Transition-metal-catalyzed C–H bond activation as a sustainable strategy for the synthesis of fluorinated molecules: an overview

• Louis Monsigny,
• Floriane Doche and
• Tatiana Besset

Beilstein J. Org. Chem. 2023, 19, 448–473, doi:10.3762/bjoc.19.35

• % yields, respectively. This reaction proved to be compatible with the presence of an ester (8c) or a halogen (8e). Other directing groups, such as substituted pyridines (9a and 9b) and pyrimidine (9c) turned out to be also efficient in this transformation (Scheme 5, 4 examples, up to 84% yield). The same

• ) were found to be suitable substrates leading to the corresponding products 12h and 12i in 91% and 83% yields, respectively. The use of other directing groups was also suitable for this transformation such as methyl and cyano-substituted pyridines 13a,b, pyrimidine (13c), pyrazole (13d), as well as the

• % yield, 19a, 84% yield), substituted pyrazole derivatives (6 examples, up to 55% yield, 19b, 55% yield), pyrimidine (19c, 31% yield) as well as quinoline and isoquinoline (19d and 19e, 65% and 66% yields, respectively). In addition, the trifluoromethylthiolated benzo[h]quinoline 20f was obtained in good

A new route for the synthesis of 1-deazaguanine and 1-deazahypoxanthine

• Raphael Bereiter,
• Marco Oberlechner and
• Ronald Micura

Beilstein J. Org. Chem. 2022, 18, 1617–1624, doi:10.3762/bjoc.18.172

• synthesis of 1-deazaguanine and 1-deazahypoxanthine. Previously published routes toward these compounds focused on ring closure of the imidazole part of the purine system after the pyrimidine core had been functionalized, however, the drawback of this approach is the passage of rather hazardous/explosive

Ferrocenoyl-adenines: substituent effects on regioselective acylation

• Mateja Toma,
• Gabrijel Zubčić,
• Jasmina Lapić,
• Senka Djaković,
• Davor Šakić and
• Valerije Vrček

Beilstein J. Org. Chem. 2022, 18, 1270–1277, doi:10.3762/bjoc.18.133

• ], or structural motifs in xeno nucleic acids [18]. In continuation of our work on ferrocenoyl-substituted pyrimidine nucleobases [19], we report herewith a combined theoretical and experimental work on purine series. The novelty of these compounds is the carbonyl linker which connects the

• kinetic and thermodynamic control of the acylation reaction. Results and Discussion It was shown that the reaction between the pyrimidine anion (uracil, thymine, or 5-fluorouracil) and FcCOCl in N,N-dimethylformamide (DMF) proceeded in a full regiospecific mode [19]. In the purine series, however, the

Synthesis and HDAC inhibitory activity of pyrimidine-based hydroxamic acids

• Virginija Jakubkiene,
• Gabrielius Ernis Valiulis,
• Markus Schweipert,
• Asta Zubriene,
• Daumantas Matulis,
• Franz-Josef Meyer-Almes and
• Sigitas Tumkevicius

Beilstein J. Org. Chem. 2022, 18, 837–844, doi:10.3762/bjoc.18.84

• to differently substituted pyrimidine rings via a methylene group bridge of varying length as potential HDAC inhibitors is described. The target compounds were obtained by alkylation of 2-(alkylthio)pyrimidin-4(3H)-ones with ethyl 2-bromoethanoate, ethyl 4-bromobutanoate, or methyl 6-bromohexanoate

• the corresponding hydroxamic acids. The synthesized hydroxamic acids were tested as inhibitors of the HDAC4 and HDAC8 isoforms. Among the synthesized pyrimidine-based hydroxamic acids N-hydroxy-6-[6-methyl-2-(methylthio)-5-propylpyrimidin-4-yloxy]hexanamide was found to be the most potent inhibitor of

• both the HDAC4 and HDAC8 isoforms, with an IC50 of 16.6 µM and 1.2 µM, respectively. Keywords: alkylation; aminolysis; HDAC inhibitors; hydroxamic acid; pyrimidine; Introduction Histone deacetylases (HDACs) are a family of intracellular proteins responsible for removing acetyl groups in histones

Post-synthesis from Lewis acid–base interaction: an alternative way to generate light and harvest triplet excitons

• Hengjia Liu and
• Guohua Xie

Beilstein J. Org. Chem. 2022, 18, 825–836, doi:10.3762/bjoc.18.83

• with the Lewis acids discussed in this review and thus lead to a significant shift of their optoelectronic properties. It has been confirmed that organic molecules containing pyrimidine, pyrazine, and indole groups display similar interactions upon the addition of Lewis acids [40][41][42]. Lewis acid

Copper-catalyzed multicomponent reactions for the efficient synthesis of diverse spirotetrahydrocarbazoles

• Shao-Cong Zhan,
• Ren-Jie Fang,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2022, 18, 796–808, doi:10.3762/bjoc.18.80

• . On the other hand, the tetrahydrospiro[carbazole-3,5'-pyrimidine] 4 can be converted to aromatized spiro[carbazole-3,5'-pyrimidine] 3 through the oxidation of DDQ. In the absence of the effective dienophile, the normal Friedel–Crafts alkylation of 2-methylindole with aromatic aldehyde gives the well

• ethyl acetate and light petroleum (v/v = 1:3–1:6) as eluent to give pure products 3a–c. 1',3'-Dimethyl-2,4-di-p-tolyl-2'H-spiro[carbazole-3,5'-pyrimidine]-2',4',6'(1'H,3'H)-trione (3a): Yellow solid, 75%, mp 190–192 °C; 1H NMR (400 MHz, CDCl3) δ 7.59 (d, J = 7.6 Hz, 1H, ArH), 7.35–7.30 (m, 4H, ArH

• about three hours. After removing the solvent by evaporating at reduced pressure, the residue was subjected to column chromatography with ethyl acetate and light petroleum (v/v = 1:5–1:8) as eluent to give pure 4a–h. 1',3'-Dimethyl-2,4-diphenyl-1,2,4,9-tetrahydro-2'H-spiro[carbazole-3,5'-pyrimidine]-2

Heteroleptic metallosupramolecular aggregates/complexation for supramolecular catalysis

• Prodip Howlader and
• Michael Schmittel

Beilstein J. Org. Chem. 2022, 18, 597–630, doi:10.3762/bjoc.18.62

• 83–85 (1:1) [98]. The thermal sliding speed of the biped across the deck 82 depends on the thermodynamic strength of the pyridine (or pyrimidine, methylpyridine) → ZnPor interactions of the biped’s feet with the ZnPor units. Obviously, weaker binding to ZnPor should lead to faster sliding [17]. With

Syntheses of novel pyridine-based low-molecular-weight luminogens possessing aggregation-induced emission enhancement (AIEE) properties

• Masayori Hagimori,
• Tatsusada Yoshida,
• Yasuhisa Nishimura,
• Yukiko Ogawa and
• Keitaro Tanaka

Beilstein J. Org. Chem. 2022, 18, 580–587, doi:10.3762/bjoc.18.60

• compound, 10-imino-2-methylpyrido[1,2-a]pyrrolo[3,4-d]pyrimidine-1,3(2H,10H)-dione (3a), in 97% yield. The chemical structure of product 3a was confirmed by 1H and 13C NMR spectroscopy (Figures S1 and S2 in Supporting Information File 1) and was obtained via the following reaction mechanism: nucleophilic

• excitation maxima (Exmax), emission maxima (Emmax), and fluorescence quantum yields (Φ) of the molecules from fluorescence spectroscopic studies. The pyrido[1,2-a]pyrrolo[3,4-d]pyrimidine derivatives 3a,b possessing a highly complex ring-fused system emitted fluorescence at 545–546 nm and 537–538 nm in

• geometries of each monomer are shown in Figure 5. The dihedral angles between the pyrimidine and maleimide rings, the amine linkage, were nearly zero degrees for 4a and 4e in all three solvents, adopting a highly planar structure as well as compound 3a. The HOMO and LUMO were distributed on the entire

Substituent effect on TADF properties of 2-modified 4,6-bis(3,6-di-tert-butyl-9-carbazolyl)-5-methylpyrimidines

• Irina Fiodorova,
• Tomas Serevičius,
• Rokas Skaisgiris,
• Saulius Juršėnas and
• Sigitas Tumkevicius

Beilstein J. Org. Chem. 2022, 18, 497–507, doi:10.3762/bjoc.18.52

• of TADF compounds through the selection of different electron-donating or accepting fragments opens great possibilities to tune the emission properties and rates. Here we present the synthesis of a series of novel pyrimidine–carbazole emitters and their photophysical characterization in view of

• effects of substituents in the pyrimidine ring on their TADF properties. We demonstrate that electron-withdrawing substituents directly connected to the pyrimidine unit have greater impact on the lowering of the energy gap between singlet and triplet states (ΔEST) for efficient TADF as compared to those

• attached through a phenylene bridge. A modification of the pyrimidine unit with CN, SCH3, and SO2CH3 functional groups at position 2 is shown to enhance the emission yield up to 0.5 with pronounced TADF activity. Keywords: carbazole; pyrimidine; RTP; synthesis; thermally activated delayed fluorescence

Bifunctional thiourea-catalyzed asymmetric [3 + 2] annulation reactions of 2-isothiocyanato-1-indanones with barbiturate-based olefins

• Jiang-Song Zhai and
• Da-Ming Du

Beilstein J. Org. Chem. 2022, 18, 25–36, doi:10.3762/bjoc.18.3

• -isothiocyanato-1-indanones with barbiturate-based olefins have been developed to afford chiral dispiro[indene-pyrrolidine-pyrimidine]s. Through this strategy, the target products could be obtained in good to excellent yields with excellent stereoselectivities. In addition, the synthetic utility was verified

• application value of this asymmetric domino Michael addition/cyclization reaction, a gram-scale experiment was performed under the optimized conditions. As exemplified in Scheme 4, the desired dispiro[indene-pyrrolidine-pyrimidine] 3ah could be obtained in 94% yield with excellent stereoselectivity (>20:1 dr

• , >99% ee), which indicated this strategy shows promising prospects for mass production. Moreover, two different transformations of the product 3ah are shown to validate synthetic utility of the reaction. As demonstrated in Scheme 5, the dispiro[indene-pyrrolidine-pyrimidine] 3ah could be easily

The PIFA-initiated oxidative cyclization of 2-(3-butenyl)quinazolin-4(3H)-ones – an efficient approach to 1-(hydroxymethyl)-2,3-dihydropyrrolo[1,2-a]quinazolin-5(1H)-ones

• Alla I. Vaskevych,
• Nataliia O. Savinchuk,
• Ruslan I. Vaskevych,
• Eduard B. Rusanov,
• Oleksandr O. Grygorenko and
• Mykhailo V. Vovk

Beilstein J. Org. Chem. 2021, 17, 2787–2794, doi:10.3762/bjoc.17.189

• literature to date. One of them is based on the construction of the central pyrimidine ring starting from ortho-disubstituted aromatic compounds 2 bearing a pyrrolidine moiety (see Scheme 1A). Examples include cyclocondensation of (2-pyrrolidin-1-yl)benzaldehyde and aniline occurring in the presence of TsOH

• [13], as well as Ir-catalyzed intramolecular dehydrative cross-coupling of 2-(pyrrolidine-1-yl)benzamide [14]. Another approach to compounds of type 1 that relies on a cascade formation of the pyrimidine and pyrrole rings have found much wider application (see Scheme 1B). One of its variations

Synthetic strategies toward 1,3-oxathiolane nucleoside analogues

• Umesh P. Aher,
• Dhananjai Srivastava,
• Girij P. Singh and
• Jayashree B. S

Beilstein J. Org. Chem. 2021, 17, 2680–2715, doi:10.3762/bjoc.17.182

• of TMSOTf for the N-glycosylation procedure afforded a racemic mixture. This could be due to the opening as well as closing of the oxathiolane ring under the reaction conditions. Optically pure β-ᴅ- and α-ᴅ-configured 1,3-oxathiolane pyrimidine and 1,3-oxathiolane purine nucleosides with natural

• nucleoside configuration were synthesized by Jeong et al. (Scheme 32 and Scheme 33) [41][42]. The purpose of this was the investigation of the structure–activity relationships as anti-HIV-1 agents. The oxathiolane intermediate 20, produced from ᴅ-mannitol, was further condensed with a range of pyrimidine and

• potent. The pyrimidine analogues 90 and 91 were also found to be active against HIV-1, with EC50 = 0.28 µM and 2.8 µM, respectively [33]. In 1992, Humber et al. [45] established a method for glycosylation of benzoylated oxathiolane 31 with silylated cytosine in the presence of trimethylsilyl iodide (TMSI

Synthesis of O⁶-alkylated preQ₁ derivatives

• Laurin Flemmich,
• Sarah Moreno and
• Ronald Micura

Beilstein J. Org. Chem. 2021, 17, 2295–2301, doi:10.3762/bjoc.17.147

• in the biosynthetic pathway of the hypermodified tRNA nucleoside queuosine (Q) (Scheme 1) [5]. The core structure of the nucleobase is 7-aminomethyl-7-deazaguanine, a pyrrolo[2,3-d]pyrimidine also termed prequeuosine base (preQ1) [6][7]. In many bacteria, preQ1 binds to specific mRNA domains and

(Phenylamino)pyrimidine-1,2,3-triazole derivatives as analogs of imatinib: searching for novel compounds against chronic myeloid leukemia

• Luiz Claudio Ferreira Pimentel,
• Lucas Villas Boas Hoelz,
• Henayle Fernandes Canzian,
• Frederico Silva Castelo Branco,
• Andressa Paula de Oliveira,
• Vinicius Rangel Campos,
• Floriano Paes Silva Júnior,
• Rafael Ferreira Dantas,
• Jackson Antônio Lamounier Camargos Resende,
• Anna Claudia Cunha,
• Nubia Boechat and
• Mônica Macedo Bastos

Beilstein J. Org. Chem. 2021, 17, 2260–2269, doi:10.3762/bjoc.17.144

• )pyrimidine-pyridine (PAPP) group as a pharmacophoric fragment, and these compounds were biologically evaluated. The synthesis of twelve new compounds was performed in three steps and assisted by microwave irradiation in a 1,3-dipolar cycloaddition to obtain 1,2,3-triazole derivatives substituted on carbon C

• in the docking studies. Keywords: chronic myeloid leukemia; 1,3-dipolar cycloaddition; imatinib; (phenylamino)pyrimidine-pyridine; 1,2,3-triazole; Introduction Changes in tyrosine kinase proteins (TKPs), either by mutation or chromosomal translocation, can turn them into potent oncogenes

• 1980s, has led to the identification of the (phenylamino)pyrimidine (PAP) structure [5][6]. The addition of an additional pyridine ring to PAP raised its cellular activity, producing PAPP, which, after some more chemical modifications, culminated in imatinib (IMT) [7]. PAPP has been used to develop new

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

• latter strategy can be divided into the conjugation of amine groups onto ONs still attached to the solid support, or onto ONs in solution after cleavage from the solid support. The C-5 position of the pyrimidine ring has in general been the most used attachment point since it is not involved in hydrogen

• bonding and is facing the major groove upon duplex formation [27]. An illustrative approach that allowed the exploration of the 5-position of the pyrimidine ring as attachment site involved the use of 5-methoxycarbonylmethyl-2'-deoxyuridine and 5-trifluoroethoxycarbonyl-2’-deoxycytidine building blocks in

• the ON synthesis [28][29][30]. The corresponding modified ONs could be converted in a versatile manner to oligomers carrying the desired amine-functionalized groups at the 5-position on the pyrimidine nucleobase [28][29][30]. Similarly, the more reactive 5-cyanomethoxycarbonylmethyl-2’-deoxyuridine

Development of N-F fluorinating agents and their fluorinations: Historical perspective

• Teruo Umemoto,
• Yuhao Yang and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

• ], electron-rich alkenes (entry 3) [65][66], alkyl sulfides (entry 4) [65][67], 1,3-dicarbonyl compounds [65][68], phosphonate esters (entry 5) [65], steroidal silyl enol ethers and enol acetates (entry 6) [65], pyrimidine bases and nucleosides (entry 7) [67][69], phenylalkynes (entry 8) [70], anthraquinones

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

• -economical approach to several tryptophan-containing peptides with significant potential for drug discovery and medicinal chemistry. Positional selectivity was observed at the C2 position due to the presence of the pyrimidine directing group. Interestingly, alkynylative conjugation of tryptophan to a steroid

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

• and diagnostics that depend on Watson–Crick hydrogen bonding to natural nucleic acids. An unexpected discovery of early studies was that the triplex-forming PNAs built of pyrimidine monomers formed a 2:1 PNA–DNA–PNA strand-invasion triplex instead of the expected 1:1 PNA–dsDNA triplex (c.f., Figure 2A

• and 2B) [1][23]. This unprecedented binding mode was enabled by PNA’s unique ability to displace the pyrimidine-rich strand of dsDNA as the so-called P-loop, which was clearly facilitated by the neutral backbone [1]. Later studies showed that there was a delicate balance between the two binding modes

• recognition of pyrimidines in hypothetical X•T–A or X•C–G triplets is complicated by two problems: 1) pyrimidines present only one hydrogen bond acceptor (C=O in T or U) or donor (-NH2 in C) in the major groove, and 2) the six-membered pyrimidine ring extends further out in the major groove than the five

Synthesis of 1-indolyl-3,5,8-substituted γ-carbolines: one-pot solvent-free protocol and biological evaluation

• Premansh Dudhe,
• Mena Asha Krishnan,
• Kratika Yadav,
• Diptendu Roy,
• Krishnan Venkatasubbaiah,
• Biswarup Pathak and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2021, 17, 1453–1463, doi:10.3762/bjoc.17.101

• shown promising biological activities in preclinical and clinical studies (Figure 1) [2][3][4][5][6]. The pyrimidine-γ-carboline alkaloid ingenine B (isolated from an Indonesian sponge) exhibits a pronounced cytotoxicity against a murine lymphoma cell line [7] and several isocanthine analogs are

Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

• of deoxyribonucleic acids (DNA) or ribonucleic acids (RNA), which contain either a purine or pyrimidine nucleobase and a furanosyl moiety of pentose sugars, 2′-deoxyribose or ribose [1][2]. Nucleotides are constituted by addition of a phosphate group at the 5′-position of the nucleosides and these

• ribonuclease A [36]. Lazrek et al. [51] synthesized C-3'-modified double-headed nucleosides 54a–g where a 1,2,3-triazol ring acts as linker of the nucleobase and the sugar moiety. First, seven N9/N1-propargylpurine/pyrimidine nucleobases 13b, 45, and 53a–g were synthesized by treating the nucleobases with

• nucleoside 92 (Scheme 20) [13]. Lazrek et al. [51] synthesized C-5′-modified double-headed nucleosides 96a–g, where a 1,2,3-triazolo ring acted as the linker between the nucleobase and the sugar moiety. First, seven N9/N1-propargylpurine/pyrimidine nucleobases 13b, 45 and 53a–e were synthesized by treating

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

• Guareschi pyridine synthesis is a modified two-component version, mechanistically similar to the Biginelli pyrimidine synthesis [33] and based on the condensation of cyanoacetamide and a β-dicarbonyl derivative [45][46]. This is the most famous Guareschi pyridine synthesis, both in textbooks and in other

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

• solvent to successfully furnish 5,6-disubstituted pyrrolo[2,3-d]pyrimidine-2,4-diones 89. Similarly, excellent yields were obtained when the thiol was replaced by malononitrile (51) even in the absence of catalyst or any promoter. The malononitrile undergoes hydrolysis forming an amide, thus giving rise

• to a series of pyrrolo[2,3-d]pyrimidine-2,4-diones acetamides 90 under microwave irradiation (Scheme 32). An interesting observation by the authors surfaced that the conventional approach to the malononitrile protocol delivered comparable yields in longer reaction time (5–8 h). A gram-scale attempt

• condensation of aromatic aldehydes and heterocyclic ketones followed by a [3 + 3] cycloaddition between A and amidine giving off the intermediate B, which undergoes 1,5-hydrogen transfer followed by 1,3-hydrogen transfer to give the final products (101, Scheme 39). 6.2.4 Imidazo(1,2-a)pyrimidine: The

DNA with zwitterionic and negatively charged phosphate modifications: Formation of DNA triplexes, duplexes and cell uptake studies

• Yongdong Su,
• Maitsetseg Bayarjargal,
• Tracy K. Hale and
• Vyacheslav V. Filichev

Beilstein J. Org. Chem. 2021, 17, 749–761, doi:10.3762/bjoc.17.65

• cell-based applications. Illustration of H-bonding in a DNA duplex and a parallel triplex. A) Depiction of Watson–Crick base-paring (left: T-A and right: C-G); B) parallel triple helices: pyrimidine-rich third strand interactions are stabilised by Hoogsteen hydrogen bonds (the duplex is in black, TFO