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

• PEC, a main theme of this Review. Protocols for sensitization-initiated electron transfer (SenI-ET) relying on a dual catalytic system of transition-metal based photocatalysts and pyrenes to generate highly reductive species are also excluded as such reported transformations are now equally achievable

• widely used as reagents, organocatalysts, or phase transfer reagents [58][59][60][61] were synthesized from aryl chlorides in various yields (20–87%) under mild photocatalytic conditions whereas previously reported protocols typically relied on transition metal catalysis or high temperature processes [62

• carboxylic acids with amines that typically generate stochiometric amounts of harmful byproducts released [80][81], while simultaneously operating under milder reaction conditions than those applied in transition metal-catalyzed carbonylative amidation protocols [82][83]. Following the same distinct, yet

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

• acid catalysts and transition metal catalysts. The goal of this review is to summarize the synthesis of various N-substituted pyrrole derivatives using a modified Clauson–Kaas reaction under diverse conventional and greener reaction conditions. Keywords: catalyst; Clauson–Kaas pyrrole synthesis; 2,5

• (2). Further, a nucleophilic attack of amines 40 with intermediate A, MeOH removal, dehydration, and aromatization steps produce N-substituted pyrroles 41 in good to excellent yields. In 2019, Wani et al. [73] used the alkaline-earth metal-based catalyst Ca(NO3)2∙4H2O for a mild, transition metal

• of N-arylpyrroles from various amines 78 via the reaction with 2,5-dimethoxytetrahydrofuran (2). Oxone is a mild, inexpensive, nontoxic, stable, and transition-metal-free catalyst that is very easy to handle during this transformation and provided high yields of the product. The authors also proposed

Intermediates and shunt products of massiliachelin biosynthesis in Massilia sp. NR 4-1

• Till Steinmetz,
• Blaise Kimbadi Lombe and
• Markus Nett

Beilstein J. Org. Chem. 2023, 19, 909–917, doi:10.3762/bjoc.19.69

• photosynthesis, respiration or nitrogen fixation, in which iron-containing proteins are engaged in electron transfer reactions. In fact, the transition metal is perfectly suited for shifting electrons due to its ability to easily interconvert between a reduced ferrous (Fe2+) and an oxidized ferric state (Fe3

Synthesis of aliphatic nitriles from cyclobutanone oxime mediated by sulfuryl fluoride (SO₂F₂)

• Xian-Lin Chen and
• Hua-Li Qin

Beilstein J. Org. Chem. 2023, 19, 901–908, doi:10.3762/bjoc.19.68

• of novel synthetic methods and strategies toward nitrile group construction continues to be a focus for synthetic chemists. The cross-coupling reactions of C–C bonds catalyzed by transition-metal complexes play a crucial role in modern organic synthesis, as they make it feasible to synthesize complex

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

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

• transition metal (Ni, Fe, V) porphyrin catalysts and oxygen. Catalytic reduction (H2, Pd/C) affords 2,2'-diaminobibenzyl (20) in the subsequent step [28]. 1.2 Ring-closing via amine condensation The initial synthesis of 10,11-dihydro-5H-dibenzo[b,f]azepine (2a) was reported in 1899 by Thiele and Holzinger

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

• α,β-unsaturated carbonyl compounds [2]. In particular, the last-mentioned method is highly synthetically relevant. This approach has the advantage of being more selective and affording more molecular complexity in one step. In addition, transition-metal catalysis allows the introduction of

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

• furfural derivatives have been developed. In particular, their direct functionalization by transition-metal-catalyzed C–H activation processes [16][17][18] has become a major area of interest where only a few methods have been reported so far. Most examples concern functionalization at C5, which is the

• synthesis has increased dramatically and has rapidly become a routine tool for classical synthesis [26][27][28][29]. In particular, many efforts have been devoted to the development of flow alternatives for transition-metal-catalyzed cross-couplings [30] and for some C–H functionalizations [31

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

• employing chiral auxiliaries [4][5] and asymmetric phase-transfer catalysis [6][7]. The former approach is commonly based on the application of chiral derivatives of glycine containing structurally diverse chiral auxiliaries, both cyclic [8][9][10][11] and acyclic [12][13]. Transition-metal complexes

Access to cyclopropanes with geminal trifluoromethyl and difluoromethylphosphonate groups

• Ita Hajdin,
• Romana Pajkert,
• Mira Keßler,
• Jianlin Han,
• Haibo Mei and
• Gerd-Volker Röschenthaler

Beilstein J. Org. Chem. 2023, 19, 541–549, doi:10.3762/bjoc.19.39

• ]. Therefore, as relevant building blocks, tremendous efforts have been made to develop reliable methods for their synthesis. Transition-metal-catalyzed cyclopropanation of alkenes with trifluoromethyldiazoalkanes is a commonly used synthetic strategy for the construction of trifluoromethylcyclopropanes

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

• Austin Pounder Eric Neufeld Peter Myler William Tam Guelph-Waterloo Centre for Graduate Work in Chemistry and Biochemistry, Department of Chemistry, University of Guelph, Guelph, Ontario, N1G 2W1, Canada 10.3762/bjoc.19.38 Abstract This review presents a comprehensive overview of transition-metal

• shed light on future directions for further development in this field. Keywords: bicyclic alkenes; cascade; catalysis; domino; transition-metal-catalyzed; Introduction A well-orchestrated sequence of events – cascade, also known as domino, tandem, and sequential reactions, constitutes a fascinating

• to domino reactions which include at least two distinct reactions. The review is divided on the basis of the transition-metal catalyst used in the reaction and will not cover metal-free methods. The literature is covered up to and including January 2023. For reasons of clarity, newly formed bonds are

Total synthesis: an enabling science

• Bastien Nay

Beilstein J. Org. Chem. 2023, 19, 474–476, doi:10.3762/bjoc.19.36

• synthetic methodology developments and to natural product isolation or biosynthesis. Thus, thematic issues dealing with total synthesis in the Beilstein Journal of Organic Chemistry have naturally been published in these fields, such as "Transition-metal and organocatalysis in natural product synthesis

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

• approaches, the transition-metal-catalyzed functionalization of various scaffolds with a panel of fluorinated groups (XRF, X = S, Se, O) offered straightforward access to high value-added compounds. This review will highlight the main advances made in the field with the transition-metal-catalyzed

• [6][7][8][9][10][11]. Among them [2][5][12][13][14][15][16][17][18], the direct functionalization of a simple C–H bond by transition-metal catalysis [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] became an important tool offering new

• retrosynthetic disconnections. In this context, a strong interest from the scientific community was shown towards the challenging synthesis of fluorinated molecules by transition-metal-catalyzed C–H bond activation [44][45][46][47][48][49][50], allowing the functionalization of complex molecules and even for

Mechanochemical solid state synthesis of copper(I)/NHC complexes with K₃PO₄

• Ina Remy-Speckmann,
• Birte M. Zimmermann,
• Mahadeb Gorai,
• Martin Lerch and
• Johannes F. Teichert

Beilstein J. Org. Chem. 2023, 19, 440–447, doi:10.3762/bjoc.19.34

• generally there are many different synthetic routes to transition metal/NHC complexes [7][8][9][10][11][12][13][14][15] not all of them are applicable to the preparation of copper(I)/NHC compounds (Scheme 1) [5][6][13][16][17][18][19]. Generally, the so-called direct routes via the appropriate imidazol(in

• ) (Scheme 1d). In some cases, this transmetallation step is carried out in situ [14][15][29][30][31][32]. Notably, these generally successful synthetic routes produce a considerable amount of transition metal waste (next to the inherent use of solvents) and are therefore in misalignment with the principles

• (Scheme 1f) [45][46][47]. These approaches are an elegant alternative to the transmetallation route performing without unwanted transition metal waste. Two possible direct mechanochemical pathways have been presented for the synthesis of copper(I)/NHC complexes: First, the complexes can be synthesized by

Group 13 exchange and transborylation in catalysis

• Dominic R. Willcox and
• Stephen P. Thomas

Beilstein J. Org. Chem. 2023, 19, 325–348, doi:10.3762/bjoc.19.28

• for catalysis, due to the generally higher abundance and lower toxicity of these elements. Group 13 elements have a rich catalogue of stoichiometric addition reactions to unsaturated bonds but cannot undergo the redox chemistry which underpins transition-metal catalysis. Group 13 exchange reactions

• after In‒N/B‒H exchange with HBpin gave a borylimine iron complex 110. A second hydroelementation and In‒N/B‒H exchange gave the bisborylamine 113 and regenerated the HInCl2 107 co-catalyst (Scheme 27). Conclusion Increasing concerns over the sustainability and toxicity of many transition-metal

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

Total synthesis of insect sex pheromones: recent improvements based on iron-mediated cross-coupling chemistry

• Eric Gayon,
• Guillaume Lefèvre,
• Olivier Guerret,
• Adrien Tintar and
• Pablo Chourreu

Beilstein J. Org. Chem. 2023, 19, 158–166, doi:10.3762/bjoc.19.15

• to overall processes with a low atom economy, generating a significant amount of chemical waste, and which can be expensive when noble metals such as palladium salts are required (Scheme 1). The high efficiency of transition-metal-catalyzed cross-coupling methods in C–C bond formation processes

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

• untapped potential in this area of research, and expect the utility of these building blocks to grow in the coming years. In particular, the recently established options to elaborate and functionalize 1,4-dithianes using mild transition-metal-catalyzed couplings, and their use in cycloaddition reactions

Practical synthesis of isocoumarins via Rh(III)-catalyzed C–H activation/annulation cascade

• Qian-Ci Gao,
• Yi-Fei Li,
• Jun Xuan and
• Xiao-Qiang Hu

Beilstein J. Org. Chem. 2023, 19, 100–106, doi:10.3762/bjoc.19.10

• of 1,2-difunctionalized arenes with alkynes or carbon monoxide (Scheme 1b, III) [13][14][15][16], have been widely applied for the assembly of isocoumarins over the past decades. Recently, the transition-metal-catalyzed ortho C–H activation/annulation of benzoic acids has emerged as an attractive

• , delivering a variety of structurally diverse isocoumarins in an efficient manner (3aa–qa, 43–82%). It is worth mentioning that the tolerance of halogen substituents (Cl, Br and I) may open up a new opportunity for further transition-metal-catalyzed cross-coupling reactions. Sensitive groups, such as ester

• , the reaction of the isocoumarin 3ia with p-toluenesulfonyl hydrazide proceeded smoothly to deliver hydrazone 5 in 66% yield (Scheme 4b, right). Of note, oxime and hydrazone compounds are versatile synthetic building blocks, which have been widely applied in transition-metal-catalyzed cross-coupling

NaI/PPh₃-catalyzed visible-light-mediated decarboxylative radical cascade cyclization of N-arylacrylamides for the efficient synthesis of quaternary oxindoles

• Dan Liu,
• Yue Zhao and
• Frederic W. Patureau

Beilstein J. Org. Chem. 2023, 19, 57–65, doi:10.3762/bjoc.19.5

• is mediated by visible light irradiation. A wide range of substrates bearing different substituents and derived from ubiquitous carboxylic acids, including α-amino acids, were synthesized and examined under this very mild, efficient, and cost effective transition-metal-free synthetic method. These

• limited substrate scopes (Scheme 1a). With the rapid development of sustainable chemistry, developing low-cost and transition-metal-free photocatalytic methods has become a strategic priority. In 2019 [54], the groups of Fu and Shang pioneered the photocatalytic decarboxylative alkylation of silyl enol

• decarboxylative radical cascade cyclization of N-arylacrylamides with various redox-active esters derived from common and/or important carboxylic acids under mild conditions. Complementary to traditional transition metal photocatalysis and organo-photocatalysis [85], the readily available and inexpensive NaI/PPh3

Improving the accuracy of ³¹P NMR chemical shift calculations by use of scaling methods

• William H. Hersh and
• Tsz-Yeung Chan

Beilstein J. Org. Chem. 2023, 19, 36–56, doi:10.3762/bjoc.19.4

• ] and polyoxometalates [33]. More recently, DFT methods have been applied to transition metal phosphorus complexes that cover a wide range of chemical shifts [34][35] using methods related to what we will describe here, but such studies are beyond the scope of this paper and typically focus on one metal

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• reactions of transition metal hydrides (Fe, Co, Mn, etc) with alkenes (e.g., Mukaiyama hydration) [20]. The last decade saw the development of milder methods for generating carbon-centered radicals as the advancement of their reactivity in cross-coupling reactions, the concept of photoredox catalysis [21

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

• oxidative coupling processes (also known as cross-dehydrogenative coupling), as well as late-stage CH-functionalization. Oxidation processes are recognized as a challenge in fine organic synthesis technology [10][11] due to selectivity problems and frequent need for toxic transition metal salts and

• SelectfluorTM (Scheme 8). As was mentioned above, the N-hydroxyimide-organocatalyzed aerobic CH-oxidation at room temperature requires transition metal salts as co-catalysts. Transition metal salts are undesirable due to potential contamination of the target products or the inactivation of the catalytic system

• in the case of chelating substrates [80]. In order to avoid the usage of transition metal salts, metal-free oxidative systems for the generation of imide-N-oxyl radicals were proposed. In the majority of such systems, an N-hydroxyimide undergoes single-electron oxidation photochemically by a

Functionalization of imidazole N-oxide: a recent discovery in organic transformations

• Koustav Singha,
• Imran Habib and
• Mossaraf Hossain

Beilstein J. Org. Chem. 2022, 18, 1575–1588, doi:10.3762/bjoc.18.168

• substitution reactions Metal-free coupling reaction through nucleophilic substitution of H-atom (SNH) In 2020, a C–H/C–Li coupling reaction between 2H-imidazole 1-oxides and pentafluorophenyllithium under transition metal-free conditions was reported by Timofey D. Moseev and co-workers [17]. The reaction

• provide the targeted products 11a–h. In the next year (2021), the same authors suggested another fascinating deoxygenative transition-metal-free SNH coupling reaction procedure of 2H-imidazole 1-oxides with polyphenols [10]. This process is convenient for producing bioactive bifunctional compounds

• . Transition-metal-free three-component reactions, cycloaddition reaction methodology and nucleophilic addition reaction, mainly these three types of reaction methodologies can be found in the literature reports. The approaches were greener and the reaction conditions were milder or not harsh in most of the

A facile approach to spiro[dihydrofuran-2,3'-oxindoles] via formal [4 + 1] annulation reaction of fused 1H-pyrrole-2,3-diones with diazooxindoles

• Pavel A. Topanov,
• Anna A. Maslivets,
• Maksim V. Dmitriev,
• Irina V. Mashevskaya,
• Yurii V. Shklyaev and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2022, 18, 1532–1538, doi:10.3762/bjoc.18.162

• compounds to molecules containing an enone fragment. Cycloaddition reactions involving diazo and enone moieties are usually carried out using transition-metal catalysis [18][19][20], with catalyst-free reactions being carried out only with the participation of reactive unsubstituted diazomethane [21][22][23