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

• years (2008–2020) and focuses on direct and indirect methods to construct anthracene and anthraquinone frameworks. Keywords: anthracenes; anthraquinones; Friedel–Crafts cyclization; intramolecular cyclization; metal-catalyzed; Introduction Anthracene is an important aromatic hydrocarbon consisting 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

• heterogeneous vanadium-based catalysts have been employed to obtain alcohols and carbonyl compounds through oxidation, including VOSO4, Na(VO3), VO(acac)2, VOX3, among others. Obtaining ketones and aldehydes from hydrocarbon compounds through vanadium-mediated activation of C(sp3)–H bonds in a benzylic position

Cationic oligonucleotide derivatives and conjugates: A favorable approach for enhanced DNA and RNA targeting oligonucleotides

• Mathias B. Danielsen and
• Jesper Wengel

Beilstein J. Org. Chem. 2021, 17, 1828–1848, doi:10.3762/bjoc.17.125

• synthesis and coupling efficiency on the synthesizer, significant loss of the hydrocarbon-linked group was observed during the alkaline deprotection conditions [115]. After insertion into a 19-mer DNA-ON, modification 79 did not show any significant increase in Tm. This trend was changed when the

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

• cells was shown [37]. Thus, the hexyl and octyl derivatives 25a,b showed the best PCE values of 5.1 and 5.2%, respectively, which is higher than analogues bearing a longer or branched hydrocarbon chain (Scheme 15 and Table 5). If the OSC active layer is prepared with the addition of diiodooctane, the

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

• ”, formally an internal redox reaction where the heterocyclic system is oxidatively aromatized and one of the substituents at C-4 reductively lost as a hydrocarbon. The reaction involves the treatment of a ketone with a solution of ethylcyanoacetate in ethanolic ammonia [7]. A precipitate of the ammonium salt

• ammonium salt of the dicyanoimide. A similar bubbling could be observed when the crystallized imide was treated with ammonia. Guareschi collected the gas evolved from the reaction, and much to his surprise, identified it as the hydrocarbon corresponding to the more substituted alkyl residue of the starting

• terms of overall redox transformation, the reaction formally “hydrolyses” a ketone into a hydrocarbon and a carboxylic acid, and the mechanism remained a black box for over a century, being eventually clarified only in 2007 by a team of British and Russian chemists [8]. One important starting

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• methodologies for these compounds in the literature. In most cases, the pyrrolidine ring is formed from an amine with a hydrocarbon chain that also carries a functional group at the appropriate distance that allows the cyclization process to take place. In the case of substituted pyrrolidines, the

• . Starting imine 135 with two well-defined stereogenic centers at the hydrocarbon backbone were prepared as a mixture of (RS)- and (SS)-diastereoisomers from ᴅ-glutamic acid. After nucleophilic addition to the imine, a successive cyclization–desulfinylation occurred to give the corresponding piperidinone

Valorisation of plastic waste via metal-catalysed depolymerisation

• Francesca Liguori,
• Carmen Moreno-Marrodán and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

• Polyolefins Due to the intrinsic chemical resistance of the hydrocarbon skeleton devoid of functional groups, polyolefins are neither prone to chemical recycling nor biodegradable [131][132]. Hence, they are more commonly repurposed via mechanical recycling, burned or just discarded [133][134

• in >97% yield into liquid hydrocarbon (alkane) products having a narrow distribution of the molecular weight (960–1130 g⋅mol−1) under 11.7 bar H2 at 300 °C and solvent-free conditions [146]. The pyrolysis oils produced may be used as lubricants, waxes or further processed into detergents and

• °C provided a hydrocarbon oil in 92% yield, 71.4% of which were attributable to styrene monomer [156]. A decrease of 56 kJ mol−1 for the activation energy of PS depolymerisation was calculated in the presence of the catalysts. More recently, high-porosity montmorillonite (Mt) was used to prepare Mg

Synthesis and physicochemical evaluation of fluorinated lipopeptide precursors of ligands for microbubble targeting

• Masayori Hagimori,
• Estefanía E. Mendoza-Ortega and
• Marie Pierre Krafft

Beilstein J. Org. Chem. 2021, 17, 511–518, doi:10.3762/bjoc.17.45

• hydrophobic chains (CnF2n+1, n = 6, 7, 8, 1–3) grafted through a lysine moiety on a hydrophilic chain composed of a lysine–serine–serine (KSS) sequence followed by 5 SG sequences. These F-lipopeptides are precursors of targeting lipopeptide conjugates. A hydrocarbon counterpart with a C10H21 chain (4) was

• interface, with equilibrium surface pressures reaching ≈7–10 mN m−1 versus less than 1 mN m−1 only for their hydrocarbon analog 4. The F-lipopeptides penetrate in the DPPC monolayers in both liquid expanded (LE) and liquid condensed (LC) phases without interfacial film destabilization. By contrast, 4

• . By contrast, the hydrocarbon lipopeptide led to microbubbles with a larger mean diameter and a significantly lower stability. Keywords: adsorption at fluid interfaces; drug delivery; microbubble targeting; molecular imaging; monolayer; perfluoroalkylated lipopeptide; solid-phase peptide synthesis

Biochemistry of fluoroprolines: the prospect of making fluorine a bioelement

• Vladimir Kubyshkin,
• Rebecca Davis and
• Nediljko Budisa

Beilstein J. Org. Chem. 2021, 17, 439–460, doi:10.3762/bjoc.17.40

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• opposite to the CF2 moiety, which was followed by the recyclization of the intermediate diradical (Scheme 42). The activation energy for the rearrangement of 90 was lower by 9.4 kcal/mol than for the parent hydrocarbon system 92. The activation energy of the trans-isomer 91 was greater than that of cis

• rearrangement of 1,1-difluoro-2-methylenecyclopropane (96) (Scheme 45) [92]. At 210 °C the rate of cleavage of the proximal bond was only 3.8 times faster than for the analogous hydrocarbon. It was also observed that the equilibrium lay significantly in favor of the rearranged product 97, which was by 1.9 kcal

• /mol more stable. The thermal ring opening of the tosyl-substituted 1,1-difluoro-2,2-dimethyl-3-methylenecyclopropane 98 led to the thermodynamically more stable products 99 and 100, respectively (Scheme 46) [93]. Spiropentane rearrangements: Gajewsky found that the rearrangement of the hydrocarbon

Vicinal difluorination as a C=C surrogate: an analog of piperine with enhanced solubility, photostability, and acetylcholinesterase inhibitory activity

• Yuvixza Lizarme-Salas,
• Alexandra Daryl Ariawan,
• Ranjala Ratnayake,
• Hendrik Luesch,
• Angela Finch and
• Luke Hunter

Beilstein J. Org. Chem. 2020, 16, 2663–2670, doi:10.3762/bjoc.16.216

• compound for medicinal chemistry. However, piperine has some problematic physicochemical properties including poor aqueous solubility and a susceptibility to UV-induced degradation. In this work, we designed an analog of piperine in which the central conjugated hydrocarbon chain is replaced with a vicinal

A new method for the synthesis of diamantane by hydroisomerization of binor-S on treatment with sulfuric acid

• Rishat I. Aminov and
• Ravil I. Khusnutdinov

Beilstein J. Org. Chem. 2020, 16, 2534–2539, doi:10.3762/bjoc.16.205

• be emphasized that the reaction selectively gives only one of the possible isomers, hydrocarbon 3с, which is confirmed by 1H and 13C NMR spectral data. The 13C NMR spectrum of compound 3с shows five characteristic carbon signals at 33.44, 35.64, 37.84, 38.30, and 40.49 ppm, coinciding with the

• starting binor-S (2) being recovered unchanged. The reaction of hydrocarbon 2 with hydrochloric acid proceeds with the addition of HCl to the cyclopropane ring and results in the formation of a mixture of mono- and dichloro derivatives, the synthesis of which has been reported [13][14]. When sulfuric acid

Design and synthesis of a bis-macrocyclic host and guests as building blocks for small molecular knots

• Elizabeth A. Margolis,
• Rebecca J. Keyes,
• Stephen D. Lockey IV and
• Edward E. Fenlon

Beilstein J. Org. Chem. 2020, 16, 2314–2321, doi:10.3762/bjoc.16.192

• trefoil knots have been prepared with an all-hydrocarbon example by the Itami group [7] and the synthesis of a single enantiomer by Leigh’s group [8]. Complexity has also been achieved with recent work showing that eight-crossing knots [9][10][11] and a nine-crossing composite knot can be synthesized [12

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

• ’ “Suman”, which means “Sunflower”), a beautifully simple yet much effective bowl-shaped C3-symmetric polycyclic aromatic hydrocarbon having three benzylic positions clipped between three phenyl rings in the triphenylene framework has attracted a tremendous attention of researchers worldwide. Therefore

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

• another, paving the synthetic roadmap to many natural and unnatural compounds. While C–H bonds are not normally considered as functional groups, these are, however, ubiquitous, for example, in hydrocarbon fuels and in alkyl groups of countless organic molecules. The modification of unactivated C–H

• (especially C(sp3)–H) bonds into other functional groups would not only enormously expand the synthetic maneuverability but would also intensify the use of hydrocarbon feedstocks in organic synthesis. In this context, the advantage of direct C–H fluorination over traditional fluorination methods is that it

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

• library of 259 molecular tweezers through an ethidium bromide (EB) displacement assay, show a negligible DNA transfection efficiency (Figure 3). However, the derivative 15, with two lipophilic hydrocarbon chains, results in a remarkable DNA delivery and transfection [35]. These two hydrocarbon chains

Polarity effects in 4-fluoro- and 4-(trifluoromethyl)prolines

• Vladimir Kubyshkin

Beilstein J. Org. Chem. 2020, 16, 1837–1852, doi:10.3762/bjoc.16.151

• additional polarity drop associated with partial mutual compensation of the CF3 and the amide dipoles (Figure 7). Indeed, this occurs experimentally. In fact, the lipophilicity contribution from the CF3 group in 3 and 4 (ΔlogPH/CF3 +0.7) is notably larger compared to an isolated CF3 group in a hydrocarbon

One-pot synthesis of isosorbide from cellulose or lignocellulosic biomass: a challenge?

• Isaline Bonnin,
• Raphaël Mereau,
• Thierry Tassaing and
• Karine De Oliveira Vigier

Beilstein J. Org. Chem. 2020, 16, 1713–1721, doi:10.3762/bjoc.16.143

• showed that the acidity is important in the conversion of lignocellulosic biomass to isosorbide and that the acid can react with the metal-supported catalyst. Another study was devoted to the use of boron phosphate for the conversion of cellulose into liquid hydrocarbon C1–C6 over Ru/C [23]. A mixture of

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

• (PDI) aggregates have become a popular choice of heterogeneous photocatalyst. As PDI is a large, planar, polyaromatic hydrocarbon molecule, it spontaneously forms ordered 1D supramolecular assemblies through efficient π–π stacking and side chain interactions [192]. Despite the PDI units having only non

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

• improve protein stability, natural hydrocarbon amino acids were replaced with Pff 77a. The effect of enhanced protein stability upon this replacement is referred as to ‘fluoro-stabilization effect’ [56]. 1.7. Knoevenagel condensation of methyl isocyanoacetate Three isomers of fluorinated phenylalanines

Photocatalytic deaminative benzylation and alkylation of tetrahydroisoquinolines with N-alkylpyrydinium salts

• David Schönbauer,
• Carlo Sambiagio,
• Timothy Noël and
• Michael Schnürch

Beilstein J. Org. Chem. 2020, 16, 809–817, doi:10.3762/bjoc.16.74

• interest [27]. In our continuing quest to develop methods for the introduction of pure hydrocarbon residues avoiding volatile reagents [28][29], our attention was drawn to stable N-alkyl-(2,4,6-triphenyl)pyridinium salts (Katritzky salts) as alkylation reagents in the context of non-directed C–H

Six-fold C–H borylation of hexa-peri-hexabenzocoronene

• Mai Nagase,
• Kenta Kato,
• Akiko Yagi,
• Yasutomo Segawa and
• Kenichiro Itami

Beilstein J. Org. Chem. 2020, 16, 391–397, doi:10.3762/bjoc.16.37

• , Nagoya, 464-8602, Japan 10.3762/bjoc.16.37 Abstract Hexa-peri-hexabenzocoronene (HBC) is known to be a poorly soluble polycyclic aromatic hydrocarbon for which direct functionalization methods have been very limited. Herein, the synthesis of hexaborylated HBC from unsubstituted HBC is described. Iridium

Synthesis, liquid crystalline behaviour and structure–property relationships of 1,3-bis(5-substituted-1,3,4-oxadiazol-2-yl)benzenes

• Afef Mabrouki,
• Malek Fouzai,
• Armand Soldera,
• Abdelkader Kriaa and
• Ahmed Hedhli

Beilstein J. Org. Chem. 2020, 16, 149–158, doi:10.3762/bjoc.16.17

• , while their hydrocarbon counterparts are non-mesomorphic [20]. On the other hand, many heterocyclic-based liquid crystals have been designed and then synthesised due to their large scope of applications [21]. In this context, the 1,3,4-oxadiazole group was of a particular interest from a synthetic

• prepared compounds perform three kinds of conformations, A, B and C. The hydrocarbon derivatives exhibit conformation A (Figure 5a–a”), whereas the fluorocarbon analogues adopt, depending on whether they carry linking segment C2H4S or not, the conformation B (Figure 5b–b”) or C (Figure 5c–c”). In Figure 6

• standard. The oxadiazole moieties are thought to be responsible for the majority of the dipole moment in the prepared compounds. Due to the electron-donating effect of alkyl groups in combination with the electron-accepting oxadiazole [35], the prepared hydrocarbon compounds are expected to perform dipole

Bacterial terpene biosynthesis: challenges and opportunities for pathway engineering

• Eric J. N. Helfrich,
• Geng-Min Lin,
• Christopher A. Voigt and
• Jon Clardy

Beilstein J. Org. Chem. 2019, 15, 2889–2906, doi:10.3762/bjoc.15.283

• potential with molecular structure is severely restricted. The canonical terpene biosynthetic pathway uses a single enzyme to form a cyclized hydrocarbon backbone followed by modifications with a suite of tailoring enzymes that can generate dozens of different products from a single backbone. This

• a linear polyene with branching methyl groups that form the core hydrocarbon structure in a single enzyme-catalyzed step [9]. The enzyme, which is called terpene cyclase, holds the linear methyl-branched polyene in a defined conformation that initiates a series of carbocation-driven cyclizations and

• rearrangements, creating the basic hydrocarbon skeleton of a terpene [10][11]. This basic hydrocarbon skeleton is then modified to generate a large number of terpenoid structures, which can be further modified by addition of other building blocks, like sugars, amino acids, or fatty acids [12]. Terpenes are named

Emission and biosynthesis of volatile terpenoids from the plasmodial slime mold Physarum polycephalum

• Xinlu Chen,
• Tobias G. Köllner,
• Wangdan Xiong,
• Guo Wei and
• Feng Chen

Beilstein J. Org. Chem. 2019, 15, 2872–2880, doi:10.3762/bjoc.15.281

•  1B). The two unidentified are putative sesquiterpenoids. Compound 3 is a putative hydrocarbon sesquiterpene with a molecular mass of 204 (Figure 1C). In contrast, compound 4 has a molecular formula of C15H22O and a molecular mass of 218 (Figure 1C). It was predicated to be a sesquiterpene aldehyde

• specific terpene synthases. PpolyTPS4 produced α-muurolene (5) as a major product, and (E)-β-caryophyllene (2) and an unidentified sesquiterpene hydrocarbon as minor products. These three terpenes could also be found in the headspace of P. polycephalum with α-muurolene as the most abundant constituent

• repeated three times with similar results. 1, linalool; 2, (E)-β-caryophyllene; 3, unidentified sesquiterpene hydrocarbon (compound 3); 4, unidentified putative sesquiterpene aldehyde (compound 4); 5, α-muurolene. B) Structures of known terpenoids. The structure of compound 2 shows the (−)-enantiomer of (E