C–H bond functionalization: recent discoveries and future directions

• Indranil Chatterjee

Beilstein J. Org. Chem. 2023, 19, 1568–1569, doi:10.3762/bjoc.19.114

• Indranil Chatterjee Department of Chemistry, Indian Institute of Technology Ropar, Nangal Road, Rupnagar, Punjab 140001, India 10.3762/bjoc.19.114 Keywords: C–H bond functionalization; The process of C–H bond functionalization can be defined as the replacement of an activated or nonactivated C−H

• the abstraction of intramolecular hydrogen atoms. Radical chemistry is a viable alternative to the two-electron process, involving C–H bond functionalization in the absence of any ligand and using low-cost redox-active metals (Fe, Cu, Mn, etc.) rather than heavy metals (Rh, Ir, etc.). Although radical

• its combination with organometallic chemistry for site-selective C−H bond functionalization [3][4]. Recent years have witnessed many viable strategies for the synthesis of complex targets utilizing photoredox catalysis, electroorganic catalysis, Lewis acid catalysis, and transition-metal-free

Morpholine-mediated defluorinative cycloaddition of gem-difluoroalkenes and organic azides

• Tzu-Yu Huang,
• Mario Djugovski,
• Sweta Adhikari,
• Destinee L. Manning and
• Sudeshna Roy

Beilstein J. Org. Chem. 2023, 19, 1545–1554, doi:10.3762/bjoc.19.111

• ; gem-difluoroalkenes; organic azides; Introduction gem-Difluoroalkenes and their synthetic preparations soared in the last decade, driven by the high demand for carbonyl mimics in medicinal chemistry and drug discovery [1]. Although a wide array of functionalization strategies for gem-difluoroalkenes

• are typically accessed in two ways: (1) direct synthesis using metal or metal-free catalysis and (2) post-functionalization of disubstituted-1,2,3-triazoles [17][18]. The direct synthesis of fully substituted triazoles entails either metal-free carbonyl-based [19][20][21] or metal-mediated and strain

• to access a set of fully decorated 1,2,3-triazoles. Functionalization of gem-difluoroalkenes with 1,3-dipoles and N-nucleophiles. Substrate scope. Reaction conditions: 1 (1 equiv), 2 (1.5 equiv) 0.4 equiv of LiHMDS (1 M in THF), morpholine (0.34–0.4 M), 75 °C, 48 h. Isolated yields are reported. a1

Synthesis of 5-arylidenerhodanines in L-proline-based deep eutectic solvent

• Stéphanie Hesse

Beilstein J. Org. Chem. 2023, 19, 1537–1544, doi:10.3762/bjoc.19.110

• Stephanie Hesse Université de Lorraine, LCP-A2MC, F-57000, Metz, France 10.3762/bjoc.19.110 Abstract Rhodanines and their derivatives are known to have many pharmacological activities that can be modulated through different functionalization sites. One of the most studied modification in those

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• of aryl sulfides by using the catalyst and the base. A catalytic cycle is shown in Scheme 4. Firstly, electrophilic Pd(TFA)2 generated from Pd(OAc)2 and TFA, which (by C–H functionalization of arene 4) led to intermediate II. Oxidative insertion of intermediate II into the N–S bond of 1 afforded

• this work. In 2018, Anbarasan and Chaitanya developed an efficient approach for the C–H bond functionalization of aryl compounds containing a directing group using N-(thioaryl)phthalimides 14 in the presence of a palladium catalyst (Scheme 15) [53]. The thiolation occurred in the presence of Pd(OAc)2

• of N‑arylpropynamides with N‑sulfanylsuccinimides. Sulfenoamination of alkenes with sulfonamides and N-sulfanylsuccinimides. Lewis acid/Brønsted acid controlled Pd-catalyzed functionalization of aryl C(sp2)–H bonds. Possible mechanism for Lewis acid/Brønsted acid controlled Pd-catalyzed

Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• and the use of a ketone was necessary to induce C–H functionalization selectivity in preference to C=C functionalization. The products were obtained in moderate to high yields (Scheme 67). 2.6 N–H and C(sp2)–H carboxylation The application of the [(IPr)CuOH] complex as catalyst for the N–H/C(sp2)–H

Synthesis of ether lipids: natural compounds and analogues

• Marco Antônio G. B. Gomes,
• Alicia Bauduin,
• Chloé Le Roux,
• Romain Fouinneteau,
• Wilfried Berthe,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2023, 19, 1299–1369, doi:10.3762/bjoc.19.96

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

• become a major strategy for ether functionalization. This review covers C–H/C–H cross-coupling reactions of ether derivatives with various C–H bond substrates via non-noble metal catalysts (Fe, Cu, Co, Mn, Ni, Zn, Y, Sc, In, Ag). We discuss advances achieved in these CDC reactions and hope to attract

• significantly different reactivity and chemical selectivity from noble metals (Ru, Rh, Pd). Compared with noble metals, copper catalysts are cheaper and easier to obtain, making Cu more advantageous for industrial applications of C–H functionalization reactions. The Glaser–Hay reaction may be one of the oldest

• Cu-catalyzed oxidative coupling reactions [43]. However, due to complex mechanisms, Cu-catalyzed C–H functionalization reactions developed only slowly in the last decade. Since recently the Cu-catalyzed oxidative coupling has emerged as a powerful synthetic strategy due to the development of CDC

Radical ligand transfer: a general strategy for radical functionalization

• David T. Nemoto Jr,
• Kang-Jie Bian,
• Shih-Chieh Kao and
• Julian G. West

Beilstein J. Org. Chem. 2023, 19, 1225–1233, doi:10.3762/bjoc.19.90

• , such as hydrogen atom transfer (HAT), alkene addition, and decarboxylation. At least as important has been innovation in radical functionalization methods, including radical–polar crossover (RPC), enabling these intermediates to be engaged in productive and efficient bond-forming steps. However, direct

• engagement of alkyl radicals remains challenging. Among these functionalization approaches, a bio-inspired mechanistic paradigm known as radical ligand transfer (RLT) has emerged as a particularly promising and versatile means of forming new bonds catalytically to alkyl radicals. This development has been

• functionalization of alkyl radicals, with successful synthetic reactions requiring efficiency and selectivity in both of these processes and inherent compatibility between each. Radical generation has benefitted from many general mechanistic approaches, including hydrogen atom transfer (HAT) [5], alkene addition [6

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

• subject to photoirradiation with N-methylpyrrole, products corresponding to both β-dicarbonyl- (77, expected) and arene- (78, unexpected) functionalization were observed. When malonate-derived ylide 76a was reacted with N-methylpyrrole, it produced 77a in 61% yield. This presumably occurred via a reaction

• an example of β-dicarbonyl functionalization. Metal-free cyclopropanations of iodonium ylides, either as intermolecular (a) or intramolecular processes (b, c). Metal-free intramolecular cyclopropanation of iodonium ylides. Reaction of ylide 6 with diphenylketene to form lactone 24 and 25. Indoline

Selective and scalable oxygenation of heteroatoms using the elements of nature: air, water, and light

• Damiano Diprima,
• Hannes Gemoets,
• Stefano Bonciolini and
• Koen Van Aken

Beilstein J. Org. Chem. 2023, 19, 1146–1154, doi:10.3762/bjoc.19.82

• on the rate than acids and bases and both the anion and cation appear to influence the reaction kinetics. A deliberate choice of salt can either significantly improve the kinetics or quench the reaction. The latter might be exploited e.g., in late-stage functionalization strategies in order to

• applicability of the reaction conditions in a late-stage functionalization of APIs, the method was carried out on albendazole, and albendazole oxide (2t) was obtained with very good yield. Flow The photochemical protocol was then transferred to a flow setup in order to obtain a scalable and thus industrially

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

• late-stage functionalization (17i and 17j) (Figure 12A). Interestingly, sodium oxalate could be used as the electron donor provided a catalytic loading of 4-cyanopyridine was added. Although the role of the latter species was not proposed by authors, it is more facile to reduce than an aryl chloride so

Aromatic C–H bond functionalization through organocatalyzed asymmetric intermolecular aza-Friedel–Crafts reaction: a recent update

• Anup Biswas

Beilstein J. Org. Chem. 2023, 19, 956–981, doi:10.3762/bjoc.19.72

• different types of C–H bonds, an aromatic C–H bond is even more inert rendering this type of bond functionalization more difficult. Herewith the term “bond functionalization” is defined as the cleavage of an existing bond with substitution by another bond. Aromatic C–H bond functionalizations have gained

• considerable attention by organic chemists because of the strategic importance of this process as well as the ability to synthesize functionalized aromatic molecules in a straightforward way. Many organic name reactions have been discovered utilizing the C–H bond functionalization concept [1]. Metals were

• ], amidines [11], isothioureas [12][13], whereas thioureas [14][15], ureas [16], phosphoric acids [17][18], and squaramides [19][20] fall into the second category. The Friedel–Crafts reaction, discovered by Charles Friedel and James Crafts in 1877 allows the aromatic C–H bond functionalization through the

Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

• Dileep Kumar Singh and
• Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

• –Kaas synthesis [37][38], Piloty–Robinson synthesis [39][40][41], and Barton–Zard reaction [42][43][44] (Scheme 1). Among these, the Clauson–Kaas pyrrole synthesis has received much attention because the synthesized pyrrole contains unsubstituted carbons that can be used for further functionalization

• functionalization. The formation of the desired products depends on the amount of triflic acid used in the reaction. Using 0.05 equivalents triflic acid gives N-sulfonylpyrroles 15 in 80–92% yields, 1.0 equivalent of triflic acid provides N-sulfonylindole 16 in 75–91% yields and 3.5 equivalents of triflic acid

• -functionalization method using a benign and naturally occurring glutathione and magnetic ferrite nanoparticles by sonication in water at room temperature. Furthermore, using this organocatalyst, various N-substituted pyrroles were prepared by reacting various amines 56 with 2,5-DMTHF (2) in water at 140 °C under

Photoredox catalysis enabling decarboxylative radical cyclization of γ,γ-dimethylallyltryptophan (DMAT) derivatives: formal synthesis of 6,7-secoagroclavine

• Alessio Regni,
• Francesca Bartoccini and
• Giovanni Piersanti

Beilstein J. Org. Chem. 2023, 19, 918–927, doi:10.3762/bjoc.19.70

• ground state catalyst [21][22][23][24][25][26]. While early research has focused on methods for the functionalization of relatively simple hydrocarbons [27][28][29][30], developments in photoredox catalysis have gained traction recently as a viable strategy for the total synthesis of natural products [31

• Hz, 1H)], strongly indicating that this product is not the desired structure 6’ but the eight-membered cycloalkene structure 6, shown in Scheme 2. Based on these results and previous reports on the benzylic and allylic C–H bond functionalization enabled by metallaphotoredox catalysis [86], we propose

Light-responsive rotaxane-based materials: inducing motion in the solid state

• Adrian Saura-Sanmartin

Beilstein J. Org. Chem. 2023, 19, 873–880, doi:10.3762/bjoc.19.64

• is the functionalization of mesoporous silica nanoparticles with light-responsive rotaxane-based molecular shuttles to control the uptake and release of target molecules [31][32][33][34]. This perspective is focused on recent examples of light-responsive rotaxane-based solid-state materials in which

• focused on the integration of new photoswitchable scaffolds which allow both the formation of the intertwined species and the arrangement of the solid materials. In this regard, the functionalization of different templates already tested in solution chemistry is envisioned as the main strategy

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

• of several methods for the synthesis of functionalized pyridines or their integration into an organic molecule, new methodologies for the direct functionalization of pyridine scaffolds have been developed during the past two decades. In addition, transition-metal-catalyzed C–H functionalization and

• rare earth metal-catalyzed reactions have flourished over the past two decades in the development of functionalized organic molecules of concern. In this review, we discuss recent achievements in the transition-metal and rare earth metal-catalyzed C–H bond functionalization of pyridine and look into

• the mechanisms involved. Keywords: C–H functionalization; heterocycles; pyridine; rare earth metal; transition-metal-catalyzed; Introduction Pyridine, one of the most important azaheterocyclic scaffolds, is found in a diverse range of bioactive natural products, pharmaceuticals, and functional

Facile access to 3-sulfonylquinolines via Knoevenagel condensation/aza-Wittig reaction cascade involving ortho-azidobenzaldehydes and β-ketosulfonamides and sulfones

• Ksenia Malkova,
• Andrey Bubyrev,
• Stanislav Kalinin and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2023, 19, 800–807, doi:10.3762/bjoc.19.60

• novel quinoline construction and functionalization techniques resulting in new or rare derivatives [17][18][19][20][21][22][23][24][25][26] is an important mission in the field of drug discovery and medicinal chemistry. The sulfonamide group is a known privileged motif in drug design often serving as a

Construction of hexabenzocoronene-based chiral nanographenes

• Ranran Li,
• Di Wang,
• Shengtao Li and
• Peng An

Beilstein J. Org. Chem. 2023, 19, 736–751, doi:10.3762/bjoc.19.54

• introduction of different main group elements beyond nitrogen summarized above would provide more diverse structures and properties. Meanwhile, the methodologies for further functionalization of the existing nanographene molecules are still needed for application purposes. Construction of HBC by Scholl

Strategies in the synthesis of dibenzo[b,f]heteropines

• David I. H. Maier,
• Barend C. B. Bezuidenhoudt and
• Charlene Marais

Beilstein J. Org. Chem. 2023, 19, 700–718, doi:10.3762/bjoc.19.51

• ) [77][78]. The allyl moiety in 144 allows for facile further functionalization. Amidation of the dihydrodibenzo[b,f]azepine (2a) derivatives with acyl halides 145 allowed for the introduction of variable length amide linkers by Kastrinsky et al. [3] (Scheme 33B). An industrial synthesis of opipramol (5

Photocatalytic sequential C–H functionalization expediting acetoxymalonylation of imidazo heterocycles

• Deepak Singh,
• Shyamal Pramanik and
• Soumitra Maity

Beilstein J. Org. Chem. 2023, 19, 666–673, doi:10.3762/bjoc.19.48

• from academia and industry. Herein, we report a direct C-3 acetoxymalonylation of imidazo heterocycles using relay C–H functionalization enabled by organophotocatalysis starring zinc acetate in the triple role of an activator, ion scavenger as well as an acetylating reagent. The mechanistic

• investigation revealed a sequential sp2 and sp3 C–H activation, followed by functionalization driven by zinc acetate coupled with the photocatalyst PTH. A variety of imidazo[1,2-a]pyridines and related heterocycles were explored as substrates along with several active methylene reagents, all generating the

• products with excellent yields and regioselectivity, thus confirming excellent functional group tolerability. Keywords: C–H functionalization; imidazo heterocycles; photoredox; regioselective; relay catalysis; Introduction Among all N-fused heterocycles, imidazo[1,2-a]pyridines (IPs) are the prevalent

Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

C3-Alkylation of furfural derivatives by continuous flow homogeneous catalysis

• Grédy Kiala Kinkutu,
• Catherine Louis,
• Myriam Roy,
• Juliette Blanchard and
• Julie Oble

Beilstein J. Org. Chem. 2023, 19, 582–592, doi:10.3762/bjoc.19.43

• .19.43 Abstract The C3-functionalization of furfural using homogeneous ruthenium catalysts requires the preinstallation of an ortho-directing imine group, as well as high temperatures, which did not allow scaling up, at least under batch conditions. In order to design a safer process, we set out to

• formation of the imine directing group and the C3-functionalization with some vinylsilanes and norbonene. Keywords: biomass; C–H activation; flow; furfural; homogeneous catalysis; Introduction The conversion of biomass derivatives into value-added products is one of the key branches of green chemistry and

• well as monomers for materials science [9][10][11][12][13][14][15]. In this context, their functionalization is fundamental to further improve their inclusion in fine organic synthesis and industrial processes. For this reason, in recent years, innovative protocols for the formation of new bonds on

Direct C2–H alkylation of indoles driven by the photochemical activity of halogen-bonded complexes

• Martina Mamone,
• Giuseppe Gentile,
• Jacopo Dosso,
• Maurizio Prato and
• Giacomo Filippini

Beilstein J. Org. Chem. 2023, 19, 575–581, doi:10.3762/bjoc.19.42

• ) and carbon–heteroatom (C–X) bonds has been and still is a central topic in organic synthesis [1][2]. Historically, organic chemists have extensively relied on the use of noble-metal-based catalysts (e.g., Pd, Rh, Ir, among others) to achieve such type of functionalization [3][4][5]. However, reliance

• tool to guide the development of greener and more convenient synthetic protocols [7][8][9][10][11][12]. In this context, photochemical approaches based on electron donor–acceptor (EDA) complexes have been successfully exploited to drive the direct C–H functionalization of a large number of organic

• to photochemically generate electrophilic radicals that can drive the functionalization of suitable electron-rich substrates [23]. Exploiting this strategy, here we report a novel metal-free methodology for the direct homolytic aromatic substitution (HAS) reaction of indoles 1 with α-iodosulfones 2

A new oxidatively stable ligand for the chiral functionalization of amino acids in Ni(II)–Schiff base complexes

• Alena V. Dmitrieva,
• Oleg A. Levitskiy,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2023, 19, 566–574, doi:10.3762/bjoc.19.41

• thermodynamically controlled stereoselectivity as compared to the parent Belokon complex. Additionally, functionalization with the tert-butyl group significantly enhances the reactivity of the deprotonated glycine complex towards electrophiles as compared to the anionic species formed from the original Belokon

• ]. Functionalization of the phenyl ring in the benzophenone gives rise to an additional axial chirality (L3), thus improving stereoselectivity observed at the removed stereocenter [24][25]. Replacing N-benzylproline for 2,7-dihydro-1H-azepine (L5) allowed obtaining a new tridentate ligand with chemically stable axial

• base chiral template is a fairly versatile “tool” that can be adapted to a specific task. A relatively new approach to functionalization of amino acids is a combination of a stereoselective synthesis in a metal-coordination environment with electrochemical activation [31]. It increases the reactivity

Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

• bridging heteroatom increases the ring-strain energy of the system, conceptualized by the decrease in bond distances. Typically, there are two modes for ring-strain release. First, functionalization of the double bond mildly alleviates the ring strain by relieving nonoptimal bond angles enforced by the

• metal catalysts towards coordination on the exo face biases the reaction outcome towards exo-selective functionalization. Upon exo coordination of a metal catalyst with the π system and subsequent migratory insertion, the resulting alkyl metal intermediate is quite limited in how it can propagate. In

• on the functionalization of the bicyclic framework itself rather than its use as a transient mediator for domino reactions [13][14][15][16][17]; however, we point the reader to several excellent reviews. The “trapped” alkyl metal intermediate can undergo subsequent migratory insertion steps with