Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

• Periklis X. Kolagkis,
• Eirini M. Galathri and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36

• and viability of these synthetic protocols, organic chemists have been opting towards the use of greener catalysts and solvents in drug development. Chemists dream to perform reactions under solvent-free conditions, which provide a greener approach towards organic transformations. Nowadays, the use of

• solvent-free reaction conditions has been introduced as a popular alternative to common organic solvents for many different organic transformations. The lack of an organic solvent can result in improved yields and reaction rates, more facile work-up processes and reduced waste, which are among the goals

• intriguing tool in the catalysis of various organic transformations that were previously considered unfeasible [89]. In 2003, the reaction of indoles with aldehydes and ketones under XB catalysis was reported by Bandgar and his research group utilizing I2 as the catalyst and acetonitrile as the optimum

Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• many applications as radical precursors. Mechanistically, NHPI esters undergo a reductive decarboxylative fragmentation to provide a substrate radical capable of engaging in diverse transformations. Their reduction via single-electron transfer (SET) can occur under thermal, photochemical, or

• reaction classes, we discuss the utility of the NHPI esters, with an eye towards their continued development in complexity-generating transformations. Keywords: decarboxylative couplings; mechanisms; NHPI-esters; radical reactions; Introduction The historical challenges of using radicals in synthetic

• , leading to their strategic incorporation as "synthons" in modern organic chemistry, with complementary reactivity to more common polar reaction manifolds [12][13][14][15]. The utility of radicals has also been expanded through the recent development of transformations involving radical-polar crossover

Facile approach to N,O,S-heteropentacycles via condensation of sterically crowded 3H-phenoxazin-3-one with ortho-substituted anilines

• Eugeny Ivakhnenko,
• Vasily Malay,
• Pavel Knyazev,
• Nikita Merezhko,
• Nadezhda Makarova,
• Oleg Demidov,
• Gennady Borodkin,
• Andrey Starikov and
• Vladimir Minkin

Beilstein J. Org. Chem. 2024, 20, 336–345, doi:10.3762/bjoc.20.34

• ). This is also the basic compound used in the transformations that are studied in this work due to the high kinetic stability and good solubility ensured by the tert-butyl groups. The largest positive charge of the C(1)–C(2)–C(3) segment is concentrated at the C(2) atom. The charge at the other

Synthesis of π-conjugated polycyclic compounds by late-stage extrusion of chalcogen fragments

• Aissam Okba,
• Pablo Simón Marqués,
• Kyohei Matsuo,
• Naoki Aratani,
• Hiroko Yamada,
• Gwénaël Rapenne and
• Claire Kammerer

Beilstein J. Org. Chem. 2024, 20, 287–305, doi:10.3762/bjoc.20.30

• ]. Similarly to the early transformations of thiepines, sulfur elimination was triggered by copper bronze at high temperature, thus leading to the conversion of the 6-membered cyclic disulfide into the corresponding thiophene. The 1,2-dithiin scaffold is found in natural products such as thiarubrines A and B

Synthesis of spiropyridazine-benzosultams by the [4 + 2] annulation reaction of 3-substituted benzoisothiazole 1,1-dioxides with 1,2-diaza-1,3-dienes

• Wenqing Hao,
• Long Wang,
• Jinlei Zhang,
• Dawei Teng and
• Guorui Cao

Beilstein J. Org. Chem. 2024, 20, 280–286, doi:10.3762/bjoc.20.29

• field [4][5][6]. Pyridazine drugs have also shown high pharmaceutical activity. Many types of pyridazine drugs have been listed for antibacterial, anti-inflammatory, and other purposes [7][8][9][10]. Nowadays, a range of transformations to spirobenzosultams have been established using N-sulfonyl

Additive-controlled chemoselective inter-/intramolecular hydroamination via electrochemical PCET process

• Kazuhiro Okamoto,
• Naoki Shida and
• Mahito Atobe

Beilstein J. Org. Chem. 2024, 20, 264–271, doi:10.3762/bjoc.20.27

• ][6][7][8]. Recent advances in photoredox and electrochemical PCET reactions have significantly expanded the substrate scope of amidyl-radical-based molecular transformations because the harsh acidic and high-temperature conditions required in the classical Hofmann–Löffler–Freytag reaction can be

Nucleophilic functionalization of thianthrenium salts under basic conditions

• Xinting Fan,
• Duo Zhang,
• Xiangchuan Xiu,
• Bin Xu,
• Yu Yuan,
• Feng Chen and
• Pan Gao

Beilstein J. Org. Chem. 2024, 20, 257–263, doi:10.3762/bjoc.20.26

• ][20]. On the other hand, sulfonium salts have emerged as appealing sources of aryl radicals for a wide range of transformations aimed at creating novel chemical bonds driven by their distinctive structural attributes and chemical tendencies (Scheme 1a) [9][21][22][23][24][25][26]. In addition to late

Substitution reactions in the acenaphthene analog of quino[7,8-h]quinoline and an unusual synthesis of the corresponding acenaphthylenes by tele-elimination

• Ekaterina V. Kolupaeva,
• Narek A. Dzhangiryan,
• Alexander F. Pozharskii,
• Oleg P. Demidov and
• Valery A. Ozeryanskii

Beilstein J. Org. Chem. 2024, 20, 243–253, doi:10.3762/bjoc.20.24

• make molecule 5 (and derivatives) more rigid and flat when compared to compound 3 but it will also affect its reactivity and the sites of functionalization. This work is devoted to the clarification of this circumstance with substitution and elimination reactions chosen as the key transformations. The

• of KMnO4 at 100 °C. The variation of the nucleophile did not give positive results either. For example, the replacement of dimethylamine with higher-boiling piperidine and n-butylamine or using liquid ammonia, which is highly reactive in such transformations, dipyridoacenaphthene 5 still returned

• equilibrium) under the action of an excess of nucleophiles as bases. Such dianions are characteristic of acenaphthene and have been repeatedly detected in subsequent transformations [18][19]. In our case, the CH-acidity of the CH2CH2 bridge should be even higher under the action of pyridine rings, and, if

Copper-catalyzed multicomponent reaction of β-trifluoromethyl β-diazo esters enabling the synthesis of β-trifluoromethyl N,N-diacyl-β-amino esters

• Youlong Du,
• Haibo Mei,
• Ata Makarem,
• Ramin Javahershenas,
• Vadim A. Soloshonok and
• Jianlin Han

Beilstein J. Org. Chem. 2024, 20, 212–219, doi:10.3762/bjoc.20.21

• challenging. On the other hand, several interesting transformations of nitrile ylides from diazo compounds have been developed in the past years [31][32][33][34][35][36][37][38]. In particular, acylglycine esters could be easily constructed with ester-containing diazo compounds as the starting materials. For

Tandem Hock and Friedel–Crafts reactions allowing an expedient synthesis of a cyclolignan-type scaffold

• Viktoria A. Ikonnikova,
• Cristina Cheibas,
• Oscar Gayraud,
• Alexandra E. Bosnidou,
• Nicolas Casaretto,
• Gilles Frison and
• Bastien Nay

Beilstein J. Org. Chem. 2024, 20, 162–169, doi:10.3762/bjoc.20.15

• reaction is possible upon elimination of the resulting benzylic alcohol on D, allowing another arylation forming E [18]. This complex sequence of transformations is herein applied to the synthesis of 1-aryltetralines, analogues of cyclolignan natural products having important medicinal applications [19][20

Copper-promoted C5-selective bromination of 8-aminoquinoline amides with alkyl bromides

• Changdong Shao,
• Chen Ma,
• Li Li,
• Jingyi Liu,
• Yanan Shen,
• Chen Chen,
• Qionglin Yang,
• Tianyi Xu,
• Zhengsong Hu,
• Yuhe Kan and
• Tingting Zhang

Beilstein J. Org. Chem. 2024, 20, 155–161, doi:10.3762/bjoc.20.14

• such as 2d, 2e, and 2f performed well, affording the brominated product 3aa in excellent yields (90–99%). However, transformations of amide 1a to the brominated product 3aa employing unactivated alkyl bromides (2g–i) as reaction partners proceeded with low efficiency (0–53%). Notably, the reactivity of

Perspectives on push–pull chromophores derived from click-type [2 + 2] cycloaddition–retroelectrocyclization reactions of electron-rich alkynes and electron-deficient alkenes

• Michio Yamada

Beilstein J. Org. Chem. 2024, 20, 125–154, doi:10.3762/bjoc.20.13

• a DCF structure and is amenable to further molecular transformations through a reaction with 1 [103]. Considering the structure of 7, the possibility of a multistep [2 + 2] CA–RE reaction via a reaction with 1 becomes feasible. To execute such a multistep [2 + 2] CA–RE reaction, it becomes

1-Butyl-3-methylimidazolium tetrafluoroborate as suitable solvent for BF₃: the case of alkyne hydration. Chemistry vs electrochemistry

• Marta David,
• Elisa Galli,
• Richard C. D. Brown,
• Marta Feroci,
• Fabrizio Vetica and
• Martina Bortolami

Beilstein J. Org. Chem. 2023, 19, 1966–1981, doi:10.3762/bjoc.19.147

• complex organic compounds, widely used both in organic chemistry and in electrochemistry as raw materials for the preparation of different molecules of pharmaceutical and industrial interest [1][2][3][4][5][6][7][8][9]. Among the different organic transformations involving alkynes, their hydration is a

Aldiminium and 1,2,3-triazolium dithiocarboxylate zwitterions derived from cyclic (alkyl)(amino) and mesoionic carbenes

• Nedra Touj,
• François Mazars,
• Guillermo Zaragoza and
• Lionel Delaude

Beilstein J. Org. Chem. 2023, 19, 1947–1956, doi:10.3762/bjoc.19.145

• prepared, while a few reports disclosed the formation of polynuclear clusters, in which the dithiocarboxylate unit underwent further chemical transformations [59][60][61]. To the best of our knowledge, 1,2,3-triazolium-5-dithiocarboxylate species are hitherto unknown in the literature, and only a single

Beyond n-dopants for organic semiconductors: use of bibenzo[d]imidazoles in UV-promoted dehalogenation reactions of organic halides

• Kan Tang,
• Megan R. Brown,
• Chad Risko,
• Melissa K. Gish,
• Garry Rumbles,
• Phuc H. Pham,
• Oana R. Luca,
• Stephen Barlow and
• Seth R. Marder

Beilstein J. Org. Chem. 2023, 19, 1912–1922, doi:10.3762/bjoc.19.142

• been used by Murphy’s group and others for a variety of transformations, such as the formation of indolines from N-allyl-2-iodoanilines [1], indanones from 3-(2-halophenyl)propanoic esters [2][3], and 3-methyl-2,3-dihydrobenzofuran from 1-allyloxy-2-halobenzenes [4]. Related species have also been used

• electropositive metals and may be of use in more elaborate chemical transformations. Mechanism of dark reactions Doping of organic semiconductors by (Y-DMBI)2 dimers [18][39] or by various dimers formed by 18-electron sandwich compounds [18][40][41], as well as redox reactions of other dimers formed by organic

• to the more strongly reducing monomers, which may help inform the use of these and related reductants in achieving other chemical transformations. (a, b) Schematics of previous approaches to dehalogenation-based reactions using molecular reductants, along with representative structures of reductants

A novel recyclable organocatalyst for the gram-scale enantioselective synthesis of (S)-baclofen

• Gyula Dargó,
• Dóra Erdélyi,
• Balázs Molnár,
• Péter Kisszékelyi,
• Zsófia Garádi and
• József Kupai

Beilstein J. Org. Chem. 2023, 19, 1811–1824, doi:10.3762/bjoc.19.133

• Budapest, Hungary 10.3762/bjoc.19.133 Abstract Synthesizing organocatalysts is often a long and cost-intensive process, therefore, the recovery and reuse of the catalysts are particularly important to establish sustainable organocatalytic transformations. In this work, we demonstrate the synthesis

• organocatalysts has been a major breakthrough in the realization of enantioselective transformations. Stereoselective synthesis is essential in the pharmaceutical industry, as the development of drugs often requires the production of enantiomerically pure chiral compounds [6][7][8]. The application of

Recent advancements in iodide/phosphine-mediated photoredox radical reactions

• Tinglan Liu,
• Yu Zhou,
• Junhong Tang and
• Chengming Wang

Beilstein J. Org. Chem. 2023, 19, 1785–1803, doi:10.3762/bjoc.19.131

• groundbreaking work of Shang and Fu on photocatalytic decarboxylative alkylations in 2019, a wide range of organic transformations, such as alkylation, alkenylation, cyclization, amination, iodination, and monofluoromethylation, have been progressively achieved using a combination of iodide and PPh3. In this

• review, we primarily focus on summarizing the recent advancements in inexpensive and readily available iodide/phosphine-mediated photoredox radical transformations. Keywords: annulation; decarboxylative; iodide/phosphine; photocatalytic; radical reaction; Introduction Over the past few decades

• provided a more sustainable and economically viable approach but also demonstrated excellent performance in various transformations. It had been successfully applied to a series of radical reactions, including trifluoromethylation, deaminative alkylation, and asymmetric versions of Minisci reactions

Decarboxylative 1,3-dipolar cycloaddition of amino acids for the synthesis of heterocyclic compounds

• Xiaofeng Zhang,
• Xiaoming Ma and
• Wei Zhang

Beilstein J. Org. Chem. 2023, 19, 1677–1693, doi:10.3762/bjoc.19.123

• aldehydes and alkenes. The first cycloaddition products 3c or 3d can also be used as intermediates for other transformations to synthesize novel heterocyclic rings via multicomponent, one-pot, and stepwise synthesis [63][64]. Presented in the following sections is our work on the development of amino acid

• -based decarboxylative [3 + 2] cycloadditions of N–H-type AMYs B3 and B4 for double cycloadditions. The stereochemistry of the cycloadditions and the combination of the cycloaddition with other transformations to be one-pot or stepwise reactions are also presented. Perspective One-step synthesis of

Tying a knot between crown ethers and porphyrins

• Maksym Matviyishyn and
• Bartosz Szyszko

Beilstein J. Org. Chem. 2023, 19, 1630–1650, doi:10.3762/bjoc.19.120

• binding guest molecules/ions, but also to undergo unusual transformations, such as metal-induced expansion/contraction. Depending on the design of the particular hybrid, they present unique features involving intriguing redox chemistry, interesting optical properties, and reactivity towards transition

• demonstrated interesting, reversible, solvent-directed macrocycle-to-macrocycle interconversions. The transformations between the [1 + 1] 36 and [2 + 2] 37 macrocycles were governed by the solvent. The smaller monomeric 36 was obtained as the major product in chloroform, methanol, and ethanol. The conversion

Lewis acid-promoted direct synthesis of isoxazole derivatives

• Dengxu Qiu,
• Chenhui Jiang,
• Pan Gao and
• Yu Yuan

Beilstein J. Org. Chem. 2023, 19, 1562–1567, doi:10.3762/bjoc.19.113

• toxic transition metals and provides a new way to synthesize isoxazole molecules. Further related transformations of products and application of this method are currently developed in our laboratory. Experimental Representative procedure for the synthesis of compound 3a. To a flame-dried 15 mL Schlenk

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• article, we focus on the application of these alternative sulfenylating reagents in organic transformations. Keywords: electrophile; N-(sulfenyl)succinimides/phthalimides; organic transformations; organosulfur; sulfenylation; Introduction Sulfur-containing compounds are of high importance in organic

Cyclization of 1-aryl-4,4,4-trichlorobut-2-en-1-ones into 3-trichloromethylindan-1-ones in triflic acid

• Vladislav A. Sokolov,
• Andrei A. Golushko,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2023, 19, 1460–1470, doi:10.3762/bjoc.19.105

• , we initiated this study on transformations of 1-aryl-4,4,4-trichlorobut-2-en-1-ones under superelectrophilic activation conditions (Scheme 1b). The main goals of this work were the investigation of the protonation of CCl3-enones (1-aryl-4,4,4-trichlorobut-2-en-1-ones) by NMR spectroscopy and DFT

• CCl3-enones, that are finally cyclized into the target CCl3-indanones. Generation of O-protonated and O,C-diprotonated species from substituted conjugated enones under superelectrophilic activation and their subsequent transformations. Synthesis of 1-aryl-4,4,4-trichloro-3-hydroxybutan-1-ones 1a–o by

• -4,4,4-trichlorobut-2-en-1-ones 2 into 3-trichloromethylindan-1-ones 3 in TfOH. Cyclization of 1-aryl-4,4,4-trichloro-3-hydroxybutan-1-ones 1 into 3-trichloromethylindan-1-ones 3 in TfOH. Plausible mechanisms for the cyclization of compounds 1 and 2 into indanones 3 in TfOH. Transformations of hydroxy

α-(Aminomethyl)acrylates as acceptors in radical–polar crossover 1,4-additions of dialkylzincs: insights into enolate formation and trapping

• Angel Palillero-Cisneros,
• Paola G. Gordillo-Guerra,
• Fernando García-Alvarez,
• Olivier Jackowski,
• Franck Ferreira,
• Fabrice Chemla,
• Joel L. Terán and
• Alejandro Perez-Luna

Beilstein J. Org. Chem. 2023, 19, 1443–1451, doi:10.3762/bjoc.19.103

• ). Asymmetric variants of these transformations are possible using the tert-butanesulfinyl chiral auxiliary on the nitrogen atom. The levels of 1,4-stereoinduction are significant but a convincing model to account for it cannot be put forward at this point. Nonetheless, from a synthetic methodology point of

Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• -workers [61] extended the application of NHC–copper catalysts to the conjugate addition of boronates to acyclic α,β-unsaturated carboxylic esters, ketones, and thioesters leading to the enantioselective formation of boron-substituted quaternary carbon stereogenic centers (Scheme 43). All transformations

• transformations of sterically congested substrates, including those carrying a quaternary center not only proceeded efficiently but also were more selective. The NHCs with larger aryl units deliver higher selectivity ((Z/E: >98:2). Cazin and co-workers [83] instead used [IMes–CuCl] as catalyst for the borylation

Visible-light-induced nickel-catalyzed α-hydroxytrifluoroethylation of alkyl carboxylic acids: Access to trifluoromethyl alkyl acyloins

• Feng Chen,
• Xiu-Hua Xu,
• Zeng-Hao Chen,
• Yue Chen and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2023, 19, 1372–1378, doi:10.3762/bjoc.19.98

• ; Introduction Acyloins (also known as α-hydroxy ketones) are widely found as structural motif in natural products [1][2][3][4][5][6][7] and bioactive molecules [8][9][10][11] (Figure 1). They can also be used as building blocks in organic synthesis [12][13][14], involved in numerous transformations to other

• carboxylic acid and pivalic anhydride than aryl bromide. The halides provided versatile synthetic handles for further transformations. Substrates bearing thiophene (3k) furan (3j) and other heterocycle (3l,m) moieties were also applicable to this reaction. This protocol allowed for the coupling of not only