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

On the mechanism of photocatalytic reactions with eosin Y

• Michal Majek,
• Fabiana Filace and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97

• with arenediazonium salts are often more selective than traditional methods such as copper(II)-mediated Meerwein arylations [11] or protocols employing stoichiometric iron(II) or titanium(III) reductants in aqueous media [12][13][14]. This renaissance of arene diazonium chemistry has recently led to

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

• tetraisopropoxytitanium was used as condensing reagent (Table 1, entries 5–8). Further treatment with titanium tetrachloride/triethyl amine gave a positive result and 46% chemical yield was obtained (Table 1, entry 9). Then, further investigation revealed that the best yield (47%) was observed when the reaction was

Silica: An efficient catalyst for one-pot regioselective synthesis of dithioethers

• Samir Kundu,
• Babli Roy and
• Basudeb Basu

Beilstein J. Org. Chem. 2014, 10, 26–33, doi:10.3762/bjoc.10.5

• and also as spacers in metal-organic frameworks [9][10][11][12][13][14]. For example, vicinal dithioether-based zirconium and titanium complexes have been used for alkene polymerization and hydroamination [15][16][17][18]. Chiral dithioethers have been prepared and their iridium complexes have been

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

• iodide and generate the corresponding radical (Scheme 13). Titanium dioxide was used as heterogeneous photocatalyst in the perfluoroalkylation of α-methylstyrene with perfluorohexyl iodide by M. Yoshida et al. [120]. While the main product arose from the formal perfluoroalkylation of a methyl sp3-C–H

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

• -picoline can be readily oxidised via another gas-phase protocol using a fixed-bed reactor charged with vanadium pentoxide on high surface titanium dioxide (5–50 wt % vanadium). A modification of the sequence utilises a dehydrative amminolysis (ammoxidation) to furnish the corresponding 3-cyanopyridine

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

• titanium-mediated, alkoxide-directed fragment coupling reaction between vinylcylopropanes and vinyldimethylchlorosilane (Scheme 3, reaction 4) in which the stereochemical outcome of the rearrangement is orchestrated by the adjacent alkoxide, which is believed to direct formation of a tricyclic

Homolytic substitution at phosphorus for C–P bond formation in organic synthesis

• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 1269–1277, doi:10.3762/bjoc.9.143

• titanium complex (Scheme 23) [49]. This represents a unique direct method for preparing triorganophosphine without recourse to any trivalent phosphorus sources such as PCl3. Conclusion Introduction of a phosphorus atom by a radical process has offered an intriguing tool for the synthesis of

Simple and rapid hydrogenation of p-nitrophenol with aqueous formic acid in catalytic flow reactors

• Rahat Javaid,
• Shin-ichiro Kawasaki,
• Akira Suzuki and
• Toshishige M. Suzuki

Beilstein J. Org. Chem. 2013, 9, 1156–1163, doi:10.3762/bjoc.9.129

• acid (HNO3, 60%) and hydrogen peroxide (H2O2, 30%) were purchased from Wako Pure Chemical Industries Ltd. and were used without further purification. Fabrication of tubular reactors A double-layered tube (o.d. 1.6 mm, i.d. 0.5 mm, length 100 cm) composed of Inconel 625 and titanium (Ti) inner layer

• (thickness 120 μm) was fabricated by E.S.Q. Co., Japan, by elongation of the titanium inlaid Inconel 625 piece by stretch-draw process, and used as the reactor support [11]. The Ti inner surface was oxidized to TiO2 with H2O2 under supercritical water conditions (450 °C, 30 MPa). The TiO2 surface, which is

Titanium-mediated reductive cross-coupling reactions of imines with terminal alkynes: An efficient route for the synthesis of stereodefined allylic amines

• Kebin Mao,
• Guoqin Fan,
• Yuanhong Liu,
• Shi Li,
• Xu You and
• Dan Liu

Beilstein J. Org. Chem. 2013, 9, 621–627, doi:10.3762/bjoc.9.69

• Chemical Technology, Shenyang 110142, People’s Republic of China 10.3762/bjoc.9.69 Abstract Low-valency titanium species, generated in situ by using Ti(OiPr)4/2 c-C5H9MgCl reagent, react with imines to give a titanium-imine complex that can couple with terminal alkynes to provide azatitanacyclopentenes

• undergoes an unexpected 1,3-amino migration on silica gel during the column chromatography. Keywords: allylic amine; azatitanacyclopentene; reductive cross-coupling; regioselectivity; terminal alkyne; titanium-imine complex; Introduction Allylic amines are fundamental three-carbon building blocks in

• alkynes produced an inseparable mixture of two regioisomers in some cases [33] or could not give the desired products [34]. Sato et al. reported that a divalent titanium reagent generated by the Ti(OiPr)4/2 iPrMgX system reacted with arylaldimines to provide the corresponding (η2-imine)Ti(OiPr)2 complex

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

• ]. As a result, Hoveyda’s zirconium-catalyzed reactions provided homobenzylmagnesium intermediates 4j, while Kambe’s titanium-catalyzed reactions afforded benzylmagnesium intermediates 4k. Kambe applied the titanocene-catalyzed reaction to a three-component coupling reaction involving a radical

• titanium-catalyzed allylmagnesiation of isoprene was reported in the 1970s, the scope of the reagents was limited to the allylic magnesium reagents [145][146]. Recently, Terao and Kambe reported copper-catalyzed regioselective carbomagnesiation of dienes and enynes using sec- or tert-alkylmagnesium

• . Zirconium-catalyzed alkylmagnesiation. Titanium-catalyzed carbomagnesiation. Three-component coupling reaction. Iron-catalyzed arylzincation reaction of oxabicyclic alkenes. Reaction of allenyl ketones with organomagnesium reagent. Regio- and stereoselective reaction of a 2,3-allenoate. Three-component

Towards a biocompatible artificial lung: Covalent functionalization of poly(4-methylpent-1-ene) (TPX) with cRGD pentapeptide

• Lena Möller,
• Christian Hess,
• Jiří Paleček,
• Yi Su,
• Axel Haverich,
• Andreas Kirschning and
• Gerald Dräger

Beilstein J. Org. Chem. 2013, 9, 270–277, doi:10.3762/bjoc.9.33

• by the Lahann group [35]. We believe that the copper-free approach described is of general importance and should be transferrable to (bio)polymers, inorganic materials or to metals such as titanium used in biomedical devices [36]. Schematic presentation of the artificial lung (A) and concept of

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

• the carbometallation of various carbon–carbon multiple bonds. Lithium, copper, zinc, magnesium, zirconium, titanium, palladium and other metals are suitable for this transformation and considerable progress has recently been made in this area. Among these systems, the carbometallation of alkynes

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

• efficient irradiation of the whole reaction media; this is especially useful if the photocatalyst is solid supported. The immobilised catalyst of choice is titanium dioxide, both with and without Pt doping, due to its photochemical stability. The photocatalyst can be effectively deposited onto a

• [44], perchloroethylene [45] and 4-chlorophenol [46], mainly with a view to air and water purification [47]. The following section will focus only on synthetic applications of such reactors. Photoexcitation of titanium dioxide semiconductors leads to the promotion of an electron to the conduction band

• , leaving behind a positive hole in the valence band. Thus titanium dioxide can function either as an oxidant by donation of an electron of a reacting molecule into an electron hole, or as a reductant by the donation of an electron in the conduction band of titanium dioxide to another molecule. One

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

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

A novel asymmetric synthesis of cinacalcet hydrochloride

• Veera R. Arava,
• Laxminarasimhulu Gorentla and
• Pramod K. Dubey

Beilstein J. Org. Chem. 2012, 8, 1366–1373, doi:10.3762/bjoc.8.158

• 2695 chromatograph with a 2487 UV detector. Preparation of 2-methylpropane-2-sulfinic acid (1-naphthalen-1-ylethyl)amide (4): (R)-tert-Butanesulfinamide (2) (16.14 g, 0.133 mol) was added to a solution of titanium tetraethoxide (54.0 g, 0.236 mol) and 1-acetylnaphthalene (3, 20.0 g, 0.117 mol) in THF

Recyclable fluorous cinchona alkaloid ester as a chiral promoter for asymmetric fluorination of β-ketoesters

• Wen-Bin Yi,
• Xin Huang,
• Zijuan Zhang,
• Dian-Rong Zhu,
• Chun Cai and
• Wei Zhang

Beilstein J. Org. Chem. 2012, 8, 1233–1240, doi:10.3762/bjoc.8.138

• employed chiral titanium Lewis acid TiCl2(TADDOLate) for the asymmetric fluorination of β-ketoesters (up to 96% ee) [17][18][19][20]. Most Selectfluor-promoted asymmetric fluorinations require a stoichiometric amount of chiral promoters to suppress the competitively direct achiral fluorination. Different

Asymmetric total synthesis of smyrindiol employing an organocatalytic aldol key step

• Dieter Enders,
• Jeanne Fronert,
• Tom Bisschops and
• Florian Boeck

Beilstein J. Org. Chem. 2012, 8, 1112–1117, doi:10.3762/bjoc.8.123

• -position, both hydroxy groups were allylated, followed by a selective, titanium tetrachloride/tetra-n-butylammonium iodide mediated deprotection of the salicylic hydroxy group. The selectivity of this deprotection is caused by the chelating effect of the carbonyl oxygen towards titanium [12], directing the

Reduction of benzylic alcohols and α-hydroxycarbonyl compounds by hydriodic acid in a biphasic reaction medium

• Michael Dobmeier,
• Josef M. Herrmann,
• Dieter Lenoir and
• Burkhard König

Beilstein J. Org. Chem. 2012, 8, 330–336, doi:10.3762/bjoc.8.36

• -group tolerance during this reduction step is essential since various other groups are usually present. A number of synthetic procedures have been developed, which allow selective reduction, but only a few one-step transformations are known, which use either titanium(III) [5][6][7][8] or different metal

Derivatives of phenyl tribromomethyl sulfone as novel compounds with potential pesticidal activity

• Krzysztof M. Borys,
• Maciej D. Korzyński and
• Zbigniew Ochal

Beilstein J. Org. Chem. 2012, 8, 259–265, doi:10.3762/bjoc.8.27

• made an attempt at synthesizing 2-arylbenzimidazole 11f and 11g according to our patented method [16]. The cyclization of diamine 9 with benzoic acids was run in anhydrous xylene with titanium tetrachloride as a catalyst (Scheme 7). 2-Mercaptobenzimidazole 11h was obtained by the reaction of diamine 9

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

• ]arene was Hampton’s variable temperature 1H NMR investigation of the interactions between titanium(IV) species and 3a [55]. In the absence of crystallographic evidence the NMR splitting patterns were compared to simulated spectra. At ambient temperature the NMR-derived symmetry was C3v, matching that of

• the macrocycle, but upon cooling an asymmetric Cs symmetry emerged. It was proposed that rapid interconversion between isomers occurred by a “turnstile” or Berry-pseudorotation mechanism. A subsequent paper from the group reported the crystal structure of the titanium(IV) isopropoxide (Ti(iPrO)4

• ) complex [56]. The structure was dimeric; each macrocycle was present as the trianion bound to the titanium by all three oxygens and pulled slightly into the cavity by iPrO−. The paper also reported the result of a reaction between the lithium salt of 3b and vanadyl chloride (VOCl3). Based on powder

Development of the titanium–TADDOLate-catalyzed asymmetric fluorination of β-ketoesters

• Lukas Hintermann,
• Mauro Perseghini and
• Antonio Togni

Beilstein J. Org. Chem. 2011, 7, 1421–1435, doi:10.3762/bjoc.7.166

• Lukas Hintermann Mauro Perseghini Antonio Togni Laboratorium für Anorganische Chemie, ETH Zürich, Wolfgang-Pauli-Str. 10, 8093 Zürich, Switzerland Department Chemie, Technische Universität München, Lichtenbergstr. 4, 85748 Garching bei München, Germany 10.3762/bjoc.7.166 Abstract Titanium-based

• Lewis acids catalyze the α-fluorination of β-ketoesters by electrophilic N–F-fluorinating reagents. Asymmetric catalysis with TADDOLato–titanium(IV) dichloride (TADDOL = α,α,α',α'-tetraaryl-(1,3-dioxolane-4,5-diyl)-dimethanol) Lewis acids produces enantiomerically enriched α-fluorinated β-ketoesters in

• TADDOL ligand structure on the catalytic activity and enantioselectivity were investigated. The absolute configuration of several fluorination products was assigned through correlation. Evidence for ionization of the catalyst complex by chloride dissociation, followed by generation of titanium β

Cyclization of 5-hexynoic acid to 3-alkoxy-2-cyclohexenones

• Anne T. Hylden,
• Eric J. Uzelac,
• Zeljko Ostojic,
• Ting-Ting Wu,
• Keely L. Sacry,
• Krista L. Sacry,
• Lin Xi and
• T. Nicholas Jones

Beilstein J. Org. Chem. 2011, 7, 1323–1326, doi:10.3762/bjoc.7.155

• (26%). Titanium(IV) chloride was also screened, however no cyclization was observed. A dramatic increase in yield (71%) was obtained with the aid of indium(III) chloride. Additional metal chloride salts have been screened under our cyclization conditions (Table 1, entries 5–8). Although these salts