Silver-catalyzed synthesis of β-fluorovinylphosphonates by phosphonofluorination of aromatic alkynes

• Yajing Zhang,
• Qingshan Tian,
• Guozhu Zhang and
• Dayong Zhang

Beilstein J. Org. Chem. 2020, 16, 3086–3092, doi:10.3762/bjoc.16.258

• is the most rapid and convenient one (Scheme 1). Although studies on alkyne difunctionalization are ongoing [23], the successful attachment of a fluorine atom to the resulting alkene through transition metal catalysis remains a challenge. In particular, the phosphonofluorination of alkynes for the

• introduction of two strong electron-withdrawing groups into double bonds has not yet been reported. With our continuous interest in, and inspiration from the well-established transition metal-catalyzed radical difunctionalization of unsaturated carbon–carbon bonds, specifically the work of Li’s group and

• -fluorovinylphosphonates under mild conditions. First, we examined the catalytic activity of various transition metal catalysts, including Au, Ag, Cu, Rh, and Pd complexes (Supporting Information File 1). Among these metal salts, silver salts, especially AgOAc, were the most effective catalysts for generating the desired

Metal-free synthesis of biarenes via photoextrusion in di(tri)aryl phosphates

• Hisham Qrareya,
• Lorenzo Meazza,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 3008–3014, doi:10.3762/bjoc.16.250

• nowadays a growing interest in the forging of Ar–Ar bonds under transition-metal-free conditions [24][25]. Apart the most common pathways, e.g., the Friedel–Crafts functionalization [26] or nucleophilic aromatic substitution [27], alternative approaches have emerged that make use of photogenerated

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

• pyrrole syntheses [9][10][11], which have been developed to harvest the pyrrole frameworks. In the past few years, the interest in developing new methods to synthesize this heterocyclic motif has rapidly grown; transition metal-catalyzed cyclization [12][13][14] and multicomponent reactions [15][16][17

Synthesis of imidazo[1,5-a]pyridines via cyclocondensation of 2-(aminomethyl)pyridines with electrophilically activated nitroalkanes

• Dmitrii A. Aksenov,
• Nikolai A. Arutiunov,
• Vladimir V. Maliuga,
• Alexander V. Aksenov and
• Michael Rubin

Beilstein J. Org. Chem. 2020, 16, 2903–2910, doi:10.3762/bjoc.16.239

• synthesis inhibitor (Figure 1) [10][11][12]. In addition, compounds with this structure were investigated as photoluminescent sensors [13] and have been employed to generate pincer and heterocyclic carbene ligands for transition metal catalysis [14][15]. A lot of efforts have been dedicated to the

Incorporation of a metal-mediated base pair into an ATP aptamer – using silver(I) ions to modulate aptamer function

• Marius H. Heddinga and
• Jens Müller

Beilstein J. Org. Chem. 2020, 16, 2870–2879, doi:10.3762/bjoc.16.236

• replaced by coordinate bonds to one (or more) transition metal ions [13][14]. They are compatible with normal DNA duplex structures [15][16] and can be used to introduce a metal-based functionality into DNA [17][18]. Importantly, metal-mediated base-pair formation has been successfully applied in metal

• ), which is incorporated into the Im:Im mispair to form a stabilizing Im–Ag(I)–Im pair, largely restores the ability of the aptamer derivative to bind to its target. The ability to modulate the aptamer affinity by adding suitable transition metal ions extends the applicability of aptamers even further, as

• it allows triggering the function at any desired point. Further optimizations will be necessary to eliminate the effect of excess transition metal ions and to enable a more complete switching of the aptamer function. This could be possible by using other metal-mediated base pairs, based either on

Optical detection of di- and triphosphate anions with mixed monolayer-protected gold nanoparticles containing zinc(II)–dipicolylamine complexes

• Lena Reinke,
• Julia Bartl,
• Marcus Koch and
• Stefan Kubik

Beilstein J. Org. Chem. 2020, 16, 2687–2700, doi:10.3762/bjoc.16.219

• with a complementary base sequence [10], the AuNPs with peripheral carboxylate groups introduced by the Hupp group [11] that responded to divalent transition metal ions, or Chen at al.’s crown ether-decorated AuNPs that allowed the sensing of potassium ions [12]. Numerous other such probes have been

Palladium nanoparticles supported on chitin-based nanomaterials as heterogeneous catalysts for the Heck coupling reaction

• Tony Jin,
• Malickah Hicks,
• Davis Kurdyla,
• Sabahudin Hrapovic,
• Edmond Lam and
• Audrey Moores

Beilstein J. Org. Chem. 2020, 16, 2477–2483, doi:10.3762/bjoc.16.201

• highly relevant in areas of research such as pharmaceuticals and materials technology [21]. Furthermore, works in heterogeneous catalysis have shown that the catalyst support plays a major role in the activity of transition-metal NPs such as Pd [7]. A model reaction was performed under the conditions

Catalytic trifluoromethylation of iodoarenes by use of 2-trifluoromethylated benzimidazoline as trifluoromethylating reagent

• Tatsuhiro Uchikura,
• Nanami Kamiyama,
• Taisuke Ishikawa and
• Takahiko Akiyama

Beilstein J. Org. Chem. 2020, 16, 2442–2447, doi:10.3762/bjoc.16.198

• ; catalysis; copper; fluorine chemistry; trifluoromethylation; Introduction The introduction of a trifluoromethyl group is one of the most attractive reactions in drug discovery [1][2]. In the past decade, trifluoromethylation reactions of aryl halides in the presence of transition-metal complexes were

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• enantioselectivities (17 examples, up to 91:9 er). Bach proposes for their reaction that an external ruthenium photocatalyst generates the triplet excited state iminium ion through an energy transfer process, which is also observed by Alemán when using an external transition metal-based sensitiser. Tertiary amine

• transition metal Lewis acids 291a–e that can coordinate to ketone substrates and form chiral photoactive complexes 292, which in many cases act as the in situ generated photocatalyst (Scheme 48) [115]. They have recently developed an example using an indazole-based ligand [116] to add to their well

Chan–Evans–Lam N1-(het)arylation and N1-alkеnylation of 4-fluoroalkylpyrimidin-2(1H)-ones

• Viktor M. Tkachuk,
• Oleh O. Lukianov,
• Mykhailo V. Vovk,
• Isabelle Gillaizeau and
• Volodymyr A. Sukach

Beilstein J. Org. Chem. 2020, 16, 2304–2313, doi:10.3762/bjoc.16.191

• presence of transition metal salts is an essential transformation that permits the preparation N-(het)aryl-substituted amines and their derivatives including various nitrogen-containing heterocycles [1][2][3][4][5], an important class of compounds throughout chemical research. The copper-catalyzed

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• palladium(II) was carried out in the presence of PdCl2(MeCN)2 in a stepwise manner, confirmed by UV–vis spectroscopic technique. The cyclopentadienyl (Cp) ligand has its own identity in the field of organometallic chemistry as a plethora of transition metal complexes contain this moiety in their structures

Regioselective cobalt(II)-catalyzed [2 + 3] cycloaddition reaction of fluoroalkylated alkynes with 2-formylphenylboronic acids: easy access to 2-fluoroalkylated indenols

• Tatsuya Kumon,
• Miroku Shimada,
• Jianyan Wu,
• Shigeyuki Yamada and
• Tsutomu Konno

Beilstein J. Org. Chem. 2020, 16, 2193–2200, doi:10.3762/bjoc.16.184

• best of our knowledge, there are no reports on the practical synthesis of disubstituted 2-fluoroalkylated indenols so far. Transition-metal-catalyzed carbocyclization reactions of alkynes with benzene derivatives having a leaving group X (X = Br, I, OTs, B(OH)2) have been widely considered as one of

Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis

• Shahboz Yakubov and
• Joshua P. Barham

Beilstein J. Org. Chem. 2020, 16, 2151–2192, doi:10.3762/bjoc.16.183

• fluorination methods, of which direct C–H fluorination is among the most powerful. Despite the challenges and limitations associated with the direct fluorination of unactivated C–H bonds, appreciable advancements in manipulating the selectivity and reactivity have been made, especially via transition metal

• catalysis and photochemistry. Where transition metal catalysis provides one strategy for C–H bond activation, transition-metal-free photochemical C–H fluorination can provide a complementary selectivity via a radical mechanism that proceeds under milder conditions than thermal radical activation methods

• metal-based catalysts in organic synthesis and due to the exhaustive coverage of transition metal-based photosensitizers in the literature, we focus on detailing the properties of small-organic-molecule photosensitizers. Section 2 also highlights common fluorinating reagents, especially those used in C

Efficient [(NHC)Au(NTf₂)]-catalyzed hydrohydrazidation of terminal and internal alkynes

• Maximillian Heidrich and
• Herbert Plenio

Beilstein J. Org. Chem. 2020, 16, 2080–2086, doi:10.3762/bjoc.16.175

• addition product were obtained. We recently reported the excellent activity of the very bulky bispentiptycenyl-substituted (NHC)Au complexes in the hydration of terminal and internal alkynes [43] as well as in other transition-metal-catalyzed transformations [44][45]. We were now interested, whether

Reactions of 3-aryl-1-(trifluoromethyl)prop-2-yn-1-iminium salts with 1,3-dienes and styrenes

• Thomas Schneider,
• Michael Keim,
• Bianca Seitz and
• Gerhard Maas

Beilstein J. Org. Chem. 2020, 16, 2064–2072, doi:10.3762/bjoc.16.173

• years, a trifluoromethyl substituent has been included quite often in the design of compounds which were developed for applications in various fields, such as biological and medicinal chemistry, agrochemicals, transition metal ligands, and materials science [1][2][3][4][5]. The particular

Isolation and structure determination of a tetrameric sulfonyl dilithio methandiide in solution based on crystal structure analysis and ⁶Li/¹³C NMR spectroscopic data

• Jürgen Vollhardt,
• Hans Jörg Lindner and
• Hans-Joachim Gais

Beilstein J. Org. Chem. 2020, 16, 2057–2063, doi:10.3762/bjoc.16.172

• of 2 with carbon and metal-based electrophiles revealed a high synthetic potential, allowing, for example, the synthesis of carbo- and heterocycles [4][6], and transition-metal carbene complexes [1][2], carrying the synthetically versatile sulfonyl group [7][8]. Dilithio methandiides 2 are accessible

A complementary approach to conjugated N-acyliminium formation through photoredox-catalyzed intermolecular radical addition to allenamides and allencarbamates

• Olusesan K. Koleoso,
• Matthew Turner,
• Felix Plasser and
• Marc C. Kimber

Beilstein J. Org. Chem. 2020, 16, 1983–1990, doi:10.3762/bjoc.16.165

• of oxidation [20][29][30][31] or through the use of a transition metal such as Au(I) [8][10][11][12][13][14][15][16][32][33][34][35][36]. The reaction of the allenamide with an electrophilic source promotes the formation of a conjugated N-acyliminium intermediate 2 [37][38][39][40] that subsequently

Metal-free synthesis of phosphinoylchroman-4-ones via a radical phosphinoylation–cyclization cascade mediated by K₂S₂O₈

• Qiang Liu,
• Weibang Lu,
• Guanqun Xie and
• Xiaoxia Wang

Beilstein J. Org. Chem. 2020, 16, 1974–1982, doi:10.3762/bjoc.16.164

• appropriate radical precursors through visible-light promoted systems [15][16], transition-metal-catalyzed systems [17][18], or transition-metal-free systems [19][20], have emerged as a powerful strategy for the synthesis of diversely functionalized chroman-4-one derivatives. Organophosphorus compounds are

• (DPPO) was not suitable for the transformation (Scheme 1b). So the development of metal-free and greener methods to approach chroman-4-ones bearing a phosphine oxide moiety is still highly desirable. Herein, we present a transition-metal-free radical cascade cyclization to access the desired chroman-4

Natural dolomitic limestone-catalyzed synthesis of benzimidazoles, dihydropyrimidinones, and highly substituted pyridines under ultrasound irradiation

• Kumar Godugu,
• Venkata Divya Sri Yadala,
• Mohammad Khaja Mohinuddin Pinjari,
• Trivikram Reddy Gundala,
• Lakshmi Reddy Sanapareddy and
• Chinna Gangi Reddy Nallagondu

Beilstein J. Org. Chem. 2020, 16, 1881–1900, doi:10.3762/bjoc.16.156

• pharmacological properties [32][33][34][35][36][37]. A wide variety of Brønsted acids and Lewis acids are employed as efficient catalysts for the Biginelli reaction [38][39][40][41][42][43][44][45][46][47]. In addition, some transition metal-based catalysts and a few nonacidic inorganic salts are also utilized as

One-pot and metal-free synthesis of 3-arylated-4-nitrophenols via polyfunctionalized cyclohexanones from β-nitrostyrenes

• Haruyasu Asahara,
• Minami Hiraishi and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2020, 16, 1830–1836, doi:10.3762/bjoc.16.150

• nitrophenol 5a. This protocol was also applicable to other nitroalkenes, 1b–f, to afford the corresponding 3-arylated-4-nitrophenols 5b–f. This reaction could be conducted in one pot without using any transition-metal reagent. Since the starting nitroalkenes were prepared by the condensation of a (hetero)aryl

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• electrocatalysis, have been achieved recently [53][54][55][56][57][58]. In addition, various transformations merging photoredox catalysis with transition-metal catalysis have been disclosed [59][60][61][62][63][64][65]. Among these different strategies, visible-light photoredox catalysis combined with nickel

• the variety of possibilities in combining transition metal C–H activation and visible-light photoactivation to reach sustainable synthesis. The particular focus is put on the mechanisms of such complex catalytic systems, highlighting the unique reactivity that arises from the original combination of

• activation, a catalytic amount of a transition metal (generally Pd, Rh and Ru) is frequently used in combination with a stoichiometric amount of an external oxidant (typically Cu or Ag salts). Such additional oxidants are required if transiently produced low-valent metal complexes need to be reoxidized by

Et₃N/DMSO-supported one-pot synthesis of highly fluorescent β-carboline-linked benzothiophenones via sulfur insertion and estimation of the photophysical properties

• Dharmender Singh,
• Vipin Kumar and
• Virender Singh

Beilstein J. Org. Chem. 2020, 16, 1740–1753, doi:10.3762/bjoc.16.146

• functional groups and aza-heterocyclic frameworks. However, organic transformations in which aromatic nitro groups act as leaving groups are less reported and require the use of transition-metal catalysts such as Cu, Rh, Pd, etc. [35][36][37]. Though, several elegant methods have been developed for the

• Dharmender Singh Vipin Kumar Virender Singh Department of Chemistry, Dr. B R Ambedkar National Institute of Technology (NIT), Jalandhar, 144011, Punjab, India Department of Chemistry, Central University of Punjab, Bathinda, 151001, Punjab, India 10.3762/bjoc.16.146 Abstract A robust transition

• -metal-free strategy is presented to access novel β-carboline-tethered benzothiophenone derivatives from 1(3)-formyl-β-carbolines using elemental sulfur activated by Et3N/DMSO. This expeditious catalyst-free reaction proceeds through the formation of β-carboline-based 2-nitrochalcones followed by an

Tuneable access to indole, indolone, and cinnoline derivatives from a common 1,4-diketone Michael acceptor

• Dalel El-Marrouki,
• Sabrina Touchet,
• Abderrahmen Abdelli,
• Hédi M’Rabet,
• Mohamed Lotfi Efrit and
• Philippe C. Gros

Beilstein J. Org. Chem. 2020, 16, 1722–1731, doi:10.3762/bjoc.16.144

• [15][16][17][18], nucleophilic and electrophilic cyclizations [19][20][21][22][23][24][25], reductive and oxidative cyclizations [26][27], and transition-metal catalysis [28][29][30][31][32][33][34][35][36][37]. There are fewer ways to access indolone derivatives, mainly based on the use of di- [12

• ][38][39] or triketones [10][13] and enaminones [40][41][42][43] as starting materials. For the synthesis of cinnoline derivatives, aryldiazenes and aryltriazenes are substrates of choice for transition-metal-catalyzed (Rh, Pd, Cu) cross-coupling reactions, followed by intramolecular cyclizations [44

• ; indoles 6, indolones 7, and cinnolines 8, starting from common substrates 1,4-diketones 5 and primary amines. The protocols developed here used mild conditions, were functional-group tolerant, transition-metal-free, proceeded in moderate to good yield, and could therefore easily be used in medicinal

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• described protocols for the fluorinated PKR are based on the cobalt-catalyzed version, and only a few examples have used other transition metal complexes. In this regard, significant advances can come from the careful selection of the metal complex and the CO source. The encouraging results described in

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

• has shifted the paradigms of photochemistry, opening new avenues of research with safer and scalable processes that can be readily implemented in academia and industry. Current state-of-the-art photocatalysts are homogeneous transition metal complexes that have favourable photophysical properties

• , wide electrochemical redox potentials, and photostability. However, these photocatalysts present serious drawbacks, such as toxicity, limited availability, and the overall cost of rare transition metal elements. This reduces their long-term viability, especially at an industrial scale. Heterogeneous

• organic synthesis is dominated by homogeneous organic dyes and phosphorescent transition metal complexes [40][41][42]. This is largely due to the higher efficiency of molecular photocatalysts, which disperse in solution and can be irradiated uniformly, especially in narrow flow channels [43]. The