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

• of course the most economical way of carrying out oxidations. However, there have also been several rather successful and highly enantioselective reports that describe analogous α-hydroxylation reactions by using alternative oxygen-transfer reagents (Scheme 10). A few years ago, Meng et al. carried

Contribution of microreactor technology and flow chemistry to the development of green and sustainable synthesis

• Flavio Fanelli,
• Giovanna Parisi,
• Leonardo Degennaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2017, 13, 520–542, doi:10.3762/bjoc.13.51

• batch mode [61]. Pericàs and co-workers taking advantage of the high catalytic activity, robustness and recyclability of the supported catalyst, performed also straightforward gram synthesis of target compounds. In the context of photocatalysis and oxidations using flow microreactors [62][63], Noël

Solvent-free, visible-light photocatalytic alcohol oxidations applying an organic photocatalyst

• Martin Obst and
• Burkhard König

Beilstein J. Org. Chem. 2016, 12, 2358–2363, doi:10.3762/bjoc.12.229

• photocatalytic oxidations with riboflavin tetraacetate, using a transparent milling chamber. However, this reactor proved to be unsuitable: the solid reaction mixture prevented light to reach the photocatalyst, both by attachment of small amounts of solid to the inner side and shielding within the milling

The direct oxidative diene cyclization and related reactions in natural product synthesis

• Juliane Adrian,
• Leona J. Gross and
• Christian B. W. Stark

Beilstein J. Org. Chem. 2016, 12, 2104–2123, doi:10.3762/bjoc.12.200

• -catalyzed methods or even anodic oxidations) [131][132][133][134][135][136]. In 2014 the Brown group proposed an auxiliary-controlled synthesis of trans-(+)-linalool oxide (79) using a permanganate-mediated type A oxidative cyclization as the key step (Scheme 16) [137]. Thus, 1,5-diene 77 was subjected to

Thiophene-forming one-pot synthesis of three thienyl-bridged oligophenothiazines and their electronic properties

• Dominik Urselmann,
• Konstantin Deilhof,
• Bernhard Mayer and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2016, 12, 2055–2064, doi:10.3762/bjoc.12.194

• proceeds with lower oxidation potentials and consistently reversible oxidations can be identified. The Stokes shifts are large and substantial fluorescence quantum yields can be measured. Computational chemistry indicates lowest energy conformers with sigmoidal and helical structure, similar to

• electronic ground state property. Therefore, the ease of oxidation of the title compounds 3 in comparison to the model 10-hexyl-10H-phenothiazine with E00/+1 = 730 mV was measured. All three thienyl-bridged oligophenothiazines 3 display cathodically shifted first oxidations in comparison to the model

Synthesis and characterization of fluorinated azadipyrromethene complexes as acceptors for organic photovoltaics

• Forrest S. Etheridge,
• Roshan J. Fernando,
• Sandra Pejić,
• Matthias Zeller and
• Geneviève Sauvé

Beilstein J. Org. Chem. 2016, 12, 1925–1938, doi:10.3762/bjoc.12.182

• . The electrochemical properties of the complexes are summarized in Table 2 with the voltammograms of the zinc(II) and BF2+ chelates shown in Figure 6 and Figure 7, respectively. For all zinc(II) complexes, cyclic voltammograms reveal two reversible oxidations, while an irreversible oxidation occurs for

A flow reactor setup for photochemistry of biphasic gas/liquid reactions

• Josef Schachtner,
• Patrick Bayer and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2016, 12, 1798–1811, doi:10.3762/bjoc.12.170

• , the solution absorbance and other parameters. Until today, such protocols under flow conditions are most advanced with photosensitized oxidations which most recently have matured to great efficacy and versatility by the works of Seeberger et al. and Noël et al. Prominent examples include the

• selective oxidations of various organic molecules (Scheme 5). From a conceptual point of view, the combination of two of the most abundant “reagents” on the surface of our planet, oxygen and visible light, with a safe, scalable, and efficient reactor technology for chemical reactions constitutes an approach

• application to oxidations with gaseous oxygen as the stoichiometric oxidant. The range of application of such a modular home-built reactor is 0.04–0.5 mmol min−1 substrate throughput, 0.4–2.5 mL min−1 liquid phase flow rates, −40 to 60 °C, and 5–40 bar oxygen pressure. The device can be easily assembled

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

• review by Strukul, special emphasis was placed on metal-catalyzed Baeyer–Villiger oxidations [196]. Green approaches in the Baeyer–Villiger reaction were highlighted by another review [200]. The present review covers a more modern aspect of this reaction, viz., the performance of the process using

• organocatalysts [262][263]. There are also Green chemistry approaches for Baeyer−Villiger oxidations based on enzyme-mediated processes, which are used for the preparation of chiral lactones. This type of biocatalysis is useful in synthetic chemistry and either isolated enzymes or living whole cells are applied

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

• between the oxidations states Pd(0)/Pd(II) is of potential interest for organometallic transformations involved in homogeneous catalysis, such as the reductive elimination. Here we report the synthesis of the diphosphinoborane (o-PCy2-C6H4)2BPh ligand CyDPBPh. CyDPBPh reacts with CpPd(η3-C3H5) yielding

Methylpalladium complexes with pyrimidine-functionalized N-heterocyclic carbene ligands

• Dirk Meyer and
• Thomas Strassner

Beilstein J. Org. Chem. 2016, 12, 1557–1565, doi:10.3762/bjoc.12.150

• ]. One of the most prominent examples are the palladium catalyzed cross-coupling reactions [2], but in addition palladium complexes recently received much attention also in the field of selective CH oxidations [3][4][5][6]. The catalytic conversion of alkanes and especially of methane into a value-added

Automated glycan assembly of a S. pneumoniae serotype 3 CPS antigen

• Markus W. Weishaupt,
• Stefan Matthies,
• Mattan Hurevich,
• Claney L. Pereira,
• Heung Sik Hahm and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2016, 12, 1440–1446, doi:10.3762/bjoc.12.139

• -automation chemical modifications and the loss of product, we assembled pneumococcal serotype 3 CPS structures utilizing glucose and glucuronic acid monosaccharide building blocks and thus avoided late-stage oxidations. Results and Discussion Mindful of this strategic framework, glucuronic acid building

Cationic Pd(II)-catalyzed C–H activation/cross-coupling reactions at room temperature: synthetic and mechanistic studies

• Takashi Nishikata,
• Alexander R. Abela,
• Shenlin Huang and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2016, 12, 1040–1064, doi:10.3762/bjoc.12.99

• their Lewis acidity. Cationic palladium complexes [123], in particular, possess a wide breadth of reactivity, having been used to catalyze Diels–Alder [124][125], aldol and Mannich reactions [126][127][128], Wacker oxidations [129], polymerizations of alkenes [130][131], and asymmetric 1,4-additions

• one electron oxidations to form monomeric Pd(III) complexes have also been studied [251], but the successful implementation of silver-free conditions with stoichiometric palladium herein would appear to eliminate this as a key step. To the best of our knowledge, the existence of Pd(IV) complexes has

Cupreines and cupreidines: an established class of bifunctional cinchona organocatalysts

• Laura A. Bryant,
• Rossana Fanelli and
• Alexander J. A. Cobb

Beilstein J. Org. Chem. 2016, 12, 429–443, doi:10.3762/bjoc.12.46

• then turn to asymmetric 1,2-additions followed by conjugate additions, a cyclopropanation, (ep)oxidations, α-functionalisation processes, cycloadditions, domino processes and finally miscellaneous reactions. We ultimately aim to demonstrate through this plethora of diverse processes, that the 6’-OH

Base metal-catalyzed benzylic oxidation of (aryl)(heteroaryl)methanes with molecular oxygen

• Hans Sterckx,
• Johan De Houwer,
• Carl Mensch,
• Wouter Herrebout,
• Kourosch Abbaspour Tehrani and
• Bert U. W. Maes

Beilstein J. Org. Chem. 2016, 12, 144–153, doi:10.3762/bjoc.12.16

• preparation of more complex molecules, typical for fine chemicals, the use of aerobic oxidations is more the exception than the norm [9]. This is partly due to the limited synthetic scope and selectivity of the available oxidation methods. Further research into selective and mild aerobic oxidations is

• therefore of vital importance. Of special interest are the transition metal- and organocatalyzed oxidations of activated methylenes such as in benzylic methylenes or their heteroaromatic analogues. Due to the activation, the formation of the corresponding ketones and aldehydes becomes feasible under mild

• conditions. Oxidations of this kind using Oxone® [10][11], NaOCl [12] or especially peroxides [13][14][15][16][17][18][19] as the terminal oxidant are quite numerous. However, transformations using molecular oxygen are rare. Ishii showed that organocatalysts such as N-hydroxyphthalimide (NHPI) in combination

Biocatalysis for the application of CO₂ as a chemical feedstock

• Apostolos Alissandratos and
• Christopher J. Easton

Beilstein J. Org. Chem. 2015, 11, 2370–2387, doi:10.3762/bjoc.11.259

• strategies to avoid energy constraints, and as a result there are several metabolic pathways for reductive transformation of CO2 (Figure 1) [23][24]. Generally, such processes are driven by coupling the CO2 transformations with oxidations that generate reducing equivalents, sometimes in conjunction with the

Photoinduced 1,2,3,4-tetrahydropyridine ring conversions

• Baiba Turovska,
• Henning Lund,
• Viesturs Lūsis,
• Anna Lielpētere,
• Edvards Liepiņš,
• Sergejs Beljakovs,
• Inguna Goba and
• Jānis Stradiņš

Beilstein J. Org. Chem. 2015, 11, 2166–2170, doi:10.3762/bjoc.11.234

• ][5][6]. In 1944 hydroperoxides were first obtained by H. Hock [7] and R. Udris [8][9][10] as the catalytic oxidation products of cumene. Heterocyclic hydroperoxides have been less represented, although some of these constitute the best choice for selective oxidations even in nature. When the peroxy

• asymmetric oxidations. We have found a sunlight activated reaction of 1,2,3,4-tetrahydropiridine with dioxygen (3O2) producing stable heterocyclic hydroperoxide in excellent yield. The reaction has significant advantages as it uses cost-free reagents: light and dioxygen. The same reaction demonstrated the

Active site diversification of P450cam with indole generates catalysts for benzylic oxidation reactions

• Paul P. Kelly,
• Anja Eichler,
• Susanne Herter,
• David C. Kranz,
• Nicholas J. Turner and
• Sabine L. Flitsch

Beilstein J. Org. Chem. 2015, 11, 1713–1720, doi:10.3762/bjoc.11.186

• screening a large mutant library of 16,500 clones using a simple, highly sensitive colony-based colorimetric screen against indole. These mutants showed distinct fingerprints of activity not only when screened in oxidations of substituted indoles but also for unrelated oxidations such as benzylic

• low cost starting materials [1]. One of the most attractive reagents in terms of cost and environmental impact for hydrocarbon oxidation is oxygen in the presence of a catalyst. In this context enzymatic oxidations are attractive, in particular cytochrome P450 monooxygenases (P450s or CYPs) due to

• their ability to catalyse selective C–H bond oxidations under mild conditions [2]. The soluble bacterial camphor monooxygenase P450cam (CYP101A1, EC 1.14.15.1) from Pseudomonas putida is one of the most studied P450s and has been engineered to accept a variety of non-natural substrates including aryl

Star-shaped tetrathiafulvalene oligomers towards the construction of conducting supramolecular assembly

• Masahiko Iyoda and
• Masashi Hasegawa

Beilstein J. Org. Chem. 2015, 11, 1596–1613, doi:10.3762/bjoc.11.175

• oxidations at 0.20, 0.29, and 0.61 V correspond to the formation of 34•+, 342+, and 344+. Therefore, the redox behavior of 34 is similar to those of 28, 29, and 31. The [18]annulenes 30 and 31 formed a fibrous structure in H2O–THF 1:1, and 31 required longer time for fiber formation than 30 owing to weaker

Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

• David W. Manley and
• John C. Walton

Beilstein J. Org. Chem. 2015, 11, 1570–1582, doi:10.3762/bjoc.11.173

• efficient. Tubes with thin internal coatings of TiO2 have also been employed with some success (see below); research to improve their reusability is underway. Review Generation of ROS and organic oxidations When TiO2 is irradiated in the presence of moisture and atmospheric oxygen, the water acts as the

• application undergoing extensive trials is of self-cleaning garments [19] that may prove effective particularly for army wear in desert conditions. ROS generated from semiconductor photoredox catalysis (SCPC) have also been put to use in a good number of preparative oxidations so taking the place of toxic

• metals (such as chromium and manganese) [20][21][22]. Many SCPC oxidations of aromatics have been reported, but of these it is perhaps the oxidation of benzene to phenol that is the most industrially significant [23][24]. Unfortunately, product selectivity is poor because the phenol itself undergoes

Tetrathiafulvalene-based azine ligands for anion and metal cation coordination

• Awatef Ayadi,
• Aziz El Alamy,
• Olivier Alévêque,
• Magali Allain,
• Nabil Zouari,
• Mohammed Bouachrine and
• Abdelkrim El-Ghayoury

Beilstein J. Org. Chem. 2015, 11, 1379–1391, doi:10.3762/bjoc.11.149

• precursors 1 and 2 as well as of ligands L1 and L2 was investigated by cyclic voltammetry (Figure 6 and Table 3). The measurements in the case of precursors 1 and 2 show two reversible oxidations at E1ox = +0.26 V, E2ox = +0.75 V and E1ox = +0.32 V, E2ox = +0.77 V vs Ag/Ag+, respectively, that are anodically

• two reversible oxidations at E1ox = +0.20 V, E2ox = +0.70 V and E1ox = +0.25 V, E2ox = +0.70 V vs Ag/Ag+, respectively) that are cathodically shifted when compared to the ones of 1 and 2 indicating that the pyridine-hydrazone group is less electron deficient than the corresponding

New tris- and pentakis-fused donors containing extended tetrathiafulvalenes: New positive electrode materials for rechargeable batteries

• Shintaro Iwamoto,
• Yuu Inatomi,
• Daisuke Ogi,
• Satoshi Shibayama,
• Yukiko Murakami,
• Minami Kato,
• Kazuyuki Takahashi,
• Kazuyoshi Tanaka,
• Nobuhiko Hojo and
• Yohji Misaki

Beilstein J. Org. Chem. 2015, 11, 1136–1147, doi:10.3762/bjoc.11.128

• oxidation relates to the orbital energy, the first oxidations of 5–9 might occur at lower potentials than TTPY. The energy differences between the HOMO and HOMO–1 of all the donors (0.041–0.113 eV) were smaller than that of TTPY (0.186 eV). In particular, the orbital energies of the HOMO and HOMO–1 of 8a

Advances in the synthesis of functionalised pyrrolotetrathiafulvalenes

• Luke J. O’Driscoll,
• Sissel S. Andersen,
• Marta V. Solano,
• Dan Bendixen,
• Morten Jensen,
• Troels Duedal,
• Jess Lycoops,
• Cornelia van der Pol,
• Rebecca E. Sørensen,
• Karina R. Larsen,
• Kenneth Myntman,
• Christian Henriksen,
• Stinne W. Hansen and
• Jan O. Jeppesen

Beilstein J. Org. Chem. 2015, 11, 1112–1122, doi:10.3762/bjoc.11.125

• aromaticity occurs: 2 contains a single aromatic, 6 π-electron 1,3-dithiolium system, and 3 possesses two such systems (Figure 1). These oxidations occur at low potential (E11/2 = 0.34 V and E21/2 = 0.73 V vs Ag/AgCl in MeCN [4]) and can be performed sequentially and reversibly. Additionally, both 2 and 3 are

A hybrid electron donor comprising cyclopentadithiophene and dithiafulvenyl for dye-sensitized solar cells

• Gleb Sorohhov,
• Chenyi Yi,
• Michael Grätzel,
• Silvio Decurtins and
• Shi-Xia Liu

Beilstein J. Org. Chem. 2015, 11, 1052–1059, doi:10.3762/bjoc.11.118

• synthesized and characterized. Both of them undergo two reversible oxidations and strongly absorb in the visible spectral region due to a photo-induced intramolecular charge-transfer (ICT) transition. To a great extent, the electronic interaction between the D and A units is affected by the presence of a

• of the reference compound 6 was carried out as well. The latter undergoes two reversible oxidations at 0.44 V and 0.75 V vs Fc+/Fc, hence at values which are lower than the oxidation potentials of the individual components DTF [24] and CPDT [25]. This observation indicates the formation of an

• electron donor and a cyanoacrylic acid either directly linked or linked through a phenyl spacer. Both of them show two reversible oxidations and strongly absorb in the visible spectral region. As evidenced by electrochemical and optical data, the electronic interaction between the D and A units is greatly

Interactions between tetrathiafulvalene units in dimeric structures – the influence of cyclic cores

• Huixin Jiang,
• Virginia Mazzanti,
• Christian R. Parker,
• Søren Lindbæk Broman,
• Jens Heide Wallberg,
• Karol Lušpai,
• Adam Brincko,
• Henrik G. Kjaergaard,
• Anders Kadziola,
• Peter Rapta,
• Ole Hammerich and
• Mogens Brøndsted Nielsen

Beilstein J. Org. Chem. 2015, 11, 930–948, doi:10.3762/bjoc.11.104

• -conjugated tetraethynylethene (TEE) spacer as in compound 1a (Figure 1), then the two TTFs behave as independent redox centres that are oxidized at the same potentials in cyclic voltammetry (two two-electron oxidations) [8][9][10]. However, by bridging the two TTFs with an additional TEE in a cyclic

• structure, as in the radiaannulene 2a, communication between the two TTFs is observed in the cyclic voltammetry experiment, and the first two-electron event showed the waves diverging from each other (two stepwise oxidations) [10]. In addition, the intermediate radical cation showed an IVCT absorption at

• slightly more difficult to oxidize owing to the presence of the electron-withdrawing alkyne system. The acyclic compounds 1a and 5–7 all undergo two reversible two-electron oxidations; that is, the two TTFs are oxidized at the same potentials when separated by butadiyne, gem- or trans-TEE, or bis

A simple and efficient method for the preparation of 5-hydroxy-3-acyltetramic acids

• Johanna Trenner and
• Evgeny V. Prusov

Beilstein J. Org. Chem. 2015, 11, 323–327, doi:10.3762/bjoc.11.37

• briefly tested, but were found to produce rather mediocre yields of hydroxylated compounds. Attempted oxidations with Oxone or air gave no product at all. Our efforts to improve the yield of the desired product by variation of reaction conditions were rather fruitless, and therefore, our attention was