1,6-oligosaccharides from glucosamine monomers by electrochemical polyglycosylation

• Md Azadur Rahman,
• Hirofumi Endo,
• Takashi Yamamoto,
• Shoma Okushiba,
• Norihiko Sasaki and
• Toshiki Nokami

Beilstein J. Org. Chem. 2024, 20, 1421–1427, doi:10.3762/bjoc.20.124

• polymerization of organic molecules is an important strategy for the preparation of functional materials, such as conducting polymers [1][2][3][4][5]. Electrochemical reactions can be controlled by electric potential or current, electrodes, and electrolytes, which are not available in conventional chemical

• reaction time and rate is possible under electrochemical conditions [11][12][13]. We have been interested in the preparation of cyclic oligosaccharides under electrochemical conditions and electrochemical conversion of linear oligosaccharides of glucosamine into the corresponding cyclic oligosaccharides by

• rate: 7.5 mL/min, recycle numbers: 3) to obtain pure cyclic oligosaccharide 16 (0.125 mmol, 79.7 mg, 62%). Preparation of cyclic oligoglucosamines a) via intramolecular glycosylation and b) via polyglycosylation and intramolecular glycosylation. Proposed reaction mechanism of the formation of 1,6

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

• preparation by using small building blocks and that lead, through appropriate transformations, to a product that becomes a substrate for another complexity-generating reaction, merit investigation [13][14][15]. Herein, we report a 3-CR-based synthesis of new properly decorated (thio)hydantoin framework able

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

• synthesis of medicinally useful molecules (Scheme 23) [90]. The Cannizzaro reaction has also been applied to the preparation of mandelic acid-based synthons, which gain potential importance in the synthesis of prostaglandins, cephalosporins, and homatropine [65][66][67][68][69]. Synthesis of useful