Gallium-containing polymer brush film as efficient supported Lewis acid catalyst in a glass microreactor

• Rajesh Munirathinam,
• Roberto Ricciardi,
• Richard J. M. Egberink,
• Jurriaan Huskens,
• Michael Holtkamp,
• Herbert Wormeester,
• Uwe Karst and
• Willem Verboom

Beilstein J. Org. Chem. 2013, 9, 1698–1704, doi:10.3762/bjoc.9.194

• Polystyrene sulfonate polymer brushes, grown on the interior of the microchannels in a microreactor, have been used for the anchoring of gallium as a Lewis acid catalyst. Initially, gallium-containing polymer brushes were grown on a flat silicon oxide surface and were characterized by FTIR, ellipsometry, and

• a flat silicon oxide surface in order to optimize the reaction conditions before attempting the functionalization of a microreactor. Polystyrene sulfonate (PSS) polymer brushes [19] were synthesized according to the procedure summarized in Scheme 2. First, a monolayer of atom transfer radical

• polymerization (ATRP) initiator was covalently anchored on silicon oxide substrates [20]. Then, a solution of styrene sulfonate in methanol/water (1:3) in the presence of 2-2’-bipyridyl and CuBr, was used to grow the PSS polymer brushes by means of ATRP. After activation of the polymer brushes with 1 M HCl, they

Organocatalyzed enantioselective desymmetrization of aziridines and epoxides

• Ping-An Wang

Beilstein J. Org. Chem. 2013, 9, 1677–1695, doi:10.3762/bjoc.9.192

• the enantioselective desymmetrization of meso-epoxides. Organocatalyzed enantioselective ring-opening of epoxides in early stage In 1981, Andrews [78] and co-workers have found that the ring-opening of cyclohexene and cyclopentene oxides with silicon halides was facilitated by the addition of

• was 87% ee. The proposed reaction mechanism is depicted in Figure 14. The first step of the catalytic cycle is the activation of SiCl4 by chiral phosphoramide OC-62 to form a complex, which was ionized to produce a highly reactive silicon cation and a chloride ion. The epoxide was activated by the

• chiral complexation of the phosphorus/silicon cation, and then followed by an attack with the chloride ion in an SN2 fashion to furnish chlorohydrin enantioselectively (Figure 14). From this description, the activation of SiCl4 was depending on the formation of the chiral complexation of the phosphorus

A reductive coupling strategy towards ripostatin A

• Kristin D. Schleicher and
• Timothy F. Jamison

Beilstein J. Org. Chem. 2013, 9, 1533–1550, doi:10.3762/bjoc.9.175

• configuration in the product (Scheme 3, reaction 1). Berson has quantified the energetic preference in this transformation, while Turos has shown that the presence of a silicon substituent on the “donor carbon” facilitates the hydrogen migration [23][24][25][26]. In contrast, Wilson has reported formation of

Development of an additive-controlled, SmI₂-mediated stereoselective sequence: Telescoped spirocyclisation, lactone reduction and Peterson elimination

• Brice Sautier,
• Karl D. Collins and
• David J. Procter

Beilstein J. Org. Chem. 2013, 9, 1443–1447, doi:10.3762/bjoc.9.163

• to “switch on” individual steps mediated by the electron transfer reagent. The sequence involves the use of two activated SmI2 reagent systems and a silicon stereocontrol element that exerts complete diastereocontrol over the cyclisation and is removed during the final stage of the sequence by

• ” individual steps: spirocyclisation, lactone reduction and Peterson elimination allow rapid access to functionalised cyclopentanols, containing two vicinal quaternary stereocentres, from simple starting materials. The sequence involves the use of two activated SmI2 reagent systems, and a silicon stereocontrol

• elimination of triols 3 would result in removal of the silicon stereocontrol element used to control the stereochemical course of C–C bond formation. In early studies, treatment of triol 3b with t-BuOK gave vinyl cyclopentanol 5b in moderate yield [45], but the reaction suffered from poor reproducibility

α-Bromodiazoacetamides – a new class of diazo compounds for catalyst-free, ambient temperature intramolecular C–H insertion reactions

• Åsmund Kaupang and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2013, 9, 1407–1413, doi:10.3762/bjoc.9.157

• leaves the diazo function intact [4]. Among the reported transformations are substitutions of the diazomethyl hydrogen for electrophiles based on boron [5][6][7], nitrogen (NO2+) [8][9][10][11][12], silicon [13][14][15], phosphorous [16][17][18], sulfur [19][20][21] and halogens [10][22][23][24][25][26

True and masked three-coordinate T-shaped platinum(II) intermediates

• Manuel A. Ortuño,
• Salvador Conejero and
• Agustí Lledós

Beilstein J. Org. Chem. 2013, 9, 1352–1382, doi:10.3762/bjoc.9.153

• in THF solution, since an interaction with the BF4− counteranion is not observed, although the elemental analysis evidences the lack of the THF molecule in the solid state [89]. Contrarily, the naphthyl derivative S17 was found together with the BF4− adduct C8 (Figure 9) [53]. For silicon-related

Preparation of optically active bicyclodihydrosiloles by a radical cascade reaction

• Koichiro Miyazaki,
• Yu Yamane,
• Ryuichiro Yo,
• Hidemitsu Uno and
• Akio Kamimura

Beilstein J. Org. Chem. 2013, 9, 1326–1332, doi:10.3762/bjoc.9.149

• -carbonyl radical that underwent radical cyclization to a terminal alkyne unit. The resulting vinyl radical attacked the silicon atom in an SHi manner to give dihydrosilole. The reaction preferentially formed trans isomers of bicyclosiloles with an approximately 7:3 to 9:1 selectivity. Keywords

• similar cascade SHi reaction, because there were several reports so far that show such SHi reaction on silicon atoms progressing efficiently [23][24][25][26][27][28]. In this paper, we report a new synthesis of chiral bicyclodihydrosiloles through an addition–cyclization–SHi cascade reaction in one-pot

Synthesis and spectroscopic properties of 4-amino-1,8-naphthalimide derivatives involving the carboxylic group: a new molecular probe for ZnO nanoparticles with unusual fluorescence features

• Laura Bekere,
• David Gachet,
• Vladimir Lokshin,
• Wladimir Marine and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2013, 9, 1311–1318, doi:10.3762/bjoc.9.147

• consecutive pulses to 126 ns. The generated femtosecond pulses illuminated a 1 cm quartz cell containing the solution under study. The photo-excited fluorescence was collected in a 90° geometry and sent into a subtractive double-monochromator (DH10, Jobin-Yvon) before being detected by a silicon avalanche

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

• devices [7]. All this is important in chemistry, and in particular for the realization of micro- and millifluidic devices. Microfluidic devices compatible with a wide range of organic solvents and reagents are usually made of silicon or glass, which requires specialized manufacturing techniques and are

Ring-opening reaction of 2,5-dioctyldithieno[2,3-b:3',2'-d]thiophene in the presence of aryllithium reagents

• Hao Zhong,
• Jianwu Shi,
• Jianxun Kang,
• Shaomin Wang,
• Xinming Liu and
• Hua Wang

Beilstein J. Org. Chem. 2013, 9, 767–774, doi:10.3762/bjoc.9.87

• packing (right). Carbon, silicon, oxygen and sulfur atoms are depicted with thermal ellipsoids set at 50% probability level, and all hydrogen atoms are omitted for clarity. The ring-opening reaction of symmetric 2,5-disubstituted-dithieno[2,3-b:3',2'-d]thiophenes in the presence of n-BuLi in THF. The ring

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

• 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

• coordination ability to the silicon atom, leading to multiple possible coordination modes of trichlorosilane, which are detrimental for the determination of a well-defined activation of the reducing agent and a control of the stereoselectivity. Notably, catalyst 5, with the pivaloyl group at the nitrogen atom

Thermotropic and lyotropic behaviour of new liquid-crystalline materials with different hydrophilic groups: synthesis and mesomorphic properties

• Alexej Bubnov,
• Miroslav Kašpar,
• Věra Hamplová,
• Ute Dawin and
• Frank Giesselmann

Beilstein J. Org. Chem. 2013, 9, 425–436, doi:10.3762/bjoc.9.45

• well-defined thickness (fixed by spherical glass spacers, Figure 5a) were also used. A special silicon glue stable up to 250 °C was used for sealing (Figure 5c) preventing evaporation of the solvent (usually water or DG). Mesomorphic lyotropic behaviour TL1–TL5 were tested for lyotropic behaviour by

Spin state switching in iron coordination compounds

• Philipp Gütlich,
• Ana B. Gaspar and
• Yann Garcia

Beilstein J. Org. Chem. 2013, 9, 342–391, doi:10.3762/bjoc.9.39

• recently, special hydrostatic pressure cells for magnetic and Mössbauer measurements have been developed, in which silicon oil is used as the pressure-transmitting medium [166][167]. The influence of pressure on SCO properties, for instance the critical ST temperature and shape and position of hysteresis

Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation

• Kei Murakami and
• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 278–302, doi:10.3762/bjoc.9.34

• -pyridyl)silyl-substituted alkynes. The key intermediate 2h was prepared by copper-catalyzed arylmagnesiation of 2g, in which the 2-pyridyl group on silicon efficiently worked as a strong directing group (Scheme 11) [69]. Furthermore, they accomplished a short and efficient synthesis of tamoxifen from 2g

Intramolecular carbolithiation of N-allyl-ynamides: an efficient entry to 1,4-dihydropyridines and pyridines – application to a formal synthesis of sarizotan

• Wafa Gati,
• Mohamed M. Rammah,
• Mohamed B. Rammah and
• Gwilherm Evano

Beilstein J. Org. Chem. 2012, 8, 2214–2222, doi:10.3762/bjoc.8.250

• presence of secondary or primary alkyl chains such as cyclohexyl (5/6i) or n-hexyl (5/6j) groups did not afford the cyclized products, which could also not be obtained either when starting from a TIPS-protected primary ynamide (5/6k), the silicon protecting group being readily cleaved under the reaction

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

• hexachloro derivative 94 was treated by Gilman and co-workers with excess dimethylsilyl chloride and magnesium in THF, the hexasilylated derivative 95 was produced and again a ring-opening reaction to a conjugated bisallene had taken place (Scheme 23) [70]. In closing this section on silicon-substituted

Metal–ligand multiple bonds as frustrated Lewis pairs for C–H functionalization

• Matthew T. Whited

Beilstein J. Org. Chem. 2012, 8, 1554–1563, doi:10.3762/bjoc.8.177

• explored by Tilley, often have substantial positive character at the silicon site (especially in cationic complexes), leading to reactivity that is dominated by the electrophilicity of silicon, with the metal playing a secondary role [17]. Prominent examples include the formation of base-stabilized

• , indicating that the metal center is not itself very reactive. However, the ability to stabilize the metallacycle is clearly derived from an enhanced transfer of electron density from ruthenium to silicon through an intervening heterocumulene. Unfortunately, retrocycloaddition to give silylene-group transfer

Influence of cyclodextrin on the solubility of a classically prepared 2-vinylcyclopropane macromonomer in aqueous solution

• Helmut Ritter,
• Jia Cheng and
• Monir Tabatabai

Beilstein J. Org. Chem. 2012, 8, 1528–1535, doi:10.3762/bjoc.8.173

• ) instrument equipped with a He–Ne-laser and an Avalanche photodiode detector. The turbidity measurements were carried out using a power-regulated semiconductor laser (λ = 670 nm) and a silicon photodiode in a TP1 turbidity photometer from TEPPER-Analytik. Glass-transition temperatures (Tg) were measured using

Synthesis and characterization of low-molecular-weight π-conjugated polymers covered by persilylated β-cyclodextrin

• Aurica Farcas,
• Ana-Maria Resmerita,
• Andreea Stefanache,
• Mihaela Balan and
• Valeria Harabagiu

Beilstein J. Org. Chem. 2012, 8, 1505–1514, doi:10.3762/bjoc.8.170

• scanning probe microscope (NT-MDT, Zelenograd, Moscow, Russia), in atomic force microscopy (AFM) configuration. The scan area was 2 × 2 µm2. Rectangular silicon cantilevers NSG10 (NT-MDT, Russia) with tips of high aspect ratio were used. All images were acquired in air, at room temperature (23 °C), in

Organocatalytic C–H activation reactions

• Subhas Chandra Pan

Beilstein J. Org. Chem. 2012, 8, 1374–1384, doi:10.3762/bjoc.8.159

• activation is well-known in the literature [26][27][28][29][30]. Stoichiometric amounts of a radical source, such as tributyltin hydride and tris(trimethylsilyl)silicon hydride [31], or irradiation [32] were also utilized for biaryl synthesis from unactivated arenes. However, organocatalysts have not been

An intramolecular inverse electron demand Diels–Alder approach to annulated α-carbolines

• Zhiyuan Ma,
• Feng Ni,
• Grace H. C. Woo,
• Sie-Mun Lo,
• Philip M. Roveto,
• Scott E. Schaus and
• John K. Snyder

Beilstein J. Org. Chem. 2012, 8, 829–840, doi:10.3762/bjoc.8.93

• 5). Little reaction occurred in toluene under microwave irradiation (Table 3, entry 6) unless silicon carbide chips were added as a microwave facilitator (Table 3, entry 7) [87]. Upon further exploration of the reaction conditions, it was discovered that the amidation/cycloaddition sequence could be

Synthesis and antifungal properties of papulacandin derivatives

• Marjolein van der Kaaden,
• Eefjan Breukink and
• Roland J. Pieters

Beilstein J. Org. Chem. 2012, 8, 732–737, doi:10.3762/bjoc.8.82

• 20, but in our hands a more complicated mixture resulted. We concluded that under our conditions deprotonation of the protecting group (protons α to silicon) may be competitive with the desired α-lithiation next to oxygen. Use of the more substituted TIPS silyl protecting group in 19 indeed solved

Facile isomerization of silyl enol ethers catalyzed by triflic imide and its application to one-pot isomerization–(2 + 2) cycloaddition

• Kazato Inanaga,
• Yu Ogawa,
• Yuuki Nagamoto,
• Akihiro Daigaku,
• Hidetoshi Tokuyama,
• Yoshiji Takemoto and
• Kiyosei Takasu

Beilstein J. Org. Chem. 2012, 8, 658–661, doi:10.3762/bjoc.8.73

• counter anion, Tf2N−, could attack the silicon atom of 2 to produce silyl triflic imide (R3SiNTf2) [8][9][10][11][12] and the corresponding ketone 3. Therefore, the use of a large amount of Tf2NH causes decomposition into 3 (Table 1, entry 2). We have previously reported the Tf2NH catalyzed (2 + 2

Fifty years of oxacalix[3]arenes: A review

• Kevin Cottet,
• Paula M. Marcos and
• Peter J. Cragg

Beilstein J. Org. Chem. 2012, 8, 201–226, doi:10.3762/bjoc.8.22

• independent of the group in the para-position. A silylated p-tert-butyloxacalix[3]arene 27 was characterized by X-ray crystallography to confirm that it was in the partial-cone conformation as shown in Figure 10. These derivatives could serve as reaction intermediates, due to the ease with which the silicon