- Facile Synthesis of Unsymmetrical Trialkoxysilanols: (RO)2(R′O)SiOH
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Trialkoxysilanols, (RO)3SiOH, are useful as ligands in transition-metal complexes because they provide models for silica-supported metal sites or precursors for the thermolytic precursor approach. However, their synthesis is mostly limited to symmetrical ones, where all RO ligands are the same. However, unsymmetrically substituted trialkoxysilanols could offer significant advantages over their symmetrical counterparts by facilitating crystallization of complexes, lowering crystallographic disorder, changing the thermal properties of the complexes made, and making the addition of pendant functional groups possible. Herein, a simple, general synthetic procedure yielding unsymmetrical trialkoxysilanols (RO)2(R′O)SiOH is presented using imidazole as a promoter.
- Docherty, Scott R.,Estes, Deven P.,Copéret, Christophe
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- Silicate esters of paclitaxel and docetaxel: Synthesis, hydrophobicity, hydrolytic stability, cytotoxicity, and prodrug potential
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We report here the synthesis and selected properties of various silicate ester derivatives (tetraalkoxysilanes) of the taxanes paclitaxel (PTX) and docetaxel (DTX) [i.e., PTX-OSi(OR)3 and DTX-OSi(OR)3]. Both the hydrophobicity and hydrolytic lability of these silicates can be (independently) controlled by choice of the alkyl group (R). The synthesis, structural characterization, hydrolytic reactivity, and in vitro cytotoxicity against the MDA-MB-231 breast cancer cell line of most of these derivatives are described. We envision that the greater hydrophobicity of these silicates (vis-à-vis PTX or DTX itself) should be advantageous from the perspective of preparation of stable aqueous dispersions of amphiphilic block-copolymer-based nanoparticle formulations.
- Wohl, Adam R.,Michel, Andrew R.,Kalscheuer, Stephen,Macosko, Christopher W.,Panyam, Jayanth,Hoye, Thomas R.
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p. 2368 - 2379
(2014/04/17)
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- Direct alkoxysilylation of alkoxysilanes for the synthesis of explicit alkoxysiloxane oligomers
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Direct alkoxysilylation, which is a powerful tool to provide explicit alkoxysiloxanes, is developed and its versatility is investigated. Siloxane pentamers Si[OSiR1(OMe)2]4 having various functional groups (R1 = methyl, vinyl, phenyl, chloropropyl and n-butyl groups) were successfully obtained by direct alkoxysilylation of Si(OR)4 (R = t-Bu, CHPh2). Thus, the versatility of the reaction is confirmed on organic functional groups R1. Functional group tolerance of the reaction is discussed on the basis of electronegativity of the R1 groups. Alkoxysilylation of Si(Ot-Bu)2(OMe) 2 and Si(Ot-Bu)(OMe)3 selectively gives trimer (MeO) 2Si[OSiMe(OMe)2]2 and dimer (MeO) 3SiOSiMe(OMe)2, respectively. Thus, the feasibility on siloxane structure is also confirmed. Various siloxane compounds are synthesized by this newly developed reaction for the first time.
- Wakabayashi, Ryutaro,Tamai, Misa,Kawahara, Kazufumi,Tachibana, Hiroki,Imamura, Yutaka,Nakai, Hiromi,Kuroda, Kazuyuki
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- PRECURSORS FOR SILICA OR METAL SILICATE FILMS
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A composition selected from the group consisting of bis(tert-butoxy)(isopropoxy)silanol, bis(isopropoxy)(tert-butoxy)silanol, bis(tert-pentoxy)(isopropoxy)silanol, bis(isopropoxy)(tert-pentoxy)silanol, bis(tert-pentoxy)(tert-butoxy)silanol, bis(tert-butoxy)(tert-pentoxy)silanol and mixtures thereof; its use to form a metal or metalloid silicate layer on a substrate and the synthesis of the mixed alkoxysilanols.
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Page/Page column 3
(2008/06/13)
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- Precursors for silica or metal silicate films
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A composition selected from the group consisting of bis(tert-butoxy)(isopropoxy)silanol, bis(isopropoxy)(tert-butoxy)silanol, bis(tert-pentoxy)(isopropoxy)silanol, bis(isopropoxy)(tert-pentoxy)silanol, bis(tert-pentoxy)(tert-butoxy)silanol, bis(tert-butoxy)(tert-pentoxy)silanol and mixtures thereof; its use to form a metal or metalloid silicate layer on a substrate and the synthesis of the mixed alkoxysilanols.
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Page/Page column 4
(2008/06/13)
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- Preparation and Properties of Novel Titanio- and Zirconiosiloxane Compounds
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Syntheses and characterization of titaniosiloxane and zirconiosiloxane compounds were investigated.Titaniosiloxane and zirconiosiloxane compounds were prepared by the reaction of di-t-butoxymethoxysilanol with titanium or zirconium alkoxides.DBMS was subjected to the reaction with bis(acetylacetonato)titanium diisopropoxide and titanium tetraisopropoxide to give titaniosiloxane compounds TS12 and TS14, respectively.Titaniosiloxane compounds were isolated by distillation or sublimation.TS12 was estimated to be cis-form from its 13C NMR spectrum in CDCl3.TS14 was stable in solution, but apt to decompose after isolation.ZS12 and ZS14 were prepared by the reaction of DBMS with bis(acetylacetonato)zirconium diisopropoxide and zirconium tetraisopropoxide, respectively.The isolation of ZS12 and ZS14 by distillation or recrystallization was difficult because of decomposition and high solubility, and the formation of ZS12 and ZS14 was confirmed by 1H, 13C, and 29Si NMR and IR spectra.
- Gunji, Takahiro,Kitakatsu, Tsutomu,Abe, Yoshimoto
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p. 2951 - 2954
(2007/10/03)
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