Bifunctional organocatalysts for the asymmetric synthesis of axially chiral benzamides

• Ryota Miyaji,
• Yuuki Wada,
• Akira Matsumoto,
• Keisuke Asano and
• Seijiro Matsubara

Beilstein J. Org. Chem. 2017, 13, 1518–1523, doi:10.3762/bjoc.13.151

• analysis of the reaction selectivity (the decrease of the enantiomeric purity of 2b was negligible after a day). Furthermore, the reaction of benzamide 5, bearing a protected phenol, was carried out (Scheme 6). It failed to give the corresponding product 6, indicating the significance of multipoint

• substituted phenols. Reactions of monobrominated substrates. Rotational barriers of substrates and intermediates calculated at the B3YLP/6-31G(d) level of theory. Reaction of substrate with protected phenol. Optimization of conditions.a Supporting Information Supporting Information File 257: Experimental

An improved preparation of phorbol from croton oil

• Alberto Pagani,
• Simone Gaeta,
• Andrei I. Savchenko,
• Craig M. Williams and
• Giovanni Appendino

Beilstein J. Org. Chem. 2017, 13, 1361–1367, doi:10.3762/bjoc.13.133

• of the oil, especially in association to phenol [3]. The extraordinarily obnoxious and vesicant properties of croton oil have fostered studies aimed at the identification of its active principles since the very early developments of organic chemistry. Thus, the first chemical study on croton oil was

Total synthesis of elansolids B1 and B2

• Liang-Liang Wang and
• Andreas Kirschning

Beilstein J. Org. Chem. 2017, 13, 1280–1287, doi:10.3762/bjoc.13.124

• ], which was first reduced at C-25 (Scheme 3). The two diastereoisomers could be separated by chromatography and the stereochemical assignment of the major isomer was based on X-ray crystallographic analysis [7]. Next, Tamao–Fleming oxidation [10] yielded phenol 15. The alkyne was transformed into vinyl

• , 131.8, 128.7, 128.3, 128.1, 124.7, 124.1, 123.7, 113.8, 86.7, 81.3, 73.9, 73.5, 64.9, 55.8, 55.3, 52.9, 46.6, 45.3, 38.0, 33.4, 31.1, 26.3, 24.2, 22.7, 21.3, −3.4, −3.3; HRMS (ESI) m/z: [M + Na]+ calculated for C39H48O3SiNa, 615.3270; found, 615.3270. Synthesis of phenol 15 To a solution of the benzyl

• flash column chromatography gave phenol 15 (96.0 mg, 0.20 mol, 99%) as a colorless solid. Rf = 0.20 (PE/EtOAc 3:1, visualized using an anisaldehyde stain or UV), [α]D20 = +26.1 (c 0.7, CH2Cl2); 1H NMR (400 MHz, CDCl3, CHCl3 = 7.26 ppm) δ 7.31–7.28 (m, 4H), 6.90 (d, J = 8.7 Hz, 2H), 6.86 (d, J = 8.6 Hz

Automating multistep flow synthesis: approach and challenges in integrating chemistry, machines and logic

• Chinmay A. Shukla and
• Amol A. Kulkarni

Beilstein J. Org. Chem. 2017, 13, 960–987, doi:10.3762/bjoc.13.97

• . In the first step, 4-(2-bromoethyl)phenol is converted to its azide derivative by passing it through a glass reactor packed with azide exchange resin (20 equiv) at 70 °C to achieve quantitative yield. MeCN and THF were used as solvents. Dimethoxybenzyl alcohol (in THF) is oxidized to the

• -(2-bromoethyl)phenol can be fixed at a desired set-point using a control valve. This process stream can be preheated at the reaction temperature (70 °C). It can then be passed through the reactor packed with azide exchange resin maintained at the desired temperature using a jacket. The azide exchange

Metal-free hydroarylation of the side chain carbon–carbon double bond of 5-(2-arylethenyl)-3-aryl-1,2,4-oxadiazoles in triflic acid

• Anna S. Zalivatskaya,
• Dmitry S. Ryabukhin,
• Marina V. Tarasenko,
• Alexander Yu. Ivanov,
• Irina A. Boyarskaya,
• Elena V. Grinenko,
• Ludmila V. Osetrova,
• Eugeniy R. Kofanov and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2017, 13, 883–894, doi:10.3762/bjoc.13.89

• and local anesthetic [15], and ataluren finds application for the treatment of fibrosis [16]. Often, oxadiazole derivatives act as inhibitors of bacterial phenylalanyl-tRNA-synthetase [17], phosphodiesterase 4B2 [18], y-secretase [19] and phenol-substituted 1,2,4-oxadiazoles exhibit powerful anti

Transition-metal-catalyzed synthesis of phenols and aryl thiols

• Yajun Liu,
• Shasha Liu and
• Yan Xiao

Beilstein J. Org. Chem. 2017, 13, 589–611, doi:10.3762/bjoc.13.58

• has not been reported. In this review, a brief overview is given of the recent advances in synthetic strategies for both phenols and aryl thiols. Keywords: aryl thiol; C–O bond; C–S bond; phenol; transition metal; Introduction Phenols and aryl thiols serve as both important intermediates in organic

• other hand, the C–H hydroxylation, either with heteroatom-containing directing groups or without directing groups, has provided various methods for the synthesis of phenols. Compared with traditional methods, the transition-metal-catalyzed phenol synthesis has several advantages: broad substrate scope

• scope of functional groups including ether, halo, hydroxy, carboxylic acid and trifluoromethyl groups were well tolerated in their protocol. Even hindered substrates such as 2,6-diisopropyl iodobenzene also afforded the corresponding phenol in satisfying yield. The developed protocol was further applied

3D printed fluidics with embedded analytic functionality for automated reaction optimisation

• Andrew J. Capel,
• Andrew Wright,
• Matthew J. Harding,
• George W. Weaver,
• Yuqi Li,
• Russell A. Harris,
• Steve Edmondson,
• Ruth D. Goodridge and
• Steven D. R. Christie

Beilstein J. Org. Chem. 2017, 13, 111–119, doi:10.3762/bjoc.13.14

• allow a much larger chemical space to be analysed (<200 °C). The formation of a fused polycyclic heterocycle 5 (Scheme 2), from pentafluoropyridine (3) and 2-(methylamino)phenol (4), was chosen as this would generate a more complex optimisation set with two starting materials, the reaction product as

• -(methylamino)phenol (4) to form the corresponding fused polycyclic heterocycle 5. Conditions and limits for the optimisation used in tandem with RD1. Ketone 1 concentration 0.40 mmol/L, semicarbazide concentration 1.20 mmol/L. Supporting Information Supporting Information File 14: General considerations

Stabilization of nanosized titanium dioxide by cyclodextrin polymers and its photocatalytic effect on the degradation of wastewater pollutants

• Tamás Zoltán Agócs,
• István Puskás,
• Erzsébet Varga,
• Mónika Molnár and
• Éva Fenyvesi

Beilstein J. Org. Chem. 2016, 12, 2873–2882, doi:10.3762/bjoc.12.286

• decomposition [27][28]. Recently, various photocatalysts modified by CDs have been described. For instance, reduced graphene oxide/β-CD/titanium dioxide showed enhanced removal of phenol and Cr(VI) [29], graphene nanosheets with self-assembled nanolayer of TiO2 stabilized by β-CD resulted in improved

cis-Diastereoselective synthesis of chroman-fused tetralins as B-ring-modified analogues of brazilin

• Dimpee Gogoi,
• Runjun Devi,
• Pallab Pahari,
• Bipul Sarma and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2016, 12, 2816–2822, doi:10.3762/bjoc.12.280

• convenient Brønsted acid-catalyzed, metal-free, stereoselective synthesis of 6a,7,8,12b-tetrahydro-6H-naphtho[2,1-c]chromen-6a-ols as B-ring-modified analogues of brazilin using starting materials derived from inexpensive 1-tetralone and phenol derivatives. Our worries concerning the formation cis–trans

From betaines to anionic N-heterocyclic carbenes. Borane, gold, rhodium, and nickel complexes starting from an imidazoliumphenolate and its carbene tautomer

• Ming Liu,
• Jan C. Namyslo,
• Martin Nieger,
• Mika Polamo and
• Andreas Schmidt

Beilstein J. Org. Chem. 2016, 12, 2673–2681, doi:10.3762/bjoc.12.264

• .12.264 Abstract The mesomeric betaine imidazolium-1-ylphenolate forms a borane adduct with tris(pentafluorophenyl)borane by coordination with the phenolate oxygen, whereas its NHC tautomer 1-(2-phenol)imidazol-2-ylidene reacts with (triphenylphosphine)gold(I) chloride to give the cationic NHC complex [Au

• bond angle of 177.35(8)° was found. However, in contrast to other gold complexes, the two imidazole rings are not coplanar [38]. In addition, the imidazole and the phenol rings are twisted about −119.84(16)° (C5–N1–C6–C7) relative to the imidazole ring. Two Au complexes are connected via one halide

• ppm) [29][39], and other Rh complexes [40][41]. Correspondingly the phenol proton signals of the three geometrically non-equivalent ligands appear at different resonance frequencies. Thus, the three unsubstituted ortho positions of the phenolate moieties are detectable at 6.93–6.97 ppm (overlapped

A new paradigm for designing ring construction strategies for green organic synthesis: implications for the discovery of multicomponent reactions to build molecules containing a single ring

• John Andraos

Beilstein J. Org. Chem. 2016, 12, 2420–2442, doi:10.3762/bjoc.12.236

• containing one asymmetric feature, namely the electrophilic carbonyl group. This molecule is made industrially from precursors that already have the 6-membered ring preformed [132]. Example routes include dehydrogenation of cyclohexanol, which in turn is made either by catalytic hydrogenation of phenol

Elongated and substituted triazine-based tricarboxylic acid linkers for MOFs

• Arne Klinkebiel,
• Ole Beyer,
• Barbara Malawko and
• Ulrich Lüning

Beilstein J. Org. Chem. 2016, 12, 2267–2273, doi:10.3762/bjoc.12.219

• ). In order to synthesize the respective methoxy compound 5c, commercially available 3-hydroxybenzoic acid (10) was used as starting material (Figure 6). Bromination introduced a bromine atom into the 4 position (11) [19], then the phenol was turned into its methyl ether. This methylation can be

Palladium-catalyzed ring-opening reactions of cyclopropanated 7-oxabenzonorbornadiene with alcohols

• Katrina Tait,
• Oday Alrifai,
• Rebecca Boutin,
• Jamie Haner and
• William Tam

Beilstein J. Org. Chem. 2016, 12, 2189–2196, doi:10.3762/bjoc.12.209

• the use of platinum catalysts [19] or palladium catalysts with zinc co-catalyst with phenol nucleophiles [20]. Meanwhile, anti-stereoisomeric products 5 and 6 are obtained when copper catalysts are used with alkyl nucleophiles [21], if rhodium [22] or iridium catalysts are used in the presence of

• investigated, starting with cyclohexanol, which resulted in a moderate yield of 63% after only 1 day (Table 5, entry 8). When benzyl alcohol was used, no reaction occurred (Table 5, entry 9) and similarly when phenol was used, no reaction occurred and 8a was recovered (Table 5, entry 10). Conclusion In

p-Nitrophenyl carbonate promoted ring-opening reactions of DBU and DBN affording lactam carbamates

• Madhuri Vangala and
• Ganesh P Shinde

Beilstein J. Org. Chem. 2016, 12, 2086–2092, doi:10.3762/bjoc.12.197

• . To evaluate the substrate feasibility, one phenol, an allylic alcohol and three sugar alcohols were subjected to the reaction. The 3,4-dimethylphenyl p-nitrophenyl carbonate (9a) and geranyl carbonate 10a gave the corresponding γ-lactams 9b and 10b in 62% and 46% yields, respectively. Similarly, the

Application of heterocyclic aldehydes as components in Ugi–Smiles couplings

• Katelynn M. Mason,
• Michael S. Meyers,
• Abbie M. Fox and
• Sarah B. Luesse

Beilstein J. Org. Chem. 2016, 12, 2032–2037, doi:10.3762/bjoc.12.191

• . In 2005, El Kaïm and co-workers extended the utility of the Ugi reaction with the development of an Ugi–Smiles reaction, replacing the carboxylic acid component with an electron-deficient phenol [4][5][6][7]. Recent efforts to assemble biologically-relevant heterocycles have used multicomponent

Ionic liquids as transesterification catalysts: applications for the synthesis of linear and cyclic organic carbonates

• Maurizio Selva,
• Alvise Perosa,
• Sandro Guidi and
• Lisa Cattelan

Beilstein J. Org. Chem. 2016, 12, 1911–1924, doi:10.3762/bjoc.12.181

• distillation reactor loaded with quaternary ammonium strongly basic anion exchange resin and alkali hydroxides: dimethyl carbonate (DMC) is achieved in practically quantitative yields (Scheme 6, bottom). The third and final step is the transesterification of DMC with phenol by a catalytic reactive distillation

• transesterification reaction of dimethyl carbonate with phenol to methyl phenyl carbonate (MPC) and diphenyl carbonate (DPhC), Deshmukh et al. studied dibutyltin oxide as a catalyst in conjunction with Brønsted and Lewis acidic ionic liquids [70]. The authors investigated the relative Lewis and Brønsted acidity of

• the ionic liquids by monitoring the IR bands in the presence of pyridine as a probe molecule. The highest conversions (30–39%) of phenol and the best selectivity toward DPhC were achieved using N-methyl-2-pyrrolidone hydrogen sulfate [NMP][HSO4] and choline chloride zinc chloride ([ChCl][ZnCl2]). The

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• rearrangements and related processes play an important role in the chemistry of oxidation processes. Thus, the key reagent in the Sharpless epoxidation of allylic alcohols [48] and in the manufacture of propylene oxide via the Prilezhaev reaction [49][50][51] is tert-butyl hydroperoxide. In industry, phenol and

• acetone are mainly produced by the Hock process, which is based on the rearrangement of cumene hydroperoxide. In 2003, phenol was produced to more than 95% by this oxidation process [52][53][54]. Another important application of organic peroxides is the synthesis of lactones from cyclic ketones via the

• oxidation is widely used in organic synthesis for the preparation of esters and lactones and the Criegee reaction is applied to transform tertiary alcohols into ketones and aldehydes. The Hock rearrangement is a key step in the cumene (cumene–phenol) process and the Kornblum–DeLaMare is an important tool in

Catalytic Chan–Lam coupling using a ‘tube-in-tube’ reactor to deliver molecular oxygen as an oxidant

• Carl J. Mallia,
• Paul M. Burton,
• Alexander M. R. Smith,
• Gary C. Walter and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2016, 12, 1598–1607, doi:10.3762/bjoc.12.156

• , unfortunately, gave a poor isolated yield of 26% and also underwent some epimerisation (25, 53% ee determined by chiral HPLC, Scheme 2). Additionally, a small amount of the product (25) reacted further with phenylboronic acid through the phenol to give 26 in 3% isolated yield. In the case of L-leucine methyl

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

• Franziska Hemmerling and
• Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

• they differ by a central, annelated furan-3-one moiety instead of an acrylate unit (Scheme 25) [149]. Their biosynthesis proceeds from chalcones by an oxidation–conjugate addition cascade catalysed by plant phenol oxidases (PPOs) [150][151]. The PPO aureusidin synthase plays a central role in aurone

• , 3,4-dihydroxy-L-phenylalanine (L-DOPA), 4-coumaric acid or caffeic acid. Grisanes. Many fungal spirobenzofuranones contain the grisane (191) moiety as the central structural motif (Scheme 26a). The spiro linkage between the B and C rings is installed by oxidative phenol coupling starting from type II

Conjugate addition–enantioselective protonation reactions

• James P. Phelan and
• Jonathan A. Ellman

Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116

• chiral calcium alkoxide complex was generated in situ by mixing Ca(OEt)2, PyBox ligand (S,S)-88, and phenol 89. The authors found that the slow addition of malonate 86 and the use of phenol 89 and ethanol as additives were all crucial for achieving high yield and enantioselectivity, although the exact

• role of the phenol was not elucidated. 1,5-Dicarbonyl compounds 90 were accessed with excellent enantioselectivity for a variety of aliphatic α-substituents, and only when R was phenyl was there a significant loss of enantioselectivity (72% yield, 74:26 er). Organocatalysts Multiple groups have

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• room temperature, generating a variety of 3-aryl-3-hydroxy-2-oxindoles in good yields (up to 95%) and with good enantioselectivities (up to 94% ee), even for N-unsubstituted isatins (Scheme 31) [47]. These conditions were also successfully extended to other phenol substrates, affording the

• phenols, the reactions exclusively gave the para-substituted products. Mechanistically, in the presence of a catalytic amount of Lewis acid, the 3-hydroxyoxindole was converted to the intermediate A through dehydration, which was then tapped by the electron-rich phenol. para-Substituted products were

• corresponding products were found to have improved diastereoselectivities. Phenols with electron-withdrawing groups failed to afford the expected products under the same conditions. Mechanistically, Ga(OTf)3 may activate the allene and phenol substrates simultaneously via the bidentate model. In contrast, the

Elucidation of a masked repeating structure of the O-specific polysaccharide of the halotolerant soil bacteria Azospirillum halopraeferens Au4

• Elena N. Sigida,
• Yuliya P. Fedonenko,
• Alexander S. Shashkov,
• Nikolay P. Arbatsky,
• Evelina L. Zdorovenko,
• Svetlana A. Konnova,
• Vladimir V. Ignatov and
• Yuriy A. Knirel

Beilstein J. Org. Chem. 2016, 12, 636–642, doi:10.3762/bjoc.12.62

• hydrolysis of the lipopolysaccharide isolated by the phenol–water extraction from the halotolerant soil bacteria Azospirillum halopraeferens type strain Au4. The polysaccharide was studied by sugar and methylation analyses, selective cleavages by Smith degradation and solvolysis with trifluoroacetic acid

New synthetic strategies for xanthene-dye-appended cyclodextrins

• Milo Malanga,
• Andras Darcsi,
• Mihaly Balint,
• Gabor Benkovics,
• Tamas Sohajda and
• Szabolcs Beni

Beilstein J. Org. Chem. 2016, 12, 537–548, doi:10.3762/bjoc.12.53

• Information File 1, Figure S17). Under the selected aqueous alkaline conditions, the phenol moiety of the fluorescein is mainly deprotonated and as phenolate can participate in the formation of fluorescein-based acyl derivatives (such as esters or anhydride, see Supporting Information File 1, Figure S17). The

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• between 2-(2-nitrovinyl)phenol (208) and cyclohexanone (209, Scheme 65) [86]. When that reaction has been performed under the “regular” conditions for a Michael reaction, product 210 has been obtained in low yields. To overcome this problem, catalysts 57 and 211 were combined and the reaction goes through

Synthesis and nucleophilic aromatic substitution of 3-fluoro-5-nitro-1-(pentafluorosulfanyl)benzene

• Javier Ajenjo,
• Martin Greenhall,
• Camillo Zarantonello and
• Petr Beier

Beilstein J. Org. Chem. 2016, 12, 192–197, doi:10.3762/bjoc.12.21

• -boiling alcohols (MeOH, EtOH), the reactions were heated under reflux using the alcohol as a solvent and excess of potassium hydroxide (Table 1, entries 1 and 2). For alcohols with higher boiling points, the reactions were performed with sodium hydride (Table 1, entries 3 and 4). For phenol, thiophenol