Synthetic approach to 2-alkyl-4-quinolones and 2-alkyl-4-quinolone-3-carboxamides based on common β-keto amide precursors

• Yordanka Mollova-Sapundzhieva,
• Plamen Angelov,
• Danail Georgiev and
• Pavel Yanev

Beilstein J. Org. Chem. 2023, 19, 1804–1810, doi:10.3762/bjoc.19.132

• conditions presented a challenge with regard to the chemoselectivity of the desired transformation, as they initially gave mixtures of 4-quinolones 5 or 8, respectively, and their corresponding N-hydroxy derivatives 4 or 7, respectively. Such a result is not surprising, considering that the reduction of the

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp³)–H to construct C–C bonds

• Hui Yu and
• Feng Xu

Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94

• afford allyl ethers. Alkyne C(sp)–H bonds are reactive, and the challenge in the cross-coupling of C(sp)–H and C(sp3)–H bonds is to control chemoselectivity. In this context, Liu et al. reported a Cu(I)/Ga(III)-catalyzed trityl ion-mediated direct CDC of the C(sp3)–H bond of THF with C(sp)–H bonds of

Acetaldehyde in the Enders triple cascade reaction via acetaldehyde dimethyl acetal

• Alessandro Brusa,
• Debora Iapadre,
• Maria Edith Casacchia,
• Alessio Carioscia,
• Giuliana Giorgianni,
• Giandomenico Magagnano,
• Fabio Pesciaioli and
• Armando Carlone

Beilstein J. Org. Chem. 2023, 19, 1243–1250, doi:10.3762/bjoc.19.92

• as a reagent has always been challenging. The low boiling point and high volatility pose a problem with its handling and safety. The small steric hindrance gives rise to a high reactivity both as an electrophile and as a pro-nucleophile, hampering chemoselectivity (further to side reactions such as

Exploring the role of halogen bonding in iodonium ylides: insights into unexpected reactivity and reaction control

• Carlee A. Montgomery and
• Graham K. Murphy

Beilstein J. Org. Chem. 2023, 19, 1171–1190, doi:10.3762/bjoc.19.86

• ylides and Lewis basic nucleophiles in which halogen bonding has been specifically invoked. The reactions discussed herein are organized to enable the reader to build an understanding of how halogen bonding might impact yield and chemoselectivity outcomes in reactions of iodonium ylides. Areas of focus

• even impacted the chemoselectivity of its subsequent reactions. Examples of this include the ortho-substituted iodoarene-derived ylides used in blue LED photoreactions between ylides and amines (Scheme 7) and radiofluorinations (Scheme 14), where ortho-ether moieties positively influenced the

• σ-holes might enhance the reaction’s chemoselectivity. Specifically, they investigated the coupling reactions between diazonium and iodonium ylides and the soft Lewis base thioamide 67 [145], intending to achieve C–S bond formation with the β-dicarbonyl, producing 68 (Scheme 16). They compared a

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

Total synthesis of grayanane natural products

• Nicolas Fay,
• Rémi Blieck,
• Cyrille Kouklovsky and
• Aurélien de la Torre

Beilstein J. Org. Chem. 2022, 18, 1707–1719, doi:10.3762/bjoc.18.181

• presented some difficulties, and the authors decided to investigate the use of a free ketone. The partial hydrogenation of alkyne 72 proved to be inefficient, due to a lack of chemoselectivity involving competitive olefin reduction on the bicylo[3.2.1]octane. To overcome the over-oxidation, 72 was treated

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• different chemoselectivity: secondary and benzyl alcohols are more easily oxidized. The great diversity of catalytic systems based on amine-N-oxyl radicals for alcohol oxidation was proposed [74][76][77][95]. Amine-N-oxyl organocatalysts with enhanced catalytic activity were developed by the modification of

• the key factor for the high chemoselectivity. Hypervalent iodine catalysis Effective hypervalent iodine(III)-catalyzed processes (for example, oxidative double C=C bond functionalization, oxidative cyclizations, CH-functionalization of carbonyl compounds, etc.) employing mainly peroxoacids or electric

Cyclometalated iridium complexes-catalyzed acceptorless dehydrogenative coupling reaction: construction of quinoline derivatives and evaluation of their antimicrobial activities

• Hongling Shui,
• Yuhong Zhong,
• Renshi Luo,
• Zhanyi Zhang,
• Jiuzhong Huang,
• Ping Yang and
• Nianhua Luo

Beilstein J. Org. Chem. 2022, 18, 1507–1517, doi:10.3762/bjoc.18.159

• accompanied by 27% yield of 1,2-dihydroquinoline 4aa (Table 1, entry 1). Then, several other cyclometalated iridium complexes were studied. The catalysts TC-2 and TC-4 containing electron-donating ligands provided quinoline 3aa in higher chemoselectivity and yield (Table 1, entries 2 and 4). On the contrary

• , the catalysts TC-3 and TC-5 containing electron-withdrawing ligands offered lower chemoselectivity and yield (Table 1, entries 3 and 5). Further catalyst screening revealed that TC-6 (6-methoxy) is the best catalyst for the ADC reaction affording the product in a yield of 95% (Table 1, entry 6). On

• surveyed (Table 2). First, several bases were examined and the results showed that different bases have different effects on the chemoselectivity and yield of the reaction. The weak bases including HCO2Na, CH3CO2K, and Na2CO3, resulted in decreased yields of quinoline 3aa (Table 2, entries 1–3

B–N/B–H Transborylation: borane-catalysed nitrile hydroboration

• Filip Meger,
• Alexander C. W. Kwok,
• Franziska Gilch,
• Dominic R. Willcox,
• Alex J. Hendy,
• Kieran Nicholson,
• Andrew D. Bage,
• Thomas Langer,
• Thomas A. Hunt and
• Stephen P. Thomas

Beilstein J. Org. Chem. 2022, 18, 1332–1337, doi:10.3762/bjoc.18.138

• relies upon stoichiometric reagents or transition-metal catalysis. Herein, a borane-catalysed hydroboration of nitriles to give primary amines is reported. Good yields (48–95%) and chemoselectivity (e.g., ester, nitro, sulfone) were observed. DFT calculations and mechanistic studies support the proposal

• for nitrile hydroboration [24]. Developed from the stoichiometric reactivity of [HBEt3]−, this method displayed good reactivity but limited chemoselectivity. Like [HBEt3]−, boranes are stoichiometric reducing agents, but are considered to be milder than [HBEt3]− [4]. Catalysis enabled by B–N/B–H

• nitriles with broad chemoselectivity, raise the standing of metal-free catalysis in nitrile hydroboration, and increase user accessibility by using commercially available catalysts and turnover reagents (Scheme 1b). Results and Discussion Investigations began by screening a combination of commercially

Electrochemical hydrogenation of enones using a proton-exchange membrane reactor: selectivity and utility

• Koichi Mitsudo,
• Haruka Inoue,
• Yuta Niki,
• Eisuke Sato and
• Seiji Suga

Beilstein J. Org. Chem. 2022, 18, 1055–1061, doi:10.3762/bjoc.18.107

• reactor; Introduction Catalytic hydrogenation of α,β-enones is a significant transformation in organic synthesis [1]. Hydrogenation of enones can give ketones, allyl alcohols, and saturated alcohols, and the control of the chemoselectivity is important. Therefore, there have been numerous studies on the

• the circulating system until 1a was consumed, the ketone 2a, obtained by the exclusive reduction of the C=C moiety, was obtained in 81% yield with a chemoselectivity of 92%. Similarly, cyclopentanone 2b was obtained from the corresponding enone 1b in 74% yield (88% selectivity). Substituted

• 72% yield with good selectivity (89%). Both 1f and 1g could be used in this reactions, and the corresponding alcohols 3f and 3g were obtained as major products. Mechanistic studies To gain further insight into the reaction mechanism of the chemoselectivity of a Pd/C cathode system, some additional

Automated grindstone chemistry: a simple and facile way for PEG-assisted stoichiometry-controlled halogenation of phenols and anilines using N-halosuccinimides

• Dharmendra Das,
• Akhil A. Bhosle,
• Amrita Chatterjee and
• Mainak Banerjee

Beilstein J. Org. Chem. 2022, 18, 999–1008, doi:10.3762/bjoc.18.100

• reaction time, and mild reaction conditions are a few noticeable merits of this environmentally sustainable mechanochemical protocol. Keywords: automated grinding; chemoselectivity; mechanochemistry; N-bromosuccinimide; PEG-400; regioselectivity; stoichiometry-controlled halogenation; Introduction Aryl

• hours for completion and showed inferior chemoselectivity producing dibrominated product 3a in higher quantity in the solution phase (Table S1, entries 6 and 7 in Supporting Information File 1). However, a thick immiscible mixture was formed when only 0.2 mL of PEG-400 were used and the reaction could

Synthesis of α-(perfluoroalkylsulfonyl)propiophenones: a new set of reagents for the light-mediated perfluoroalkylation of aromatics

• Durbis J. Castillo-Pazos,
• Juan D. Lasso and
• Chao-Jun Li

Beilstein J. Org. Chem. 2022, 18, 788–795, doi:10.3762/bjoc.18.79

• superstoichiometric amounts of starting materials, generation of undesired perfluoroalkylated byproducts, and poor chemoselectivity. Modern perfluoralkylation methodologies exceedingly rely on the use of perfluoroalkyl iodides as their principal source of perfluoroalkyl synthons. Indeed, while these molecules are

Recent developments and trends in the iron- and cobalt-catalyzed Sonogashira reactions

• Surendran Amrutha,
• Sankaran Radhika and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 262–285, doi:10.3762/bjoc.18.31

• is shown in Scheme 5. Non-green protocols Nakamura et al. disclosed an Fe-catalyzed Sonogashira coupling between an alkynyl unit with primary and secondary alkyl halides (Scheme 6) [24]. They reported the coupling of an unactivated alkyl halide with the Fe catalyst can switch its chemoselectivity

Recent advances and perspectives in ruthenium-catalyzed cyanation reactions

• Thaipparambil Aneeja,
• Cheriya Mukkolakkal Abdulla Afsina,
• Padinjare Veetil Saranya and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 37–52, doi:10.3762/bjoc.18.4

• , and easily available N-cyano-N-phenyl-p-toluenesulfonamide (NCTS) as the cyanating reagent. The reaction exhibited high chemoselectivity and good functional group tolerance. The optimized conditions for the reaction were [RuCl2(p-cymene)]2 (5 mol %), AgSbF6 (20 mol %), NaOAc (20 mol %) in DCE at 120

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• observed generating spiro succinimidetetrahydropyridine derivatives 172. To understand the chemoselectivity of the reaction, the authors performed a DFT mechanistic study. After the iminyl radical is generated it will undergo a 1,5-HAT to form the more stable alkyl radical which will add across the alkene

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• poor chemoselectivity [40]. However, the realization of this redox-neutral aryl–aryl cross-coupling is a formidable challenge. Therefore, the discovery of efficient catalysts and ligands to achieve high stereoselectivity is a fundamental issue in catalytic asymmetric synthesis [14]. In this section, we

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

• these results, the late-stage diversification using the [Mn(t-BuPc)Cl] catalyst was applied to more complex natural compounds such as the isosteviol derivative 45 and the betulinic acid derivative 47, which underwent conversion in good and high yields and with high chemoselectivity. The functionalized

• ′-bipyrrolidine) controls the site- and chemoselectivity in the hydroxylating step of the methylene C(sp3)–H bond while milder oxidation conditions help to increase the chemoselectivity. The methylation step is accomplished using a modestly nucleophilic organoaluminium reagent (AlMe3) to activate the hemiaminal

• , operating under mild conditions without the need of directing groups, using traceless electrons as sole redox reagents, presenting high scope and chemoselectivity. The robustness of the reaction was proved by the late-stage modification of pharmaceutically relevant compounds by promoting the azidation of a

Sustainable manganese catalysis for late-stage C–H functionalization of bioactive structural motifs

• Jongwoo Son

Beilstein J. Org. Chem. 2021, 17, 1733–1751, doi:10.3762/bjoc.17.122

• tryptophan-containing peptides (Scheme 13). A wide variety of complex peptides was explored, affording glycosylated conjugates with high stereoselectivity. The free NH functional group was tolerated in the manganese catalysis protocol, suggesting that the chemoselectivity was controlled by chelation of the

• , late-stage intramolecular C–H macrocyclization was also investigated (Scheme 15). To avoid unwanted intermolecular oligomerization, the reaction was performed at a high dilution, furnishing either C- or N-terminus-alkenylated products with excellent chemoselectivity. In this macrocyclization, cyclic

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• strategy in total synthesis can be found [82][83][84][85][86][87][88][89][90]. The reaction’s mild conditions and high chemoselectivity allowed its use even in advanced steps in a total synthesis route when diverse functional groups were present in the intermediates. Two representative examples of the

A straightforward conversion of 1,4-quinones into polycyclic pyrazoles via [3 + 2]-cycloaddition with fluorinated nitrile imines

• Greta Utecht-Jarzyńska,
• Karolina Nagła,
• Grzegorz Mlostoń,
• Heinz Heimgartner,
• Marcin Palusiak and
• Marcin Jasiński

Beilstein J. Org. Chem. 2021, 17, 1509–1517, doi:10.3762/bjoc.17.108

• 1,4-naphthoquinone (1a) and 1,4-anthraquinone (1b), which were selected as model dipolarophiles. In addition, an important issue of the work was the examination of the chemoselectivity governing the formation of five-membered rings via competitive cycloaddition of the in-situ-generated 1,3-dipoles

• -quinone methides with common nitrile imines proceeded with different chemoselectivity, and in these cases, the exocyclic C=C bond played the role of the exclusive dipolarophilic center, yielding corresponding spiropyrazoles [39][40]. This unusual selectivity in [3 + 2]-cycloadditions of less electron

Free-radical cyclization approach to polyheterocycles containing pyrrole and pyridine rings

• Ivan P. Mosiagin,
• Olesya A. Tomashenko,
• Dar’ya V. Spiridonova,
• Mikhail S. Novikov,
• Sergey P. Tunik and
• Alexander F. Khlebnikov

Beilstein J. Org. Chem. 2021, 17, 1490–1498, doi:10.3762/bjoc.17.105

• target compounds and can be performed on a gram scale. The free bases can be obtained from the synthesized hydrobromides in quantitative yield by basification at rt. The use 2/4-(ortho-bromo/iodophenyl)-substituted pyrrolylpyridinium bromides allows control over the chemoselectivity of the intramolecular

Iodine-catalyzed electrophilic substitution of indoles: Synthesis of (un)symmetrical diindolylmethanes with a quaternary carbon center

• Thanigaimalai Pillaiyar,
• Masoud Sedaghati,
• Andhika B. Mahardhika,
• Lukas L. Wendt and
• Christa E. Müller

Beilstein J. Org. Chem. 2021, 17, 1464–1475, doi:10.3762/bjoc.17.102

• unsymmetrical 3,3'-diindolylmethanes (DIMs) with a quaternary carbon center has been developed via iodine-catalyzed coupling of trifluoromethyl(indolyl)phenylmethanols with indoles. In contrast to previously reported methods, the new procedure is characterized by chemoselectivity, mild conditions, high yields

Nitroalkene reduction in deep eutectic solvents promoted by BH₃NH₃

• Chiara Faverio,
• Monica Fiorenza Boselli,
• Patricia Camarero Gonzalez,
• Alessandra Puglisi and
• Maurizio Benaglia

Beilstein J. Org. Chem. 2021, 17, 1041–1047, doi:10.3762/bjoc.17.83

• , nitrocyclohexene was reduced in 60% yield in a ChCl/glycerol mixture, while 6c was obtained in similar yields in glycerol or DES B. Noteworthy, the reduction of nitrobutadiene 5d produced nitro derivative 6d in 63% yield in glycerol and 44% in DES B, with complete control of the chemoselectivity. Remarkably, the

• reduction of nitrodiene 5e, featuring an ester group, was also accomplished with complete chemoselectivity in 50% yield in DES B and in 60% yield in glycerol. The reduction of the nitro group to an amine, followed by cyclization would afford the unsaturated δ-lactam, a valuable precursor for further

• also demonstrated. A wide variety of alkyl- and aryl-substituted nitroalkenes were reduced with high chemoselectivity, including β-substituted nitroolefins, and thus paving the way to the study of innovative, sustainable and stereoselective reductive methods to synthesize enantiopure nitroalkanes

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• synthesis of unnatural α-amino acids 129 and precise alkylation modification of peptides in the later stage (Scheme 45). Even in the presence of other amino acid residues, this protocol has excellent regio- and chemoselectivity, providing a sequence of novel corresponding dipeptides with good yield. The

Particle size effect in the mechanically assisted synthesis of β-cyclodextrin mesitylene sulfonate

• Stéphane Menuel,
• Sébastien Saitzek,
• Eric Monflier and
• Frédéric Hapiot

Beilstein J. Org. Chem. 2020, 16, 2598–2606, doi:10.3762/bjoc.16.211

• study, we found that the reactivity depended more upon diffusion phenomena in the crystalline parts of the material than on the increase in the surface area of the CD particles resulting from grinding. Keywords: beta-cyclodextrin; chemoselectivity; grinding; mechanosynthesis; reactivity; Introduction

• constituting the reaction mixture on the reactivity for the synthesis of β-CDMts under ball-milling conditions. Additionally, in the presence of a base such as KOH, we show that the chemoselectivity of the reaction is significantly altered in favor of the β-CD product mono-substituted on the primary face, thus