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Butyl Groups (butyl + groups)
Selected AbstractsHydrosilanes Are Not Always Reducing Agents for Carbonyl Compounds, II: Ruthenium-Catalyzed Deprotection of tert -Butyl Groups in Carbamates, Carbonates, Esters, and EthersEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2010Shiori Hanada Abstract Hydrosilanes act as a reagent to cleave the C,O bond of OtBu groups in carbamates, carbonates, esters, and ethers by catalysis of a triruthenium cluster. The reaction offers a novel deprotection method for OtBu groups under neutral conditions, showing unique selectivities that have never been accomplished with conventional Brønsted or Lewis acidic promoters. Possible mechanisms for C,O cleavage are discussed on the basis of NMR spectroscopic analysis. [source] Synthesis of new calix[4]arene-based phosphorus ligands and their application in the Rh(I) catalyzed hydroformylation of 1-octeneHETEROATOM CHEMISTRY, Issue 7 2001C. Kunze The synthesis of calix[4]arene-based phosphorus diamides and phosphites is described. These oligocyclic ligands have been tested in the Rh(I)- catalyzed hydroformylation of 1-octene. Depending on the reaction conditions, yields up to 99% and n/iso -selectivities between 0.7 and 2.6 have been observed. tert -Butyl groups on the upper rim of the calix[4]arene template had a beneficial effect on the catalytic reaction. In general biuret-derived P-ligands were superior. For comparison, the corresponding "monomeric" ligands have also been synthesized and were employed in the catalytic reaction. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:577,585, 2001 [source] Synthesis and Electrochemical Study of an Original Copper(II)-Capped Salen,Cyclodextrin ComplexEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 29 2010Elise Deunf Abstract A new metallocapped cyclodextrin (CD) was synthesized by the regioselective debenzylation, induced by diisobutylaluminium hydride (DIBAL-H), of perbenzylated cyclodextrins. This reaction allowed for the efficient preparation of an unprecedented CD,salen type copper(II) complex. The electrochemical behavior of both the bound and unbound CD,salen compounds was investigated by cyclic voltammetry. Notably, it was shown that the presence of tert -butyl groups at the ortho - and para -positions of the salen aromatic rings stabilized the copper(II) phenoxyl radical species that was generated upon the one-electron oxidation of the starting compound. Importantly, this stabilization remained effective when the salen-type ligand was covalently attached to the CD. This allowed for investigations of the reactivity of the copper(II) phenoxyl radical complex towards a primary alcohol to be performed by cyclic voltammetry. This reaction can be considered as mimicking the behavior of galactose oxidase. However, under these conditions, no reactivity was observed in the presence of benzyl alcohol. This may be due to distortion, either of the initially square planar salen ligand after its grafting to the CD primary face, and/or of the CD itself. On the other hand, the electrochemical reduction of the un-grafted copper(II) salen-type ligand led to a transient anionic species that exhibited significant stability on the time-scale of the slow cyclic voltammetry measurement in the absence of the CD, but was unstable in the presence of the CD. In the latter case, it was demonstrated that the anionic species was protonated by the CD. Importantly, this protonation was not fast enough to prevent catalytic activation of iodomethane by the electro-generated copper(I)-capped salen CD complex. [source] Platinum Complexes of Aromatic SelenolatesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 25 2010Amy L. Fuller Abstract Several synthetic methods are used to prepare naphthalene-based aromatic 1,2-diselenoles. A new one-pot synthesis starting from naphthalene is used to produce theknown compound naphtho[1,8- c,d][1,2]diselenole (Se2naph).Friedel,Crafts alkylation is used on Se2naph to substitute either one tert -butyl group to form 2- tert -butylnaphtho[1,8- c,d][1,2]diselenole (mt-Se2naph) or two tert -butyl groups to form 2,7-di- tert -butylnaphtho[1,8- c,d][1,2]diselenole (dt-Se2naph). Bromination of mt-Se2naph results in dibromination of the naphthalene ring, rather than reaction at selenium, to give 4,7-dibromo-2- tert -butylnaphtho[1,8- c,d][1,2]diselenole (mt-Se2naphBr2). Reduction of the Se,Se bond in Se2naph, mt-Se2naph, dibenzo[c,e][1,2]diselenine (dibenzSe2), or diphenyl diselenide (Se2Ph2) with LiBEt3 H, followed by in-situ addition of [PtCl2{P(OPh)3}2] yields the four-coordinate mono- and dinuclear platinum(II) bis(phosphite) complexes [Pt(Se2naph){P(OPh)3}2] (1), [Pt(mt-Se2naph){P(OPh)3}2] (2), [Pt2(dibenzSe2)2{P(OPh)3}2] (3), cis -[Pt(SePh)2{P(OPh)3}2] (4), and trans -[Pt2(SePh)4{P(OPh)3}2] (5). [source] A Density Functional Study of Ethylene Insertion into the M-methyl (M = Ti, Zr) Bond for Different Catalysts, with a QM/MM Model for the Counterion, B(C6F5)3CH3,ISRAEL JOURNAL OF CHEMISTRY, Issue 4 2002Kumar Vanka Single site homogeneous catalysts have been studied extensively in recent years as alternatives to traditional heterogeneous catalysts. The current theoretical study uses density functional theory to study the insertion process of the ethylene monomer into the titanium-carbon chain for contact ion-pair systems of the type [L1L2TiCH3 -,-CH3 -B(C6F5)3], where L1, L2, are Cp, NPH3, and other ligands. Different modes of approach cis and trans to the ,-CH3 bridge were considered. The counterion, B(C6F5)3CH3,, was modeled by QM/MM methods. The value of ,Htot,the total barrier to insertion,was found to be positive (in the range of 4,15 kcal/mol). The ability of the ancillary ligands, L1 and L2, to stabilize the ion-pair was found to be an important factor in determining the value of ,Htot. On replacing the titanium metal center with zirconium, the ,Htot values were found to be lowered (in the range of 2,9 kcal/mol), indicating that they would be better catalysts than their titanium analogues. The size of the ligands L1 and L2 was increased by replacing hydrogens in the ligands with tertiary butyl groups. The value of ,Htot was found to increase (in the range of 10,28 kcal/mol) in contrast to the simple systems, for both the cis and trans cases of approach, with the cis mode of approach giving lower values of ,Htot. Solvent effects were incorporated with cyclohexane (, = 2.023) as the solvent, and were found to have a minor influence, ±(0.5,1.5) kcal/mol) on the insertion barrier for all the cases studied. [source] Block copolymer preparation by atom transfer radical polymerization under emulsion conditions using a nanoprecipitation techniqueJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2008Delphine Chan-Seng Abstract Living-radical polymerization of acrylates were performed under emulsion atom transfer radical polymerization (ATRP) conditions using latexes prepared by a nanoprecipitation technique previously employed and optimized for the polymerization of styrene. A macroinitiator of poly(n -butyl acrylate) prepared under bulk ATRP was dissolved in acetone and precipitated in an aqueous solution of Brij 98 to preform latex particles, which were then swollen with monomer and heated. Various monomers (i.e. n -butyl acrylate, styrene, and tert -butyl acrylate) were used to swell the particles to prepare homo- and block copolymers from the poly(n -butyl acrylate) macroinitiator. Under these conditions latexes with a relatively good colloidal stability were obtained. Furthermore, amphiphilic block copolymers were prepared by hydrolysis of the tert -butyl groups and the resulting block copolymers were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The bulk morphologies of the polystyrene- b -poly(n -butyl acrylate) and poly(n -butyl acrylate)- b -poly(acrylic acid) copolymers were investigated by atomic force microscopy (AFM) and small angle X-ray scattering (SAXS). © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 625,635, 2008 [source] pH-Switchable Complexation between Double Hydrophilic Heteroarm Star Copolymers and a Cationic Block PolyelectrolyteMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2008Zhishen Ge Abstract Double hydrophilic heteroarm star copolymers of poly(methacrylic acid) (PMAA) and poly(ethylene oxide) (PEO) were synthesized via atom-transfer radical polymerization (ATRP) using the "in-out" method. The synthesis consisted of three steps. Namely, ATRP was applied to the preparation of a star macroinitiator with PEO arms and a cross-linked core resulting from the polymerization of divinylbenzene (DVB) in the first step, chain extension with tert -butyl methacrylate (tBMA) under ATRP conditions, and subsequent hydrolysis of the tert -butyl groups afforded (PEO)n -PDVB-(PMAA)n heteroarm star copolymers with a cross-linked microgel core. This novel type of double hydrophilic heteroarm star copolymer can be considered as unimolecular micelles with hybrid coronas. The star copolymers exhibited pH-dependent solubility in water, being soluble at high pH and insoluble at low pH, due to the formation of hydrogen-bonded complexes between the PEO and PMAA arms. A mixed solution of the heteroarm star copolymer and a PEO- b -PQDMA diblock copolymer, where PQDMA is poly(2-(dimethylamino)ethyl methacrylate) fully quaternized with methyl iodide, remained stable in the whole pH range, and exhibited an intriguing pH-switchable complexation behavior accompanied with structural rearrangement. [source] Structures of alkyl-substituted Tröger's base derivatives illustrate the importance of Z, for packing in the absence of strong crystal synthonsACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2010Christophe M. L. Vande Velde Crystal structures of Tröger's base (5,11-methano-2,8-dimethyl-5,6,11,12-tetrahydrodibenzo[b,f][1,5]diazocine) analogues with the methyl groups replaced by ethyl, iso -propyl and tert -butyl groups were studied. The incidence of Z, > 1 structures increases to rather conspicuous levels. The reasons behind this trend are expanded upon, and a possible explanation is given in the flexibility of the alkyl substituents and van der Waals stabilization. In combination these effects allow for an additional stabilization of the packing by small changes in the molecular conformations, thus expanding the size of the asymmetric unit. [source] Synthesis, crystal structure and spectroscopic properties of a novel carbacylamidophosphate: N -(3-nitrobenzoyl)- N,,N,,-bis(tert -butyl)phosphoric triamideACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2009Khodayar Gholivand The new compound N -(3-nitrobenzoyl)- N,,N,,-bis(tert -butyl)phosphoric triamide was synthesized by reacting 3-nitrobenzoyl phosphoramidic dichloride and tert -butyl amine, and characterized by multinuclear (1H, 13C and 31P) NMR and FTIR spectroscopy techniques. Structural and conformational properties were analyzed using single-crystal X-ray diffraction, vibrational spectra and theoretical calculations. The crystal structure contains three symmetry-independent disordered molecules, connected via intermolecular N,H...O=P and N,H...O=C hydrogen bonds to form a centrosymmetric hexameric chain extended along the [2,1,] direction. The disorder is mainly caused by rotation of the tert -butyl groups around the C,N bonds. [source] Organotin(IV) tryptophanylglycinates: potential non-steroidal antiinflammatory agents; crystal structure of dibutyltin(IV) tryptophanylglycinateAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 9 2009Mala Nath Abstract Diorganotin(IV) derivatives of tryptophanylglycine (H2Trp,Gly) with general formula R2Sn(Trp,Gly), where R = Me, n -Bu, Ph and n -Oct, and triorganotin(IV) derivatives R,3 Sn(HTrp,Gly) where R, = Me, n -Bu and Ph, have been synthesized and structurally characterized in the ,solid state as well as in solution on the basis of various spectroscopic techniques, viz. FT-IR, multinuclear 1H, 13C and 119Sn NMR, 119Sn Mössbauer and single crystal X-ray diffraction. These investigations suggest that tryptophanylglycine in R2Sn(Trp,Gly) acts as dianionic tridentate coordinating through carboxylate oxygen [C(O)O,], amino nitrogen (NH2) and N,peptide, while in the case of R,3 Sn(HTrp,Gly), the ligand acts as monoanionic bidentate coordinating through C(O)O, and NH2. This is further confirmed by the single-crystal X-ray structure of n -Bu2Sn(Trp,Gly) which shows that two butyl groups and peptide nitrogen (N,peptide) are in the equatorial positions, while the two axial positions are occupied by the carboxylic oxygen [C(O)O,] and the amino nitrogen (NH2) atom from the same ligand molecule in the distorted trigonal,bipyramidal geometry around tin. The anti-inflammatory (using the carrageenan-induced paw edema bioassay in rats), cardiovascular activities and acute toxicity (LD50) of some of these compounds have been examined. All of the studied R2Sn(Trp,Gly) and Ph3Sn(HTrp,Gly) exhibit very high anti-inflammatory activities comparable to that of phenylbutazone along with high safety margin (LD50 > 400 mg kg,1) with no side effects on the cardiovascular system. Copyright © 2009 John Wiley & Sons, Ltd. [source] An EPR and ENDOR Investigation of a Series of Diazabutadiene,Group 13 ComplexesCHEMISTRY - A EUROPEAN JOURNAL, Issue 10 2005Robert J. Baker Dr. Abstract Paramagnetic diazabutadienegallium(II or III) complexes, [(Ar-DAB)2Ga] and [{(Ar-DAB.)GaX}2] (X=Br or I; Ar-DAB={N(Ar)C(H)}2, Ar=2,6-diisopropylphenyl), have been prepared by reactions of an anionic gallium N-heterocyclic carbene analogue, [K(tmeda)][:Ga(Ar-DAB)], with either "GaI" or [MoBr2(CO)2(PPh3)2]. A related InIII complex, [(Ar-DAB.)InCl2(thf)], has also been prepared. These compounds were characterised by X-ray crystallography and EPR/ENDOR spectroscopy. The EPR spectra of all metal(III) complexes incorporating the Ar-DAB ligand, [(Ar-DAB.)MX2(thf)n] (M=Al, Ga or In; X=Cl or I; n=0 or 1) and [(Ar-DAB)2Ga], confirmed that the unpaired spin density is primarily ligand centred, with weak hyperfine couplings to Al (a=2.85 G), Ga (a=17,25 G) or In (a=26.1 G) nuclei. Changing the N substituents of the diazabutadiene ligand to tert -butyl groups in the gallium complex, [(tBu-DAB.)GaI2] (tBu-DAB={N(tBu)C(H)}2), changes the unpaired electron spin distribution producing 1H and 14N couplings of 1.4 G and 8.62 G, while the aryl-substituted complex, [(Ar-DAB.)GaI2], produces couplings of about 5.0 G. These variations were also manifested in the gallium couplings, namely aGa ,1.4 G for [(tBu-DAB.)GaI2] and aGa ,25 G for [(Ar-DAB.)GaI2]. The EPR spectra of the gallium(II) and indium(II) diradical complexes, [{(Ar-DAB.)GaBr}2], [{(Ar-DAB.)GaI}2], [{(tBu-DAB.)GaI}2] and [{(Ar-DAB.)InCl}2], revealed doublet ground states, indicating that the GaGa and InIn bonds prevent dipole,dipole coupling of the two unpaired electrons. The EPR spectrum of the previously reported complex, [(Ar-BIAN.)GaI2] (Ar-BIAN=bis(2,6-diisopropylphenylimino)acenaphthene) is also described. The hyperfine tensors for the imine protons, and the aryl and tert -butyl protons were obtained by ENDOR spectroscopy. In [(Ar-DAB.)GaI2], gallium hyperfine and quadrupolar couplings were detected for the first time. [source] Synthesis, Crystal Structure and in vitro Antitumor Activity of Di- n -butyltin p -[N, N -Bis(2-chloroethyl)amino]benzoatesCHINESE JOURNAL OF CHEMISTRY, Issue 12 2005Zhong-Wei Zhang Abstract Di- n -butyltin oxide reacted with p- [N,N -bis(2-chloroethyl)amino]benzoic acid to yield the compounds {{4-[(ClCH2CH2)2N]C6H4COOSnBu2}2O}2 (1) and {4-[(ClCH2CH2)2N]C6H4COO}2SnBu2 (2), which have been characterized by IR and 1H NMR spectra. The X-ray diffractional studies of 1 reveal the structure of the molecule to be a dimer, in which the two Bu2Sn groups were linked via two bridging oxygen atoms to form a central Bu4Sn2O2 unit. And the tin atom adopts two carbons from two n -butyl groups and three oxygen atoms from the acid and the bridging oxygen. In vitro test showed compound 1 to exhibit high cytotoxicity against P388 and HL-60 cell lines. [source] The effect of substituents on the aggregation and gelation of azo sulphonate dyesCOLORATION TECHNOLOGY, Issue 3 2005Kunihiro Hamada The aggregation and gelation of sodium 1-phenylazo-2-hydroxy-6-naphthalene sulphonate azo dyes containing fluoro, ethyl, n -propyl, iso -propyl, n -butyl, sec -butyl and tert -butyl groups in the para -position to the azo group have been compared with those containing methyl and trifluoromethyl groups. The behaviour of dyes containing a fluoro group was also studied using 19F NMR spectroscopy. Aqueous solutions of sodium 1-(4- sec -butylphenylazo)-2-hydroxy-6-naphthalene sulphonate at concentrations greater than 0.01 mol dm,3 became gelatinous, whereas the other dyes containing alkyl groups did not show this effect. Although the gelation of aqueous dye solutions of fluorinated dyes has been reported previously, it had not been noticed with dyes containing hydrocarbon chains. Aggregation constants have been determined, and the thermodynamic parameters found to be influenced by chain branching and by the number of carbon atoms present. Important information has been established about the spatial arrangement of fluorine in the aromatic ring. [source] | |||||||||||||||||||||||||