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

• ChsNC in the +2 oxidation state (Figure 3). These results align with our previous work where ChsNCs tend to stabilize Au in the +1 oxidation state as opposed to metallic Au. Since the Heck coupling primarily follows a classic oxidative addition/reductive elimination pathway with Pd(0) being the active

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

• (I)–CF3 species, generated through the reaction of benzimidazoline 2 with CuI under basic conditions, underwent an oxidative addition reaction with the aryl iodide to generate a Cu(III) complex. A subsequent reductive elimination furnished the trifluoromethylarene and Cu(I). Because an electron

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

Synthesis of 1,4-benzothiazinones from acylpyruvic acids or furan-2,3-diones and o-aminothiophenol

• Ekaterina E. Stepanova,
• Maksim V. Dmitriev and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2020, 16, 2322–2331, doi:10.3762/bjoc.16.193

• the suspension of acid 2a with DCC, formation of the white precipitate of dicyclohexylurea was observed, which gave the evidence of intramolecular cyclization to furandione 5a with dicyclohexylurea elimination occurring. The formation of furandione 5a explained well our observations when DMAP was used

Synthesis of 6,13-difluoropentacene

• Matthias W. Tripp and
• Ulrich Koert

Beilstein J. Org. Chem. 2020, 16, 2136–2140, doi:10.3762/bjoc.16.181

• 14 then rapidly decomposes to 6,13-pentacenequinone (15) after elimination of HF. The final aromatization of diol 13 to the target molecule 5 proceeded smoothly in 74% yield using SnCl2 in 1,4-dioxane and aqueous HCl [11][12]. F2PEN 5 can be stored under inertgas atmosphere at −20 °C for a month

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

• substituted oxazoles and 2-aminothiazoles from α-azidochalcones and potassium thiocyanate employing potassium persulfate and ferric nitrate, respectively. This new route gains a streamlined workup and the elimination of air-sensitive techniques to afford the product in good yield in a greener medium over a

The biomimetic synthesis of balsaminone A and ellagic acid via oxidative dimerization

• Sharna-kay Daley and
• Nadale Downer-Riley

Beilstein J. Org. Chem. 2020, 16, 2026–2031, doi:10.3762/bjoc.16.169

• 16 in 29, 34, and 19% yields, respectively (Table 1). As anticipated, the reaction of naphthalene 17 with CAN under aqueous conditions resulted in preferential oxidative demethylation to give quinone 7, as opposed to oxidative dimerization. The elimination of water from the reaction posed a few

Syntheses of spliceostatins and thailanstatins: a review

• William A. Donaldson

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

• -methyl-3-buten-1-yl tosylate in the presence of Grubbs’ 2nd generation catalyst yielded 59, which, upon elimination with potassium tert-butoxide led to the diene 50. The reductive amination of 50 afforded an inseparable mixture of the C-14 amines (6:1 ratio). However, the amidation of this mixture with

• and the amidation with 12c afforded 129. The synthesis was completed by the elimination of the 1° iodide, silyl ether cleavage, and hydration of the exocyclic enol ether. Of all the syntheses of FR901464 (1), the coupling of 91 with 48 is the most efficient sequence (6 steps, 45% yield). Nicolaou

Synthesis of 3(2)-phosphonylated thiazolo[3,2-a]oxopyrimidines

• Ksenia I. Kaskevich,
• Anastasia A. Babushkina,
• Vladislav V. Gurzhiy,
• Dmitrij M. Egorov,
• Nataly I. Svintsitskaya and
• Albina V. Dogadina

Beilstein J. Org. Chem. 2020, 16, 1947–1954, doi:10.3762/bjoc.16.161

• -trifluoromethyl-2-thiouracil (1e) enhances the acidity of the N3H hydrogen by direct conjugation to the carbonyl moiety. As a result, 2-thiouracil 1e acts as an ambident nucleophile. Thus, the attack of the carbon atom attached to the chlorine by the N3 nitrogen atom is accompanied by the elimination of hydrogen

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

• authors, Pd–NHC complexes can evolve through two different pathways towards the formation of a catalytically active cocktail of Pd species. In the first one, a reductive elimination takes place from the Pd(II) intermediate with the concomitant release of NHC-containing byproducts. In the second pathway

Regiodivergent synthesis of functionalized pyrimidines and imidazoles through phenacyl azides in deep eutectic solvents

• Paola Vitale,
• Luciana Cicco,
• Ilaria Cellamare,
• Filippo M. Perna,
• Antonio Salomone and
• Vito Capriati

Beilstein J. Org. Chem. 2020, 16, 1915–1923, doi:10.3762/bjoc.16.158

• undergo a base-promoted loss of nitrogen to form α-imino ketones upon protonation [38]. A plausible mechanism for the formation of pyrimidine derivative 7a from 2a, in competition with imidazoles 3a/3a', is depicted in Scheme 5. The key intermediate 5a, formed by elimination of nitrogen from the enol

• intramolecular nucleophilic attack to the terminal imino group of 9a, provides cyclized adduct 10a, and finally pyrimidine derivative 7a by aromatization/elimination of NH3. To the best of our knowledge, this is the first one-pot synthesis of functionalized pyrimidines using phenacyl azides as the sole starting

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

• products were obtained. The aromatization is considered to proceed as shown in Scheme 4. After the iodization at the 4-position, which leads to the formation of the intermediate 6, the aromatization is achieved by the successive elimination of hydrogen iodide and methanol, with concurrent tautomerism to

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

• elimination of hydrated HCl and formation of 13. The calculated free energy of activation was found to be 15.4 kcal/mol with respect to RC1 (7f+CSI) (Figure 5). The final step of path 2 takes place from RC5 (13+H2O) passing through TS5 and forming the target product 9f. This step requires an activation free

• corresponding barrier was calculated to be 13.0 kcal/mol relative to initial reactant complex RC6 (7f+CSI) (Figure 7). Elimination of 18, accompanied by C=O bond formation, constitutes the final step of the reaction observed. Optimized structures are given in Figure 10. The elimination reaction, via the

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

• metal catalyst X2M into an aromatic C–H bond of a substrate (generally facilitated by the presence of a directing group (DG)), delivers a metal–aryl complex. Coordination and subsequent insertion of an alkene into the M–aryl bond then provides the desired coupling product after β-hydride elimination

• reaction media in order to transfer electrons from the low-valent metal complex formed in situ after reductive elimination of the product (Figure 4, right). In this way, the metalacyclic intermediate is reoxidized while the photosensitizer is reduced, thus completing the C–H activation catalytic cycle. By

• that both, the excited Ir photocatalyst and the superoxide anion generated during the transformation, were able to oxidize the low-valent Pd(0) species resulting from the reductive elimination (Figure 6). Under such dual catalysis protocol, various oxidant-sensitive functional groups were tolerated

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

• stereochemical outcome of the overall process. A carbon monoxide ligand then undergoes migratory insertion into one of the Co–C bonds in cobaltacycle V, followed by reductive elimination to release the final product (Scheme 3). As mentioned above, the regiochemistry of this transformation is, in most cases

• corresponding mesylate 38b proved sufficient for the synthesis of N-tethered substrates 37 (Z = NTs), through simple nucleophilic substitution (via c). It is noteworthy that under standard PK reaction conditions, fluoroenyne 39 evolves to diene 40. The formation of compound 40 is possible by elimination of HF

• from the PK product 41, meaning that the fluoro-PKR does initially take place and that the desired product 41 could be isolated by avoiding the subsequent elimination reaction. This hypothesis was confirmed when the less basic DMSO was used as the promoter instead of NMO, allowing the successful

Rearrangement of o-(pivaloylaminomethyl)benzaldehydes: an experimental and computational study

• Csilla Hargitai,
• Györgyi Koványi-Lax,
• Tamás Nagy,
• Péter Ábrányi-Balogh,
• András Dancsó,
• Gábor Tóth,
• Judit Halász,
• Angéla Pandur,
• Gyula Simig and
• Balázs Volk

Beilstein J. Org. Chem. 2020, 16, 1636–1648, doi:10.3762/bjoc.16.136

• , gave isomeric aldehyde 2a (48%) and the dimer-like racemic product 3a (11%). Both transformations were rationalized by the intermediacy of the isoindole 4a (Scheme 1). The formation of aldehyde 2a can be explained by a protonation of the ring tautomer 1a, followed by an acid-catalyzed water elimination

• explained by the protonation of ring tautomers 9 to 10 (Scheme 4), followed by a water elimination, and subsequent deprotonation of cations 11 to afford isoindoles 4 [3][4][5]. The protonation of the latter [6], followed by the attack of water at position 1 of cations 12, and subsequent deprotonation of

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

• defluorination, presumably via a Tsuji–Trost-like elimination of the allylic fluoride [18][19]. This sequence represents a marked improvement from the Wittig-including route, lowering the number of synthetic steps and increasing the overall yield [2]. Furthermore, no problematic byproducts are formed, and good

• the exact mechanism is not known, it may involve a reactive carbene intermediate formed by α-elimination of the phosphonate as described in previous reports [23]. Alternatively, a base-promoted autoxidation of phosphonate 7 in the presence of trace amounts of oxygen, followed by olefination may be

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

• protection and elimination of the allylic hydroxy group. We believe that this crucial strategy could be primarily resolved by a quaternary phosphonium salt. After the initial screening of various quaternary phosphonium salts, the azidophosphonium salt [Ph3P+CBr3]N3−, reported by Blanco and co-workers, was

NHC-catalyzed enantioselective synthesis of β-trifluoromethyl-β-hydroxyamides

• Alyn T. Davies,
• Mark D. Greenhalgh,
• Alexandra M. Z. Slawin and
• Andrew D. Smith

Beilstein J. Org. Chem. 2020, 16, 1572–1578, doi:10.3762/bjoc.16.129

• [2 + 2] cycloaddition with the trifluoroacetophenone derivative to give VI [60]. Elimination of the NHC catalyst completes the catalytic cycle and provides the corresponding β-lactone product. Subsequent ring opening with a suitable nucleophilic amine leads to the isolable β-trifluoromethyl-β

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

• flash column chromatography on silica gel, presumably, owing to facile β-elimination of hydrogen fluoride. To isolate a stable product, the reaction mixture was treated with sodium borohydride in ethanol, which effected the reduction of the keto group affording the corresponding alcohol 4a in 52% yield

One-pot synthesis of 1,3,5-triazine-2,4-dithione derivatives via three-component reactions

• Gui-Feng Kang and
• Gang Zhang

Beilstein J. Org. Chem. 2020, 16, 1447–1455, doi:10.3762/bjoc.16.120

• nucleophilic addition of another molecule 2 takes place to furnish the tricomponent adduct 4, which undergoes elimination of ammonia to afford the corresponding ring-closed intermediate 7 [37]. The latter undergoes a proton-transfer process to form intermediate 10 [38]. Thereafter, the subsequent step involves

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

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

• cyclopropylcarbinyl radical 5. Then, the radical 5 opens to form the homoallylic radical 6, followed by the addition of olefins to this radical form the 5-hexenyl radical 7. The ring closure of the radical 7 and the elimination of a thiyl radical furnishes the final product 9. When it came to annulations of complex

• cyclization, and an elimination give the desired product 27 (Scheme 7). The use of PhSSPh obviated the undesired reactions, which occurred when using Ph3SnH and Bu3SnH, respectively, as the catalyst for this reaction. Oxidation reactions Not only can disulfide catalysts induce cycloadditions of olefins but

Recent synthesis of thietanes

• Jiaxi Xu

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

• accompanied by elimination reactions. 3. Synthesis via cycloadditions Cycloadditions, especially the photochemical [2 + 2] cycloaddition (thia-Paternò–Büchi reaction) of thiones and thioamides with olefins [15][16][17][18], and formal cycloadditions are alternative routes for the construction of thietane

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

• the radical 65 gives a C-centered radical 66, which is captured by TEMPO to form intermediate 67. Elimination of TEMPOH leads to a β-unsaturated oxime 68, which could undergo cyclization by ionic or radical mechanisms to give isoxazoline 63 [114][115]. A similar cyclization with the formation of

• , respectively (Scheme 48) [137]. Presumably, the C-centered radical formed after 5-exo-trig cyclization of the oxime radical recombines with TEMPO. The resulting adduct undergoes β-elimination of TEMPOH with the formation of final unsaturated compounds. The intermediate coupling product of the C-centered

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

• oxidative addition of the Pd(0) species to alkene intermediate 8a leads to Pd-complex I. Intramolecular coordination of Pd-complex I with the C–C double bond forms complex II which is followed by the syn insertion of alkene to give complex III [50][51]. Subsequent β-hydride elimination of III gives complex