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

• solvent-free photocatalysis is the application of heterogeneous, semiconducting photocatalysts, often based on titanium dioxide and other metal oxides [6][7][8]. However, to the best of our knowledge, no solvent-free visible-light driven transformation of a solid substrate applying an organic

Useful access to enantiomerically pure protected inositols from carbohydrates: the aldohexos-5-uloses route

• Felicia D’Andrea,
• Giorgio Catelani,
• Lorenzo Guazzelli and
• Venerando Pistarà

Beilstein J. Org. Chem. 2016, 12, 2343–2350, doi:10.3762/bjoc.12.227

• ][20][21], by microbial oxidation; 3) carbocyclization involving organometallic intermediates (Ferrier II reaction [22] performed on 6-O-acyl-hex-5-enopyranosides followed by reduction [23][24]; trialkylaluminium [25][26] or titanium(IV)-assisted [27] conversion of hex-5-enopyranosides and SmI2

Cp₂TiCl/D₂O/Mn, a formidable reagent for the deuteration of organic compounds

• Antonio Rosales and
• Ignacio Rodríguez-García

Beilstein J. Org. Chem. 2016, 12, 1585–1589, doi:10.3762/bjoc.12.154

• donor. Cp2TiCl, consists of titanium, one of the most abundant transition metals in the Earth’s crust [16], that can be easily prepared from commercial Cp2TiCl2 by using reductants such as Mn, Zn or Al [17][18], generating in THF, in absence of water a green solution, or a blue one in the presence of

• -ordination of water to Cp2TiCl might weakens the strength of the O–H bond. In this way a single electron transfer from titanium to oxygen might facilitate the HAT from the titanocene aqua-complex to the free radicals. Theoretical calculations supported that the coordination of water to Cp2TiIIICl weakens the

3,6-Carbazole vs 2,7-carbazole: A comparative study of hole-transporting polymeric materials for inorganic–organic hybrid perovskite solar cells

• Wei Li,
• Munechika Otsuka,
• Takehito Kato,
• Yang Wang,
• Takehiko Mori and
• Tsuyoshi Michinobu

Beilstein J. Org. Chem. 2016, 12, 1401–1409, doi:10.3762/bjoc.12.134

• a UV-O3 cleaner (Filgen, Model UV253E) for 20 min. The electron-accepting TiO2 compact layer was spin-coated (1500 rpm for 30 s) from a mildly acidic (after addition of 12 μM HCl) solution of titanium(IV) isopropoxide in anhydrous ethanol and sintered at 120 °C for 10 s. The mesoporous TiO2 layer

Selective bromochlorination of a homoallylic alcohol for the total synthesis of (−)-anverene

• Frederick J. Seidl and
• Noah Z. Burns

Beilstein J. Org. Chem. 2016, 12, 1361–1365, doi:10.3762/bjoc.12.129

• active bromochlorination catalyst is not yet known, we speculate that the procedural changes in entries 2–4 do not alter its structure, but rather change the distribution of titanium species responsible for off-cycle reactivity. Titanium alkoxides are known to undergo facile ligand exchange at −20 °C

• the trace formation of these highly reactive dichlorotitanium species early in the reaction, thereby preventing background bromochlorination. Lowering the concentration of the reaction may favour lower-order titanium aggregates over oligomeric species [12]. It has been our observation that high

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

• with benzaldehyde (PhCHO) is followed by the exergonic first aldol addition showing a small activation barrier of 1.82 kcal mol−1 via a half−chair like transition state (TS-C-A1), which is in accord with the anti-selective aldol addition of titanium enolates [53][54]. TS-C-A1 leads to the formation of

Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

• Rajeev S. Menon,
• Akkattu T. Biju and
• Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

• in Cheng’s group revealed an intriguing divergent catalytic dimerisation of 2-formylcinnamates 72. Co-operative catalysis by NHC precatalyst 73 and a Lewis acid (titanium isopropoxide) afforded isochromenone derivatives 74 via a sequence of reactions initiated by a benzoin condensation. Treatment of

Synthesis of constrained analogues of tryptophan

• Elisabetta Rossi,
• Valentina Pirovano,
• Marco Negrato,
• Giorgio Abbiati and
• Monica Dell’Acqua

Beilstein J. Org. Chem. 2015, 11, 1997–2006, doi:10.3762/bjoc.11.216

• -acetamidoacrylate (2) and its congeners with cyclic/acyclic dienes and azadienes occur under conventional heating or microwave irradiation [24]. Moreover, the use of titanium tetrachloride as Lewis acidic promoter has been reported [25]. Finally, simple functionalization reactions of indoles with 2 are reported in

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• -allylation sequence. The starting cycloadduct 321 was obtained by the double DA reaction between 1,3-cyclohexadiene and 1,4-benzoquinone. Further, treatment of 323 with catalyst 2 in the presence of titanium isopropoxide furnished the expected RRM product 324 in 92% yield (Scheme 70). Bicyclo[2.2.2]octene

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

• choices. It is widely accepted that titanium dioxide (TiO2) in its various mineral forms is by far the most effective and reliable. This is down to its harmlessness, low cost, high activity and stability under irradiation. TiO2 has a large band gap which lies in the UVA region of the spectrum (anatase

A new method for the synthesis of α-aminoalkylidenebisphosphonates and their asymmetric phosphonyl-phosphinyl and phosphonyl-phosphinoyl analogues

• Anna Kuźnik,
• Roman Mazurkiewicz,
• Mirosława Grymel,
• Katarzyna Zielińska,
• Jakub Adamek,
• Ewa Chmielewska,
• Marta Bochno and
• Sonia Kubica

Beilstein J. Org. Chem. 2015, 11, 1418–1424, doi:10.3762/bjoc.11.153

• mmol) were added to a glass beaker (25 mL) equipped with a cylindrical Pt mesh anode (20 cm2) and a rotating flat cathode (platinised titanium, 1.2 cm2). In the case of 1-(N-acetylamino)methylphosphonate (5a), NaCl (70 mg, 1.2 mmol) was placed in the beaker in its entirety at the beginning of oxidation

• titanium, 1.2 cm2). Electrolysis was carried out while stirring at 0.1 A until a 4.5–10 F/mol charge had passed (Table 2). After evaporation of MeOH under reduced pressure, the residue was extracted with CH2Cl2 followed by further evaporation of the solvent from the extracts in vacuo to obtain diethyl 1-(N

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• stereochemistry of the newly generated C–C double bonds in 78 was confirmed as trans with the aid of the NMR vicinal coupling constant. Finally, intramolecular McMurry coupling of 78 using titanium trichloride and lithium aluminum hydride (LAH) heated under reflux in THF provided the cyclophane derivative 79 (20

Design and synthesis of fused polycycles via Diels–Alder reaction and ring-rearrangement metathesis as key steps

• Sambasivarao Kotha and
• Ongolu Ravikumar

Beilstein J. Org. Chem. 2015, 11, 1259–1264, doi:10.3762/bjoc.11.140

• + Na]+ calcd for C25H32NaO2, 359.1982; found, 359.1986. Synthesis of compound 11 Analogously as described in [2], to a stirred solution of compound 10 (20 mg, 0.05 mmol) in toluene (20 mL) degassed with nitrogen for 10 minutes, purged with ethylene gas for another 10 minutes and then added titanium

Adsorption mechanism and valency of catechol-functionalized hyperbranched polyglycerols

• Stefanie Krysiak,
• Qiang Wei,
• Klaus Rischka,
• Andreas Hartwig,
• Rainer Haag and
• Thorsten Hugel

Beilstein J. Org. Chem. 2015, 11, 828–836, doi:10.3762/bjoc.11.92

• hyperbranched polyglycerol as a hydrophilic core with numerous DOPA (catechol) groups attached. A similar system has already proven to be advantageous for an antifouling coating on titanium oxide surfaces [21][22]. An added benefit of this system is that the oxidation of catechol to quinones makes crosslinking

• unclear, which underscores how little is known about the nature of the interaction between the catechol group of DOPA and metal oxide surfaces. To determine the force of a single catechol group on titanium dioxide, we performed AFM single molecule force spectroscopy measurements with tips functionalized

• pN peak to the catechol/titanium dioxide interaction and the shoulder at 700 pN to the interaction of multiple catechols. In a next step, the hyperbranched polyglycerols (hPGs) with different amounts of catechol end groups were desorbed from TiO2. The measurements were again performed with a pulling

Synthesis of tripodal catecholates and their immobilization on zinc oxide nanoparticles

• Franziska Klitsche,
• Julian Ramcke,
• Julia Migenda,
• Andreas Hensel,
• Tobias Vossmeyer,
• Horst Weller,
• Silvia Gross and
• Wolfgang Maison

Beilstein J. Org. Chem. 2015, 11, 678–686, doi:10.3762/bjoc.11.77

• ], carboxylates [5] and phosphates [6] as well as phosphonates [7] for metal and metal oxide surfaces. In addition, bifunctional catechols like dopamine or DOPA (L-3,4-dihydroxyphenylalanine, Figure 1B), have received considerable interest as anchor groups for important metal surfaces such as titanium oxide, iron

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

• purification of enamines 1a–i. One of the main modifications made to the synthetic procedure is at the end of the reaction, wet diethyl ether was added in order to precipitate all titanium salts (this strategy was previously used after formation of imine bonds using TiCl4) [16]. Enamine 1g was more stable than

Matsuda–Heck reaction with arenediazonium tosylates in water

• Ksenia V. Kutonova,
• Marina E. Trusova,
• Andrey V. Stankevich,
• Pavel S. Postnikov and
• Victor D. Filimonov

Beilstein J. Org. Chem. 2015, 11, 358–362, doi:10.3762/bjoc.11.41

• cinnamates were synthesized by the O-alkylation of cinnamic acids with dihaloalkanes or haloalkyl alcohols [14][16][18] or by the ring opening of tetrahydrofuran with cinnamic acid anhydrides or haloanhydrides, catalyzed by yttrium trichloride [19], titanium chloride, stannic chloride or allylsamarium

Multicomponent versus domino reactions: One-pot free-radical synthesis of β-amino-ethers and β-amino-alcohols

• Bianca Rossi,
• Nadia Pastori,
• Simona Prosperini and
• Carlo Punta

Beilstein J. Org. Chem. 2015, 11, 66–73, doi:10.3762/bjoc.11.10

• : aminoalcohols; free-radical addition; imine; multicomponent reaction; titanium salts; Introduction Multicomponent reactions (MCRs) represent a green approach towards the synthesis of polyfunctionalized molecules by promoting multiple bond-forming mechanisms in a one-pot synthesis [1][2][3][4][5][6][7

• our ongoing investigation of the role of titanium salts in mediating selective radical transformations [13][14], we have developed new, simple protocols for the synthesis of complex organic compounds through nucleophilic radical addition to imines generated in situ [15]. Several recent contributions

• approach. In fact, our procedure requires neither the preformation of imines nor anhydrous media, due to the coordinating effect of titanium salts, which promote the one-pot synthesis of amino derivatives according to a classical MCR. The basic approach consists of the simple mixing of an aniline, an

The Shono-type electroorganic oxidation of unfunctionalised amides. Carbon–carbon bond formation via electrogenerated N-acyliminium ions

• Alan M. Jones and
• Craig E. Banks

Beilstein J. Org. Chem. 2014, 10, 3056–3072, doi:10.3762/bjoc.10.323

• -acyliminium ion cyclisation strategy in the presence of a disubstituted acetylene nucleophile. Anodic oxidation proceeded in high yield and a smooth cyclisation of the pendant acetylene nucleophile was triggered by treatment with titanium tetrachloride. Ozonolysis of the chloromethyl alkene intermediate

Detonation nanodiamonds biofunctionalization and immobilization to titanium alloy surfaces as first steps towards medical application

• Juliana P. L. Gonçalves,
• Afnan Q. Shaikh,
• Manuela Reitzig,
• Daria A. Kovalenko,
• Jan Michael,
• René Beutner,
• Gianaurelio Cuniberti,
• Dieter Scharnweber and
• Jörg Opitz

Beilstein J. Org. Chem. 2014, 10, 2765–2773, doi:10.3762/bjoc.10.293

• on chemical modification of the nanodiamond surface with phosphate groups and their electrochemically assisted immobilization on titanium-based materials to increase adhesion at biomaterial surfaces. The starting material is detonation nanodiamond, which exhibits a heterogeneous surface due to the

• functional groups resulting from the nitrogen-rich explosives and the subsequent purification steps after detonation synthesis. Nanodiamond surfaces are chemically homogenized before proceeding with further functionalization. Suspensions of resulting surface-modified nanodiamonds are applied to the titanium

• alloy surfaces and the nanodiamonds subsequently fixed by electrochemical immobilization. Titanium and its alloys have been widely used in bone and dental implants for being a metal that is biocompatible with body tissues and able to bind with adjacent bone during healing. In order to improve titanium

Encapsulation of biocides by cyclodextrins: toward synergistic effects against pathogens

• Véronique Nardello-Rataj and
• Loïc Leclercq

Beilstein J. Org. Chem. 2014, 10, 2603–2622, doi:10.3762/bjoc.10.273

• nanoparticles Various nanoparticles have been successfully developed as antimicrobial agents. As an example, zinc oxide and titanium dioxide nanoparticles have been prepared by chemical and sol–gel methods [91]. Biocidal applications of these nanoparticles may lead to valuable discoveries in various fields such

An integrated photocatalytic/enzymatic system for the reduction of CO₂ to methanol in bioglycerol–water

• Michele Aresta,
• Angela Dibenedetto,
• Tomasz Baran,
• Antonella Angelini,
• Przemysław Łabuz and
• Wojciech Macyk

Beilstein J. Org. Chem. 2014, 10, 2556–2565, doi:10.3762/bjoc.10.267

• rutin (rutin@TiO2) shows an electron injection into the conduction band of TiO2 as the result of a direct molecule-to-band charge transfer (MBCT) within the surface-formed, colored, charge-transfer complex of titanium(IV) [21]. TiO2 with an adsorbed chromium(III) anionic complex [CrF5(H2O)]2– acts as a

• the chemical stability and photostability of photocatalysts, are also under continuous investigation for their further improvement and bring the whole reaction closer to a potential application. Conclusion Titanium dioxide modified with chromium(III) complex, [CrF5(H2O)]2−@TiO2, exhibits great ability

• Synthesis of photosensitized TiO2 The modification of TiO2 with rutin was carried out as reported in the literature [27]. A titanium dioxide powder, P25 Evonik (500 mg), was added to 10 cm3 of aqueous rutin solution (10−2 mol dm−3). The suspension was sonicated (10 minutes) and the colored precipitate was

Multicomponent reactions in nucleoside chemistry

• Mariola Koszytkowska-Stawińska and
• Włodzimierz Buchowicz

Beilstein J. Org. Chem. 2014, 10, 1706–1732, doi:10.3762/bjoc.10.179

• opinion the method is worth noting since it represents an interesting extension of the Vorbrüggen N-glycosylation process. Thus, the reaction sequence leading to nucleosides 119 was initiated by the titanium(IV) chloride-promoted alkylation of 2,3-dihydrofurane 117 with ethyl pyruvate at −78 °C (1 hour

Triazol-substituted titanocenes by strain-driven 1,3-dipolar cycloadditions

• Andreas Gansäuer,
• Andreas Okkel,
• Lukas Schwach,
• Laura Wagner,
• Anja Selig and
• Aram Prokop

Beilstein J. Org. Chem. 2014, 10, 1630–1637, doi:10.3762/bjoc.10.169

• functional groups is difficult due to the nucleophilicity of the cyclopentadienyl anions before metalation and the electrophilicity of titanium after metalation [21][22]. We have devised a conceptually different approach addressing these issues. It relies on the use of carboxylate-containing titanocene

Homogeneous and heterogeneous photoredox-catalyzed hydroxymethylation of ketones and keto esters: catalyst screening, chemoselectivity and dilution effects

• Axel G. Griesbeck and
• Melissa Reckenthäler

Beilstein J. Org. Chem. 2014, 10, 1143–1150, doi:10.3762/bjoc.10.114

• Axel G. Griesbeck Melissa Reckenthaler University of Cologne, Department of Chemistry, Organic Chemistry, Greinstr. 4, D-50939 Köln, Germany; Fax: +49(221)470 5057 10.3762/bjoc.10.114 Abstract The homogeneous titanium- and dye-catalyzed as well as the heterogeneous semiconductor particle

• contrast to that, photochemical redox activation is possible in the presence of titanium(IV) catalysts [19][20][21][22]. As shown in a series of papers by Sato and coworkers, carbonyl compounds 1 as well as imines couple with methanol to give the 1,2-diols or 1,2-amino alcohols, respectively, when

• irradiated in the presence of stoichiometric or sub-stoichiometric amounts of titanium tetrachloride (Scheme 1). In order to run these reactions to completion, not less than 0.5 equivalents of TiCl4 were necessary which accounts for severe catalyst consumption. Furthermore, the addition of TiCl4 to methanol