Synthesis of nonracemic hydroxyglutamic acids

• Dorota G. Piotrowska,
• Iwona E. Głowacka,
• Andrzej E. Wróblewski and
• Liwia Lubowiecka

Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22

• boron trifluoride-catalyzed reaction with trimethylsilyl cyanide were separated chromatographically. Their transformation into (2R,3S)-2 and (2S,3S)-2, respectively, required the removal of the p-methoxybenzyl group and an acidic hydrolysis (Scheme 14) [65]. From D-glucose D-Glucose may be used as a

• cleanly liberates (2S,3S,4S)-4 (Scheme 25) [100]. This methodology opens the way to (3S,4S)-3-hydroxy-4-methoxy- (104) and 3,4-dimethoxy-L-glutamic acid (105) since selective opening of the lactone ring in 95 can be accomplished by boron trifluoride etherate-catalyzed methanolysis at low temperatures to

• -tartaric acid [104][105] were reduced and the respective hydroxylactams were acetylated to produce acetoxylactams 107a and 107b, necessary intermediates in the next step (Scheme 26) [106][107]. The introduction of the cyano group was accomplished by boron trifluoride-catalyzed reaction with trimethylsilyl

[3 + 2]-Cycloaddition reaction of sydnones with alkynes

• Veronika Hladíková,
• Jiří Váňa and
• Jiří Hanusek

Beilstein J. Org. Chem. 2018, 14, 1317–1348, doi:10.3762/bjoc.14.113

• -2-yl, quinolin-2-yl, 5,6-dihydro-4H-1,3-oxazin-2-yl). Such sydnones reacted with potassium 2-substituted acetylene trifluoroborates under boron trifluoride diethyl etherate catalysis to give corresponding pyrazolo[3',4':4,5][1,2]azaborolo[2,3-a]pyridin-5-ium-4-uides (or quinolin-5-ium-4-uide) in

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

• Diels–Alder reaction. Ghosh’s group reported an exclusive peri-, regio-, and stereoselective cycloaddition reaction of 5H-benzo[7]annulen-5-one (Scheme 35) [137]. The intermolecular [4 + 2] cycloaddition of 2,3-benzotropone (12) with cyclopentadiene (202) in the presence of boron trifluoride occurred

• depicted in Scheme 38 (Scheme 45) [161]. Sato’s group reported the synthesis of 7-hydroxy-2,3-benzotropone (241) via the ring expansion pathway of β-naphthoquinone (280) with diazomethane under various conditions and hydrolysis steps (Scheme 46) [169]. The boron trifluoride etherate-promoted ring expansion

Cross-coupling of dissimilar ketone enolates via enolonium species to afford non-symmetrical 1,4-diketones

• Keshaba N. Parida,
• Gulab K. Pathe,
• Shimon Maksymenko and
• Alex M. Szpilman

Beilstein J. Org. Chem. 2018, 14, 992–997, doi:10.3762/bjoc.14.84

•  1d) [28][29][30]. The final example is the intermolecular cross-coupling of two dissimilar trimethylsilyl enol ethers described herein (Scheme 1e). Results and Discussion Previously we have established that as little as 1.25 equiv of Koser’s reagent and 1.25 equiv of boron trifluoride in

Aminosugar-based immunomodulator lipid A: synthetic approaches

• Alla Zamyatina

Beilstein J. Org. Chem. 2018, 14, 25–53, doi:10.3762/bjoc.14.3

• isopropylidene group furnished diol 13. Regioselective boron trifluoride diethyl etherate-promoted glycosylation of the 6-OH group in 13 with Kdo-fluoride donor 14 afforded an inseparable mixture of α- and β-anomeric products (α/β = 9:1) [78]. Phosphitylation of the remaining OH group in position 4’ and facile

Curcuminoid–BF₂ complexes: Synthesis, fluorescence and optimization of BF₂ group cleavage

• Henning Weiss,
• Jeannine Reichel,
• Helmar Görls,
• Kilian Rolf Anton Schneider,
• Mathias Micheel,
• Michael Pröhl,
• Michael Gottschaldt,
• Benjamin Dietzek and
• Wolfgang Weigand

Beilstein J. Org. Chem. 2017, 13, 2264–2272, doi:10.3762/bjoc.13.223

• yields strongly decrease when employing other aldehydes [12]. This procedure also requires a rather extensive work-up including several extraction steps and chromatography [8]. A second, more recent approach first published by Rao et al. relies on boron trifluoride as the complexing agent [13]. The

• structure motif using (a) boric oxide or (b) boron trifluoride. BF2 group hydrolysis of complex 2b. Suggested mechanism of BF2 complex hydrolysis. BF3·Et2O-promoted synthesis of curcuminoid–BF2 complexes 2a–h. Optimization of reaction conditions for BF2 group cleavage. Hydrolysis reactions. Absorption and

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

• under metal-free conditions and the operational simplicity render this transformation an attractive approach. Nevertheless, in an additional work, the angular –OH group of (±)-5k was reductively removed on treatment with Et3SiH and boron trifluoride etherate to get chroman-fused tetralin (±)-14 with the

The in situ generation and reactive quench of diazonium compounds in the synthesis of azo compounds in microreactors

• Faith M. Akwi and
• Paul Watts

Beilstein J. Org. Chem. 2016, 12, 1987–2004, doi:10.3762/bjoc.12.186

• -naphthol. The method boasts of shorter reaction times [4] with high yields (Scheme 2). Mirjalili et al. also used silica supported boron trifluoride and was able to carry out diazotization at room temperature [5] after they discovered that the diazonium salts obtained were stable at room temperature even

• temperature: Azo coupling reaction. PTSA-catalyzed diazotization and azo coupling reaction. Ferric hydrogen sulfate (FHS) catalyzed azo compound synthesis. Synthesis of azo compounds in the presence of silica supported boron trifluoride. Phase transfer catalyzed azo coupling of 5-methylresorcinol in

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

• theoretically studied mechanism of the oxidation reaction promoted by H2O2 and the Lewis acid BF3 [217][219]. In the first step, the hydrogen peroxide–boron trifluoride complex 8 reacts with ketone 9 to form adduct 10. The latter intermediate rearranges through transition state 11 into the tetrahedral

• peroxide 115, which rearranges through an acid-catalyzed Baeyer–Villiger-type rearrangement into 116. Hydroxy-10H-acridin-9-ones 117 proved to be promising antipsoriatic agents [287]. The oxidation of aldimines 118a–f with m-chloroperbenzoic acid in the presence of boron trifluoride etherate produces

Synthesis of highly functionalized 2,2'-bipyridines by cyclocondensation of β-ketoenamides – scope and limitations

• Paul Hommes and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2016, 12, 1170–1177, doi:10.3762/bjoc.12.112

• oxidative coupling of acetylacetone 1a employing iodosylbenzene in the presence of boron trifluoride in methanol [41] followed by the standard amination procedure indeed furnished β-enaminoketone 2i in moderate yield (Scheme 3). This intermediate could be N-acylated via its potassium salt with activated

Thermal and oxidative stability of Atlantic salmon oil (Salmo salar L.) and complexation with β-cyclodextrin

• Daniel I. Hădărugă,
• Mustafa Ünlüsayin,
• Alexandra T. Gruia,
• Cristina Birău (Mitroi),
• Gerlinde Rusu and
• Nicoleta G. Hădărugă

Beilstein J. Org. Chem. 2016, 12, 179–191, doi:10.3762/bjoc.12.20

• complexation of ASO. A boron trifluoride–methanol complex (20%, Merck & Co., Inc.) was used for FA derivatization. Finally, Hydranal-Titrant 5, Hydranal-Solvent and Hydranal-Water Standard 10.0 (Sigma-Aldrich, Buchs, Switzerland) were used for the KFT water analysis of β-CD/ASO complexes. ASO extraction The

• profile of nondegraded and degraded ASO was obtained by GC–MS analysis of the corresponding methyl esters (as well as acetals and ketals of FA degradation compounds). For derivatization, approximately 20 mg of ASO or the corresponding sample was dissolved in 3 mL of boron trifluoride–methanol solution in

Synthesis of constrained analogues of tryptophan

• Elisabetta Rossi,
• Valentina Pirovano,
• Marco Negrato,
• Giorgio Abbiati and
• Monica Dell’Acqua

Beilstein J. Org. Chem. 2015, 11, 1997–2006, doi:10.3762/bjoc.11.216

• results are summarized in Table 1. The reaction was ineffective under thermal conditions (Table 1, entry 1). As a consequence we tested simple Lewis acids as potential promoters for the transformation. Magnesium perchlorate, scandium and copper triflate and boron trifluoride failed to give the desired

Synthesis of novel N-cyclopentenyl-lactams using the Aubé reaction

• Madhuri V. Shinde,
• Rohini S. Ople,
• Ekta Sangtani,
• Rajesh Gonnade and
• D. Srinivasa Reddy

Beilstein J. Org. Chem. 2015, 11, 1060–1067, doi:10.3762/bjoc.11.119

• ·OEt2 Boron trifluoride etherate (0.07 mL, 0.71 mmol) was added to a solution of azido alcohol 3 (0.10 g, 0.71 mmol) and ketones (2.0 mmol, 3 equiv) in HFIP (0.2 mL) cooled to 0 °C. The mixture was warmed to room temperature and stirred for 2–5 h. Upon completion, the reaction was quenched with 15% aq

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

Efficient deprotection of F-BODIPY derivatives: removal of BF₂ using Brønsted acids

• Mingfeng Yu,
• Joseph K.-H. Wong,
• Cyril Tang,
• Peter Turner,
• Matthew H. Todd and
• Peter J. Rutledge

Beilstein J. Org. Chem. 2015, 11, 37–41, doi:10.3762/bjoc.11.6

• diversifying the F-BODIPY framework [9]. F-BODIPYs are readily prepared by condensing aldehydes, acyl chlorides or anhydrides with pyrroles and trapping the resulting dipyrrin in situ with boron trifluoride [9][10][11]. F-BODIPYs are generally stable and chemically robust, with photophysical properties that

• infra), and given previous reports on the ability of nitrogen oxides (e.g., NO, N2O3 and N2O4) to complex with boron trifluoride [26][27][28][29], the nitro group is presumably the key factor in the complexation of 8 with Et2O. Washing with aqueous and organic solvents did not completely remove the

Redox active dendronized polystyrenes equipped with peripheral triarylamines

• Toshiki Nokami,
• Naoki Musya,
• Tatsuya Morofuji,
• Keiji Takeda,
• Masahiro Takumi,
• Akihiro Shimizu and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2014, 10, 3097–3103, doi:10.3762/bjoc.10.326

•  2. Di(p-bromophenyl)carbinol (1) was treated with SOCl2 to obtain di(p-bromophenyl)methyl chloride (2) in quantitative yield. A Friedel–Crafts-type alkylation [29] of diphenylsilane 3 with 2 in the presence of boron trifluoride etherate as a Lewis acid gave 4 in 86% yield. The oxidation potential of

Solution processable diketopyrrolopyrrole (DPP) cored small molecules with BODIPY end groups as novel donors for organic solar cells

• Diego Cortizo-Lacalle,
• Calvyn T. Howells,
• Upendra K. Pandey,
• Joseph Cameron,
• Neil J. Findlay,
• Anto Regis Inigo,
• Tell Tuttle,
• Peter J. Skabara and
• Ifor D. W. Samuel

Beilstein J. Org. Chem. 2014, 10, 2683–2695, doi:10.3762/bjoc.10.283

• ). Compound 6 was prepared by acid-catalysed condensation of 5-bromothiophene-2-carbaldehyde with 3-ethyl-2,4-dimethylpyrrole, followed by oxidation with DDQ. Deprotonation with triethylamine and subsequent treatment with boron trifluoride diethyl etherate yielded 6. The entire synthesis was carried out as a

Amino acid motifs in natural products: synthesis of O-acylated derivatives of (2S,3S)-3-hydroxyleucine

• Oliver Ries,
• Martin Büschleb,
• Markus Granitzka,
• Dietmar Stalke and
• Christian Ducho

Beilstein J. Org. Chem. 2014, 10, 1135–1142, doi:10.3762/bjoc.10.113

• to introduce an N,O-acetal moiety by transformation of 7 into the dimethyloxazolidine 8, a reaction which required careful optimization though (Scheme 2, Table 1). Using boron trifluoride and 2,2-dimethoxypropane (2,2-DiMP), as known from the synthesis of the structurally related Garner's aldehyde

cis–trans Isomerization of silybins A and B

• Michaela Novotná,
• Radek Gažák,
• David Biedermann,
• Florent Di Meo,
• Petr Marhol,
• Marek Kuzma,
• Lucie Bednárová,
• Kateřina Fuksová,
• Patrick Trouillas and
• Vladimír Křen

Beilstein J. Org. Chem. 2014, 10, 1047–1063, doi:10.3762/bjoc.10.105

• , we propose mechanisms for the stereospecific isomerization. The isomerization process is initiated by BF3 complexation. Boron trifluoride may complex silybin through a coordinate bond, in which the two electrons originate from the oxygen atoms of silybin. Silybin and BF3 are hard bases (η = 4.8 eV in

N-Alkylated dinitrones from isosorbide as cross-linkers for unsaturated bio-based polyesters

• Oliver Goerz and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 902–909, doi:10.3762/bjoc.10.88

• -toluenesulfonic acid, phenothiazine (98%), zinc iodide (98%), and boron trifluoride diethyl etherate (46%) were purchased from Sigma-Aldrich and used as received. Isosorbide (98%) and E-benzaldoxime (97%) were purchased from Alfa Aesar, and isosorbide was recrystallized from acetone/ethyl acetate. All used

An oxidative amidation and heterocyclization approach for the synthesis of β-carbolines and dihydroeudistomin Y

• Suresh Babu Meruva,
• Akula Raghunadh,
• Raghavendra Rao Kamaraju,
• U. K. Syam Kumar and
• P. K. Dubey

Beilstein J. Org. Chem. 2014, 10, 471–480, doi:10.3762/bjoc.10.45

• ). General procedure for the synthesis of dihydroeudistomin (7a–7j) To a stirred solution of N-(2-(1H-indol-3-yl)ethyl)-2-oxo-2-phenylacetamide (9a, 2.0 g, 6.8 mmol) in diethyl ether (20 mL) was added 48% boron trifluoride etherate (10.1 g, 34.2 mmol) in a round-bottom flask under a N2 atmosphere, and the

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

• Alexander O. Terent'ev,
• Dmitry A. Borisov,
• Vera A. Vil’ and
• Valery M. Dembitsky

Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6

The chemistry of isoindole natural products

• Klaus Speck and
• Thomas Magauer

Beilstein J. Org. Chem. 2013, 9, 2048–2078, doi:10.3762/bjoc.9.243

• diastereoisomers. The Lewis acid induced key step, a domino epoxide-opening/rearrangement/cyclization cascade, most likely proceeded in a stepwise manner via intermediate 179. Activation of the epoxide with boron trifluoride etherate induces the planned sigmatropic [1,2]-methyl and [1,2]-hydride shifts to generate

• prenyl side chain and introduction of the formyl group was accomplished within five steps to give 191a (Scheme 25). The envisioned deprotection of 191a using Lewis acidic conditions led to an unexpected and unprecedented metal-free carbonyl–olefin metathesis. Coordination of boron trifluoride etherate to

Asymmetric synthesis of quaternary aryl amino acid derivatives via a three-component aryne coupling reaction

• Elizabeth P. Jones,
• Peter Jones,
• Andrew J. P. White and
• Anthony G. M. Barrett

Beilstein J. Org. Chem. 2011, 7, 1570–1576, doi:10.3762/bjoc.7.185

• electrophile in the presence of boron trifluoride etherate (Table 1, entry 10) gave alcohol 6j. When (S)-propylene oxide was used instead there was no reaction, and indeed Schöllkopf noted significant levels of kinetic resolution when such reactions were performed with racemic oxiranes [23]. In our previous

Photocycloaddition of aromatic and aliphatic aldehydes to isoxazoles: Cycloaddition reactivity and stability studies

• Axel G. Griesbeck,
• Marco Franke,
• Jörg Neudörfl and
• Hidehiro Kotaka

Beilstein J. Org. Chem. 2011, 7, 127–134, doi:10.3762/bjoc.7.18

• and benzaldehyde, while at −78 °C, no reaction could be observed. In contrast, the use of an excess of Grignard reagent (3 equiv) at −78 °C again led to decomposition. The application of boron trifluoride at −78 °C also led to decomposition, followed by a normal nucleophilic attack of the Grignard