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

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

• (Scheme 23) [59]. The authors rationalized the formation of 45 by considering that the inherent weakening of the C—X bond going down the halogen series may favor the generation of radical A with chloride and bromide derivatives, especially given the tertiary position of the halide and the stoichiometric

Facile synthesis of 7-alkyl-1,2,3,4-tetrahydro-1,8-naphthyridines as arginine mimetics using a Horner–Wadsworth–Emmons-based approach

• Rhys A. Lippa,
• John A. Murphy and
• Tim N. Barrett

Beilstein J. Org. Chem. 2020, 16, 1617–1626, doi:10.3762/bjoc.16.134

• occur via a radical pathway. When iodide 29 was replaced by a superior oxidant in 1,2-dibromoethane, formation of dimer 32 increased (17% isolated yield). This supports the previously reported proposals that dimerisation occurs via single-electron oxidation of the 2-picolyl anion by the halide

• /pseudohalide oxidant followed by recombination of the resulting picolyl radical [28][29][30]. Whilst trace oxygen may be involved, as indicated by the presence of alcohol 31, no dimerisation or alcohol formation was seen in the absence of a halide/pseudohalide-based oxidant, during C-phosphorylation or

Azidophosphonium salt-directed chemoselective synthesis of (E)/(Z)-cinnamyl-1H-triazoles and regiospecific access to bromomethylcoumarins from Morita–Baylis–Hillman adducts

• Soundararajan Karthikeyan,
• Radha Krishnan Shobana,
• Kamarajapurathu Raju Subimol,
• J. Helen Ratna Monica and
• Ayyanoth Karthik Krishna Kumar

Beilstein J. Org. Chem. 2020, 16, 1579–1587, doi:10.3762/bjoc.16.130

• -lactams [6], quinolin-5-ones [7], spirobisglutarimides [8], indolizines [9], and spiro carbocyclic frameworks [10]. However, most of the reported synthetic transformations utilize either allylic hydroxy-protected or allyl halide-substituted MBH adducts [11][12][13][14][15][16][17][18][19][20][21][22][23

• transformations for complex molecules [29][30][31]. Two individual research groups have reported the multistep pathway to access the cinnamyl-1H-1,2,3-triazole derivatives IX from acetates of MBH adducts (Scheme 2) [32][33]. The other preferable moiety for triazole transformations is the allyl halide of MBH

Disposable cartridge concept for the on-demand synthesis of turbo Grignards, Knochel–Hauser amides, and magnesium alkoxides

• Mateo Berton,
• Kevin Sheehan,
• Andrea Adamo and
• D. Tyler McQuade

Beilstein J. Org. Chem. 2020, 16, 1343–1356, doi:10.3762/bjoc.16.115

• optimization (Table S4, Supporting Information File 1), solubility issues hindered the formation of a concentrated solution (>0.8 M). The crystallization of iPrMgBr in the collection flask forced us to reduce the initial concentration of the organic halide to 0.9 M, yielding iPrMgBr (0.75 M, 82%, note: the

• yields reported herein refer to the amount of organometallic reagent produced in a steady state; no detectable halide was recovered, and the organometallic reagent purity was high unless otherwise stated, Table S4, entry 3, Supporting Information File 1). The reactivity order of organic halides against

• consistent results over a relatively large amount (≈100 mmol) of organic halide that was converted. We offer two explanations: (1) the higher purity of Mg chips (99.98%) and (2) the higher surface area (SA) of the Mg powder (≈130 mesh, SA ≈ 30 cm2/g) than Mg chips (≈20 mesh, SA ≈ 4 cm2/g). We hypothesize

Synthesis of pyrrolidinedione-fused hexahydropyrrolo[2,1-a]isoquinolines via three-component [3 + 2] cycloaddition followed by one-pot N-allylation and intramolecular Heck reactions

• Xiaoming Ma,
• Suzhi Meng,
• Xiaofeng Zhang,
• Qiang Zhang,
• Shenghu Yan,
• Yue Zhang and
• Wei Zhang

Beilstein J. Org. Chem. 2020, 16, 1225–1233, doi:10.3762/bjoc.16.106

• IV which undergoes dissociation to afford product 9a. The hydridopalladium(II) halide is converted to the catalytically active Pd(0) with a base. Conclusion In summary, we have developed an efficient method through a three-component [3 + 2] cycloaddition followed by a one-pot N-allylation and an

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

• the nature of the halide: as a trend, aryl iodides are easier to reduce than aryl bromides and aryl chlorides [67][77]. Under organophotocatalytic conditions, the reduction can be achieved following two main strategies for accessing stronger reduction potentials: (a) tuning the electronics of the

Copper-based fluorinated reagents for the synthesis of CF₂R-containing molecules (R ≠ F)

• Louise Ruyet and
• Tatiana Besset

Beilstein J. Org. Chem. 2020, 16, 1051–1065, doi:10.3762/bjoc.16.92

• 87% yield) was investigated (Scheme 8) [52]. Finally, the Poisson’s group developed a methodology for the Ullman cross-coupling reaction between the in situ-generated CuCF2PO(OEt)2 and aryl iodides containing a coordinating group (e.g., CO2CH3, COCH3, NO2), at the ortho-position of the halide [52

Fluorinated phenylalanines: synthesis and pharmaceutical applications

• Laila F. Awad and
• Mohammed Salah Ayoup

Beilstein J. Org. Chem. 2020, 16, 1022–1050, doi:10.3762/bjoc.16.91

• reported herein different methods for their synthesis. 1.1. Negishi cross coupling of aryl halide and organozinc compounds Jackson and co-workers reported the synthesis of a range of phenylalanine derivatives via Negishi cross-coupling reactions of aryl halides and Zn homoenolates of the protected (R

• involved a Negishi cross coupling of an aryl halide and the Zn homoenolate of the protected (R)-iodoalanine 2 using a Pd(0) catalyst. This method provided a versatile range of fluorinated phenylalanine products with high enantioselectivities and in acceptable yields. 2. Synthesis of β-fluorophenylalanines

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

Rhodium-catalyzed reductive carbonylation of aryl iodides to arylaldehydes with syngas

• Zhenghui Liu,
• Peng Wang,
• Zhenzhong Yan,
• Suqing Chen,
• Dongkun Yu,
• Xinhui Zhao and
• Tiancheng Mu

Beilstein J. Org. Chem. 2020, 16, 645–656, doi:10.3762/bjoc.16.61

• no substituent group provided benzaldehyde (1) with 93% yield. For iodobenzene derivatives with electron-donating groups (Me, OMe), 83–95% yield of aldehydes 2–7 were obtained. As expected, the yields increased in the order of ortho < meta < para-substituted compounds. As for aryl iodides with halide

• . Afterwards, the hot mixture was filtered. Finally, the solid was washed with ether and dried under vacuum overnight to afford RhCl(PPh3)3 as maroon powder. The preparations of RhBr(PPh3)3 and RhI(PPh3)3 were similar only with different halide ions. Rhodium-catalyzed reductive carbonylation of iodobenzene

Copper-catalyzed O-alkenylation of phosphonates

• Nuria Vázquez-Galiñanes,
• Mariña Andón-Rodríguez,
• Patricia Gómez-Roibás and
• Martín Fañanás-Mastral

Beilstein J. Org. Chem. 2020, 16, 611–615, doi:10.3762/bjoc.16.56

• all cases the corresponding enol phosphonates 3a–d in good yields. Importantly, no double alkenylation product was observed in any case. Benzyl and alkyl diethyl phosphonates bearing halide groups also worked well and led to enol phosphonates 3e and 3f in good yields without any traces of side

A systematic review on silica-, carbon-, and magnetic materials-supported copper species as efficient heterogeneous nanocatalysts in “click” reactions

• Pezhman Shiri and
• Jasem Aboonajmi

Beilstein J. Org. Chem. 2020, 16, 551–586, doi:10.3762/bjoc.16.52

• “click” reactions of alkyl halide, NaN3, and acetylene were performed successfully in the presence of 100 (1.0 mol %) as the catalyst and 10 mol % of sodium ascorbate as a reducing agent in water at 50 °C (Scheme 22). Further, the nanocatalyst 100 was durable and could be recycled eight times without any

KOt-Bu-promoted selective ring-opening N-alkylation of 2-oxazolines to access 2-aminoethyl acetates and N-substituted thiazolidinones

• Qiao Lin,
• Shiling Zhang and
• Bin Li

Beilstein J. Org. Chem. 2020, 16, 492–501, doi:10.3762/bjoc.16.44

• purified by silica gel chromatography and a mixture of petroleum ether/ethyl acetate as eluent. General procedure for KOt-Bu/I2-promoted N-alkylation of thiazolidin-2-one derivatives KOt-Bu (1 mmol, 112 mg), I2 (1 mmol, 254 mg), 2-(methylthio)-4,5-dihydrothiazole (0.5 mmol), benzyl halide (1.0 mmol) and

Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• suggested a possible mechanism based on the measured and reported redox potential (Scheme 1). Upon irradiation at 530 nm using green light, the Cu(I) catalyst transitions to an excited state. Then, the excited copper complex transfers an electron to the alkyl halide, which can generate an alkyl radical that

• subsequently adds to the alkene. The resulting C-centered radical is oxidized by the Cu(II) complex, regenerating the Cu(I) catalyst, and the formed carbocation is trapped by the halide. Worth to mention is that very recently, Reiser and Engl demonstrated the possible use of [Cu(dmp)2Cl]Cl as an efficient

• ketones and furanyl ketones, for instance, with good yield. To explain the reaction outcome, the authors suggested that the [Cu(I)(dap)2]Cl catalyst acted as an electron shuttle between the halide derivative and the allylmetal reagent, precluding a direct electron transfer between the allylstannane and

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

• plastics [26][27][28][29][30][31] represent some practical examples. Nevertheless, cyanines have held a long history regarding their practical use, which started to use such materials as sensitizers in silver halide photography [32][33][34] until the point when electronic media took their place in imaging

• sciences to save pictures. Many fundamental knowledge was grown up in this period as shown for example by several reviews [35][36][37][38][39][40]. Particularly, the use of model systems and the knowledge obtained by exploration systems in silver halide photography [32][33][34][41][42][43][44][45] also

• presented for in situ generation of Cu(I) to initiate the polymerization with the alkyl bromide. In this system, the Cu(II) complex was exposed to UV light to form Cu(I) which can react with alkyl halide resulting in generation of reactive radicals and Cu(II), Scheme 9. Those reactive radicals add monomer

Visible-light-induced addition of carboxymethanide to styrene from monochloroacetic acid

• Kaj M. van Vliet,
• Nicole S. van Leeuwen,
• Albert M. Brouwer and
• Bas de Bruin

Beilstein J. Org. Chem. 2020, 16, 398–408, doi:10.3762/bjoc.16.38

• nitriles [21], carbonyl or imine species [22], iodonium or diazonium salts [23], or halide species [24]. The formation of radicals from halide species by photoredox catalysis has been widely studied. It has been applied as a mild method for the dehalogenation of several compounds [25][26][27]. In the light

Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• lithium halogen elimination, halide migration, and ring-opening reactions [56][57]. Butylphosphines are also formed alongside the main product, and in most cases pure phosphine pyridines are obtained using column chromatography followed by extractions adding to the number of synthesis steps. This method

• dibromomethane to furnish the desired ligand 19. The nature of the halide in the precursors also influences the reaction progress. Fluorine and chlorine usually require strong bases for the metal–halogen exchange, while relatively mild bases can be used for bromo and iodo derivatives. Structurally inflexible

Halogen-bonding-induced diverse aggregation of 4,5-diiodo-1,2,3-triazolium salts with different anions

• Xingyu Xu,
• Shiqing Huang,
• Zengyu Zhang,
• Lei Cao and
• Xiaoyu Yan

Beilstein J. Org. Chem. 2020, 16, 78–87, doi:10.3762/bjoc.16.10

• triazolium salts show diverse aggregation via halogen bonding between C–I bonds and anions. Triazolium with halide anions exists as a tetramer with saddle conformation. Triazolium tetrafluoroborate exists as a trimer with Chinese lantern shape conformation. Triazolium trifluoroacetate and acetate exist as

• compounds show XB interactions between the triazolium moiety and anions, and different aggregations are formed. Triazolium with halide anions exists as tetramers with saddle conformation. Triazolium tetrafluoroborate exists as trimer with Chinese lantern shape conformation. Triazolium trifluoroacetate and

• dichloromethane solution (Scheme 2). 2-Br and 2-Cl were synthesized by ion exchange between 2-BF4 and the respective potassium halide in acetonitrile. A single crystal of 2-Br was obtained by slow diffusion of n-pentane into a dichloromethane solution. While the single crystal of 2-Cl was obtained by slow

SnCl₄-catalyzed solvent-free acetolysis of 2,7-anhydrosialic acid derivatives

• Kesatebrhan Haile Asressu and
• Cheng-Chung Wang

Beilstein J. Org. Chem. 2019, 15, 2990–2999, doi:10.3762/bjoc.15.295

• thiosialoside and halide donors. Keywords: acetolysis; acetolysis products; 2,7-anhydrosialic acid; SnCl4; Introduction Sialic acids are the most prevalent monosaccharides that are found at the nonreducing ends of glycans, and they are involved in many biologically important ligand–receptor interactions [1

• can be transformed smoothly into thioglycoside [15][16][35] and sialyl halide [38][39] donors when treated with a thiol in the presence of triflic acid, BF3⋅OEt2, and HCl, respectively. Through comparison with the reported mechanism of Sc(OTf)3-catalyzed acetolysis of 1,6-anhydro-β-hexopyranoses [32

• thiosialoside and sialyl halide donors in order to serve as alternative building blocks for the synthesis of sialic acid-containing glycans. Representative structures of bacterial glycans containing sialic acid. a) ORTEP diagram of compound 4. Thermal ellipsoids indicate 50% probability. b) HMBC spectrum of 6

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

• the electrophilic fluorination reagent F-TEDA-PF6 (Scheme 53). Also, the reaction was applied to late-stage fluorination of small molecules. However, this method uses toxic arylstannanes as starting materials and requires an additional synthetic step from the triflate or halide to the stannanes

Azologization and repurposing of a hetero-stilbene-based kinase inhibitor: towards the design of photoswitchable sirtuin inhibitors

• Christoph W. Grathwol,
• Nathalie Wössner,
• Sören Swyter,
• Adam C. Smith,
• Enrico Tapavicza,
• Robert K. Hofstetter,
• Anja Bodtke,
• Manfred Jung and
• Andreas Link

Beilstein J. Org. Chem. 2019, 15, 2170–2183, doi:10.3762/bjoc.15.214

• and 2e were obtained in moderate yield using 3a as the aryl halide in the Heck reaction. The use of 3b in the Heck reaction resulted in a substantial improvement of yield in the synthesis of 2g but not for 2c. Interchanging the roles by using 5-vinylnicotinamide (5a) or methyl 5-vinylnicotinate (5b

1,2,3-Triazolium macrocycles in supramolecular chemistry

• Mastaneh Safarnejad Shad,
• Pulikkal Veettil Santhini and
• Wim Dehaen

Beilstein J. Org. Chem. 2019, 15, 2142–2155, doi:10.3762/bjoc.15.211

• synthesized the novel tetra-1,2,3-triazolium zinc porphyrin cage 3 (Figure 4) and have probed its characteristics by using UV–visible spectroscopy, determining the association constants for complex formation in 5% water/acetone. This receptor has shown affinity toward all of the halide ions and especially

• literature there are still challenges to find selective iodide receptors due to its low basicity, large size and low charge density. There is an expectation that the combination of strong hydrogen-bonding sites and a large cavity could cause strong complexation with larger halide ions [55]. In 2016 a

• −, Br− and I− were found as 4.4 × 101 M−1, 1.7 × 101 M−1, 8.5 M−1, respectively. Thus, the interaction of 1,2,3-triazolium CH is decreasing with increasing halide size. Besides, the complexes of halides with the macrocycles were shown to have visible charge-transfer absorptions in the molecular crystals

Synthesis of benzo[d]imidazo[2,1-b]benzoselenoazoles: Cs₂CO₃-mediated cyclization of 1-(2-bromoaryl)benzimidazoles with selenium

• Mio Matsumura,
• Yuki Kitamura,
• Arisa Yamauchi,
• Yoshitaka Kanazawa,
• Yuki Murata,
• Tadashi Hyodo,
• Kentaro Yamaguchi and
• Shuji Yasuike

Beilstein J. Org. Chem. 2019, 15, 2029–2035, doi:10.3762/bjoc.15.199

• probably deprotonation of the heterocyclic rings with a base. Moreover, nucleophilic aromatic substitution (SNAr) reactions between an aryl halide and a selenium reagent such as aryl selenide anion or diaryl diselenide for C(Ar)–Se bond formation using a base have been reported [20][21][22]. However, the

Fluorinated azobenzenes as supramolecular halogen-bonding building blocks

• Esther Nieland,
• Oliver Weingart and
• Bernd M. Schmidt

Beilstein J. Org. Chem. 2019, 15, 2013–2019, doi:10.3762/bjoc.15.197

• ][22][23][24]. Huber and co-workers demonstrated the activation of a carbonyl group by halogen bonding, and successfully applied this concept to catalysts for Michael addition reactions [25] and also employed neutral [26], and hypervalent iodolium derivatives as activators in a halide abstraction