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

• , diversely functionalized pyridines have been synthesized via C–H activation under transition-metal and rare earth metal catalysis, including C–H alkylation, alkenylation, arylation, heteroarylation, borylation, etc. Recently, metal-free approaches have also been developed for the C–H functionalization of N

• elimination to furnish the C3-arylated product 152. Heteroarylation C-2 Heteroarylation Heteroaryl groups are a common core in natural products and pharmaceuticals. In addition, the heterodiaryl systems widely occur in biologically important organic molecules, dyes, fragrances, advanced materials, and

• activation of 9 provides the hydroxy copper species 169, which on deoxygenative elimination furnishes the desired product 167. C-3 Heteroarylation In 2013, Su and co-workers [103] developed a catalytic methodology for the distal heteroarylation of pyridines 170 via Rh(III)-catalyzed dehydrogenative cross

1,4-Dithianes: attractive C2-building blocks for the synthesis of complex molecular architectures

• Bram Ryckaert,
• Ellen Demeyere,
• Frederick Degroote,
• Hilde Janssens and
• Johan M. Winne

Beilstein J. Org. Chem. 2023, 19, 115–132, doi:10.3762/bjoc.19.12

• co-workers could offer more opportunities here (Scheme 7) [43][44]. Furthermore, some recently reported photoredox-catalyzed thioether (C–H) alkylation and heteroarylation reactions developed by Alfonzo and Hande have demonstrated the use of 1,4-dithianes as viable substrates in such attractive bond

Deoxygenative C2-heteroarylation of quinoline N-oxides: facile access to α-triazolylquinolines

• Geetanjali S. Sontakke,
• Rahul K. Shukla and
• Chandra M. R. Volla

Beilstein J. Org. Chem. 2021, 17, 485–493, doi:10.3762/bjoc.17.42

• Geetanjali S. Sontakke Rahul K. Shukla Chandra M. R. Volla Department of Chemistry, Indian Institute of Technology Bombay, Powai-400076, Mumbai, India 10.3762/bjoc.17.42 Abstract A metal- and additive-free, highly efficient, step-economical deoxygenative C2-heteroarylation of quinolines and

• simplicity of the developed protocol. The current transformation was also found to be compatible for the late-stage modification of natural products. Keywords: amination; heteroarylation; quinoline N-oxides; regioselective; triazoles; Introduction Quinoline is a key heterocyclic moiety found in many

• to amination and amidation, there are few reports on metal-free C2-heteroarylation of pyridine N-oxides. In 1984, Rogers demonstrated the synthesis of 2-triazolylpyridines from 2-azidopyridines and phenylacetylene [51]. Along the same lines, Keith reported methodologies for the C2-imidazolylation and

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• generation of aryl radicals. Although inaccessible to date, a two-step strategy was recently developed by the Procter group. They reported a one-pot organophotocatalytic strategy for the heteroarylation of nonprefunctionalized arenes (Scheme 15) [87]. First, a triaryl sulfonium salt 15.3 is generated from

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• supported the energy transfer pathway. Thus, the proposed triplet sensitization mechanism of the photocatalytic ATRA reaction is depicted in Scheme 25. In 2016, Ji and co-workers developed a new photoredox cross-dehydrogenative coupling (CDC) method for the α-heteroarylation of amides (α to nitrogen, e.g

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

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• . Parallel to this, 4CzIPN was also used as an organoredox catalyst for the alkylation of heteroarenes [85], the oxidation of silicates [86], the alkylation of imines [87], the α-arylation/heteroarylation of 2-trifluoroboratochromanones [88]. In these different situations, comparisons with reference

Rhodium-catalyzed C–H functionalization of heteroarenes using indoleBX hypervalent iodine reagents

• Erwann Grenet,
• Ashis Das,
• Paola Caramenti and
• Jérôme Waser

Beilstein J. Org. Chem. 2018, 14, 1208–1214, doi:10.3762/bjoc.14.102

• develop a new C–H heteroarylation of pyridinones. Herein, we report the selective C–H heteroarylation of the C-6 position of bipyridinones by a rhodium-catalyzed reaction with indoleBX (reaction 2, Scheme 1A). In addition, we demonstrate that the mild conditions developed allow the heteroarylation of the

• these conditions to different quinoline N-oxides (Scheme 3). This class of substrates had also been used for C–H alkynylation using EBX reagents [28]. During our previous work, we had attempted the C8-heteroarylation of quinoline N-oxide with Me-indoleBX 6a. However, the transformation required a

• cyanoborohydride to deliver the N–H unprotected pyridinone 13 in 74% yield (Scheme 4) [29]. A rearrangement of the N-oxide furnished the corresponding isoquinolone 14 in 62% yield. Conclusion In summary, we have developed the C-6 selective C–H heteroarylation of pyridin-2-ones using indoleBXs as coupling partners

Reactivity of bromoselenophenes in palladium-catalyzed direct arylations

• Aymen Skhiri,
• Ridha Ben Salem,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2017, 13, 2862–2868, doi:10.3762/bjoc.13.278

• de Sfax, Faculté des Sciences de Sfax, Route de la Soukra km 4, 3038 Sfax, Tunisia 10.3762/bjoc.13.278 Abstract The reactivity of 2-bromo- and 2,5-dibromoselenophenes in Pd-catalyzed direct heteroarylation was investigated. From 2-bromoselenophene, only the most reactive heteroarenes could be

• employed to prepare 2-heteroarylated selenophenes; whereas, 2,5-dibromoselenophene generally gave 2,5-di(heteroarylated) selenophenes in high yields using both thiazole and thiophene derivatives. Moreover, sequential catalytic C2 heteroarylation, bromination, catalytic C5 arylation reactions allowed the

• haloselenophene. Wipf et al. reported in 2014 that using ethyl oxazole-4-carboxylate as reaction partner, the corresponding 2,5-bis(oxazol-2-yl)selenophene derivative was formed in 45% yield (Scheme 1c) [17]. Moreover, to our knowledge the Pd-catalyzed direct heteroarylation of 2-bromoselenophene has not yet been

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• difunctionalisation of unactivated alkenes with CF3SO2Na and an heteroaryl group in which the heteroarylation was realised by a distal heteroaryl ipso-migration was provided in 2017 by Zhu and co-workers (Scheme 32) [54]. A variety of nitrogen containing heteroaryl groups showcased the migratory aptitude selectively

Sydnone C-4 heteroarylation with an indolizine ring via Chichibabin indolizine synthesis

• Florin Albota,
• Mino R. Caira,
• Constantin Draghici,
• Florea Dumitrascu and
• Denisa E. Dumitrescu

Beilstein J. Org. Chem. 2016, 12, 2503–2510, doi:10.3762/bjoc.12.245

• formation of single bonds between two aromatic or heteroaromatic rings involves palladium-catalyzed cross-coupling reactions and cyclization of functional groups attached to an aromatic and heteroaromatic ring. Thus, arylation and heteroarylation at the C-4 position of sydnones has been performed by

Regiocontroled Pd-catalysed C5-arylation of 3-substituted thiophene derivatives using a bromo-substituent as blocking group

• Mariem Brahim,
• Hamed Ben Ammar,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2016, 12, 2197–2203, doi:10.3762/bjoc.12.210

• regiospecific access to C5-arylated 2-bromothiophenes without cleavage of the thienyl C–Br bond, ii) on the reaction scope using a set of aryl bromides and 2-bromo-3-substituted thiophenes, iii) conditions allowing either the sequential C5-arylation followed by C2-arylation or C2-heteroarylation followed by C5

• , provides a powerful and simple access to non-symmetrically 2,5-di(hetero)arylated thiophene derivatives. 3-Substituted thiophene derivatives containing a heteroaryl unit at the C2-position and an aryl at C5 can also be obtained by direct heteroarylation at the C2-position of the C3-substituted 2

• -substituted thiophenes. Blocking groups allowing regioselective C5-arylation of thiophenes. Reactivity of 2-bromothiophene with aryl bromides. Reactivity of 2-bromo-3-methylthiophene with (hetero)aryl bromides. Reactivity of 3-substituted 2-bromothiophenes with aryl bromides. 5-Heteroarylation of 2-aryl-5

Cu(I)-catalyzed N,N’-diarylation of natural diamines and polyamines with aryl iodides

• Svetlana P. Panchenko,
• Alexei D. Averin,
• Maksim V. Anokhin,
• Olga A. Maloshitskaya and
• Irina P. Beletskaya

Beilstein J. Org. Chem. 2015, 11, 2297–2305, doi:10.3762/bjoc.11.250

• microparticles [30]. We initiated our studies in this field by the elaboration of Cu(I)-catalyzed N-arylations and N,N’-diarylations of the model triamine, tetraamine and oxadiamine with aryl iodides and bromides [31] and elucidated some regularities of the catalytic N-heteroarylation of polyamines [32]. However

Palladium-catalyzed 2,5-diheteroarylation of 2,5-dibromothiophene derivatives

• Fatma Belkessam,
• Aidene Mohand,
• Jean-François Soulé,
• Abdelhamid Elias and
• Henri Doucet

Beilstein J. Org. Chem. 2014, 10, 2912–2919, doi:10.3762/bjoc.10.309

• –2 mol % palladium catalysts, the target 2,5-diheteroarylated thiophenes were obtained in moderate to good yields and with a wide variety of heteroarenes such as thiazoles, thiophenes, furans, pyrroles, pyrazoles or isoxazoles. Moreover, sequential heteroarylation reactions allow the access to 2,5

• and 3,5-dimethylisoxazole resulted in good yields of 21 and 22, respectively. To our knowledge, the sequential Pd-catalyzed direct diheteroarylation of 2,5-dibromothiophene has not yet been reported. A sequential heteroarylation would allow the synthesis of non-symmetrically 2,5-disubstituted

• -dibromothiophene. Heteroarylation of 2-bromothiophene. Reactivity of 4,7-dibromobenzothiadiazole. Influence of the reaction conditions for palladium-catalyzed direct arylation using 2,5-dibromothiophene and 2-ethyl-4-methylthiazole as coupling partners (Scheme 1).a Supporting Information Supporting Information

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

New developments in gold-catalyzed manipulation of inactivated alkenes

• Michel Chiarucci and
• Marco Bandini

Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294

• also in the correlated gold-catalyzed oxidative heteroarylation of unsaturated olefins (see section 6). 3.2 Selected examples Initial reports on the gold-catalyzed hydroamination of olefins were presented by He [36] and Widenhoefer [37], independently. He and Brouwer disclosed the intermolecular

• first example of C–H functionalization by alkylgold intermediates. The optimized conditions required the use of the electrophilic complex [(p-CF3Ph)3PAuNTf2] and 30 equivalents of water, in order to increase the solubility of Selectfluor in THF. Heteroarylation of alkenes with arylboronic acids under

Recent advances in direct C–H arylation: Methodology, selectivity and mechanism in oxazole series

• Cécile Verrier,
• Pierrik Lassalas,
• Laure Théveau,
• Guy Quéguiner,
• François Trécourt,
• Francis Marsais and
• Christophe Hoarau

Beilstein J. Org. Chem. 2011, 7, 1584–1601, doi:10.3762/bjoc.7.187

• methodology The first examples of direct C–H heteroarylation of various azoles were reported by Ohta, including the direct C5-selective pyrazinylation of oxazole with chloropyrazines in the presence of Pd(PPh3)4 as catalyst and potassium acetate base (Scheme 4) [36][37]. This protocol was successfully applied