Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• be asymmetric α-phopshorylation approaches or the introduction of other heteroatoms (e.g., boron), which are all transformations that are without doubt important, but so far much less systematically addressed as most of the examples we showed herein. We are therefore convinced that the field of

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

• against competing microorganisms was not the evolutionary driver for the emergence of the toxin. It is generally assumed in the literature that mycolactones reach their cellular targets by passive diffusion [91]. Based on competition experiments with the fluorescent, boron-dipyrromethene (BODIPY)-labeled

Total syntheses of the archazolids: an emerging class of novel anticancer drugs

• Stephan Scheeff and
• Dirk Menche

Beilstein J. Org. Chem. 2017, 13, 1085–1098, doi:10.3762/bjoc.13.108

• a boron-mediated anti-aldol reaction [67] of lactate-derived ethyl ketone 13 with aldehyde 12, which in turn was available from aldehyde 9 by HWE olefination. This Paterson aldol reaction and related aldol reactions, which have been amply used by the Menche group [68][69][70], proceeded with

• ’ during thiazole formation on large scale, requiring an oxidation–reduction sequence (90%) in this case. Completion of the total synthesis After evaluation of several strategies, the assembly of the two northern fragments 4 and 5 could be realized by an aldol condensation, involving a boron-mediated aldol

• full stereochemistry in the first place. The various approaches discussed within this manuscript show the various tactics and strategies that may be employed in complex polyketide synthesis. Notable features of the total synthesis by the Menche group include the robustness of boron mediated aldol

Substitution of fluorine in M[C₆F₅BF₃] with organolithium compounds: distinctions between O- and N-nucleophiles

• Anton Yu. Shabalin,
• Nicolay Yu. Adonin and
• Vadim V. Bardin

Beilstein J. Org. Chem. 2017, 13, 703–713, doi:10.3762/bjoc.13.69

• Bu, the nucleophilic substitution of the fluorine atom at the para position to boron is the predominant route. When R = Ph, the ratio M[4-RC6F4BF3]/M[2-RC6F4BF3] is ca. 1:1. Substitution of the fluorine atom at the ortho position to boron is solely caused by the coordination of RLi via the lithium

• ]. Over the last 15 years, we reported the successful application of polyfluorinated organoborates K[RC6F4BF3], K[C6F5B(OMe)3] and K[CF2=CFBF3] as boron-containing reagents in the Pd-catalyzed cross-coupling reactions with C-electrophiles [22][23][24][25][26][27]. Nowadays a common approach to these

• compounds is based on the transformation of polyfluoroarenes under the action of appropriate reagents into the corresponding organometallic derivatives followed by treating them with suitable boron-containing electrophiles (Scheme 1) [28][29]. In order to further expand this powerful tool for the

Fluorescent carbon dots from mono- and polysaccharides: synthesis, properties and applications

• Stephen Hill and
• M. Carmen Galan

Beilstein J. Org. Chem. 2017, 13, 675–693, doi:10.3762/bjoc.13.67

• to improve the PL properties of CDs, the use of boron as an additive, which is an electron-accepting element, has also been explored by Hao et al. [38]. The CDs were produced by the addition of boric acid (B(OH)3) into the hydrothermal carbonisation of glucose, using a Teflon autoclave at 180 °C for

• 12 h (Scheme 7). The resultant fluorescent nanoparticles had an average diameter of 4 nm and were negatively charged with ZP values of −40.7 mV. XPS and FTIR analysis confirmed the presence of B in the CD structure. Although, the addition of boron did not change the typical blue fluorescence profile

Continuous N-alkylation reactions of amino alcohols using γ-Al₂O₃ and supercritical CO₂: unexpected formation of cyclic ureas and urethanes by reaction with CO₂

• Emilia S. Streng,
• Darren S. Lee,
• Michael W. George and
• Martyn Poliakoff

Beilstein J. Org. Chem. 2017, 13, 329–337, doi:10.3762/bjoc.13.36

• ., boron salts from reductive amination [4]. Hydrogenation offers a greener approach but is often only applicable to simple substrates due to chemoselectivity issues. An approach that has received much attention recently is the concept of hydrogen borrowing catalysis [5][6][7][8][9][10][11][12][13][14][15

Solution-phase automated synthesis of an α-amino aldehyde as a versatile intermediate

• Hisashi Masui,
• Sae Yosugi,
• Shinichiro Fuse and
• Takashi Takahashi

Beilstein J. Org. Chem. 2017, 13, 106–110, doi:10.3762/bjoc.13.13

• ), to which a solution of 2,2-dimethoxypropane in dichloromethane and a solution of boron trifluoride·ethyl ether complex in dichloromethane were added. Originally, the respective solutions were loaded into the reagent reservoirs (RR1 and RR3). After stirring at 25 °C for 3 h, the reaction was quenched

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

Direct arylation catalysis with chloro[8-(dimesitylboryl)quinoline-κN]copper(I)

• Sem Raj Tamang and
• James D. Hoefelmeyer

Beilstein J. Org. Chem. 2016, 12, 2757–2762, doi:10.3762/bjoc.12.272

• ) intermediate may be well-stabilized by boron as a Z-type ligand, and the mesityl groups surrounding boron may favor the association of arenes for the deprotonation–metalation and the oxidative addition steps. Wang et al. proposed concerted metalation–deprotonation via a sigma bond metathesis involving a cyclic

Orthogonal protection of saccharide polyols through solvent-free one-pot sequences based on regioselective silylations

• Serena Traboni,
• Emiliano Bedini and
• Alfonso Iadonisi

Beilstein J. Org. Chem. 2016, 12, 2748–2756, doi:10.3762/bjoc.12.271

• activation effect of boron complexes [33]. Over the last years, we have addressed our interest towards the development of solvent-free protocols aimed at regioselective protection of highly functionalized saccharide substrates. This effort led to a simple protocol for the selective benzylation of primary

Benzothiadiazole oligoene fatty acids: fluorescent dyes with large Stokes shifts

• Lukas J. Patalag and
• Daniel B. Werz

Beilstein J. Org. Chem. 2016, 12, 2739–2747, doi:10.3762/bjoc.12.270

• as the carbohydrate part of glycolipids [7][8]. A further alternative is to render the lipid and especially the fatty acid part fluorescently active by the introduction of fluorescent moieties (Figure 1). Prominent examples in this area are NBD- (nitrobenzoxadiazole) [9][10], BODIPY- (boron

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

• (crystallographic numbering, cf. Figure 2: C9) is clearly detectable at δ = 9.22 ppm in DMSO-d6, while the boron and fluorine atoms give resonance frequencies at δ = −3.45 ppm, and δ = −133.91, −159.97, −165.18 ppm in the 11B NMR and 19F NMR spectra, respectively. A single crystal X-ray analysis of the borane

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

• after the reaction under oxygen atmosphere at 50 °C (Scheme 24) [252]. The boron-containing catalysts LiB(C6F5)4 or Ca[B(C6F5)4]2 were developed for the Baeyer–Villiger oxidation of ketones with aqueous H2O2 to give the lactones in high yields [253][254]. A regioselective Baeyer–Villiger oxidation of

• 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

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

• favourable thermodynamics with an increase in the electropositive nature of boron, which in turn increases the rate of the transmetallation step. Changing the group at the 4-position of the phenylboronic acid gave good yields for both electron-rich (19, 79% yield) and electron-poor (33, 76% yield

A T-shape diphosphinoborane palladium(0) complex

• Patrick Steinhoff and
• Michael E. Tauchert

Beilstein J. Org. Chem. 2016, 12, 1573–1576, doi:10.3762/bjoc.12.152

• diphospinoborane (o-PR2-C6H4)2BR’ ligand RDPBR’) has received considerable attention [1][2][3], with first catalytic applications emerging [4]. The acyclic boron group in these ligands can adopt a variety of coordination modes (Figure 1) [5]. The borane can act as a σ-acceptor ligand in case of η1-B coordination

• (e.g., 1 [6] and 2 [7]), or as a boron containing π-ligand adopting η2-B,C (3) [8] or η3-B,C,C coordination (4 and 5) [5][9][10]. Changes of the hapticity appear to have significant influence onto the reactivity of the coordinated transition metal towards substrates [8]. For zerovalent palladium

• solid-state structure of 9 displayed a slightly distorted T-shape geometry around the palladium center. A short Pd1–B1 distance of 2.243(2) Å (cf. complex 2: 2.194(3) Å) and a significant pyramidalization at the boron center (ΣBα = 341°) is observed, indicating a strong Pd(0)→B bond. The distance

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

Scope and mechanism of the highly stereoselective metal-mediated domino aldol reactions of enolates with aldehydes

• M. Emin Cinar,
• Bernward Engelen,
• Martin Panthöfer,
• Hans-Jörg Deiseroth,
• Jens Schlirf and
• Michael Schmittel

Beilstein J. Org. Chem. 2016, 12, 813–824, doi:10.3762/bjoc.12.80

• enolates (Ti [23], Zr [24], Si [25], and Sn [26]) and boron enolates [27] have adopted a considerable significance because of their high potential to control the stereochemical outcome of the bond formation [28][29][30]. However, the other group III metal enolates have been almost completely omitted over

• center: it should (a) exhibit Lewis acidity, (b) be sufficiently electropositive, and (c) display a sufficiently large ion radius so that the reaction cascade can take place in the periphery of the metal. The latter requirement is apparently prohibitive for a boron(III)-mediated reaction because the ion

Iridium/N-heterocyclic carbene-catalyzed C–H borylation of arenes by diisopropylaminoborane

• Mamoru Tobisu,
• Takuya Igarashi and
• Naoto Chatani

Beilstein J. Org. Chem. 2016, 12, 654–661, doi:10.3762/bjoc.12.65

• C–H borylation of arenes has been widely used in organic synthesis because it allows the introduction of a versatile boron functionality directly onto simple, unfunctionalized arenes. We report herein the use of diisopropylaminoborane as a boron source in C–H borylation of arenes. An iridium(I

• (Scheme 1). The most commonly used boron sources are pinacolborane (HBpin, 1a) and bis(pinacolato)diboron (B2pin2, 1b), which form pinacol esters of arylboronic acids. Although the pinacol ester products prepared in these reactions are amenable to a range of transformations, their reactivity is generally

• arylboronic acid is synthetically useful because it can be readily deprotected with a dilute aqueous acid [20]. We envisioned that diisopropylaminoborane (1g) [21] could be a useful boron source because the resulting aminoborylated products are sufficiently labile to be converted into various boron

Self and directed assembly: people and molecules

• Tony D. James

Beilstein J. Org. Chem. 2016, 12, 391–405, doi:10.3762/bjoc.12.42

• using boron as a chiral catalyst was a good idea. We quickly came up with a research plan over a beer or two (Figure 13). Then on our return to the UK we quickly put these ideas into practice with the investigation of a “chiral boron reagent” formed between binol and trimethoxy borate for the Lewis acid

• catalyst of diastereoselective aza-Diels–Alder reactions [68] (Figure 14). While, the structure of the “chiral boron reagent” still remains unknown during our investigation of analogues we discovered a very interesting three-component self-assembly. Chiral binol, a chiral amine and 2-formylbenzeneboronic

• in 2002. (Left) Private photo taken in Osaka. (Right) Photo taken in Tokyo by Katsuhiko Ariga. Preparation of chiral boron reagent and use as catalyst for aza-Diels–Alder reactions. Chiral three component self-assembling system. Reaction of trimethylsilyl cyanide with tricarbonyl (η5-cyclohexadienyl

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

Spiro-fused carbohydrate oxazoline ligands: Synthesis and application as enantio-discrimination agents in asymmetric allylic alkylation

• Jochen Kraft,
• Martin Golkowski and
• Thomas Ziegler

Beilstein J. Org. Chem. 2016, 12, 166–171, doi:10.3762/bjoc.12.18

• ester 11 as boron source (Scheme 2) [22][23][24]. 2-Pyridineboronic acid 11 was chosen due to its increased nucleophilicity compared to other boron sources like pinacol boronic esters or MIDA boronates [25][26]. The cross coupling proceeded smoothly in THF and gave ligands 9 and 10 in good yields

Assembly of synthetic Aβ miniamyloids on polyol templates

• Sebastian Nils Fischer and
• Armin Geyer

Beilstein J. Org. Chem. 2015, 11, 2646–2653, doi:10.3762/bjoc.11.284

• the Hot=Tap oligomer. The mixture of azide 9, 2-formylphenylboronic acid (14) and LVFFA shows a single signal set for the esterified product (Figure 8). Another advantage of this system is the cooperativity of imine formation and esterification, because the imino nitrogen coordinates the boron atom

Copper-catalyzed stereoselective conjugate addition of alkylboranes to alkynoates

• Takamichi Wakamatsu,
• Kazunori Nagao,
• Hirohisa Ohmiya and
• Masaya Sawamura

Beilstein J. Org. Chem. 2015, 11, 2444–2450, doi:10.3762/bjoc.11.265

• the present copper catalysis is proposed in Figure 1. An alkoxycopper complex (A) is initially formed by the reaction of CuOAc, t-BuOK and P(OPh)3. Boron-to-cupper transmetalation between A and the alkylborane 2 occurs to form an alkylcopper(I) species (B) and a t-butoxyborane (9-BBN-Ot-Bu) [12][13

Chiral Cu(II)-catalyzed enantioselective β-borylation of α,β-unsaturated nitriles in water

• Lei Zhu,
• Taku Kitanosono,
• Pengyu Xu and
• Shū Kobayashi

Beilstein J. Org. Chem. 2015, 11, 2007–2011, doi:10.3762/bjoc.11.217

• Lei Zhu Taku Kitanosono Pengyu Xu Shu Kobayashi Department of Chemistry, School of Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, Japan 10.3762/bjoc.11.217 Abstract The promising performance of copper(II) complexes was demonstrated for asymmetric boron conjugate addition to α,β

• substrates were suitable despite being insoluble in water. Keywords: carbon–boron bond formation; catalytic asymmetric synthesis; chiral copper(II) catalysis; β-hydroxy nitriles; Introduction In recent years, optically active organoboranes have attracted considerable attraction as versatile synthons for

• the synthesis of biologically interesting compounds and of other materials. In particular, compounds with a nitrile group in the β-position with respect to the boron moiety represent an important subset of organoboron intermediates because these compounds contain two functional groups. Their C–B