Regioselectivity of the S_EAr-based cyclizations and S_EAr-terminated annulations of 3,5-unsubstituted, 4-substituted indoles

• Jonali Das and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2022, 18, 293–302, doi:10.3762/bjoc.18.33

• catalysis diazo compound 30 delivered 3,4-fused tricyclic indole derivative 32 which underwent spontaneous rearrangement to thermodynamically more stable naphthalene derivative 33 upon standing for a few hours. To the best of our knowledge, this is the only report of catalyst-controlled C3 versus C5

Iridium-catalyzed hydroacylation reactions of C1-substituted oxabenzonorbornadienes with salicylaldehyde: an experimental and computational study

• Angel Ho,
• Austin Pounder,
• Krish Valluru,
• Leanne D. Chen and
• William Tam

Beilstein J. Org. Chem. 2022, 18, 251–261, doi:10.3762/bjoc.18.30

• (EDGs) led to naphthol compounds 9, while electron-withdrawing groups (EWGs) led to the anticipated ring-opened 1,1,2-trisubstituted naphthalene framework 10 [61]. On the other hand, Edmunds and co-workers described a ring-opening reaction of C1-substituted OBDs 5 with arylboronic acids that was

• catalyzed by rhodium/diene to afford the 1,2,4-trisubstituted naphthalene framework 8 with complete regio- and stereocontrol (Scheme 1) [62][63]. In 2015, the Nishimura group reported the first iridium-catalyzed addition of salicylaldehydes 14 to bicyclic alkenes 11 (Scheme 1) [64]. Although a variety of

Trichloroacetic acid fueled practical amine purifications

• Aleena Thomas,
• Baptiste Gasch,
• Enzo Olivieri and
• Adrien Quintard

Beilstein J. Org. Chem. 2022, 18, 225–231, doi:10.3762/bjoc.18.26

• feasibility of a TCA-induced amine purification, we first focused on the study of the different parameters crucial for such a process. For such purpose, we initially studied the purification of a model 1:1 mixture of dicyclohexylamine and naphthalene (Table 1). Gratifyingly, adding 3 equivalents of TCA to

• this mixture dissolved in EtOAc, precipitation of the amine salt enabled the removal of naphthalene in the solvent. Beside the choice of the solvent for the crystallization which strongly depends on the solubility of the protonated amine salts involved, we first focused on the optimization of the

• potential of this system. In order to highlight the interest of this technique and its broad applicability, dicyclohexylamine could be purified from various mixtures containing 1 equivalent of structurally different impurities (Table 2). Aside from naphthalene (Table 2, entry 1), dicyclohexylamine could be

Multi-faceted reactivity of N-fluorobenzenesulfonimide (NFSI) under mechanochemical conditions: fluorination, fluorodemethylation, sulfonylation, and amidation reactions

• José G. Hernández,
• Karen J. Ardila-Fierro,
• Dajana Barišić and
• Hervé Geneste

Beilstein J. Org. Chem. 2022, 18, 182–189, doi:10.3762/bjoc.18.20

• milling (Figure 1b and Figure S5 in Supporting Information File 1). Other substrates such as naphthalene and N-Boc-aniline proved unreactive under the milling conditions with NFSI. However, the more activated arene 2-naphthol underwent double fluorination affording 1,1-difluoronaphthalen-2(1H)-one as the

1,2-Naphthoquinone-4-sulfonic acid salts in organic synthesis

• Ruan Carlos B. Ribeiro,
• Patricia G. Ferreira,
• Amanda de A. Borges,
• Luana da S. M. Forezi,
• Fernando de Carvalho da Silva and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 53–69, doi:10.3762/bjoc.18.5

• colored product and determine its concentration by a spectrophotometric method, is the most convenient, simple, and inexpensive method for analytical work. Hiyama [53] noted that little is known about the biological activities of sulfonic naphthalene derivatives, despite being important intermediates for

• the synthesis of dyes. Then, he prepared several naphthalene sulfonic derivatives and tested them for their effects on bacteria and viruses, but none of the compounds presented important activity. Hashimoto and co-workers [54] were the first to apply β-NQSNa for the qualitative analysis of

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• high loading of 20 mol % CPA 18 with a 1-pyrenyl group at the 6,6’-position of the spiro backbone was preferred as the best catalyst for this transformation. Encouragingly, the double atroposelective C–H amination reaction took place and afforded the desired 1,5-dicarbazole naphthalene derivative 63 in

• context, Bai and co-workers (2019) developed the direct intermolecular enantioselective C–H amination of N-aryl-2-naphthylamines 92 with azodicarboxylates 93 to prepare N–C atropisomers of nonbiaryl naphthalene-1,2-diamine 94. In the presence of chiral phosphoric acids (CPA 15), the desired product 94 was

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

• vinylindoline derivatives 125 was achieved by utilizing chiral ligands like chiral binaphane (Scheme 37) [91]. They had observed that the formation of six- and seven-membered rings required elevated temperatures. Subsequently, the same group studied the cyclization of arylene 126 to furnish naphthalene

Chemical syntheses and salient features of azulene-containing homo- and copolymers

• Vijayendra S. Shetti

Beilstein J. Org. Chem. 2021, 17, 2164–2185, doi:10.3762/bjoc.17.139

• , anti-Kasha photophysics, and a small HOMO–LUMO gap when compared to its isomer, naphthalene. These properties make azulene-containing polymers an intriguing entity in the field of functional polymers, especially for organic electronic applications like organic field-effect transistors (OFET) and

• ). The striking feature of azulene is its permanent dipole moment (1.08 D) and blue color unlike its colorless isomer naphthalene [4]. Azulene possesses an unequal distribution of electron density between its highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO

• ) resulting in a relatively small electron repulsion energy in the first singlet excited state and thus, a small HOMO–LUMO (S0–S1) gap compared to naphthalene. The large energy gap between its S2 and S1 states (up to 15000 cm−1) makes internal conversion less probable, making azulene emit from the S2 state

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

• -bromonaphthoquinone (140) reacted with vinylacetic acid to afford the allylated compound 141. Then, reduction of 141 and sequential O-methyl-protection furnished naphthalene 142. A Suzuki–Miyaura coupling reaction between 142 and boronic acids afforded 2-naphthylbenzaldehydes 143, which were further subjected to a

• -phenanthrene derivatives 152, also in excellent yields (91–98%) [68]. In 2015, Gribble et al. published a new method to synthesize dibenzo[a,c]anthracene (158) based on a triple benzannulation of naphthalene derivative 153 via a 1,3,6-naphthotriyne synthetic equivalent 155 (Scheme 35) [69]. First, reaction of

• 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

Natural products in the predatory defence of the filamentous fungal pathogen Aspergillus fumigatus

• Jana M. Boysen,
• Nauman Saeed and
• Falk Hillmann

Beilstein J. Org. Chem. 2021, 17, 1814–1827, doi:10.3762/bjoc.17.124

• more likely to survive internalization by lung epithelial cells [147][154][155]. Although DHN-melanin is generally associated with immune evasion it was recently found to be recognized in higher animals via the C-type lectin receptor (MelLec) which interacts with the naphthalene-diol domain of DHN

Development of N-F fluorinating agents and their fluorinations: Historical perspective

• Teruo Umemoto,
• Yuhao Yang and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

• aromatics such as phenol, cresol, and naphthalene were fluorinated in chloroform at 22 °C (Scheme 18). The N-F imide reagent 7-1a fluorinated the sodium salt of diethyl 1-methylmalonate at −10 °C to give the corresponding fluoro product in high yield (96%). Later (1991 and 1992), the same laboratory

Volatile emission and biosynthesis in endophytic fungi colonizing black poplar leaves

• Christin Walther,
• Pamela Baumann,
• Katrin Luck,
• Beate Rothe,
• Peter H. W. Biedermann,
• Jonathan Gershenzon,
• Tobias G. Köllner and
• Sybille B. Unsicker

Beilstein J. Org. Chem. 2021, 17, 1698–1711, doi:10.3762/bjoc.17.118

• ]. Endophytic fungi themselves can produce VOCs. Currently, around 300 fungal VOCs have been characterized, including aliphatic alcohols, ketones, aldehydes, acids and esters, terpenoids, benzenoids, naphthalene derivatives, and cycloalkanes [25][26][27]. Endophytic fungal VOCs are frequently described to

• Muscodor vitigenus and characterized the volatile blend in culture [32]. Naphthalene, an insect deterrent that is used, e.g., in mothballs [33], was the most dominant compound in the fungal volatile blend and showed a repellent effect on the wheat stem sawfly Cephus cinctus in a Y-tube olfactometer

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

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

• studies on naphthalene and the conversion of naphthalene to phthalides, a reaction that, two decades later, became of critical relevance for the industrial synthesis of indigo. It is surprising that, after spending only three years in Siena, Guareschi obtained, in 1879, the prestigious Chair of Medicinal

• of 47. In Turin, Guareschi pursued an amazing range of research topics. The one of ptomaines (alcaloidi cadaverici, cadaverous alkaloids) and the chemistry of naphthalene led to considerable fame for Guareschi because of both his original contributions and his comprehensive reviews of the area. Thus

• the chemistry of naphthalene. The last one dates from 1887 and deals with the formation of isomers in the electrophilic aromatic substitution of naphthalene with chlorine and bromine [32]. This work was done in collaboration with Pietro Biginelli (1860–1937), the only collaborator of Guareschi who

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

Heterogeneous photocatalytic cyanomethylarylation of alkenes with acetonitrile: synthesis of diverse nitrogenous heterocyclic compounds

• Guanglong Pan,
• Qian Yang,
• Wentao Wang,
• Yurong Tang and
• Yunfei Cai

Beilstein J. Org. Chem. 2021, 17, 1171–1180, doi:10.3762/bjoc.17.89

• naphthalene, the reaction successfully provided the benzoindoline 3g in 56% yield. Substrates with an N-Boc group also worked well to deliver the corresponding indoline 3h in 77% yield. Moreover, a scale-up reaction of 1a (2 mmol) was conducted, affording the corresponding product 3a (0.28 g) in a yield of 62

• , delivering the corresponding regioisomers 8l and 8l’ in 62% with 1:1.6 ratio. Moreover, the naphthalene and tetrahydroisoquinoline-derived acrylamides were also compatible, giving the polycyclic products 8m and 8n in 77% and 70%, respectively. Additionally, protecting groups such as isopropyl, benzyl, or

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

Synthesis, structural characterization, and optical properties of benzo[f]naphtho[2,3-b]phosphoindoles

• Mio Matsumura,
• Takahiro Teramoto,
• Masato Kawakubo,
• Masatoshi Kawahata,
• Yuki Murata,
• Kentaro Yamaguchi,
• Masanobu Uchiyama and
• Shuji Yasuike

Beilstein J. Org. Chem. 2021, 17, 671–677, doi:10.3762/bjoc.17.56

• and IR). All the corresponding aromatic proton and carbon atoms on the two naphthalene rings were equivalent in the 1H and 13C NMR spectra of phospholes. These results show that all phosphole derivatives had a symmetric structure in solution. The 31P NMR spectra of these show the typical low-field

• recrystallization. The molecular structure of 2, determined through single-crystal X-ray diffraction analysis, is illustrated in Figure 2, and selected geometrical parameters are shown in Table 1. The results revealed that the naphthalene and fused phosphole rings are almost coplanar (mean deviation = 0.030 Å). The

• angle between each naphthalene ring containing ten carbon atoms is 1.64°, which is smaller than that for group 15 analogs (i.e., N-phenyldibenzo[b,h]carbazole: 4.47° or 2.57° [22], for crystal data, see Figure S2, Supporting Information File 1 and Sb-phenyldinaphtho[2,3-b:2′,3′-d]stibole: 8.05° [23

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

• %), olefins (22.5%) and naphthalene (4.1%) at total HDPE conversion at 350 °C [144]. In another example, hydrocracking of PE was performed over Pt NPs supported on SrTiO3 perovskite nanocuboids [145]. Virgin PE (Mw = 18000–420000 g⋅mol−1) or PE from single-use plastic bags (Mw = 115000 g⋅mol−1) was converted

The synthesis of chiral β-naphthyl-β-sulfanyl ketones via enantioselective sulfa-Michael reaction in the presence of a bifunctional cinchona/sulfonamide organocatalyst

• Deniz Tözendemir and
• Cihangir Tanyeli

Beilstein J. Org. Chem. 2021, 17, 494–503, doi:10.3762/bjoc.17.43

• respect, a bifunctional quinine-derived sulfonamide organocatalyst was developed to catalyze the asymmetric sulfa-Michael reaction of naphthalene-1-thiol with trans-chalcone derivatives. The target sulfa-Michael adducts were obtained with up to 96% ee under mild conditions and with a low (1 mol

• nucleophiles [27][28][29][30]. Thionaphthols, however, are overlooked in sulfa-Michael addition reactions. And to our best knowledge, no study is present concerned with SMAs with naphthalene-1-thiol as the nucleophile for the addition to enones. Encouraged by the good results obtained with enantioselective

• sulfa-Michael additions of thiols to chalcones with sulfonamide-type organocatalysts in the literature [30][31], in this study, a new quinine sulfonamide organocatalyst derivative was developed to catalyze the enantioselective SMA of naphthalene-1-thiol to trans-chalcones under mild conditions and with

Unexpected rearrangements and a novel synthesis of 1,1-dichloro-1-alkenones from 1,1,1-trifluoroalkanones with aluminium trichloride

• Beatrice Lansbergen,
• Catherine S. Meister and
• Michael C. McLeod

Beilstein J. Org. Chem. 2021, 17, 404–409, doi:10.3762/bjoc.17.36

• %. Naphthalene 6h and 2-pyridine 6i were also successfully obtained, however, the reactions with the 3- and 4-pyridines 5j and 5k resulted in complex mixtures from which no desired product, nor starting material, could be observed. The scope of this chemistry also extends to substrates with a shorter

Helicene synthesis by Brønsted acid-catalyzed cycloaromatization in HFIP [(CF₃)₂CHOH]

• Takeshi Fujita,
• Noriaki Shoji,
• Nao Yoshikawa and
• Junji Ichikawa

Beilstein J. Org. Chem. 2021, 17, 396–403, doi:10.3762/bjoc.17.35

• can be successfully applied to cyclization at multiple reaction sites. By using bisacetals bearing a naphthalene core (Ar2) as substrates, tandem cyclization achieved the efficient synthesis of several ortho-fused six-hexagon benzenoids [21]. On the basis of our work mentioned above, we assumed that

• , respectively. Thus, phenylboronic acid ester 3 bearing an acetal moiety functions as a reagent for fused naphthalene ring extension through our cross-coupling/cycloaromatization sequence [31][32][33][34][35]. Hetero[5]helicenes 12 were synthesized via tandem cycloaromatization using teraryl precursors, in

• silica gel column chromatography (hexane/EtOAc = 10:1) gave 1a (1.19 g, 80%). 1,8-Bis{2-[(1,3-dioxolan-2-yl)methyl]phenyl}naphthalene (4b) A DMF (6.7 mL) and H2O (3.3 mL) solution of 1,8-diiodonaphthalene (2b, 759 mg, 2.00 mmol), boronate ester 3 (1.28 g, 4.40 mmol), Pd2(dba)3·CHCl3 (52 mg, 50 μmol

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

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

• isomerization [36]. Several nitrogen nucleophiles have been evaluated as catalysts to promote the difluorocarbene formation from TFDA in order to bring about the cyclopropanation of a 2-siloxybuta-1,3-diene derivative; 1,8-bis(dimethylamino)naphthalene (proton sponge) was found to be particularly effective [37

• reaction of 2-(2,2-difluorocyclopropyl)naphthalene (167) with sodium arylsulfinates 168 under palladium catalysis afforded the 2-fluoroallylic sulfones 166 in moderate to good yields with (Z)-selectivity. This method showed a good compatibility with a broad range of substrates and substituents. As

Selected peptide-based fluorescent probes for biological applications

• Debabrata Maity

Beilstein J. Org. Chem. 2020, 16, 2971–2982, doi:10.3762/bjoc.16.247

• excimer (490 nm) to monomer emission (406 nm, Figure 3B). Thus, monitoring the relative fluorescence intensities at two wavelengths (F406/F490) allowed the ratiometric detection of nucleic acids. Schmuck et al. reported a similar cationic peptide beacon 3 coupled with a FRET pair, a naphthalene donor and

• a dansyl acceptor, for ratiometric detection of dsDNA (Figure 4 [33]. Compound 3 contains two Gly–Ser–Lys tripeptide arms attached via their C-terminus to a central lysine spacer (Figure 4A). Compound 3 is in unfolded form in unbound conditions as it exhibits the naphthalene emission at 383 nm upon

• arms attached through their C-terminus to a central lysine. Two heparin sensors 10 and 11 are developed by attaching the N-terminus of the peptide beacon with pyrenes and fluorescence resonance energy transfer (FRET) pair (naphthalene and dansyl), respectively for ratiometric detection of heparin