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

• benzimidazoline 2 was completely consumed after 24 h, the yield of the trifluoromethylation product continued to increase up to 48 h. This suggests that product generation proceeded slower than the cleavage of the C–CF3 bond of benzimidazoline. We propose a mechanism for the reaction, as shown in Figure 5. The Cu

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

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

• cleavage reactions [80] and 1,5-HAT [81] and iii) the excited state of the simple organic molecule target can possess an ultrashort lifetime [82] that precludes photochemistry in favor of photophysical or nonradiative deactivation, e.g., fluorescence or internal conversion (IC). Instead of direct UV

• on polar aprotic solvents, which are typically required for SET processes. Photosensitization also permits the facile and complementary access to radical intermediates via homolytic cleavage, without the need for SET [101][102]. 1.1.5 Justification and scope of the review: Considering these

• the excitation of the complex RC1 directly allowed N–F cleavage to form the Selectfluor® radical cation. The reaction of the C3 2° pentane radical with Selectfluor® in an FAT was exergonic, with an energy barrier of 7.6 kcal⋅mol−1 relative to Int7, affording Int8 (Scheme 19). Since the Selectfluor

GlypNirO: An automated workflow for quantitative N- and O-linked glycoproteomic data analysis

• Toan K. Phung,
• Cassandra L. Pegg and
• Benjamin L. Schulz

Beilstein J. Org. Chem. 2020, 16, 2127–2135, doi:10.3762/bjoc.16.180

• , downloaded April 20, 2018 with 20,303 reviewed proteins) [26]. Cleavage specificity was set as C-terminal to Arg/Lys with a maximum of one missed cleavage. The precursor mass tolerance was 10 ppm and fragment ion mass tolerances for CID and HCD were 0.5 Da and 20 ppm, respectively. Carbamidomethylation of

Access to highly substituted oxazoles by the reaction of α-azidochalcone with potassium thiocyanate

• Mysore Bhyrappa Harisha,
• Pandi Dhanalakshmi,
• Rajendran Suresh,
• Raju Ranjith Kumar and
• Shanmugam Muthusubramanian

Beilstein J. Org. Chem. 2020, 16, 2108–2118, doi:10.3762/bjoc.16.178

• give the intermediate A which undergoes homolytic cleavage yielding B. Subsequent cyclisation results in the oxazole ring. During these optimization trials, it was interesting to note the formation of 2-aminothiazole, when ferric chloride was employed along with thiocyanate (Table 1, entry 3). There is

pH- and concentration-dependent supramolecular self-assembly of a naturally occurring octapeptide

• Goutam Ghosh and
• Gustavo Fernández

Beilstein J. Org. Chem. 2020, 16, 2017–2025, doi:10.3762/bjoc.16.168

• nanostructures as well as the secondary structures. Results and Discussion Solid-phase peptide synthesis and purification The target octapeptide was synthesized in the solid phase following four steps, including: i) deprotection of the Fmoc protecting group, ii) coupling of an amino acid, iii) cleavage of the

• temperature, and this was stirred for 2 hours following the same procedure as before. At the final stage, we cleaved the peptide from the resin by using a proper cleavage cocktail: TFA/phenol/water/TIPS 88:5:5:2. DTT was included, as this peptide contains cysteine. After adding the cleavage cocktail to the

Syntheses of spliceostatins and thailanstatins: a review

• William A. Donaldson

Beilstein J. Org. Chem. 2020, 16, 1991–2006, doi:10.3762/bjoc.16.166

• fashion similar to that of the dihydropyranone 58 [16], the 1,4-addition of dimethyl copper lithium to 65 gave the desired cis-50 as a single diastereomer [31], allowing for a convergence with the route in Scheme 7. Alternatively, the Wittig methenylation of 63, followed by a silyl ether cleavage gave 66

• cleavage of the secondary triisopropylsilyl ether were prerequisites for a vanadium-catalyzed stereoselective epoxidation of the exocyclic double bond to give 90. The C-4 hydroxy group was eventually protected as a triethylsilyl ether. Through abortive attempts, Jacobsen found that the generation of the

• cleavage afforded the methyl ketone 96. The cyclic hemiketal 97 was unstable at an elevated temperature (37 °C), with t1/2 = 48 h. Both the Jacobsen (10 steps, 24.4% yield) and the Koide syntheses (11 steps, 22.3% yield) are relatively efficient in terms of the length and overall yield. Syntheses of the C

Synthesis of monophosphorylated lipid A precursors using 2-naphthylmethyl ether as a protecting group

• Jundi Xue,
• Ziyi Han,
• Gen Li,
• Khalisha A. Emmanuel,
• Cynthia L. McManus,
• Qiang Sui,
• Dongmian Ge,
• Qi Gao and
• Li Cai

Beilstein J. Org. Chem. 2020, 16, 1955–1962, doi:10.3762/bjoc.16.162

• methoxide in guanidine hydrochloride buffer solution (pH ≈ 9) to remove the O-3,4,6-acetyl groups [14]. Because the deacetylation reaction was later neutralized with cation exchange resin, extra washing with saturated NaHCO3 during reaction work-up seemed necessary to avoid cleavage of the TBS ether in

• by treatment with triethylamine, and the resulting amine again was immediately acylated with (R)-3-(2-naphthylmethoxy)tetradecanoic acid (7) to afford disaccharide 28 with four fatty acid chains. After cleavage of the anomeric TBS moiety employing HF in pyridine, the resulting anomeric hydroxy group

Synergy between supported ionic liquid-like phases and immobilized palladium N-heterocyclic carbene–phosphine complexes for the Negishi reaction under flow conditions

• Edgar Peris,
• Raúl Porcar,
• María Macia,
• Jesús Alcázar,
• Eduardo García-Verdugo and
• Santiago V. Luis

Beilstein J. Org. Chem. 2020, 16, 1924–1935, doi:10.3762/bjoc.16.159

• , Ananikov and co-workers reported that for Pd–NHC systems the reactivity of the systems is mainly determined by the cleavage of the metal−NHC bond, while the catalyst performance is strongly affected by the stabilization of in situ-formed metal clusters [15][30][40]. In the mechanism suggested by these

Design, synthesis and application of carbazole macrocycles in anion sensors

• Alo Rüütel,
• Ville Yrjänä,
• Sandip A. Kadam,
• Indrek Saar,
• Mihkel Ilisson,
• Astrid Darnell,
• Kristjan Haav,
• Tõiv Haljasorg,
• Lauri Toom,
• Johan Bobacka and
• Ivo Leito

Beilstein J. Org. Chem. 2020, 16, 1901–1914, doi:10.3762/bjoc.16.157

• reference [6]. It is worth noting that the described cleavage problem during nitration was specific to tert-butyl groups. We also studied the possibility of hexyl substituents instead of tert-butyl groups [25]. In this case, the nitration process yielded only the desired product. However, since this

On the hydrolysis of diethyl 2-(perfluorophenyl)malonate

• Ilya V. Taydakov and
• Mikhail A. Kiskin

Beilstein J. Org. Chem. 2020, 16, 1863–1868, doi:10.3762/bjoc.16.153

• of diethyl 2-(perfluorophenyl)malonate, acid-catalyzed reactions were also tested. Trifluoroacetic acid (TFA) is a common reagent for the catalytic cleavage of tert-butyl esters, but in the stoichiometric quantity it is also suitable for the cleavage of nonvolatile methyl or ethyl esters due to

Synthesis, docking study and biological evaluation of ᴅ-fructofuranosyl and ᴅ-tagatofuranosyl sulfones as potential inhibitors of the mycobacterial galactan synthesis targeting the galactofuranosyltransferase GlfT2

• Marek Baráth,
• Jana Jakubčinová,
• Zuzana Konyariková,
• Stanislav Kozmon,
• Katarína Mikušová and
• Maroš Bella

Beilstein J. Org. Chem. 2020, 16, 1853–1862, doi:10.3762/bjoc.16.152

• % and 54% yield, respectively. Moderate yields of 2-thio-ᴅ-tagatofuranosides 17 can be explained by cleavage of the benzyl protecting group [21] as well as further side reactions (Scheme 4). In order to increase the yield of 2-thio-ᴅ-tagatofuranosides 17, compound 12 was converted to the more reactive

• diacetate 18 under acetolysis conditions (Ac2O/BF3∙OEt2) [22]. However, besides the expected diacetate 18, 1,2,6-tri-O-acetate 19 was observed and isolated as a byproduct (Scheme 4). The cleavage of the O-benzyl ethers followed by acetylation of the liberated hydroxy groups under acidic conditions was

One-pot synthesis of oxazolidinones and five-membered cyclic carbonates from epoxides and chlorosulfonyl isocyanate: theoretical evidence for an asynchronous concerted pathway

• Esra Demir,
• Ozlem Sari,
• Yasin Çetinkaya,
• Ufuk Atmaca,
• Safiye Sağ Erdem and
• Murat Çelik

Beilstein J. Org. Chem. 2020, 16, 1805–1819, doi:10.3762/bjoc.16.148

• reaction of CSI with epoxides in different solvents under mild conditions and compared the reaction mechanism with previously proposed mechanisms using theoretical calculations. Keshava Murthy and Dhar [41] postulated a mechanism involving a zwitterionic intermediate. C–O bond cleavage in this unstable and

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

• the C–H cleavage step slightly, yet significantly absorbed light in the relevant blue region. This absorption was believed to trigger the overall catalytic cycle at room temperature as no product formation was observed in the dark. The mechanistic scenario thus foresees an initial pyridine-directed

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

• addition of the trisulfur radical anion to the double bond in 2-nitrochalcone (1bA) may yield the intermediate 7. The further abstraction of hydrogen in intermediate 7 may result in formation of intermediate 8. The cleavage of the S–S bond in 8 under basic conditions may generate sulfur anion 9. The

Synthesis of Streptococcus pneumoniae serotype 9V oligosaccharide antigens

• Sharavathi G. Parameswarappa,
• Claney L. Pereira and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2020, 16, 1693–1699, doi:10.3762/bjoc.16.140

• mannosamine was obtained from 33, that in turn was a product of the benzylation of 32. Cleavage of the benzylidene group in 33 yielded 34 that was selectively acetylated at the primary alcohol at low temperature to obtain 35 [30]. The subsequent removal of the benzyl groups using hydrogenation with Pd/C in an

A dynamic combinatorial library for biomimetic recognition of dipeptides in water

• Florian Klepel and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2020, 16, 1588–1595, doi:10.3762/bjoc.16.131

• SPPS. Thus one cysteine moiety is left deprotected and can be addressed selectively either by dimerization with another CFC(Acm) or with inversely substituted tripeptide (C(Acm)FC). These linear peptide dimers were subsequently cyclized by oxidative cleavage of the Acm groups to give a(CFC)2 and p(CFC

Photoredox-catalyzed silyldifluoromethylation of silyl enol ethers

• Vyacheslav I. Supranovich,
• Vitalij V. Levin and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2020, 16, 1550–1553, doi:10.3762/bjoc.16.126

• )trimethylsilane followed by a reduction of the primary products with sodium borohydride is described. An 18 W, 375 nm LED was used as the light source. The reaction is performed in the presence of a gold photocatalyst, which effects the generation of a (trimethylsilyl)difluoromethyl radical via cleavage of the

• carbon-based radical via cleavage of the carbon–bromine bond by a gold photocatalyst. Reaction of silyl enol ethers. Yields refer to isolated yields. aReaction time 24 h; b1.0 equiv of silane 1 was used; cketone was isolated. Reactions of (bromodifluoromethyl)trimethylsilane (1). Optimization studies

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

Photocatalyzed syntheses of phenanthrenes and their aza-analogues. A review

• Alessandra Del Tito,
• Havall Othman Abdulla,
• Davide Ravelli,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 1476–1488, doi:10.3762/bjoc.16.123

• conditions finally afforded the desired phenanthridine 8.7 in 90% yield [69]. Carbon-based radicals could be likewise generated via a C–H hydrogen-atom transfer path. As an example, ethers were used as hydrogen donors and underwent a C–H cleavage step promoted by a photogenerated tert-butoxyl radical. The so

• preparation of phenanthridines with the intermediacy of imidoyl radicals. As an example, the process depicted in Scheme 10 involved a visible-light homolytic radical aromatic substitution (HAS) starting from trifluoroacetimidoyl chlorides 10.1a–e. Thus, the photocatalyzed cleavage of the C(sp2)–Cl bond in

• photocatalyzed reduction of acyloximes 14.1a,b offered a smooth entry to iminyl radicals (Scheme 14) [76]. The process took place at room temperature and involved the cleavage of a C–O bond, followed by a cyclization to give access to the benzo[c]phenanthridine alkaloids noravicine (14.2a) and nornitidine (14.2b

In silico rationalisation of selectivity and reactivity in Pd-catalysed C–H activation reactions

• Liwei Cao,
• Mikhail Kabeshov,
• Steven V. Ley and
• Alexei A. Lapkin

Beilstein J. Org. Chem. 2020, 16, 1465–1475, doi:10.3762/bjoc.16.122

• -addition, respectively [15]. Even though the mechanisms are inherently different, three most important aspects should be primarily taken into account when classifying and rationalising C–H activation reactions: the proximity of C–H bond to the transition metal; the energy of C–H bond cleavage within the

• feature of the proton abstraction (PA) mechanism [25] is that the formation of the metal–carbon bond (M–C) occurs simultaneously with the cleavage of the carbon–hydrogen (C–H) bond, while the hydrogen is being transferred to a basic centre, Scheme 1. Assuming the reaction proceeds through the formation of

The McKenna reaction – avoiding side reactions in phosphonate deprotection

• Katarzyna Justyna,
• Joanna Małolepsza,
• Damian Kusy,
• Waldemar Maniukiewicz and
• Katarzyna M. Błażewska

Beilstein J. Org. Chem. 2020, 16, 1436–1446, doi:10.3762/bjoc.16.119

• reagent of choice for phosphonate ester cleavage, compared with its more and less reactive analogs, iodotrimethylsilane (ITMS) [11][12] and chlorotrimethylsilane (CTMS) [13], respectively. While being one of the most popular methods for the deprotection of organophosphorus esters, the McKenna reaction may

• be accompanied by side reactions such as the cleavage of tert-butyl carboxyester, [14][15] or other ester groups [16], as well as the formation of decomposition products [17][18][19][20]. Instead of focusing only on the experiments that “did work”, we decided to follow an alternative strategy

• reaction with BTMS, and underwent exchange of the chlorine substituent for bromine. This reaction can be partially circumvented by using nonpolar solvents, amines and lower temperatures. Section 5: Cleavage of the tert-butyl carboxyester group BTMS is known for its chemoselectivity and cleaves phosphonate

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118

• , cyclopentanone, and three carbon ring-expanded 1,3-diones from vinyl spiro epoxides [14]. The reaction is initiated by the addition of a thiyl radical to the vinyl epoxide 24, followed by the epoxide fragmentation to the alkoxy radical 25. Then, the β-cleavage to form the carbon-centered radical 26, the final

• by the excitation with visible light, the homolytic cleavage of disulfide generates an arylthiyl radical (ArS•), which adds to diphenylacetylene to form a free-radical intermediate 28. Subsequently, this intermediate traps a molecule of singlet oxygen (1O2), and the thiyl radical is regenerated to

• give the four-membered ring intermediate 29. Finally, the rearrangement of the four-membered intermediate provides the diketone 30 as the product (Scheme 8). In 2017, Wang and co-workers reported an oxidative cleavage of aromatic alkenes at ambient temperature with visible-light irradiation, using

Synthesis of new fluorescent molecules having an aggregation-induced emission property derived from 4-fluoroisoxazoles

• Kazuyuki Sato,
• Akira Kawasaki,
• Yukiko Karuo,
• Atsushi Tarui,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2020, 16, 1411–1417, doi:10.3762/bjoc.16.117

• diketone (Scheme 5). As an alternative method to synthesize F-BKIs 9, we turned our attention to the ring-opening reaction of isoxazoles. The reductive cleavage of the N–O bond in isoxazoles can be achieved by transition metals or their complexes to give the corresponding enaminoketones [35][37

• in the aggregated state and exhibited a redshift in the emission intensity. We also achieved the first synthesis of α-fluorinated boron ketoiminates (F-BKIs) by the reductive cleavage of the N–O bond in 4-fluorinated isoxazoles and demonstrated that F-BKIs exhibited AIE property similarly to their

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

• second displacement was an intramolecular SN2 process performed under mild basic conditions, affording the desired thietane 116 in 92% yield. After deprotection, oxidative cleavage, and reduction, a thietanose 117 was obtained in 63% overall yield. The thietanose 117 was further applied to synthesize a

• cleavage and aromatization to give substituted pyridines 255 [75] (Scheme 49). In 1989, Kanaoka and co-workers further studied the photo [2 + 2] cycloadditions of thiobarbiturates 256–258, whose skeletons consisted of a combination of a thioamide and an amide or a thioamide (two-imides system), and olefins

• were obtained via a ring cleavage of the thietanes, that had formed in the [2 + 2] photocycloaddition of the thiocarbonyl moiety and the olefin. However, the reaction of 1,3,3-trimethylindoline-2-thione (300) and isobutene (215c) afforded the corresponding spiroindoline-thietane derivative 301 [80