HPW-Catalyzed environmentally benign approach to imidazo[1,2-a]pyridines

• Luan A. Martinho and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2024, 20, 628–637, doi:10.3762/bjoc.20.55

• 1, aromatic/heteroaromatic aldehydes 2, and isocyanides 3 to obtain the imidazo[1,2-a]pyridine derivatives 4 (Scheme 2). In general, the efficiency of the HPW-catalyzed GBB reaction is very dependent upon the type of 2-aminopyridine or isocyanide compound used, and not influenced by different

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

• chemoselective and regioselective CDC between pyridines and ethers, which used Sc(OTf)3 as the catalyst and DTBP as the oxidant (Scheme 36) [101]. This strategy allowed the synthesis of a series of α-substituted pyridine derivatives. The control experiments showed that the mechanism may proceed via a radical

• . With the development of the CDC reaction, the catalytic effect of rare earth metals on CDC has also been explored. Xing et al. developed an Y(OTf)3-catalyzed CDC reaction of ethers, especially open chain ethers with pyridine derivatives (Scheme 40) [108]. The method has the advantages of simple

New one-pot synthesis of 4-arylpyrazolo[3,4-b]pyridin-6-ones based on 5-aminopyrazoles and azlactones

• Vladislav Yu. Shuvalov,
• Ekaterina Yu. Vlasova,
• Tatyana Yu. Zheleznova and
• Alexander S. Fisyuk

Beilstein J. Org. Chem. 2023, 19, 1155–1160, doi:10.3762/bjoc.19.83

• formation of the target products with low yields [21]. Therefore, the development of a new effective method for the preparation of 4-arylpyrazolo[3,4-b]pyridin-6-ones is an urgent task. Results and Discussion One of the rational approaches to the synthesis of fused pyridine derivatives is based on the

Pyridine C(sp²)–H bond functionalization under transition-metal and rare earth metal catalysis

• Haritha Sindhe,
• Malladi Mounika Reddy,
• Karthikeyan Rajkumar,
• Akshay Kamble,
• Amardeep Singh,
• Anand Kumar and
• Satyasheel Sharma

Beilstein J. Org. Chem. 2023, 19, 820–863, doi:10.3762/bjoc.19.62

• . In the same year, Tsurugi and Mashima reported the use of rare earth metal complexes for the insertion of nonpolar unsaturated substrates (C=N) into the ortho-C–H bond of pyridine derivatives [54]. They carried out the C–H aminoalkylation of pyridines 1 using yttrium complex 26 with nonactivated

• providing various ortho-aminoalkylated products 36 whereas ortho-alkylated pyridine derivatives 38 were obtained when using NP1-Sc as the catalyst (Scheme 8). Attributing to the strong coordination of unsubstituted pyridine with Rh(I) catalysts, C–H alkylations of pyridine lacking ortho-blocking groups is a

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

• catalysis reported by He and Pan [137]. Palladium-catalyzed (ethoxycarbonyl)difluoromethylthiolation reaction of 2-(hetero)aryl and 2-(α-aryl-vinyl)pyridine derivatives reported by Besset [138]. Pd(II)-catalyzed trifluoromethylselenolation of benzamides derived from 5-methoxy-8-aminoquinoline reported by

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

• [74][76][80][86][87][88]. To facilitate the anodic oxidation of N-hydroxyphthalimide, basic pyridine derivatives are used as the N-hydroxyphthalimide proton acceptors [87]. In many cases electrolysis can be performed in the galvanostatic mode in a simple undivided cell, which is convenient for

An isoxazole strategy for the synthesis of 4-oxo-1,4-dihydropyridine-3-carboxylates

• Timur O. Zanakhov,
• Ekaterina E. Galenko,
• Mikhail S. Novikov and
• Alexander F. Khlebnikov

Beilstein J. Org. Chem. 2022, 18, 738–745, doi:10.3762/bjoc.18.74

• , Supporting Information File 1). Compounds 2 have several reactive centers that make them attractive starting materials for the synthesis of new libraries of 4-pyridone and pyridine derivatives (Scheme 6). The methoxycarbonyl group of compound 2c was selectively reduced to give 3-(hydroxymethyl)pyridin-4(1H

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

• electron-withdrawing groups [13][14][15]. Previously, we have reported various pyridine derivatives, including polysubstituted pyridines and fused pyridines, which exhibited strong fluorescence in organic solvents (ethanol and dichloromethane) [16][17][18][19], while their fluorescence in aqueous media was

• heterocyclic compounds, such as ring-fused pyridines (pyrido[1,2-a]pyrrolo[3,4-d]pyrimidines) and secondary aminopyridines (N-methyl-4-((pyridin-2-yl)amino)-substituted maleimides), by changing the substituents at position 5 of the 2-aminopyridine. Interestingly, among these pyridine derivatives, secondary

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

• interesting results [137]. The authors observed that the desired product 95 was obtained with very low yield, due to the competition between the Kochi–Anderson [76] reaction and the Minisc reaction (Scheme 31) generating a mixture of polymeric pyridine derivatives [142]. The Minisci reaction [142] is a

Multi-faceted reactivity of N-fluorobenzenesulfonimide (NFSI) under mechanochemical conditions: fluorination, fluorodemethylation, sulfonylation, and amidation reactions

• José G. Hernández,
• Karen J. Ardila-Fierro,
• Dajana Barišić and
• Hervé Geneste

Beilstein J. Org. Chem. 2022, 18, 182–189, doi:10.3762/bjoc.18.20

• reactivity of pyridine derivatives with NFSI, which are known to generate phenylsulfonyl fluoride via a transient generation of N-sulfonylpyridinium salts [37]. Analysis by 19F NMR spectroscopy of the crude reaction mixture of 3b and NFSI revealed the presence of PhSO2F (Scheme 3d), thus confirming the

Direct C(sp³)–H allylation of 2-alkylpyridines with Morita–Baylis–Hillman carbonates via a tandem nucleophilic substitution/aza-Cope rearrangement

• Siyu Wang,
• Lianyou Zheng,
• Shutao Wang,
• Shulin Ning,
• Zhuoqi Zhang and
• Jinbao Xiang

Beilstein J. Org. Chem. 2021, 17, 2505–2510, doi:10.3762/bjoc.17.167

• ; Morita–Baylis–Hillman carbonates; Introduction Pyridines are among the most important heterocyclic structural moieties in many biologically active natural products, pharmaceuticals, and agrochemicals [1][2][3]. Therefore, the development of efficient strategies for functionalized pyridine derivatives

• synergistic catalyzed allylic alkylation between electron-deficient 2-ethyl benzoxazoles and MBH carbonates by the combination of a Lewis base and a metal salt [24]. In their studies, although pyridine derivatives were also applicable in the reaction, the presence of a strong electron-withdrawing NO2 group

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

• in many natural products, pharmaceuticals, and bioactive molecules. For instance, some pyridine derivatives have been used for therapy of HIV, cancer, inflammation, microbial infection and so on [1][2][3][4][5]. In addition, it is also an important synthetic unit, which is frequently used as catalyst

• or ligand in organic chemistry [6][7][8][9][10]. Therefore, the development of efficient methods for the synthesis of pyridine derivatives has attracted considerable attention [11][12][13][14]. The industrial synthetic methods of pyridines mainly involve: i) extraction from coal tar; ii) condensation

• 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

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

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

• by direct fluorination (10% F2/N2) of the pyridine in acetonitrile and in the presence of a suitable salt at low temperature (method B in Scheme 10). This one-step process was successfully applied to many other pyridine derivatives (method B in Figure 2). It was finally shown that the stable N

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

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

• B undergoes cyclocondensation to yield the spiro product 139, whereas for 139a intermediate B falls prey to intramolecular cyclo condensation (Scheme 54). The synthesis of regioselectively functionalized macrocyclane-fused pyrazolo[3,4-b]pyridine derivatives 142 was demonstrated by Jiang and co

Decarboxylative trifluoromethylthiolation of pyridylacetates

• Ryouta Kawanishi,
• Kosuke Nakada and
• Kazutaka Shibatomi

Beilstein J. Org. Chem. 2021, 17, 229–233, doi:10.3762/bjoc.17.23

• trifluoromethylthiolated product at all, despite complete saponification of the methyl ester. Conclusion In conclusion, we demonstrated the decarboxylative trifluoromethylthiolation of lithium 2- and 4-pyridylacetates to synthesize pyridine derivatives with a trifluoromethylthio group at a tertiary carbon center adjacent

Regioselective synthesis of heterocyclic N-sulfonyl amidines from heteroaromatic thioamides and sulfonyl azides

• Vladimir Ilkin,
• Vera Berseneva,
• Tetyana Beryozkina,
• Tatiana Glukhareva,
• Lidia Dianova,
• Wim Dehaen,
• Eugenia Seliverstova and
• Vasiliy Bakulev

Beilstein J. Org. Chem. 2020, 16, 2937–2947, doi:10.3762/bjoc.16.243

• transformed to the corresponding N-sulfonyl amidines by reactions in 1-propanol via two- or one-pot procedures. Pyridine-2,6-dithioamide was shown to react with mesyl and arylsulfonyl azides to form pyridine derivatives bearing two N-sulfonyl amidine moieties in excellent yield. Depending on the structure of

Three-component reactions of aromatic amines, 1,3-dicarbonyl compounds, and α-bromoacetaldehyde acetal to access N-(hetero)aryl-4,5-unsubstituted pyrroles

• Wenbo Huang,
• Kaimei Wang,
• Ping Liu,
• Minghao Li,
• Shaoyong Ke and
• Yanlong Gu

Beilstein J. Org. Chem. 2020, 16, 2920–2928, doi:10.3762/bjoc.16.241

• acetal (2a) and 1,3-dicarbonyl compounds was developed by using AlCl3 as a catalyst. The developed chemistry is also successful for the synthesis of functionalized pyrazolo[3,4-b]pyridine derivatives. This study offered a complementary method to construct pyrrole scaffolds through [1 + 2 + 2] annulation

• . Direct synthesis of pyrrole-3-carboxamide derivatives. Plausible mechanism of the three-component reaction. Synthesis of polysubstituted pyrazolo[3,4-b]pyridine derivatives. Optimization of the conditions for the reaction between 1a, 2a, and 3a.a Supporting Information Supporting Information File 500

Copper-catalysed alkylation of heterocyclic acceptors with organometallic reagents

• Yafei Guo and
• Syuzanna R. Harutyunyan

Beilstein J. Org. Chem. 2020, 16, 1006–1021, doi:10.3762/bjoc.16.90

• alkenylpyridines in the substrate scope. The reason for this was the markedly lower reactivity of alkenylpyridines towards nucleophilic addition as compared to other alkenylheteroarenes. For the same reason, the synthesis of chiral pyridine derivatives has always been considered a challenge in organic chemistry

Palladium-catalyzed Sonogashira coupling reactions in γ-valerolactone-based ionic liquids

• László Orha,
• József M. Tukacs,
• László Kollár and
• László T. Mika

Beilstein J. Org. Chem. 2019, 15, 2907–2913, doi:10.3762/bjoc.15.284

• form 2,5-bis(2-phenylethynyl)pyridine (3m) under identical conditions (Table 3, entries 12 and 13). By comparison with the conversion of 4-chloro-1-iodobenzene (1g), no formation of 1,4-bis(phenylethynyl)benzene was detected. It agrees with the activated substituents of 2-substituted pyridine

• derivatives. It can be concluded that by varying electronic and steric properties of substituents of the iodoaromatic substrates at all ortho-, meta-, and para- positions, no significant changes in the product yields were achieved according to previous studies [26][41]. Regarding the negligible influence of

Emission solvatochromic, solid-state and aggregation-induced emissive α-pyrones and emission-tuneable 1H-pyridines by Michael addition–cyclocondensation sequences

• Natascha Breuer,
• Irina Gruber,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 2684–2703, doi:10.3762/bjoc.15.262

• -dimethylaminophenyl substituent furnishes α-pyrone 6g (Table 4, entry 13). For synthesizing 1H-pyridine derivatives 8 with an electron-donating group we employed the isolated dimer 7 and were able to isolate 1H-pyridines 8 in 52 and 34% yield (Scheme 10). Crystal structure of 1H-pyridine 5a The structure of 1H

• Supporting Information File 1) [50][51][52][53][54][55][56][57]. Photophysical properties Photophysical properties of 1H-pyridines 5 and 8 1H-Pyridine derivatives 5 are yellow or orange compounds under daylight (Figure 3, top) and fluoresce in solution (Figure 3, center) and in the solid state (Figure 3

• ) Å, C11–H···N2 127°. Symmetry transformations are i = 1−x, 1−y, 1−z; ii = x, 3/2−y, −1/2+z, iii = 1−x, −1/2+y, −1/2−z. 1H-Pyridine derivatives 5 as solids under daylight (top), under UV light (λexc = 365 nm, c(5) = 10−4 M) in dichloromethane solution (center), and under UV light (λexc = 365 nm) in

Photochromic diarylethene ligands featuring 2-(imidazol-2-yl)pyridine coordination site and their iron(II) complexes

• Andrey G. Lvov,
• Max Mörtel,
• Anton V. Yadykov,
• Frank W. Heinemann,
• Valerii Z. Shirinian and
• Marat M. Khusniyarov

Beilstein J. Org. Chem. 2019, 15, 2428–2437, doi:10.3762/bjoc.15.235

• (III) with terarylene III showing the photomodulation of emission intensity [23]. A number of diarylethene ligands with a perfluorocyclopentene bridge were designed. Yu and co-workers reported a series of 2-(thiazol-2-yl)pyridine derivatives [24][25][26]. Reversible photoinduced release and trapping of

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• (Scheme 79). Also, phenyl, thiophene, and pyridine derivatives achieved regioselectively trifluoromethylation with N-pivalamide as a directing group. The authors also proposed a possible radical pathway for this reaction. The final trifluoromethylated compounds were generated from pivalamido arenes and

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

• of biologically active imidazo[1,2-a] pyridine derivatives [108]. Encouraged by the direct synthetic strategies for imidazo[1,2-a]pyridines (IPs), Donthiri et al. have reported an efficient Cu-catalyzed C–H functionalization of pyridines with vinyl azide derivatives [109]. Their use of vinyl azide

• , perhaps because the α,β-unsaturated double bond affected the iodination. Mohan et al. successfully developed an efficient copper-catalyzed aerobic oxidative amination of C(sp3)–H bonds to synthesize imidazo[1,5-a]pyridine derivatives [122]. The reaction was also applicable to amino acid derivatives, as

• single-electron transfer (SET) with CuI followed by hydride abstraction/intramolecular nucleophilic addition and loss of a proton forming the desired compound 49 (Scheme 19). Cu(I)-catalyzed intramolecular oxidative C–H amidation of N-pyridylenaminones 61 for the synthesis of imidazo[1,2-a]pyridine