Tuneable access to indole, indolone, and cinnoline derivatives from a common 1,4-diketone Michael acceptor

• Dalel El-Marrouki,
• Sabrina Touchet,
• Abderrahmen Abdelli,
• Hédi M’Rabet,
• Mohamed Lotfi Efrit and
• Philippe C. Gros

Beilstein J. Org. Chem. 2020, 16, 1722–1731, doi:10.3762/bjoc.16.144

• process, leading respectively to an indole 6 (after dehydration and aromatization) or an indolone 7. The reaction was first investigated by mixing the diketone 5b as the Michael acceptor and benzylamine under various conditions (Table 1). We first investigated the reactivity in the presence of a set of

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

• to sorbitol and 3) dehydration of sorbitol to isosorbide (Scheme 1). Isosorbide, a molecule obtained from biomass can find many applications such as additives, pharmaceuticals [2][3] and monomers for polymer industries [4][5][6]. For instance, one polymer obtained from isosorbide, poly(ethylene-co

• dehydration of ᴅ-sorbitol using a strong acid catalyst [10][11]. ᴅ-Sorbitol is produced from the hydrogenation of glucose obtained mostly from the hydrolysis of starch, but also from sucrose or cellulose. Consequently, the cellulose valorization can be realized from the one-pot conversion of cellulose to

• pressures and high temperatures to allow efficient hydrogenation of glucose and dehydration of sorbitol and sorbitans [12][18]. In 2010, Almeida et al. studied each step for the synthesis of isosorbide from cellulose using molten ZnCl2 associated with different catalysts [19]. Based on the study of each

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

• the transformation of trimethoxy derivative 1d reveals that dehydration is almost isoergonic (ΔG9d→11d = −1.6 kJ·mol−1), but the formation of the isoindole intermediate (11d→4d) is endergonic (unlike in the case of the three other derivatives), with a larger activation free energy (ΔG#11TS = 40.2

• turned out that the acid catalyst (TFA in this case), as expected, had a crucial role in the protonation and deprotonation as well as in the dehydration and hydration elementary steps of the reaction sequence. Without catalyst, the 9a→11a→4a transformations required an energy investment of 150.7 and

Activated carbon as catalyst support: precursors, preparation, modification and characterization

• Melanie Iwanow,
• Tobias Gärtner,
• Volker Sieber and
• Burkhard König

Beilstein J. Org. Chem. 2020, 16, 1188–1202, doi:10.3762/bjoc.16.104

• agents promote a cross-link formation due to their dehydration properties, which causes a rigid matrix. This structure is less susceptible to volatile loss and volume contraction during the carbonization resulting in higher activated carbon yields since no carbon burn-off is necessary [6][85]. Additional

• to the precursor solution consisting of sucrose as carbon source and NaCl or NaNO3 as inorganic salt. The pyrolysis of the precursor solution leads to dehydration of carbon as well as iron salt conversion to crystalline or non-crystalline iron species depending on the production conditions. The

• components lignin, cellulose and xylan by KOH activation with TPD. The different prepared materials showed no significant difference of the surface functionalities. All TPD spectra show a water peak at about 500 K according to dehydration of carboxylic acid during formation of anhydrides, a CO peak at 900 K

A systematic review on silica-, carbon-, and magnetic materials-supported copper species as efficient heterogeneous nanocatalysts in “click” reactions

• Pezhman Shiri and
• Jasem Aboonajmi

Beilstein J. Org. Chem. 2020, 16, 551–586, doi:10.3762/bjoc.16.52

• reactions, Ugi–Smiles reactions, Mizoroki–Heck reactions, aldol reactions, oxidation and dehydration reactions, Mannich reactions, and multicomponent reactions. Because of the mentioned reasons as well as due to the low toxicity of silica nanoparticles, they are often a good option [24]. For this review

Efficient synthesis of 3,6,13,16-tetrasubstituted-tetrabenzo[a,d,j,m]coronenes by selective C–H/C–O arylations of anthraquinone derivatives

• Seiya Terai,
• Yuki Sato,
• Takuya Kochi and
• Fumitoshi Kakiuchi

Beilstein J. Org. Chem. 2020, 16, 544–550, doi:10.3762/bjoc.16.51

• examining various carbonyl methylenation methods, we found that the dimethylenation products 6 can be obtained in high yields through methylation of the carbonyl groups, followed by dehydration. Thus, the reaction of 4aa with methyllithium and subsequent treatment of the crude diol with NaH2PO2·H2O and NaI

Synthesis of 4-amino-5-fluoropyrimidines and 5-amino-4-fluoropyrazoles from a β-fluoroenolate salt

• Tobias Lucas,
• Jule-Philipp Dietz and
• Till Opatz

Beilstein J. Org. Chem. 2020, 16, 445–450, doi:10.3762/bjoc.16.41

• (5). First, a Finkelstein halogen exchange reaction and a dehydration reaction were combined to obtain fluoroacetonitrile (7) in 82% yield [36]. The latter then underwent a Claisen condensation with ethyl formate to obtain 8 in 77% yield with a purity of 90%. The product contained about 10% (1H NMR

Oligomeric ricinoleic acid preparation promoted by an efficient and recoverable Brønsted acidic ionic liquid

• Fei You,
• Xing He,
• Song Gao,
• Hong-Ru Li and
• Liang-Nian He

Beilstein J. Org. Chem. 2020, 16, 351–361, doi:10.3762/bjoc.16.34

• promote the intermolecular dehydration esterification. The reaction temperature, catalyst loading, and vacuum degree on the reaction outcome were in detail investigated and the acid value of the product was used to evaluate the reaction results (Table 2). It was easily found that a higher temperature was

• the cation of IL and attacks the intermediate A (step I), generating a tetrahedral intermediate B. Finally, dehydration and deprotonation of the tetrahedral intermediate occurs (step II), forming dimeric ricinoleic acid C. The carboxyl and hydroxy groups in the dimeric ricinoleic acid may further

• dehydration esterification of ricinoleic acid and catalyst recycling The dehydration esterification of ricinoleic acid was investigated using ILs as catalyst. In a typical run, 10 g (30 mmol) ricinoleic acid and 1 g (2.6 mmol) [HSO3-BDBU]H2PO4 were added into a 100 mL glass flask equipped with magnetic

[1,3]/[1,4]-Sulfur atom migration in β-hydroxyalkylphosphine sulfides

• Katarzyna Włodarczyk,
• Piotr Borowski and
• Marek Stankevič

Beilstein J. Org. Chem. 2020, 16, 88–105, doi:10.3762/bjoc.16.11

• an SH group at the β-carbon atom, under the reaction conditions. The latter result was slightly different from the two previous ones, as here, the sulfur atom migrated to the β and not the γ-carbon atom. Moreover, the parent alcohol 19 underwent mainly a dehydration reaction and the formation of α,β

Nanangenines: drimane sesquiterpenoids as the dominant metabolite cohort of a novel Australian fungus, Aspergillus nanangensis

• Heather J. Lacey,
• Cameron L. M. Gilchrist,
• Andrew Crombie,
• John A. Kalaitzis,
• Daniel Vuong,
• Peter J. Rutledge,
• Peter Turner,
• John I. Pitt,
• Ernest Lacey,
• Yit-Heng Chooi and
• Andrew M. Piggott

Beilstein J. Org. Chem. 2019, 15, 2631–2643, doi:10.3762/bjoc.15.256

• in Figure 1. The absolute configuration of 9 was then confirmed to be the same as 2 by single crystal X-ray diffraction analysis (Table S2 and Figure S7 in Supporting Information File 1). HRESI(+)MS analysis of nanangenine H (10) revealed a protonated dehydration product ([M – H2O + H]+ m/z 379.2473

A new approach to silicon rhodamines by Suzuki–Miyaura coupling – scope and limitations

• Thines Kanagasundaram,
• Antje Timmermann,
• Carsten S. Kramer and
• Klaus Kopka

Beilstein J. Org. Chem. 2019, 15, 2569–2576, doi:10.3762/bjoc.15.250

• –11b (Scheme 2) [22][28]. Hereby, the boroxines 9b–11b were accessible by thermal dehydration of the corresponding boronic acids 9a–11a. With this procedure product 13 was obtained in only 6% yield, which is presumably due to a competing coupling reaction of the boroxine moiety of 9b with the chlorine

Aggregation-induced emission effect on turn-off fluorescent switching of a photochromic diarylethene

• Luna Kono,
• Yuma Nakagawa,
• Ayako Fujimoto,
• Ryo Nishimura,
• Yohei Hattori,
• Toshiki Mutai,
• Nobuhiro Yasuda,
• Kenichi Koizumi,
• Satoshi Yokojima,
• Shinichiro Nakamura and
• Kingo Uchida

Beilstein J. Org. Chem. 2019, 15, 2204–2212, doi:10.3762/bjoc.15.217

• property. Generally, the fluorescence quantum yields decreased with increasing the permittivity of the solvents. No fluorescence was observed for methanol and acetonitrile solutions, indicating the suppression of ESIPT, because the solvents were used without dehydration. The intensity of the fluorescence

Friedel–Crafts approach to the one-pot synthesis of methoxy-substituted thioxanthylium salts

• Kenta Tanaka,
• Yuta Tanaka,
• Mami Kishimoto,
• Yujiro Hoshino and
• Kiyoshi Honda

Beilstein J. Org. Chem. 2019, 15, 2105–2112, doi:10.3762/bjoc.15.208

• useful properties, several research groups have developed methodologies to synthesize them. The typical synthetic methods for thioxanthylium salts include the reaction of thioxanthone with aryl bromide in the presence of n-butyllithium or Grignard reagents followed by dehydration by acids such as

• hexafluorophosphoric acid (Scheme 1a and 1b) [3][4][9][10], oxidation of thioxanthene in the presence of PbO2 followed by dehydration by tetrafluoroboric acid [1], the reaction of 4,4’-bis(dimethylamino)diphenylmethane with sulfur in the presence of ZnCl2 [11], and the ring-closure reaction of diaryl sulfide in the

• the product 3a in 82% yield (Table 1, entries 10–12). Decreasing the amount of TfOH did not improve the yield (Table 1, entry 13). It is suggested that the cyclization and dehydration were efficiently promoted at high temperature. Fortunately, when the reaction was carried out with benzoic acid, which

Characterization of two new degradation products of atorvastatin calcium formed upon treatment with strong acids

• Jürgen Krauß,
• Monika Klimt,
• Markus Luber,
• Peter Mayer and
• Franz Bracher

Beilstein J. Org. Chem. 2019, 15, 2085–2091, doi:10.3762/bjoc.15.206

• /dehydration process in the side chain), treatment with conc. aqueous hydrochloric acid gave a complex, bridged molecule under C–C-bond formation of the lactone moiety with the pyrrole, migration of the isopropyl group and loss of the carboxanilide residue. The novel degradation products were characterized by

• dehydration of the δ-hydroxy group and some epimers resulting from acid-catalyzed isomerization reactions. In contrast, Vukkum et al. [13] describe, besides lactones 2 and 3, an α,β-unsaturated carboxylic acid 4. Treatment under more drastic conditions (6 M HCl, reflux, 3 h) was reported to result mainly in

• hydroxylactone 2 (55% yield). This outcome was confirmed by comparison with published NMR data [18][19]. At elevated temperature (reflux, 4 h; Table 1, entry 2) a mixture of lactone 2 and known unsaturated lactone 3 [15] (arising from acid-catalyzed dehydration of 2) was obtained. Under even more drastic acidic

A review of the total syntheses of triptolide

• Xiang Zhang,
• Zaozao Xiao and
• Hongtao Xu

Beilstein J. Org. Chem. 2019, 15, 1984–1995, doi:10.3762/bjoc.15.194

• difficulty in extraction of 40 and 41 from the large quantity of alumina. Dehydration of the mixture of 40 and 41 in benzene quantitatively afforded a 1:2 mixture of 42 and its C-3 epimer 41. Reduction of the epimers with sodium borohydride and subsequent treatment with hydrochloric acid (2 N) gave single

• , followed by successive treatment with PhCH2OCH2Li and HCl–THF (pH 1) gave triolmonobenzyl ether 64. Protection of the phenolic hydroxy group to its corresponding monoacetate followed by oxidation of the primary hydroxy group and dehydration yielded α,β-unsaturated aldehyde 65. Oxidation of 65 to the

• form the A- and D-ring. The second one involves the reaction of the bicyclic intermediate 13 and 2-isopropyl-1,4-benzoquinone (14) to form the B- and C-ring. Finally, a regio- and stereoselective reduction, methylation and dehydration procedure and a selenylation, oxidation and elimination procedure

Reactions of 2-carbonyl- and 2-hydroxy(or methoxy)alkyl-substituted benzimidazoles with arenes in the superacid CF₃SO₃H. NMR and DFT studies of dicationic electrophilic species

• Dmitry S. Ryabukhin,
• Alexey N. Turdakov,
• Natalia S. Soldatova,
• Mikhail O. Kompanets,
• Alexander Yu. Ivanov,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2019, 15, 1962–1973, doi:10.3762/bjoc.15.191

• and Discussion The protonation of formyl and acetylbenzimadazoles 1 and 2 gave N,O-diprotonated species I and II, respectively (see Table 1). Protonation of the hydroxy group of benzimidazoles 3–8 in strong acids gave dicationic species III, V, VII, and VIII, the dehydration of the latter resulted in

• water. According to DFT calculations, protonation of the benzimidazole nitrogen N3 and the oxygen of the carbonyl or hydroxymethyl group in 1–8 leading to dicationic species I–III, V, VII, and VIII is thermodynamically favorable (−18.6 to −25.8 kcal/mol, Table 1). On the other hand, the dehydration of

• 56.9 ppm, which are close to the shifts in starting neutral precursors 3a and 7, proves unambiguously that no dehydration of these species leading to heteroaromatic benzyl-type cations take place. Based on HSQC and HMBC N–H correlations, we were able to measure 15N chemical shifts of nitrogen atoms for

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• . Dehydration of 170 was completed in the presence of acid. Catalytic hydrogenation of the C=C bond in 171 took place preferentially (9:1) from the less hindered side to finally give (3R,5S)-168 as the hydrochloride salt. Substituted imidazolin-2-ones are of interest as potential aminoacyl-tRNA synthase

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

Water inside β-cyclodextrin cavity: amount, stability and mechanism of binding

• Stiliyana Pereva,
• Valya Nikolova,
• Silvia Angelova,
• Tony Spassov and
• Todor Dudev

Beilstein J. Org. Chem. 2019, 15, 1592–1600, doi:10.3762/bjoc.15.163

• supramolecular host–guest structures. The water content of CDs has been a subject of numerous investigations. The data (both experimental and theoretical) are scattered and, still, no consensus has been reached on the number and position of water molecules, and the energetics of the hydration/dehydration of

• disordered and mobile, and that the OH groups of the host β-CD may rotate [17]. Studies with molecular dynamics simulations have found only four water molecules inside the host β-CD cavity [18]. The energetics of the CD hydration/dehydration have been investigated as well. Experimental studies have been able

• enthalpy of this process has been found to be ≈40–45 kJ mol−1 [10][11][14]. The brief literature survey outlined above shows that, although a significant body of information has been accumulated on the β-CD hydration/dehydration, the intimate mechanism of the process is still not completely understood

Enantioselective PCCP Brønsted acid-catalyzed aza-Piancatelli rearrangement

• Gabrielle R. Hammersley,
• Meghan F. Nichol,
• Helena C. Steffens,
• Jose M. Delgado,
• Gesine K. Veits and
• Javier Read de Alaniz

Beilstein J. Org. Chem. 2019, 15, 1569–1574, doi:10.3762/bjoc.15.160

• (Figure 1) [38]. First, the pKa values measured in acetonitrile (MeCN) are lower than chiral phosphoric acids (Brønsted acid pKa = 8.85 vs chiral phosphoric acids pKa = 12–14) [38]. Given the enhanced acidity, we reasoned that this type of chiral Brønsted acid catalyst could facilitate the dehydration

Synthesis of (macro)heterocycles by consecutive/repetitive isocyanide-based multicomponent reactions

• Angélica de Fátima S. Barreto and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2019, 15, 906–930, doi:10.3762/bjoc.15.88

• materials. Diisocyanides were prepared from commercial diamines in two steps: formylation followed by dehydration of the diformamides. The easiness to obtain the starting materials provides a variety of macrocycles using the Passerini-MiBs. Recently, the use of a double Ugi four-component macrocyclization

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

• milling frequency of 22.5 Hz (Figure 6b) [59]. The stoppers were constructed in situ with 1,8-diaminonaphthalene through the formation of an imine via dehydration of the amine and aldehyde. Interestingly, a synthesis of the smallest [2]rotaxane also has been demonstrated by the same group [60]. They

Efficient synthesis of 4-substituted-ortho-phthalaldehyde analogues: toward the emergence of new building blocks

• Clémence Moitessier,
• Ahmad Rifai,
• Pierre-Edouard Danjou,
• Isabelle Mallard and
• Francine Cazier-Dennin

Beilstein J. Org. Chem. 2019, 15, 721–726, doi:10.3762/bjoc.15.67

• of this reaction was very low (only 13%) mainly due to major production of OPA as is also described in a study of Wenkert et al. [20]. In order to circumvent the dehydration of 3 which generate OPA under oxidative conditions, a protection strategy of the hydroxy group was undertaken. The only

The LANCA three-component reaction to highly substituted β-ketoenamides – versatile intermediates for the synthesis of functionalized pyridine, pyrimidine, oxazole and quinoxaline derivatives

• Tilman Lechel,
• Roopender Kumar,
• Mrinal K. Bera,
• Reinhold Zimmer and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2019, 15, 655–678, doi:10.3762/bjoc.15.61

• reasonable overall yields (Scheme 20) [30]. This pathway via the pyrimidine N-oxides represents a good alternative to the direct oxidation of the 4-methyl group by selenium dioxide (see Scheme 11). The subsequent transformation of the aldehyde PM71 to the oxime followed by dehydration afforded nitrile PM72

Synthesis of the polyketide section of seragamide A and related cyclodepsipeptides via Negishi cross coupling

• Jan Hendrik Lang and
• Thomas Lindel

Beilstein J. Org. Chem. 2019, 15, 577–583, doi:10.3762/bjoc.15.53

• . Under Yamaguchi conditions, we observed complete decomposition in both cases. Shiina conditions gave a complex product mixture, if the TIPS group was present, whereas the desilylated acid provided a product that apparently had undergone dehydration, as judged by TLC–MS coupling. In course of their