- Olefin metathesis catalysts bearing a pH-responsive NHC ligand: A feasible approach to catalyst separation from RCM products
-
Two novel ruthenium-based olefin metathesis catalysts, H 2ITap(PCy3)Cl2Ru=CH-Ph 12 and H 2ITapCl2Ru=CH-(C6H4-O-iPr) 13 (H2ITap = 1,3-bis(2′,6′-dimethyl-4′- dimethylami
- Balof, Shawna L.,P'Pool, Steven J.,Berger, Nancy J.,Valente, Edward J.,Shiller, Alan M.,Schanz, Hans-Joerg
-
experimental part
p. 5791 - 5799
(2009/02/07)
-
- Design and synthesis of spiro-heterocycles by ring-closing metathesis
-
Synthesis of diverse spiro-heterocyclic compounds via the ring-closing (RCM) metathesis approach is described. Specifically, synthesis of various derivatives of barbituric acid, Meldrum's acid, tetronic acid and thiotetronic acid are described by RCM approach.
- Kotha, Sambasivarao,Deb, Ashoke Chandra
-
p. 1120 - 1134
(2008/12/23)
-
- Enantioselective synthesis of nicotinic receptor probe 7,8-difluoro-1,2,3, 4,5,6-hexahydro-1,5-methano-3-benzazocine
-
(Chemical Equation Presented) The development of a concise enantioselective synthesis of nicotinic alkaloid 1 is presented. The route features the synthesis and use of a "stable" aliphatic triflate 21 in an alkylation step to generate Heck precursor 24 and an enantioselective cyclization to establish a compound with the key [3.2.1]-bicyclic core, 29.
- Bashore, Crystal G.,Vetelino, Michael G.,Wirtz, Michael C.,Brooks, Paige R.,Frost, Heather N.,McDermott, Ruth E.,Whritenour, David C.,Ragan, John A.,Rutherford, Jennifer L.,Makowski, Teresa W.,Brenek, Steven J.,Coe, Jotham W.
-
p. 5947 - 5950
(2007/10/03)
-
- Occlusion of Grubbs' catalysts in active membranes of polydimethylsiloxane: Catalysis in water and new functional group selectivities
-
The Grubbs' first and second generation catalysts were occluded into cross-linked slabs of polydimethylsiloxane with volumes from 1 mm3 to 1 cm3 by swelling the polymer with catalyst and methylene chloride. Methylene chloride was evaporated under vacuum to yield occluded catalysts where their solvent was polydimethylsiloxane. These occluded catalysts were reacted with alkenes dissolved in H2O or H2O/MeOH mixtures that diffused into the polydimethylsiloxane to react by ring-closing metathesis and cross metathesis. Control experiments revealed that the catalysts remained occluded and metathesis did not occur in the solvent. Occlusion of these catalysts allowed commercially available Grubbs' catalysts to be used with H2O as the solvent while isolating the H2O sensitive ruthenium methylidene from exposure to H2O. Functional group selective experiments were carried out where the polydimethylsiloxane was an "active" membrane to exclude salts. Polydimethylsiloxane is a hydrophobic polymer, so the deprotonated salt of diallylmalonic acid did not diffuse into it while a diallylether diffused into it and reacted by metathesis. Thus, by controlling the polarity of reagents their reactivity can be controlled owing to the properties of polydimethylsiloxane rather than those of the Grubbs' catalysts. Occlusion of catalysts in polydimethylsiloxane has been shown to add new selectivities to mature catalysts. Copyright
- Mwangi, Martin T.,Runge, M. Brett,Bowden, Ned B.
-
p. 14434 - 14435
(2008/02/02)
-
- The influence of the hydroxylic solvents on the reaction rates of diazodiphenylmethane with cycloalkylcarboxylic and cycloalkenylcarboxylic acids
-
The rate constants for the reaction of diazodiphenylmethane with cyclohexylcarboxylic, cyclopentylcarboxylic, cyclohex-3-enylcarboxylic and cyclopent-3-enylcarboxylic acids have been determined in ten alcohols at 30°C using the UV-spectroscopic method. In order to explain the kinetic results through solvent effects, the second order rate constants of the examined acids are correlated using the total solvatochromic equation, of the form: log k = Ao Sπ* + aα + bβ, where π*, β and α represent the solvent dipolarity/polarizability, solvent hydrogen bond acceptor basicities and hydrogen bond donor acidities, respectively. The correlation of the kinetic data were carried out by means of multiple linear regression analysis and solvent effects on the reaction rates have been analysed in terms of the initial state and the transition state contributions.
- Nikoli?, Jasmina B.,U??umli?, Gordana S.,Krsti?, Vera V.
-
p. 1995 - 2000
(2007/10/03)
-
- A short and stereoselective synthesis of (±)-aristeromycin
-
A new stereoselective three-step total synthesis of (±)-aristeromycin starting from readily available 1-hydroxymethyl-3-cyclopentene is described.
- Hutchison,Grim,Chen
-
p. 451 - 452
(2007/10/02)
-
- 2. 2. 1.
-
A new class of bicyclic compounds containing a single silicon atom at the bridge, 2-exo- and endo-substituted 2-methyl-2-silabicyclo left bracket 2. 2. 1 right bracket heptanes, have been prepared from the corresponding 3-cyclopentenylmethylhydrosilane by the intramolecular hydrosilylation catalyzed by chloroplatinic acid, and their structures were unequivocally assigned by **1H and **1**3C NMR spectra. Dramatic crossover from inversion to retention was found in the phenylation of chlorosilanes with phenyllithium and phenylmagnesium bromide in ether. Regio- and stereoselective insertion of dichlorocarbene generated from phenyl(bromodichloromethyl)mercury, or from chloroform and sodium hydroxide in the presence of a phase transfer catalyst, into C//(//6//)-H//(//e//x//o//) bond of 2-silanorbornanes is observed.
- Hosomi,Mikami,Sakurai
-
p. 2784 - 2794
(2007/10/02)
-