1,721,026 research outputs found
MultiPEG: high molecular weight multifunctional poly(ethylen glicol)s assembled by a dendrimer-like approach
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Synthesis and characterization of new multifunctional high-molecular weight PEG derivatives (MultiPEG)s
No full textPostsynthetic conjugation of biopolymers with high molecular mass poly(ethylene glycol): Optimization of a solution process tested on synthetic oligonucleotides
No full textThe reaction of oligonucleotides with high molecular weight monomethoxy poly(ethylene glycol)s (MPEGs) has been tested to set up a convenient procedure for the postsynthetic conjugation in solution of biopolymers. A first oligonucleotide was previously modified in 5', using a liquid-phase procedure, with a linker carrying a terminal primary amino group to enhance its nucleophilic reactivity. Two procedures commonly utilized for the activation of the terminal OH groups of the MPEG were evaluated, that is, the reaction with pNO(2)-phenyl chloroformate and with N,N-disuccinimidyl carbonate. Both water as well as organic solution conditions were employed and compared. In a second test, a X-amino modified, commercial 20-mer was also conjugated in a microscale condition to verify the effect of size and concentration of MPEG on the postsynthetic conjugation of these biopolymers under troublesome synthetic conditions
Role of the NH functionality and solvent in terdentate CNN alkoxide ruthenium complexes for the fast transfer hydrogenation of ketones in 2-propanol
No full textMetallation of pentaphyrin with Lu(III) dramatically increases reactive-oxygen species production and cell phototoxicity
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Bulky Diphosphine Acetate Ruthenium Complexes: Synthesis and Catalytic Activity in Ketone Transfer Hydrogenation and Alkyne Dimerization
No full textSeveral mononuclear ruthenium complexes containing bulky diphosphines have been easily prepared from acetate ruthenium precursors. The cyclohexyl complex [Ru(η2-OAc)2(DCyPF)] (1-cy; DCyPF = 1,1′-bis(dicyclohexylphosphino)ferrocene) is synthesized from [Ru(η2-OAc)2(PPh3)2] and DCyPF in toluene at reflux, whereas the ethylenediamine (en) derivatives trans-[Ru(η1-OAc)2(PP)(en)] (PP = 1,1′-bis(diisopropylphosphino)ferrocene (DiPPF) (2), DCyPF (3)) have been obtained in a one-pot reaction from [Ru(η2-OAc)2(PPh3)2], PP, and en in n-heptane. Treatment of the isopropylphosphine complex [Ru(η2-OAc)2(DiPPF)] (1-ip) with 2-(aminomethyl)pyridine (ampy) in methanol affords the isolation of a mixture of the cationic [Ru(η2-OAc)(DiPPF)(ampy)]OAc (5a) and cis-[Ru(η1-OAc)2(DiPPF)(ampy)] (5b) (4/1 molar ratio), via trans-[Ru(η1-OAc)2(DiPPF)(ampy)] (4) characterized at low temperature. The analogous cyclohexyl compound trans-[Ru(η1-OAc)2(DCyPF)(ampy)] (6), synthesized from [Ru(η2-OAc)2(PPh3)2], DCyPF and ampy in heptane, slowly converts into [Ru(η2-OAc)(DCyPF)(ampy)]OAc (7) at RT. The monocarbonyl derivatives [Ru(η1-OAc)(η2-OAc)(PP)(CO)] (PP = 1,3-bis(cyclohexylphosphino)propane (DCyPP) (8), (R)-1-[(S)-2-(dicyclohexylphosphino)ferrocenyl]ethyldicyclohexylphosphine (Josiphoscy) (9)) are obtained from [Ru(ηsu1-OAc)(η2-OAc)(PPh3) 2(CO)] and the suitable diphosphine. Treatment of [Ru(η1-OAc)(η2-OAc)(DiPPF)(CO)] (10) with phenylacetylene and in the presence of pyridine leads to the alkynyl complex [Ru(η2-OAc)(CCPh)(DiPPF)(CO)] (11), characterized by X-ray diffraction analysis. Protonation of 10 with 2 equiv of TFA at RT gives [Ru(η1-OCOCF3)(η2-OCOCF3)(DiPPF)(CO)] (12). The dicarbonyl trans,cis-[Ru(η1-OAc)2(DiPPF)(CO)2] (13) is obtained by reaction of 1-ip with CO (1 atm) in CH2Cl2, whereas the isomer cis,cis-[Ru(η1-OAc)2(DiPPF)(CO)2] (14) can be prepared from carbonylation of 10. When 13 is heated in the solid state, 10 is formed by decarbonylation. These complexes promote the transfer hydrogenation of acetophenone in 2-propanol (S/C = 1000-2000) with NaOiPr (2 mol %), affording a TOF value of up to 81000 h-1 for complex 9 at 30 °C. Complex 10 catalyzes the head-to-head dimerization of terminal alkynes to 1,4-enynes in toluene at reflux with high stereoselectivity for the kinetic Z isomer
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