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

Coupled chemo(enzymatic) reactions in continuous flow

• Ruslan Yuryev,
• Simon Strompen and
• Andreas Liese

Beilstein J. Org. Chem. 2011, 7, 1449–1467, doi:10.3762/bjoc.7.169

• D-28 by a transketolase-catalyzed reaction with added D,L-25. Catalase was used to regenerate the reduced cofactor FADH by oxidation with oxygen. In order to decrease enzyme deactivation caused by shear forces, a bubble-free aeration through a silicon membrane was implemented. A space-time yield of

• biofilm membrane reactor (Scheme 24) [52][53]. Cells of Pseudomonas sp. were grown in a biofilm attached to the inner surface of a silicon tube, through which a nutrient solution was constantly pumped. In a specially designed hermetic reaction compartment the tube was partially submerged into liquid 73

Scaling up of continuous-flow, microwave-assisted, organic reactions by varying the size of Pd-functionalized catalytic monoliths

• Ping He,
• Stephen J. Haswell,
• Paul D. I. Fletcher,
• Stephen M. Kelly and
• Andrew Mansfield

Beilstein J. Org. Chem. 2011, 7, 1150–1157, doi:10.3762/bjoc.7.133

• any observable change in the reaction conversion. Results and Discussion Synthesis of silica monolith and Pd-supported silica monolith catalyst The reaction parameters, such as polymer concentration, acid strength, water content, amount of silicon alkoxide, reaction temperature and reaction time, all

Intramolecular hydroamination of alkynic sulfonamides catalyzed by a gold–triethynylphosphine complex: Construction of azepine frameworks by 7-exo-dig cyclization

• Hideto Ito,
• Tomoya Harada,
• Hirohisa Ohmiya and
• Masaya Sawamura

Beilstein J. Org. Chem. 2011, 7, 951–959, doi:10.3762/bjoc.7.106

• mixture. The tube was sealed with a cap equipped with a Teflon-coated silicon rubber septum. The tube was taken from the glove box, and was placed in a water bath (25 °C). After the reaction was complete (as monitored by TLC), the reaction mixture was passed through a pad of silica gel and was

Homoallylic amines by reductive inter- and intramolecular coupling of allenes and nitriles

• Peter Wipf and
• Marija D. Manojlovic

Beilstein J. Org. Chem. 2011, 7, 824–830, doi:10.3762/bjoc.7.94

• reagent to allylzirconocenes, transient allylzinc intermediates can be successfully added to phosphoryl- and sulfonylimines to provide homoallylic amines in good yields and diastereoselectivities [15]. Of particular interest was the reaction of tin- or silicon-substituted allenes that furnish bis-metallic

Gold-catalyzed alkylation of silyl enol ethers with ortho-alkynylbenzoic acid esters

• Haruo Aikawa,
• Tetsuro Kaneko,
• Naoki Asao and
• Yoshinori Yamamoto

Beilstein J. Org. Chem. 2011, 7, 648–652, doi:10.3762/bjoc.7.76

• ; Findings Silyl enol ethers have been widely used in organic synthesis as effective carbon nucleophiles for the construction of carbon frameworks [1][2][3][4]. Generally, they react with a variety of electrophiles to give carbonyl compounds as products due to cleavage of the silicon–oxygen bond. For example

• complex 8 as a leaving compound [43][44][45][46]. In the case of ordinary substitution reactions with alkyl halides (path a in Scheme 1), generated halide ions would attack the silyl group, due to their strong affinities with the silicon atom, and cleave the silicon–oxygen bond of 7. However, in the

Stereogenic boron in 2-amino-1,1-diphenylethanol-based boronate–imine and amine complexes

• Sebastian Schlecht,
• Walter Frank and
• Manfred Braun

Beilstein J. Org. Chem. 2011, 7, 615–621, doi:10.3762/bjoc.7.72

• hetero elements has been investigated thoroughly for compounds with stereogenic sulfur [1], phosphorus [2], nitrogen [3] and silicon atoms [4]. By comparison, stereogenic tetrahedral-coordinated boron has been studied to a much lesser extent. This is partly because it was incorporated in a chiral

Unusual behavior in the reactivity of 5-substituted-1H-tetrazoles in a resistively heated microreactor

• Bernhard Gutmann,
• Toma N. Glasnov,
• Tahseen Razzaq,
• Walter Goessler,
• Dominique M. Roberge and
• C. Oliver Kappe

Beilstein J. Org. Chem. 2011, 7, 503–517, doi:10.3762/bjoc.7.59

• = 0.0832 × 10−3 s−1 at 240 °C (Figure 3). Control experiments in a microwave reaction vial constructed from strongly microwave absorbing silicon carbide (SiC), which shields the vessel contents from the electromagnetic field and therefore mimics a conventionally heated autoclave experiment, provided

• at 215 nm. The experiments were carried out either in a standard 10 mL Pyrex tube or a vessel made from sintered silicon carbide and gave identical results. Bechamp reduction (Table 1) A 0 M, 0.25 M, 0.5 M and 1 M aqueous HCl solution in ethanol was prepared from conc. HCl and ethanol. A sample of 1

Reciprocal polyhedra and the Euler relationship: cage hydrocarbons, C_nH_n and closo-boranes [B_xH_x]²⁻

• Michael J. McGlinchey and
• Henning Hopf

Beilstein J. Org. Chem. 2011, 7, 222–233, doi:10.3762/bjoc.7.30

• polycycloalkanes have been constructed from other elemental species: Clusters containing lithium, transition metals, silicon, phosphorus, arsenic, bismuth, lead, etc. have been characterized [61][62][63][64], and their architectures continue to delight us. The existence of molecules of such exquisite symmetry

Self-assembly and semiconductivity of an oligothiophene supergelator

• Pampa Pratihar,
• Suhrit Ghosh,
• Vladimir Stepanenko,
• Sameer Patwardhan,
• Ferdinand C. Grozema,
• Laurens D. A. Siebbeles and
• Frank Würthner

Beilstein J. Org. Chem. 2010, 6, 1070–1078, doi:10.3762/bjoc.6.122

• air. Silicon cantilevers (Olympus Corporation, Japan) with a resonance frequency of ~300 kHz and spring constant of ~42 N/m were used. A solution of T1 in methylcyclohexane (MCH) with a concentration of 2 × 10−3 M was spin-coated onto highly oriented pyrolytic graphite (HOPG) at 6000 rpm. The sample

Kinetics and mechanism of vanadium catalysed asymmetric cyanohydrin synthesis in propylene carbonate

• Michael North and
• Marta Omedes-Pujol

Beilstein J. Org. Chem. 2010, 6, 1043–1055, doi:10.3762/bjoc.6.119

• silicon species [82] or the formation of cyanide anions. The most effective catalysts possess both Lewis acidity and Lewis basicity and so can simultaneously activate both the aldehyde and TMSCN [1]. We have recently shown [52] that a Hammett analysis correlating the rate of reaction of meta- and para

• largely be located on silicon as shown in Figure 8a. This was found to be the case (ρ = +0.4) for asymmetric cyanohydrin synthesis catalysed by bimetallic aluminium(salen) complex 6 in the presence of triphenylphosphine oxide [83][84], indicating that most of the catalysis in this case was due to

Formation of epoxide-amine oligo-adducts as OH-functionalized initiators for the ring-opening polymerization of ε-caprolactone

• Julia Theis and
• Helmut Ritter

Beilstein J. Org. Chem. 2010, 6, 938–944, doi:10.3762/bjoc.6.105

• provided with a magnetic stirring bar was loaded with diglycidyl ether of bispenol A (1) (1.702 g, 5.00 mmol) and 4-nitroanisole (2) (0.766 g, 5.00 mmol). The solids were dissolved in 4-methyl-1-cyclohexene (2.404 g, 25.0 mmol). After the addition of 10% Pd/C (125 mg) the tube was sealed with a silicon

Pyridinium based amphiphilic hydrogelators as potential antibacterial agents

• Sayanti Brahmachari,
• Sisir Debnath,
• Sounak Dutta and
• Prasanta Kumar Das

Beilstein J. Org. Chem. 2010, 6, 859–868, doi:10.3762/bjoc.6.101

• few hours under vacuum before imaging. The morphology of the dried gel of compound 2 was also studied using AFM (Veeco, model AP0100) in the non-contact mode. A piece of gel was mounted on a silicon wafer and dried for a few hours under vacuum before imaging. Fluorescence spectroscopy The emission

Aromatic and heterocyclic perfluoroalkyl sulfides. Methods of preparation

• Vladimir N. Boiko

Beilstein J. Org. Chem. 2010, 6, 880–921, doi:10.3762/bjoc.6.88

• analogues continues to grow. Previous reviews in this area are either dated [19] or focus on specialist aspects such as perfluoroalkyl radicals [20][21][22], fluorinated carbanions [23], organometallic compounds [24][25], perfluoroalkyl sulfenyl halides [26], perfluoroalkyl silicon reagents [27][28][29][30

CAAC Boranes. Synthesis and characterization of cyclic (alkyl) (amino) carbene borane complexes from BF₃ and BH₃

• Julien Monot,
• Louis Fensterbank,
• Max Malacria,
• Emmanuel Lacôte,
• Steven J. Geib and
• Dennis P. Curran

Beilstein J. Org. Chem. 2010, 6, 709–712, doi:10.3762/bjoc.6.82

• boron [6][7][13]. Most of the first generation carbene-boranes have been made from N-heterocyclic carbenes in which the carbene carbon is stabilized by two donating nitrogen atoms (imidazolylidene, triazolylidene, etc) or other heteroatoms (phosphorous, silicon, oxygen) [14][15][16][17][18]. An

Chromo- and fluorophoric water-soluble polymers and silica particles by nucleophilic substitution reaction of poly(vinyl amine)

• Katja Hofmann,
• Ingolf Kahle,
• Frank Simon and
• Stefan Spange

Beilstein J. Org. Chem. 2010, 6, No. 79, doi:10.3762/bjoc.6.79

•  2a shows a typical XPS wide-scan spectrum of the bare silica support which was unloaded. The spectrum contains the expected peaks from silicon (Si 2s and Si 2p) and oxygen (O 1s, O 2s and the O KLL Auger series). The small C 1s peak shows the presence of typical hydrocarbon surface contaminations

• ]:[O] = 0.152 (nitrogen can be considered as label for the organic adsorption layer and oxygen the label for the silicon support). The coupling of PVAm with the fluorophore group 1 introduces an additional amount of carbonyl groups (carbon atoms of the cyclic amide in structure 1-P) into the organic