@article {2288, title = {Substituent effects on aryltrifluoroborate solvolysis in water: Implications for Suzuki-Miyaura coupling and the design of stable F-18-labeled aryltrifluoroborates for use in PET imaging}, journal = {Journal of Organic Chemistry}, volume = {73}, number = {12}, year = {2008}, note = {ISI Document Delivery No.: 313RGTimes Cited: 17Cited Reference Count: 41Ting, Richard Harwig, Curtis W. Lo, Justin Li, Ying Adam, Michael J. Ruth, Thomas J. Perrin, David M.}, month = {Jun}, pages = {4662-4670}, type = {Article}, abstract = {Whereas electron withdrawing substituents retard the rate of aryltrifluoroborate solvolysis, electron-donating groups enhance it. Herein is presented a Hammett analysis of the solvolytic lability of aryltrifluoroborates where log(k(solv)) values correlate to sigma values with a rho value of approximately -1. This work provides a predictable rubric for tuning the reactivity of boron for several uses including F-18-labeled PET reagents and has mechanistic implications for ArBF3-enhanced ligandless metal-mediated cross coupling reactions with aryltrifluoroborates.}, keywords = {AMINO-ACIDS, AROMATIC SUBSTITUTION, CHEMISTRY, CHYMOTRYPSIN, CONSTANTS, FLUORIDE, HYDROLYSIS, ORGANOBORON COMPOUNDS, POTASSIUM ARYL, TRIFLUOROMETHYL GROUP}, isbn = {0022-3263}, url = {://000256757100038}, author = {Ting, R. and Harwig, C. W. and Lo, J. and Li, Y. and Adam,Michael J. and Ruth, T. J. and Perrin,David M.} } @article {2288, title = {Substituent effects on aryltrifluoroborate solvolysis in water: Implications for Suzuki-Miyaura coupling and the design of stable F-18-labeled aryltrifluoroborates for use in PET imaging}, journal = {Journal of Organic Chemistry}, volume = {73}, number = {12}, year = {2008}, note = {ISI Document Delivery No.: 313RGTimes Cited: 17Cited Reference Count: 41Ting, Richard Harwig, Curtis W. Lo, Justin Li, Ying Adam, Michael J. Ruth, Thomas J. Perrin, David M.}, month = {Jun}, pages = {4662-4670}, type = {Article}, abstract = {Whereas electron withdrawing substituents retard the rate of aryltrifluoroborate solvolysis, electron-donating groups enhance it. Herein is presented a Hammett analysis of the solvolytic lability of aryltrifluoroborates where log(k(solv)) values correlate to sigma values with a rho value of approximately -1. This work provides a predictable rubric for tuning the reactivity of boron for several uses including F-18-labeled PET reagents and has mechanistic implications for ArBF3-enhanced ligandless metal-mediated cross coupling reactions with aryltrifluoroborates.}, keywords = {AMINO-ACIDS, AROMATIC SUBSTITUTION, CHEMISTRY, CHYMOTRYPSIN, CONSTANTS, FLUORIDE, HYDROLYSIS, ORGANOBORON COMPOUNDS, POTASSIUM ARYL, TRIFLUOROMETHYL GROUP}, isbn = {0022-3263}, url = {://000256757100038}, author = {Ting, R. and Harwig, C. W. and Lo, J. and Li, Y. and Adam,Michael J. and Ruth, T. J. and Perrin,David M.} } @article {1481, title = {Catalyst poisoning in catalyzed imine hydrogenation: A novel zwitterionic Rh(I)/o-hydroxy-substituted imine complex}, journal = {Journal of Molecular Catalysis a-Chemical}, volume = {257}, number = {1-2}, year = {2006}, note = {ISI Document Delivery No.: 089DITimes Cited: 3Cited Reference Count: 38Marcazzan, Paolo Patrick, Brian O. James, Brian R.}, month = {Sep}, pages = {26-30}, type = {Article}, abstract = {During investigation of the homogeneous H-2-hydrogenation of the ketimine (o-HOC6H4)C(Me)=NCH2Ph catalyzed by the [Rh(COD)(PPh3)(2)]PF6 precursor in MeOH at ambient conditions, we have isolated [Rh{eta(4)-(C6H4O)C(-)(Me)=N(+)(H)CHPh}(PPh3)(2)]PF6 (3), an unusual zwitterionic Rh complex in which the imine is coordinated via the C-4 part of the o-hydroxy-arene moiety in a quinoid form; this tautomer is generated via proton transfer from the O-atom to the N-atom within the molecular, benzenoid form. Precipitation of 3 from the MeOH solution, even under H-2, causes sequestration of the Rh and complete suppression of the catalytic activity. (In a previously studied system with the corresponding, non-hydroxy-substituted ketimine, PhC(Me) = NCH2Ph, the Rh was sequestered as an inactive o-metalated species). The solid state structure of 3 is retained in CH2Cl2 solution, but in MeOH and Me2CO reversible loss of the ketimine generates the cis-[Rh(PPh3)(2)(solvent)(2)]PF6 species. (c) 2006 Elsevier B.V. All rights reserved.}, keywords = {amine, BEHAVIOR, CATALYSIS, CATIONIC RHODIUM COMPLEXES, CHEMICALS, FINE, HYDROGENATION, HYDROLYSIS, imine complex, LIGAND, LIGANDS, OLEFINS, phosphine, RHODIUM COMPLEX, SCHIFF-BASES, SELECTIVE HYDROGENATION, zwitterion}, isbn = {1381-1169}, url = {://000240860100005}, author = {Marcazzan, P. and Patrick, B. O. and James, Brian R.} } @article {1132, title = {Expeditious, high-yielding construction of the food aroma compounds 6-acetyl-1,2,3,4-tetrahydropyridine and 2-acetyl-1-pyrroline}, journal = {Journal of Organic Chemistry}, volume = {70}, number = {26}, year = {2005}, note = {ISI Document Delivery No.: 995HBTimes Cited: 10Cited Reference Count: 38}, month = {Dec}, pages = {10872-10874}, type = {Article}, abstract = {The key compound responsible for the aroma of bread, 6-acetyl-1,2,3,4-tetrahydropyridine (1), has been constructed in an efficient three-step procedure from 2-piperidone in an overall yield of 56\%. Compound I was liberated in the final step under basic conditions. A related synthetic route produced 2-acetyl-1-pyrroline (2), the principal component of cooked rice, in 10\% overall yield.}, keywords = {BICYCLIC ENAMINES, BREAD FLAVOR COMPONENT, COOKED RICE, HYDROLYSIS, MECHANISM, MODEL SYSTEMS, POPCORN, QUANTITATIVE-ANALYSIS, ROAST-SMELLING ODORANTS, TERTIARY ENAMINES}, isbn = {0022-3263}, url = {://000234090300034}, author = {Harrison, T. J. and Dake, G. R.} } @article {4197, title = {Mechanisms of cellulases and xylanases}, journal = {Biochemical Society Transactions}, volume = {26}, number = {2}, year = {1998}, note = {ISI Document Delivery No.: ZT170Times Cited: 22Cited Reference Count: 24664th Meeting of the Biochemical-SocietyDEC 15-17, 1997READING, ENGLANDBiochem Soc}, month = {May}, pages = {156-160}, type = {Proceedings Paper}, keywords = {ACID-SEQUENCE SIMILARITIES, ACTIVE-SITE, BACILLUS-CIRCULANS XYLANASE, CLASSIFICATION, ENZYME, FAMILIES, GLUCOSIDASE, glycosidase, GLYCOSYL HYDROLASES, HYDROLYSIS, nucleophile}, isbn = {0300-5127}, url = {://000074056400019}, author = {Birsan, C. and Johnson, P. and Joshi, M. and MacLeod, A. and McIntosh, L. and Monem, V. and Nitz, M. and Rose, D. R. and Tull, D. and Wakarchuck, W. W. and Wang, Q. and Warren, R. A. J. and White, A. and Withers, S. G.} } @article {3332, title = {QUANTITATIVE KINETIC-ANALYSIS BY HIGH-RESOLUTION SI-29 NMR-SPECTROSCOPY OF THE INITIAL-STAGES IN THE SOL-GEL FORMATION OF SILICA-GEL FROM TETRAETHOXYSILANE}, journal = {Chemistry of Materials}, volume = {7}, number = {10}, year = {1995}, note = {ISI Document Delivery No.: TB561Times Cited: 38Cited Reference Count: 24}, month = {Oct}, pages = {1800-1806}, type = {Article}, abstract = {Silicon-29 NMR spectroscopy has been used to determine concentration time dependences of the intermediate species formed in the hydrolysis and first condensation steps in the sol-gel formation of silica gel from tetraethoxysilane. A detailed kinetic analysis of these data yields the rate constants k(1) to k(4) for the hydrolysis reactions and k(5) for the first condensation reaction. It is necessary for the fitting process to consider the last hydrolysis step as an equilibrium process, yielding k(4f) and k(4b) For the first time, from measurements made at different pH values, catalyst independent rate constants have been obtained. For the hydrolysis and condensation reactions, these follow the general trend k(1) < k(2) < k(3) > k(5) with the associated errors reflecting the concentrations of the intermediate species.}, keywords = {CONDENSATION-REACTIONS, HYDROLYSIS, POLYMERIZATION, TEOS}, isbn = {0897-4756}, url = {://A1995TB56100009}, author = {Fyfe, C. A. and Aroca, P. P.} } @article {3107, title = {PREPARATION OF 2-SUBSTITUTED AND 4-SUBSTITUTED 3-HYDROXY-5-METHYLFURANS AND THE ALUMINUM AND GALLIUM COMPLEXES OF 3-HYDROXY-5-METHYL-2-(N-METHYLFORMAMIDO)FURAN}, journal = {Canadian Journal of Chemistry-Revue Canadienne De Chimie}, volume = {72}, number = {5}, year = {1994}, note = {ISI Document Delivery No.: NU280Times Cited: 3Cited Reference Count: 40}, month = {May}, pages = {1362-1369}, type = {Article}, abstract = {In model studies designed to study the synthesis of potentially hexadentate chelates based on the linkage of three furan rings to a triamine via amide linkages, new 2- and 1-substituted 3-hydroxy-5-methylfurans have been prepared. Particularly, 3-hydroxy-5-methyl-(N-methylformamido)fur (Hahm) and its Al and Ga complexes (M(ahm)(3)) have been prepared and thoroughly characterized by a variety of techniques, in the solid state and in solution. Solution equilibrium studies (mu = 0.6 M NaCl, 25 degrees C) uncovered a complicated set of equilibria in the Al3+/Hahm system; the solution potentiometric data were best explained by the presence of mixed ligand (HL = Hahm, L(-) = ahm(-)) hydroxo species [Al-3(OH)(4)L(3)](2+) and [AI(OH)(2)L(2)](-), in addition to the expected [AlL(n)]((3-n)+) (n = 1, 2, 3) species. Further solution studies at HL:M ratios of 3:1 (mu = 0.15 M NaCl, 25 degrees C) showed that Hahm is a relatively weak complexing agent for both Al and Ga, forming tris-ligand species with overall formation constants of 10(19.5) and 10(20.6), respectively.}, keywords = {0.6 M NA(CL), 3-HYDROXY-4-PYRIDINONES, ACID, AQUEOUS-SOLUTION, EQUILIBRIUM, HYDROLYSIS, indium, SILICON(IV)}, isbn = {0008-4042}, url = {://A1994NU28000020}, author = {Lutz, T. G. and Clevette, D. J. and Hoveyda, H. R. and Karunaratne, V. and Nordin, A. and Sjoberg, S. and Winter, M. and Orvig, Chris} } @article {2829, title = {COORDINATION CHEMISTRY OF 2-(2{\textquoteright}-HYDROXYPHENYL)-2-BENZOXAZOLE WITH GALLIUM(III) AND ALUMINUM(III) - 2 UNCOMMON GROUP-13 METAL ENVIRONMENTS STABILIZED BY A BIOLOGICALLY RELEVANT BINDING GROUP}, journal = {Inorganic Chemistry}, volume = {32}, number = {22}, year = {1993}, note = {ISI Document Delivery No.: ME779Times Cited: 28Cited Reference Count: 36}, month = {Oct}, pages = {4909-4913}, type = {Article}, abstract = {{The coordination chemistry of Ga(III) and Al(III) with 2-(2{\textquoteright}-hydroxyphenyl)-2-benzoxazole (Hhbo) was investigated both in the solid state (X-ray crystallography) and in solution (H-1, C-13, Al-27 N MR) These two group 13 metal ions exhibit different reactivities toward this bulky bidentate ligand leading with Ga(III) to the formation of Ga(hbo)3 (1) and [Ga(hbo)2(0,0{\textquoteright}-CH3CO2)] (2) complexes depending on the reaction conditions. With AI(III), the only complex formed is[Al(mu-OH)(hbo)2]2(3). The Ga bis(ligand) acetate complex 2 (C28H19GaN2O6) crystallizes in the monoclinic space group C2/c with a = 16.008(3) angstrom}, keywords = {ACID, AQUEOUS-SOLUTION, COMPLEXES, EQUILIBRIUM, HYDROLYSIS, PERSPECTIVE, PROTEINS, RIBONUCLEOTIDE REDUCTASE, SILICON(IV), SPECIATION}, isbn = {0020-1669}, url = {://A1993ME77900041}, author = {Hoveyda, H. R. and Rettig, S. J. and Orvig, Chris} } @article {7321, title = {BINDING-ENERGY AND CATALYSIS - FLUORINATED AND DEOXYGENATED GLYCOSIDES AS MECHANISTIC PROBES OF ESCHERICHIA-COLI (LACZ) BETA-GALACTOSIDASE}, journal = {Biochemical Journal}, volume = {286}, year = {1992}, note = {ISI Document Delivery No.: JN815Times Cited: 86Cited Reference Count: 40Part 3}, month = {Sep}, pages = {721-727}, type = {Article}, abstract = {Kinetic parameters for the hydrolysis of a series of deoxy and deoxyfluoro analogues of 2{\textquoteright},4{\textquoteright}-dinitrophenyl beta-D-galactopyranoside by Escherichia coli (lacZ) beta-galactosidase have been determined and rates found to be two to nine orders of magnitude lower than that for the parent compound. These large rate reductions result primarily from the loss of transition-state binding interactions due to the replacement of sugar hydroxy groups, and such interactions are estimated to contribute at least 16.7 kJ (4 kcal).mol-1 to binding at the 3, 4 and 6 positions and more than 33.5 kJ (8 kcal).mol-1 at the 2 position. The existence of a linear free-energy relationship between log(k(cat.)/K(m)) for these compounds and the logarithm of the first-order rate constant for their spontaneous hydrolysis demonstrates that electronic effects are also important and provides direct evidence for oxocarbonium ion character in the enzymic transition state. A covalent intermediate which turns over only extremely slowly (t1/2 = 45 h) accumulates during hydrolysis of the 2-deoxyfluorogalactoside, and kinetic parameters for its formation have been determined. This intermediate is nonetheless catalytically competent, since it re-activates much more rapidly in the presence of the transglycosylation acceptors methanol or glucose, thereby providing support for the notion of a covalent intermediate during hydrolysis of the parent substrates.}, keywords = {ALPHA-D-GLUCOPYRANOSYL, D-GLUCOPYRANOSYL PHOSPHATES, ENZYME, GLYCOGEN-PHOSPHORYLASE, HYDROLYSIS, inhibitors, OLIGOSACCHARIDE, SITE, SPECIFICITY, SUBSTRATE}, isbn = {0264-6021}, url = {://A1992JN81500010}, author = {McCarter, J. D. and Adam,Michael J. and Withers, S. G.} }