Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• furylmercurials 91 via syn-addition of acetylene, which on carbonylation yielded the furan-containing carbonyl compound 92 (Scheme 30) [83]. It was proposed that initially mercuration of acetylene bonds via mercurinium like ions or π-complex takes place. Then the structure was stabilized through hydrogen bonding

• between alcohol and carbonyl groups (path a) or by hemiketal formation (path b). Thus, the chloride ion attacks from the frontside, producing syn-addition molecules that, upon dehydration, formed furan rings. Later they had reported similar mercuration of arylacetylenes to synthesize a broad spectrum of

• cyclization of secondary and tertiary l-alkynyl-2,3-epoxyalcohols 131a [94]. This is an example of a Hg(II)-salt-catalyzed rearrangement of 1-alkynyl-2,3-epoxy alcohols to substituted furans. The furan 133a was formed by dehydration of intermediate 132a through the corresponding oxonium cation. When R3 is an

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• brominated naphthalene 153 with PhLi yielded compound 154, which collapsed to naphthotriyne 155 at elevated temperatures. Sequential addition of furan generated the trisadduct 156. Then, dibenz[a,c]anthracene 158 was obtained in good yield (86%) in two steps by hydrogenation of 156 and further dehydration of

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

• amiodarone (93, antiarrhythmic activity) (Scheme 32A) [166]. The method consists of a tandem, regioselective Fe(III)-catalyzed C–H halogenation, followed by an Fe or Cu-catalyzed O-arylation to access the benzo[b]furan derivatives in high yields. Several natural products and pharmacologically active targets

• bearing the furan ring were synthesized in moderate to good yields. Overall, the new protocol presented a broad scope and excellent functional group tolerance, allowing the synthesis of valuable molecules like corsifuran C (94), moracin F (95), and caleprunin B (96) (Scheme 32D). In 2020, Chattopadhyay

Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications

• Nikita Brodyagin,
• Martins Katkevics,
• Venubabu Kotikam,
• Christopher A. Ryan and
• Eriks Rozners

Beilstein J. Org. Chem. 2021, 17, 1641–1688, doi:10.3762/bjoc.17.116

• precursors in vitro [133]. Furan (F, Figure 8) as a reactive nucleobase mimic was well accommodated in a duplex with DNA without decreasing its thermal stability [134]. Upon oxidation of the furan ring, F-modified PNAs reacted preferentially with cytosine and adenine and irreversibly crosslinked with ssDNA

Recent advances in the application of isoindigo derivatives in materials chemistry

• Andrei V. Bogdanov and
• Vladimir F. Mironov

Beilstein J. Org. Chem. 2021, 17, 1533–1564, doi:10.3762/bjoc.17.111

• arrangement of the isoindigo and DPP fragments relative to each other was demonstrated [96]. Thus, the dihedral angle 179° in a furan polymer determines the conductivity μh/μe = 0.01 cm2⋅V−1⋅s−1/1.6⋅10−3 cm2⋅V−1⋅s−1, while polymers containing thiophene or p-phenylene spacers did not possess conductivity at

Cascade intramolecular Prins/Friedel–Crafts cyclization for the synthesis of 4-aryltetralin-2-ols and 5-aryltetrahydro-5H-benzo[7]annulen-7-ols

• Jie Zheng,
• Shuyu Meng and
• Quanrui Wang

Beilstein J. Org. Chem. 2021, 17, 1481–1489, doi:10.3762/bjoc.17.104

• [10][11][12][13][14]. For example, Nagumo and coworkers have developed a Prins/Friedel–Crafts cyclization of homocinnamyl alcohols with aromatic aldehydes under the action of BF3·Et2O affording 2H-indeno[1,2-b]furan derivatives [15]. Likewise, Hinkle and coworkers reported in 2017 a three-step domino

• diastereoselectivity (cis/trans ratio = 1:99). The preferential formation of the trans-configured products for furan nucleophiles may be due to the fact that the addition of furan is reversible leading to equilibration to the more stable trans product. To test this hypothesis, we monitored the reaction by HPLC (Table

• , the reactions with other 2-(2-vinylphenyl)ethanals 13b–g carrying different substituents on the benzene ring or on the side chain with veratrole and furan as the nucleophiles were investigated. As can be seen from Scheme 7, under comparable conditions, most reactions proceeded smoothly with the

Organocatalytic asymmetric Michael/acyl transfer reaction between α-nitroketones and 4-arylidenepyrrolidine-2,3-diones

• Chandrakanta Parida and
• Subhas Chandra Pan

Beilstein J. Org. Chem. 2021, 17, 1447–1452, doi:10.3762/bjoc.17.100

• available bifunctional thiourea catalyst was employed in the methodology. Reactions of α-nitroketones with unsaturated pyrazolone and with 4-benzylidenepyrrolidine-2,3-dione. Reaction of 4-benzylidenedihydrofuran-2,3-dione (4) with α-nitroketones 2b,c. Reaction conditions: furan 4 (0.1 mmol), α-nitroketone

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

Synthesis of trifluoromethyl ketones by nucleophilic trifluoromethylation of esters under a fluoroform/KHMDS/triglyme system

• Yamato Fujihira,
• Yumeng Liang,
• Makoto Ono,
• Kazuki Hirano,
• Takumi Kagawa and
• Norio Shibata

Beilstein J. Org. Chem. 2021, 17, 431–438, doi:10.3762/bjoc.17.39

• effect on the yield of the reaction of 1g (Table 2, entries 3–6, 58–72%). Next, a range of common oxygen and sulfur-containing compounds such as furan, tetrahydrofuran, 1,4-dioxane, thiophene, benzo[b]thiophene, dibenzo[b,d]thiophene, and diphenylsulfane were also screened. These substances also have

Identification of volatiles from six marine Celeribacter strains

• Anuj Kumar Chhalodia,
• Jan Rinkel,
• Dorota Konvalinkova,
• Jörn Petersen and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2021, 17, 420–430, doi:10.3762/bjoc.17.38

• (20), in addition to 3-methylbutan-4-olide (21) and 4-methylhex-5-en-4-olide (22), was detected in strain-specific patterns, with almost all of these compounds present in C. marinus; only C. halophilus did not emit lactones. Furans included furan-2-ylmethanol (23), furfural (24), and 2-acetylfuran (25

Diels–Alder reaction of β-fluoro-β-nitrostyrenes with cyclic dienes

• Savva A. Ponomarev,
• Roman V. Larkovich,
• Alexander S. Aldoshin,
• Andrey A. Tabolin,
• Sema L. Ioffe,
• Jonathan Groß,
• Till Opatz and
• Valentine G. Nenajdenko

Beilstein J. Org. Chem. 2021, 17, 283–292, doi:10.3762/bjoc.17.27

• dienes. Moreover, it was found that furan did not react with nitrostyrenes 1. Furthermore, we performed some subsequent transformations of the fluorinated norbornenes prepared to investigate their chemical properties and to demonstrate their utility (Scheme 6). These reactions were carried out to involve

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

• studies on biological activity, chemosensors, and fluorescence, were developed via the reaction of furan-2,3-diones or acylpyruvic acids in the presence of carbodiimides with o-aminothiophenols. The target enaminones were formed together with pharmaceutically interesting 2-hydroxy-2H-1,4-benzothiazin-3(4H

• )-ones. A selective synthetic approach to 2-hydroxy-2H-1,4-benzothiazin-3(4H)-ones was developed via the solvent-switchable reaction of furan-2,3-diones with o-aminothiophenol. Preliminary biological assays (antimicrobial, acute toxicity) of the new compounds were carried out. Keywords: acylpyruvic acid

• ; 1,4-benzothiazine; cyclocondensation; diversity-oriented synthesis; furan-2,3-dione; Introduction Enaminones fused to the 1,4-benzoxazine-2-one I or quinoxaline-2(1H)-one II moiety (Figure 1) represent an intensively investigated class of enamines. Undying interest in these compounds is due to the

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

• synthesized through the oxidation of lawsone (6), in the presence of sodium persulfate, followed by methylation [25]. The cyclization of binaphthyl 16 was then attempted taking into consideration the photolytic cyclization of binaphthyls to form pentacyclic furan derivatives [8][18][22]. However, the

Automated high-content imaging for cellular uptake, from the Schmuck cation to the latest cyclic oligochalcogenides

• Rémi Martinent,
• Javier López-Andarias,
• Dimitri Moreau,
• Yangyang Cheng,
• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2020, 16, 2007–2016, doi:10.3762/bjoc.16.167

• ion-pair interaction. For example, the replacement of the pyrrole core to pyridine in 8 or to furan results in a much weaker binding because of the repulsion force between the lone pair on the heteroatom and the oxoanion. The superior oxoanion binding of the Schmuck cation makes GCP-based peptides

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

• ) in different positions provided good to excellent isolated yields of the corresponding products 3b–g and 3j–o that ranged from 94 to 98% in a stipulated period of time, as specified in Table 5. Further, heteroaromatic aldehydes, such as furan-2-aldehyde (2p) and thiophene-2-aldehyde (2q) produced the

• 3-Br: 2s) underwent the reaction with ethyl acetoacetate (4) and urea (5) to form the corresponding products (7h–j) in good isolated yields that ranged from 93–96% (Table 6, entries 8–10). Heteroaromatic aldehydes, such as furan-2-aldehyde (2p) and thiophene-2-aldehyde (2q) showed a good reactivity

Synthesis and highly efficient light-induced rearrangements of diphenylmethylene(2-benzo[b]thienyl)fulgides and fulgimides

• Vladimir P. Rybalkin,
• Sofiya Yu. Zmeeva,
• Lidiya L. Popova,
• Valerii V. Tkachev,
• Andrey N. Utenyshev,
• Olga Yu. Karlutova,
• Alexander D. Dubonosov,
• Vladimir A. Bren,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2020, 16, 1820–1829, doi:10.3762/bjoc.16.149

• fulgides 3Z and 3E are shown in Figure 1 and Figure 2. Fulgide 3Z possesses Z-configuration at the double bond С(4)=С(5). The 3-methoxy-2-benzo[b]thiophene moiety in 3Z is planar and is almost coplanar with the planar furan-2,5-dione fragment (the dihedral angle is equal to 3.9°). The phenyl rings are

• rotated about the C–Ph bonds by respectively 84.9° (Ph(C(15)-C(20)) and 109.0° (Ph(C(21)-C(26)) relative to the furan-2,5-dione plane. The list of lengths and valence angles of 3Z is given in Table S1 (Supporting Information File 1). Fulgide 3E has E-configuration at the double bond С(4)=С(5). The 3

• -methoxy-2-benzo[b]thiophene moiety in 3E is rotated relative to the furan-2,5-dione fragment by an angle of 36.5°. The torsion angle of the phenyl ring Ph(C(15)–C(20)) relative to the furan-2,5-dione plane (41.5°) is almost twice lesser than that in 3Z, whereas the torsion angle of the phenyl ring Ph(C(21

Microwave-assisted efficient one-pot synthesis of N²-(tetrazol-5-yl)-6-aryl/heteroaryl-5,6-dihydro-1,3,5-triazine-2,4-diamines

• Moustafa Sherief Moustafa,
• Ramadan Ahmed Mekheimer,
• Saleh Mohammed Al-Mousawi,
• Mohamed Abd-Elmonem,
• Hesham El-Zorba,
• Afaf Mohamed Abdel Hameed,
• Tahany Mahmoud Mohamed and
• Kamal Usef Sadek

Beilstein J. Org. Chem. 2020, 16, 1706–1712, doi:10.3762/bjoc.16.142

• (150 MHz, DMSO-d6) δ 61.28, 120.92, 123.91, 130.73, 132.27, 143.13, 147.95, 154.42, 157.62, 157.94; anal. calcd for C10H10N10O2: C, 39.74; H, 3.33; N, 46.34; found: C, 39.68; H, 3.47; N, 46.52. 6-(Furan-2-yl)-N2-(5H-tetrazol-5-yl)-5,6-dihydro-1,3,5-triazine-2,4-diamine (4i). Colorless crystals; mp 208

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

• ). The cyclization of internal alkyne substrate 24b yielded pyrrolidine ring-fused cyclopentenone 25b in similar yield but lower diastereoselectivity. Finally, N-propargyl-N-[2-(trifluoromethyl)allyl] ether 24d, containing an ether linkage instead of the aforementioned sulfonamide linkage, gave furan

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

• reactions. We further extended the scope of this transformation to five-membered heterocyclic MBH adducts. To our delight, except pyrroles, the proposed methodology was amenable to MBH adducts of furan and thiophene (3n–q, 70–80%). The mechanistic pathway for the triazolation proceeded via a nucleophilic

• the presence of CuI (5 mol %), triphenylphosphine (1 equiv), bromomethane (1.1 equiv), and sodium azide (2 equiv). Unexpectedly, the reaction yielded (Z)-methyl-2-(bromomethyl)-3-phenylacrylate (58%) over the expected triazole. Similarly, the MBH adduct derived from furan, 1i, and phenylacetylene (2b

• ) also yielded (Z)-methyl 2-(bromomethyl)-3-(furan-2-yl)acrylate (42%) rather than the expected triazole (Scheme 4). Thereby, it was clearly evident that the addition of the individual reagents prevented the formation of complicated triazoles. Interestingly, the MBH adducts derived from salicylaldehydes

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

• -donating functional groups. Substrates containing pyridine, furan, and thiophene as heterocyclic fragments were also successfully converted into the corresponding alcohols 4. However, in the reaction of the enol ether derived from 2-acetyl-N-methylpyrrole, ketone 3p did not undergo reduction with sodium

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

Recent synthesis of thietanes

• Jiaxi Xu

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

• (198), or N-phenylmaleimide (199) with the formation of the corresponding spirothietane derivatives 200–202 in good yields. The analogous photoreactions of 2-thioparabanate (203) in the presence of indene (198), benzo[b]furan (204), or N-phenylmaleimide (199) gave spirothietanes 205–207 as well [64

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• reported a metal-free photoarylation of five-membered heteroarenes with aryldiazonium salts and meso-arylated porphyrin derivatives as photoredox catalyst [11]. Compounds such as furan, thiophene, and N-Boc-pyrrole derivatives were obtained by this methodology in 29–81% yields (Scheme 3). The key-step of

Reaction of indoles with aromatic fluoromethyl ketones: an efficient synthesis of trifluoromethyl(indolyl)phenylmethanols using K₂CO₃/n-Bu₄PBr in water

• Thanigaimalai Pillaiyar,
• Masoud Sedaghati and
• Gregor Schnakenburg

Beilstein J. Org. Chem. 2020, 16, 778–790, doi:10.3762/bjoc.16.71

• trifluoroacetophenones did not significantly influence the yield of the reaction. The trifluoromethyl ketones having electron-rich heteroaromatics such as 2-(trifluoroacetyl)furan (2g) and 2-(trifluoroacetyl)thiophene (2h) gave the desired products 3g (97%) and 3h (98%) in excellent yields. Next, the role of fluorine in

Synthesis and circularly polarized luminescence properties of BINOL-derived bisbenzofuro[2,3-b:3’,2’-e]pyridines (BBZFPys)

• Ryo Takishima,
• Yuji Nishii,
• Tomoaki Hinoue,
• Yoshitane Imai and
• Masahiro Miura

Beilstein J. Org. Chem. 2020, 16, 325–336, doi:10.3762/bjoc.16.32

• condensed (hetero)acenes from rather simple polyarenes, in which several aromatic units are connected with each other through appropriate linker units [2][3][4][5][6][7][8][9][10][11]. Recently, we reported the synthesis and optical properties of a series of furan-fused aromatics via the formal

• connecting the naphthyl rings [34][35][36]. In these compounds, the hydroxy groups are remained untouched or protected as the corresponding ethers or esters. We envisioned that the assembly of the binaphthyl-fused furan motif embedding the BINOL hydroxy groups into the polyaromatic scaffolds would lead to

• the development of new chiroptical materials. Such molecules, however, have hardly been investigated to date probably because of the synthetic difficulty to obtain them as pure enantiomers. There have been only a few reports for the binaphthyl-fused furan-ring construction from the C3-alkynylated