Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

• Yi Liu,
• Puying Luo,
• Yang Fu,
• Tianxin Hao,
• Xuan Liu,
• Qiuping Ding and
• Yiyuan Peng

Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163

• structural motifs to provide the functionalized pyridine and pyrrole derivatives. The functionalization reactions cover iodination, bromination, trifluoromethylation, azidation, carbonylation, arylation, alkylation, selenylation, sulfenylation, amidation, esterification, and hydroxylation. We also briefly

• introduce the applications of the products and the reaction mechanisms for the synthesis of corresponding N-heterocycles. Keywords: 1,3-enyne; functionalization; pyridine; pyrrole; tandem annulation; Introduction The pyridine moiety is an important class of six-membered N-heterocycles that is widely found

• pyridine derivatives have been developed through the intramolecular or intermolecular tandem addition annulation/functionalization of alkynes with some N-containing compounds, such as nitriles, oximes, and imines [15][16][17][18][19]. The pyrrole structural motif is also an invaluable five-membered N

A novel methodology for the efficient synthesis of 3-monohalooxindoles by acidolysis of 3-phosphate-substituted oxindoles with haloid acids

• Li Liu,
• Yue Li,
• Tiao Huang,
• Dulin Kong and
• Mingshu Wu

Beilstein J. Org. Chem. 2021, 17, 2321–2328, doi:10.3762/bjoc.17.150

• challenge in chemistry. In order to achieve this goal, and on the basis of our previous experiences in the functionalization of oxindoles [33][34], we herein designed a nucleophilic substitution method of an isatin-derived 3-phosphate-substituted oxindole with haloid acids, leading to 3-monohalooxindoles

A visible-light-induced, metal-free bis-arylation of 2,5-dichlorobenzoquinone

• Pieterjan Winant and
• Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 2315–2320, doi:10.3762/bjoc.17.149

• options for further functionalization. When 4-nitroaniline (4e) was used, the monoarylated product precipitated from the reaction mixture. Due to the very limited solubility of this intermediate, the latter was unable to react further. Changing the solvent to DMSO to try to tackle the solubility issue did

• , explaining the lowered yield. The reaction also required six equivalents and 72 h of reaction time to produce the product. ortho-Substituted anilines are interesting substrates as the product enables several possibilities for post-functionalization. Despite the inherent steric hindrance originating from the

Post-functionalization of drug-loaded nanoparticles prepared by polymerization-induced self-assembly (PISA) with mitochondria targeting ligands

• Janina-Miriam Noy,
• Fan Chen and
• Martina Stenzel

Beilstein J. Org. Chem. 2021, 17, 2302–2314, doi:10.3762/bjoc.17.148

• be taken into account that the drug can interfere with the block copolymer aggregation. Alternatively, the use of reactive polymers for the polymerization creates a functional anchor to enable post-functionalization of the PISA nanoparticles with drugs such as doxorubicin [35][36]. In a different

Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• halogens are often regarded as surrogates for further functionalization, their role in natural and physiological processes is much more diverse. One of these processes is the ability of large complex molecules and enzymes to recognize halide anions via hydrogen bonds in aqueous media [5]. Amongst others

Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• Lusina Mantry Rajaram Maayuri Vikash Kumar Parthasarathy Gandeepan Department of Chemistry, Indian Institute of Technology Tirupati, Tirupati – Renigunta Road, Settipalli Post, Tirupati, Andhra Pradesh 517506, India 10.3762/bjoc.17.143 Abstract Catalytic C‒H functionalization has become a

• metallaphotoredox catalysis enabled C‒H functionalizations with unique reaction pathways under mild reaction conditions. Given the relative earth-abundance and cost-effective nature, nickel catalysts for photoredox C‒H functionalization have received significant attention. In this review, we highlight the

• developments in the field of photoredox nickel-catalyzed C‒H functionalization reactions with a range of applications until summer 2021. Keywords: C–H activation; functionalization; nickel; photocatalysts; photoredox; visible light; Introduction During the last decades, transition-metal-catalyzed

Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

• Ranadeep Talukdar

Beilstein J. Org. Chem. 2021, 17, 2102–2122, doi:10.3762/bjoc.17.137

• ]. The reason behind the C-2 attachment of the boron atom rather than at the C-3 position of the indole ring was explained by McGough et al. [37]. They performed a base-free catalytic I2-assisted indole C–H functionalization (electrophilic borylation) using the N-protected indole 1 and NHC·borane 4a that

Preparation of mono-substituted malonic acid half oxyesters (SMAHOs)

• Tania Xavier,
• Sylvie Condon,
• Christophe Pichon,
• Erwan Le Gall and
• Marc Presset

Beilstein J. Org. Chem. 2021, 17, 2085–2094, doi:10.3762/bjoc.17.135

• [46][47][48], such as the α-carboxylation of an ester [49], the selective functionalization of a bromomalonate derivative [50], or the monoesterification of a malonic acid derivative [51][52][53]. However, even if the above-mentioned strategies appear obvious for the preparation of the simplest SMAHOs

A study on selective transformation of norbornadiene into fluorinated cyclopentane-fused isoxazolines

• Zsanett Benke,
• Attila M. Remete and
• Loránd Kiss

Beilstein J. Org. Chem. 2021, 17, 2051–2066, doi:10.3762/bjoc.17.132

• Abstract This work presents an examination of the selective functionalization of norbornadiene through nitrile oxide 1,3-dipolar cycloaddition/ring-opening metathesis (ROM)/cross-metathesis (CM) protocols. Functionalization of commercially available norbornadiene provided novel bicyclic scaffolds with

• the CM transformations with the goal of exploring substrate and steric effects, catalyst influence and chemodifferentiation of the olefin bonds furnishing the corresponding functionalized, fluorine-containing isoxazoline derivatives. Keywords: functionalization; metathesis; nitrile oxide

• selective functionalization of readily available norbornadiene across nitrile oxide cycloaddition/ROM/CM protocols in view of the access of various fluorine-containing molecular entities as well as to explore the chemical behavior of olefin bonds in the reaction with some fluorinated alkene derivatives in

Progress and challenges in the synthesis of sequence controlled polysaccharides

• Giulio Fittolani,
• Theodore Tyrikos-Ergas,
• Denisa Vargová,
• Manishkumar A. Chaube and
• Martina Delbianco

Beilstein J. Org. Chem. 2021, 17, 1981–2025, doi:10.3762/bjoc.17.129

Asymmetric organocatalyzed synthesis of coumarin derivatives

• Natália M. Moreira,
• Lorena S. R. Martelli and
• Arlene G. Corrêa

Beilstein J. Org. Chem. 2021, 17, 1952–1980, doi:10.3762/bjoc.17.128

• . Catalysis via covalent bonding Organocatalysts made from chiral secondary amines have been widely used in the last years. According to Jørgensen, in general, the carbonyl functionalization employing amine catalysts can be separated in four different types [29]. When aldehydes are employed, both

• % ee) (Scheme 10). A catalytic asymmetric β-C−H functionalization of ketones 33 with 4-hydroxycoumarins 1 was developed by Zhu et al. [43]. The enamine, formed via reaction of the aminocatalyst 35 with the ketone, is oxidased by IBX resulting in the electrophilic imine, which in turn undergoes a

• a high diastereoisomeric control and in most cases with good enantioselectivity of the products. It becomes even more attractive, since it allows an in situ rearrangement of the acyl group that can be used in other functionalization methodologies. However, it presents a limitation relative to the

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

• (III) salts and AlMe3 as a base for the regioselective ortho functionalization of aromatic secondary amides has been recently reported [121]. The reaction is performed with 1–2 mol % of CrCl3 or Cr(aca)3, a stoichiometric amount of AlMe3 and bromoalkynes (Scheme 15B), allyl bromide or 1,4-dihydro-1,4

• , it is present in compounds that have a significant anti-inflammatory activity (43 and 44) (Scheme 16A) [125]. The introduction of two distinct aryl moieties into arenes was also shown to be feasible through the sequential functionalization with two different Grignard reagents. For this purpose, the

• . The photo-electro methodology allowed the late-stage functionalization of valuable bioactive molecules, and the structures of a adapalene precursor (65) and ibuprofen derivative (66) were successfully azidated in moderate yields (Scheme 23C). Some silylated compounds like 67 have proven to be

Cationic oligonucleotide derivatives and conjugates: A favorable approach for enhanced DNA and RNA targeting oligonucleotides

• Mathias B. Danielsen and
• Jesper Wengel

Beilstein J. Org. Chem. 2021, 17, 1828–1848, doi:10.3762/bjoc.17.125

• strategy that has been employed to optimize the delivery profile of ASOs, is the functionalization of ASOs with cationic amine groups, either by direct conjugation onto the sugar, nucleobase or internucleotide linkage. The introduction of these positively charged groups has improved properties like

• to a Watson–Crick interacting ON, both targeting the same ssDNA) exhibited the ability to invade double-stranded DNA (dsDNA) targets in vitro [56]. The functionalization with aminoalkyl variants onto the nucleobase is not limited to the C-5 position on the pyrimidine base. Another important site is

• therapeutically relevant monomers like 2’-OMe- and 2’-O-MOE-RNA [3]. Additionally, the attachment of amine-functionalized groups at the 2’-position can be readily performed and allows for the amine-functionalized group to be positioned into the minor groove of the ON duplex [73]. Aminoalkyl functionalization of

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

• Jongwoo Son Department of Chemistry, Dong-A University, Busan 49315, South Korea Department of Chemical Engineering (BK21 FOUR Graduate Program), Dong-A University, Busan 49315, South Korea 10.3762/bjoc.17.122 Abstract The late-stage C–H functionalization of bioactive structural motifs is a

• organic synthesis. Among the 3d metals, manganese catalysts have gained increasing attention for late-stage diversification due to the sustainability, cost-effectiveness, ease of operation, and reduced toxicity. Herein, we summarize recent manganese-catalyzed late-stage C–H functionalization reactions of

• biologically active small molecules and complex peptides. Keywords: bioactive molecules; 3d transition metals; late-stage functionalization; manganese catalyst; sustainable catalysis; Introduction Manganese, a 3d transition metal, allows for a potentially ideal sustainable catalytic system because of the

Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications

• Nikita Brodyagin,
• Martins Katkevics,
• Venubabu Kotikam,
• Christopher A. Ryan and
• Eriks Rozners

Beilstein J. Org. Chem. 2021, 17, 1641–1688, doi:10.3762/bjoc.17.116

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

• Pezhman Shiri,
• Ali Mohammad Amani and
• Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

• applications of these five-membered N-heterocycles are the result of both their easy synthetic procedures and ring functionalization [9][31][32]. Typically, 1,2,3-triazole derivatives are prepared via a 1,3-dipolar cycloaddition reaction between azides and alkynes [33]. It is worth noting that the metal

• insensitivity to air are advantages of this reaction (Scheme 37) [60]. In 2017, De Borggraeve et al. explained a convenient procedure for the preparation of triazolo[1,5-a]indolones 131 through an intramolecular cyclization via an unprecedented Pd-catalyzed carbonylative C–H functionalization of 1-(2-bromoaryl

• bond functionalization reaction sequence with triazole-bearing aryl iodide 140, catalyzed by alloy-structured Pd/Cu bimetallic nanoparticles stabilized by a binaphthyl moiety, Pd/Cu-BNP 139. The Pd/Cu-BNP nanoparticles 139 were demonstrated to be an efficient and recyclable catalyst, and triazoles

Copper-mediated oxidative C−H/N−H activations with alkynes by removable hydrazides

• Feng Xiong,
• Bo Li,
• Chenrui Yang,
• Liang Zou,
• Wenbo Ma,
• Linghui Gu,
• Ruhuai Mei and
• Lutz Ackermann

Beilstein J. Org. Chem. 2021, 17, 1591–1599, doi:10.3762/bjoc.17.113

• -pyridylhydrazide allowed for domino C–H/N–H functionalization. The approach featured remarkable functional group compatibility and ample substrate scope. Thereby, highly functionalized aromatic and heteroaromatic isoindolin-1-ones were accessed with high efficacy with rate-limiting C–H cleavage. Keywords

• : benzhydrazides; copper; 3-methyleneisoindolin-1-one; removable directing group; Introduction Inexpensive copper-promoted oxidative C−H activations [1][2][3][4][5][6][7][8][9][10][11] have been recognized as competent tools for the efficient assembly and late-stage functionalization of organic molecules due to

• -catalyzed C−H activations with the MHP auxiliary [41][42][43][44]. In continuation of studies on sustainable 3d transition metal-catalyzed C−H activation [41][42][43][44][45][46][47][48][49], we have now discovered a robust copper-promoted oxidative C−H/N−H functionalization with terminal alkynes (Figure 1d

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

• Thiago S. Silva Fernando Coelho Laboratory of Synthesis of Natural Products and Drugs, Department of Organic Chemistry, Chemistry Institute, University of Campinas, PO Box 6154 - 13083-970, Campinas – SP, Brazil 10.3762/bjoc.17.112 Abstract Olefin double-bond functionalization has been

• nucleophiles, along with transition-metal catalysis, in olefin alkylation reactions [18][19][20][21]. Apart from the early examples of olefin functionalization with transition metals, such as the well-known ethylene oxidation catalyzed by Pd(II) (the Wacker reaction) [23][24], the use of carbon nucleophiles in

• substrates (Scheme 2 and Scheme 4), and an external proton source (acetic acid) was required to furnish the hydroalkylated products 7 (Scheme 5A). The quaternary carbon centers were synthetized in moderate to excellent yields by this methodology, and its potential use in late-stage functionalization was

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

• structural motifs present in naturally occurring compounds as well as synthetic drugs and other functionalized organic molecules of great practical importance, e.g., in materials chemistry (Figure 1) [1][2][3][4]. Selective functionalization of 1,4-quinones is a challenging task in current organic synthesis

Substituted nitrogen-bridged diazocines

• Pascal Lentes,
• Jeremy Rudtke,
• Thomas Griebenow and
• Rainer Herges

Beilstein J. Org. Chem. 2021, 17, 1503–1508, doi:10.3762/bjoc.17.107

• makes them promising candidates for applications in photopharmacology. The halogen substituents allow further functionalization via cross-coupling reactions. Keywords: bridged azobenzene; diazocine; photopharmacology; photoswitch; triazocine; visible light switch; water-soluble switch; Introduction

• point for further functionalization [17][20][24]. We conclude that CH2NAc and CH2NCHO bridged diazocines (triazocines) are promising candidates for applications in biological environments and particularly as photoswitches in light-activatable drugs. Bridged diazocines synthesized and investigated in

Total synthesis of ent-pavettamine

• Memory Zimuwandeyi,
• Manuel A. Fernandes,
• Amanda L. Rousseau and
• Moira L. Bode

Beilstein J. Org. Chem. 2021, 17, 1440–1446, doi:10.3762/bjoc.17.99

• subsequent functionalization giving rise to two C5 units with compatible groups required for linking: in this case an amine and an aldehyde. In order for the synthesis to yield ent-pavettamine instead of pavettamine, the key was to functionalize the “opposite end” of each of the C5 units required for linking

• , when compared to our original pavettamine synthesis [1]. This opposite functionalization ensured that the enantiomer would result from the synthesis. For purposes of comparison between the original route and the route described here, our efforts commenced with the synthesis of the common C5 unit 4

• selective functionalization and protection of the primary and secondary hydroxy groups (and later amino groups) was critical for the successful synthesis of the target compound. Unfortunately, each protecting group incorporated increased the synthesis by two non-productive steps; nonetheless our aim to

Heterogeneous photocatalytic cyanomethylarylation of alkenes with acetonitrile: synthesis of diverse nitrogenous heterocyclic compounds

• Guanglong Pan,
• Qian Yang,
• Wentao Wang,
• Yurong Tang and
• Yunfei Cai

Beilstein J. Org. Chem. 2021, 17, 1171–1180, doi:10.3762/bjoc.17.89

• cyanomethylarylation of N-aryl/benzoyl acrylamide or allylamine involving the key C–H functionalization of readily available acetonitrile is a straightforward and powerful method to access these useful structures [13][14][15][16][17]. Over the last decade, although numerous protocols have been disclosed for the direct

Synthesis of 10-O-aryl-substituted berberine derivatives by Chan–Evans–Lam coupling and investigation of their DNA-binding properties

• Peter Jonas Wickhorst,
• Mathilda Blachnik,
• Denisa Lagumdzija and
• Heiko Ihmels

Beilstein J. Org. Chem. 2021, 17, 991–1000, doi:10.3762/bjoc.17.81

• strands [30]. Due to their straightforward synthetic accessibility by substitution at the 9-hydroxy functionality of berberrubine (1b), 9-O-substituted berberine derivatives are particularly attractive. But so far, only functionalization at this position by alkylation [23][24][25][26] and nucleophilic

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• products [1][2][3][4][5][6][7][8]. Prins and related cyclization reactions [9][10], hetero-Diels–Alder cyclization [11], cyclization onto epoxides [12], Petasis–Ferrier rearrangement [13], intramolecular oxa-Michael reactions [14], cyclization through oxidative C–H bond functionalization [15], ring-closing

Beyond ribose and phosphate: Selected nucleic acid modifications for structure–function investigations and therapeutic applications

• Christopher Liczner,
• Kieran Duke,
• Gabrielle Juneau,
• Martin Egli and
• Christopher J. Wilds

Beilstein J. Org. Chem. 2021, 17, 908–931, doi:10.3762/bjoc.17.76

• location of the methylene bridge to tailor the properties of these nucleosides. The incorporation of nitrogen at C2' has been explored for further functionalization while retaining the LNA scaffold. Singh et al. were the first to report the synthesis of C2'-amino-LNAs (Figure 7C) in 1998 [150], with the