Hydrogenation of unactivated enamines to tertiary amines: rhodium complexes of fluorinated phosphines give marked improvements in catalytic activity

• Sergey Tin,
• Tamara Fanjul and
• Matthew L. Clarke

Beilstein J. Org. Chem. 2015, 11, 622–627, doi:10.3762/bjoc.11.70

• here could be useful in this regard. While it is possible some heterogeneous hydrogenation catalysts could accomplish enamine reductions, the issues with functional group tolerance would be problematic in many cases. From a more general synthetic viewpoint, the use of reagents such as sodium

• triacetoxyborohydride or sodium cyanoborohydride can be appealing at small scale where the practical issues noted above are not so important. However, the formation of tertiary amines from aryl ketones using hydride reagents has been reported to be problematic [31]. In addition, the hydride reductions, whether carried

• out as reductive amination or reduction of enamines need stoichiometric acetic acid to promote the formation of the iminium ion that is the substrate reduced in hydride reductions, which might not be compatible with other functional groups. To the best of our knowledge, the hydrogenation of

Stereoselective cathodic synthesis of 8-substituted (1R,3R,4S)-menthylamines

• Carolin Edinger,
• Jörn Kulisch and
• Siegfried R. Waldvogel

Beilstein J. Org. Chem. 2015, 11, 294–301, doi:10.3762/bjoc.11.34

• positive effect on reductions on lead cathodes due to the formation of an ionic coating on the electrode surface and concomitant inhibition of cathodic corrosion and evolution of molecular hydrogen [46][47]. The chosen additives differ in size and number of ammonium groups. The use of additive 11 leads to

Cathodic reductive coupling of methyl cinnamate on boron-doped diamond electrodes and synthesis of new neolignan-type products

• Taiki Kojima,
• Rika Obata,
• Tsuyoshi Saito,
• Yasuaki Einaga and
• Shigeru Nishiyama

Beilstein J. Org. Chem. 2015, 11, 200–203, doi:10.3762/bjoc.11.21

• /meso = 74:26) and E-3 (25%), along with 41% of 1a. Similar cathodic reductions of cinnamate derivatives were carried out using Hg [10][11], Cu [12][13], Pb [13][14], Zn [13], Sn [13], and Ag [13], and the major products were the cyclic products (type 3) through Diekmann-type cyclization, whereas the

Recent advances in the electrochemical construction of heterocycles

• Robert Francke

Beilstein J. Org. Chem. 2014, 10, 2858–2873, doi:10.3762/bjoc.10.303

• using electron transfer mediators (Scheme 1) play an important role. With regard to selectivity, the direct method is often complementary to typical chemical oxidations and reductions, since electrochemical oxidation or reduction proceeds via discrete electron transfer steps rather than atom transfer

Electrocarboxylation: towards sustainable and efficient synthesis of valuable carboxylic acids

• Roman Matthessen,
• Jan Fransaer,
• Koen Binnemans and
• Dirk E. De Vos

Beilstein J. Org. Chem. 2014, 10, 2484–2500, doi:10.3762/bjoc.10.260

• promising technology for environmentally friendly chemical processes [26]. The electroreduction of CO2 can be applied for the synthesis of fuels like formic acid [27], methanol [28] or methane [29] via two-, six- and eight-electron reductions, respectively (Scheme 2). This way electric energy from periodic

Scalable synthesis of 5,11-diethynylated indeno[1,2-b]fluorene-6,12-diones and exploration of their solid state packing

• Bradley D. Rose,
• Peter J. Santa Maria,
• Aaron G. Fix,
• Chris L. Vonnegut,
• Lev N. Zakharov,
• Sean R. Parkin and
• Michael M. Haley

Beilstein J. Org. Chem. 2014, 10, 2122–2130, doi:10.3762/bjoc.10.219

• reductions with potentials of −0.78 to −0.84 V for the first reduction and −1.18 to −1.26 V for the second reduction. The small differences in the absorbance and cyclic voltammetry essentially fall within experimental error. Interestingly these compounds have a low energy S0→S1 transition at ca. 500–525 nm

Synthesis of rigid p-terphenyl-linked carbohydrate mimetics

• Maja Kandziora and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2014, 10, 1749–1758, doi:10.3762/bjoc.10.182

• 81:19 mixture of diastereomers in 72% yield (Scheme 5). In contrast, the reduction with L-selectride at −10 °C selectively furnished pure diastereomer 12a in 73% yield. In accordance with previous observations of reductions of related phenylthio-substituted bicyclic compounds [25], a hydride attack

The Ugi four-component reaction as a concise modular synthetic tool for photo-induced electron transfer donor-anthraquinone dyads

• Sarah Bay,
• Gamall Makhloufi,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 1006–1016, doi:10.3762/bjoc.10.100

• diphenothiazine unit [79][80]. These values for first and second oxidation can also be found in the donor-only reference compound 10a. Furthermore two quasi-reversible reductions stemming from the anthraquinone core can be detected for E1/2−1/0 between −850 to −900 mV and for E1/2−2/−1 between −1370 and −1500 mV

Synthesis of chiral N-phosphinyl α-imino esters and their application in asymmetric synthesis of α-amino esters by reduction

• Yiwen Xiong,
• Haibo Mei,
• Lingmin Wu,
• Jianlin Han,
• Yi Pan and
• Guigen Li

Beilstein J. Org. Chem. 2014, 10, 653–659, doi:10.3762/bjoc.10.57

• prepared above were subjected to this system to examine the reaction scope. As shown in Table 4, reduction of these chiral α-imino esters provided excellent yields (up to 98%) and diastereoselectivities (up to 99:1). Almost all the reductions could achieve more than 90% yield, only for the case of para

• correspondingly. Conclusion In conclusion, we have developed a method for the synthesis of chiral N-phophinyl α-imino esters for the first time, which have been used as precursors for asymmetric reductions with L-Selectride as reductant. Varieties of α-amino esters were obtained in excellent chemical yields and

Integration of enabling methods for the automated flow preparation of piperazine-2-carboxamide

• Richard J. Ingham,
• Claudio Battilocchio,
• Joel M. Hawkins and
• Steven V. Ley

Beilstein J. Org. Chem. 2014, 10, 641–652, doi:10.3762/bjoc.10.56

• –Ponndorf–Verley reductions [22] and Oppenauer oxidations [23] where zirconia activation is required). In fact, it seems that the extent of hydration of pyrazine-2-carbonitrile is proportional to the initial water content of the zirconium catalyst. To confirm this hypothesis, we ran a control experiment in

Concise, stereodivergent and highly stereoselective synthesis of cis- and trans-2-substituted 3-hydroxypiperidines – development of a phosphite-driven cyclodehydration

• Peter H. Huy,
• Julia C. Westphal and
• Ari M. P. Koskinen

Beilstein J. Org. Chem. 2014, 10, 369–383, doi:10.3762/bjoc.10.35

• selectivities (dr up 2.6:1, Table 4, entry 4), which is in harsh contrast to previously reported reductions of related para-methoxybenzylamino and benzylamino ketones with DIBALH giving rise of the best diastereoselectivities [59][60]). Albeit up to four equivalents of DIBALH were utilized, only 40–60

Tuning the interactions between electron spins in fullerene-based triad systems

• Maria A. Lebedeva,
• Thomas W. Chamberlain,
• E. Stephen Davies,
• Bradley E. Thomas,
• Martin Schröder and
• Andrei N. Khlobystov

Beilstein J. Org. Chem. 2014, 10, 332–343, doi:10.3762/bjoc.10.31

• of the precursor compounds 7 and 8 (Figure S5, Supporting Information File 1), we suggest that this series of reductions corresponds to the addition of up to 3 electrons per fullerene cage (in total 6 electrons per molecule). No oxidation processes were found in the range up to 1.5 V (vs Fc+/Fc). For

• triads 1 and 4, containing C60 only, these potentials are similar to those of their precursor 7. A similar correlation was noted for the C70 containing triads 3 and 6 and their precursor 8. Comparison of 1 with 3, 4 with 6 and 7 with 8 shows that the first and second reductions of C60, in general, occur

• overlap of C60/C70-based reductions. These processes are separated by an additional process that appears as a shoulder on the first reduction in 2 and 5 (Figure 2 and Figure S6, Supporting Information File 1). A similar feature is noted to cathodic potential of the second reduction process. For 2 and 5 we

Synthesis of new enantiopure poly(hydroxy)aminooxepanes as building blocks for multivalent carbohydrate mimetics

• Léa Bouché,
• Maja Kandziora and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2014, 10, 213–223, doi:10.3762/bjoc.10.17

• ; 1,2-oxazines; rearrangements; reductions; Introduction Since carbohydrates play a crucial role in biochemistry, compounds mimicking their structure and/or function (carbohydrate mimetics) have attracted great attention in academic research and in drug development [1][2][3]. These mimetics should not

• experience of our group this step often leads to irreproducible results in particular in the case of the oxepane derivatives. This was confirmed by reductions performed with 14 and 15. In Scheme 9, we present the best results obtained under these “standard conditions”. The aminooxepanes 26 and 27 [49] were

• [54]. Acetic acid in methanol (1:5) was a good medium for our reductions and substrate 14 was now smoothly reduced under hydrogen atmosphere with palladium on charcoal. After filtration through a pad of acidic DOWEX® resin followed by elution with aqueous ammonia the clean poly(hydroxy)aminooxepane 26

Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C₂-symmetric building block: a strategy for the synthesis of decanolide natural products

• Bernd Schmidt and
• Oliver Kunz

Beilstein J. Org. Chem. 2013, 9, 2544–2555, doi:10.3762/bjoc.9.289

• -butanol solvent mixture than the analogous enone reductions outlined in Scheme 3 and Table 2. Compared to these reactions, the saturated ester 25 was obtained in a nearly quantitative yield using half the amount of Cu precatalyst and BDP ligand. In order to obtain enantiomerically pure 21, an enzyme

An investigation of the observed, but counter-intuitive, stereoselectivity noted during chiral amine synthesis via N-chiral-ketimines

• Thomas C. Nugent,
• Richard Vaughan Williams,
• Andrei Dragan,
• Alejandro Alvarado Méndez and
• Andrei V. Iosub

Beilstein J. Org. Chem. 2013, 9, 2103–2112, doi:10.3762/bjoc.9.247

• improved understanding of the factors controlling the stereochemical outcome of yet unknown N-chiral imine reductions. In this light we have investigated the stereochemical outcome for the reduction of mediocre cis/trans ratio imines in the presence of a heterogeneous hydrogenation catalyst and molecular

• tautomerization processes. In general it was argued that tautomerization was promoted by high reaction temperatures, or the employed heterogeneous hydrogenation catalyst, or the use of a protic solvent [40][47][51]. Two of these studies are closely related to this one because they are hydrogen-based reductions

• reductions in the present study were performed in aprotic solvent at room temperature, except for Table 1, entry 5, where the reduction was carried out at 35 °C (Table 1 and Table 2). Current study – background We restricted this study to the hydrogen-based reduction of imines because hydrogen is by far the

The chemistry of amine radical cations produced by visible light photoredox catalysis

• Jie Hu,
• Jiang Wang,
• Theresa H. Nguyen and
• Nan Zheng

Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234

• light-mediated reductions such as reductive dehalogenation [47][48][49][50][51], reductive radical cyclization [52][53][54], reduction of activated ketones [49], and reduction of aromatic azides [55]. The third mode involves deprotonation of amine radical cation 2 to form α-amino radical 3, which is

3D-printed devices for continuous-flow organic chemistry

• Vincenza Dragone,
• Victor Sans,
• Mali H. Rosnes,
• Philip J. Kitson and
• Leroy Cronin

Beilstein J. Org. Chem. 2013, 9, 951–959, doi:10.3762/bjoc.9.109

• ATR-IR flow cell. As a proof of concept, we utilized two types of organic reactions, imine syntheses and imine reductions, to show how different reactor configurations and substrates give different products. Keywords: 3D printing; flow chemistry; flow IR; in-line analysis; imine reduction; imine

• examples of reductions in microfluidic devices have been reported in the literature [5][23][24][25]. The condensation reactions were conducted using a 2 M solution of benzaldehyde (1a) in MeOH as before, which was pumped through inlet B’ into reactor R2’ at 0.0125 mL min−1 and mixed with a 2 M solution of

Synthesis, photophysical and electrochemical characterization of terpyridine-functionalized dendritic oligothiophenes and their Ru(II) complexes

• Amaresh Mishra,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2013, 9, 866–876, doi:10.3762/bjoc.9.100

• Table 2. The attachment of tpy-ligands to the dendrons resulted in the appearance of multiple quasi-reversible one-electron reduction processes. The CV response of ligand 8 in the negative potential regime showed the typical two quasi-reversible waves due to successive one-electron reductions of the tpy

Reductions of aldehydes and ketones with a readily available N-heterocyclic carbene borane and acetic acid

• Vladimir Lamm,
• Xiangcheng Pan,
• Tsuyoshi Taniguchi and
• Dennis P. Curran

Beilstein J. Org. Chem. 2013, 9, 675–680, doi:10.3762/bjoc.9.76

• -dimethylimidazol-2-ylidene borane. Aldehydes are reduced over 1–24 h at room temperature with 1 equiv of acetic acid and 0.5 equiv of the NHC-borane. Ketone reductions are slower but can be accelerated by using 5 equiv of acetic acid. Aldehydes can be selectively reduced in the presence of ketones. On a small

• for such reductions, boron reductants are widely used in the field of synthetic chemistry due to their availability and favorable reaction profiles [1][2][3]. For instance, sodium borohydride (NaBH4) is an inexpensive salt that is one of the most popular hydride sources for the reduction of aldehydes

• ketones towards reduction by achiral and chiral carbene boranes [12], and we showed that some high-temperature reductions of halides were probably occurring by ionic rather than radical pathways [13]. Recently, we discovered in collaboration with Mayr that NHC-boranes are good hydride sources by

Enantioselective reduction of ketoimines promoted by easily available (S)-proline derivatives

• Martina Bonsignore,
• Maurizio Benaglia,
• Laura Raimondi,
• Manuel Orlandi and
• Giuseppe Celentano

Beilstein J. Org. Chem. 2013, 9, 633–640, doi:10.3762/bjoc.9.71

• -established methodology to perform enantioselective reductions of carbon nitrogen double bonds [1]. In the past decade different classes of enantiomerically pure Lewis bases have been developed, including N-formyl derivatives, oxazolines, imidazole derivatives, sulfonamides and picolinamides [2][3]. Some of

• donor functionality as the carboxylic acid group; it is worth mentioning that also phosphoric acid catalyzed reductions of C=N bonds with Hantzsch ester involve the coordination and activation of the substrate through the formation of a H-bond between the hydrogen atom of the phosphoric acid and the

• selectivity was achieved by tuning the metal catalyst. In the trichlorosilane-mediated reductions in this work we aimed to exploit the imine activation by the acid proton of the carboxylic group, which can act at the same time as a Lewis basic site to coordinate the silicon atom and hopefully control the

Synthesis of SF₅-containing benzisoxazoles, quinolines, and quinazolines by the Davis reaction of nitro-(pentafluorosulfanyl)benzenes

• Petr Beier and
• Tereza Pastýříková

Beilstein J. Org. Chem. 2013, 9, 411–416, doi:10.3762/bjoc.9.43

• arylacetonitriles to provide the SF5-containing benzisoxazoles. Good yields were obtained with arylacetonitriles containing the electron-neutral or electron-donor group, while those with the electron-acceptor group were found to be unreactive. Reductions of the benzisoxazoles gave ortho-aminobenzophenones in high

• arylacetonitriles containing electron-neutral or electron-donor groups. Reductions of the benzisoxazoles with iron powder in acetic acid provided high yields of SF5-containing ortho-aminobenzophenones, which underwent condensation reactions to quinolines or quinazolines. This methodology provides straightforward

Glycosylation efficiencies on different solid supports using a hydrogenolysis-labile linker

• Mayeul Collot,
• Steffen Eller,
• Markus Weishaupt and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2013, 9, 97–105, doi:10.3762/bjoc.9.13

• necessitates aqueous solutions to perform Staudinger reductions in the placement of amino groups as well as for ester saponification used to remove temporary protective groups prior to sulfation. A range of different glycosylation conditions were explored, whereby the couplings were performed either twice by

Hydrophobic analogues of rhodamine B and rhodamine 101: potent fluorescent probes of mitochondria in living C. elegans

• Laurie F. Mottram,
• Safiyyah Forbes,
• Brian D. Ackley and
• Blake R. Peterson

Beilstein J. Org. Chem. 2012, 8, 2156–2165, doi:10.3762/bjoc.8.243

• -shifted absorbance and emission spectra (5–9 nm), modest reductions in molar extinction coefficent and quantum yield, and enhanced partitioning into octanol compared with aqueous buffer of 10-fold or more. Comparison of living C. elegans (nematode roundworm) animals treated with the classic fluorescent

Reactions of nitroxides XIII: Synthesis of the Morita–Baylis–Hillman adducts bearing a nitroxyl moiety using 4-acryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl as a starting compound, and DABCO and quinuclidine as catalysts

• Jerzy Zakrzewski

Beilstein J. Org. Chem. 2012, 8, 1515–1522, doi:10.3762/bjoc.8.171

• electron. However, there are also reactions that do involve the free electron (e.g., many types of reductions, or a disproportionation in an acidic environment). To the best of our knowledge, nitroxyl radicals have not yet been applied in the MBH reaction (to date), and the potential influence of the

A simple and efficient dual optical signaling chemodosimeter for toxic Hg(II)

• Sabir H. Mashraqui,
• Sapna A. Tripathi,
• Sushil S. Ghorpade and
• Smita R. Britto

Beilstein J. Org. Chem. 2012, 8, 1352–1357, doi:10.3762/bjoc.8.155

• −3 M led to partial reductions of the probe’s maxima at 493 and 462 nm, accompanied by the appearance of a new, weakly absorbing band at 347 nm. However, unlike Hg2+, the desulfurization product 1 could not be detected with Ag+. Though it has not been investigated in detail, the findings mentioned