Fluoropolyethers end-capped by polar functional groups. II. Effect of catalyst and reagents concentration, solvent nature, and temperature on reaction kinetics of ?,?-bis(hydroxy)-terminated fluoropolyethers with cycloalyphatic and aromatic diisocyanates

Mashlyakovskiy, Leonid; Khomko, Elena; Zaiviy, Vladimir; Tonelli, Claudio

doi:10.1002/1099-0518(20000715)38:14<2579::aid-pola90>3.0.co;2-i

Cited by 15 publications

(28 citation statements)

References 15 publications

(24 reference statements)

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“…102 The interaction of a catalyst with impurities can also lead to an increase in catalyst activity. Dialkyltin catalysts can be deactivated in a formulation, by absorption on a pigment or filler surface, or by ionic impurities.…”

Section: Catalyst Interactionsmentioning

confidence: 99%

Tin in Catalysis

et al. 2008

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In numerous natural products and synthetic compounds, ester moieties constitute major organic functional groups. Consequently, (trans)esterification reactions are widely applied in industry, 1 e.g. in the synthesis of fatty acid esters, 2,3 of polyesters 4−9 and of macrolides. 10 More specifically, polylactones and polylactides are multipurpose, bio-compatible and -degradable polyesters, which are suitable for biomedical and pharmaceutical applications. 11−14 Tin-based Lewis acids like mono-and dialkyltin compounds 4,15−19 and tetraalkyldistannoxane derivatives 8,20−22 are very efficient catalysts for transesterification reactions under mild conditions. A considerable drawback in the use of these organotin compounds in organic synthesis is the difficulty of their quantitative removal from the reaction mixture, because some organotin compounds are toxic. These limitations to the exploitation of such reagents and/or catalysts in biomedical and pharmaceutical synthesis applications 23,24 have been recently overcome by exploring alternative and less toxic catalysts, and by the improvement of workup procedures of several types of homogeneous organotin catalysts. Otera et al. have described the synthesis and catalytic activity of perfluoroalkyl distannoxanes, which combine the advantages of efficient catalysis based on organotins with fluorous biphasic technology. 21,25 These types of organotin catalysts, being highly soluble in fluorocarbon solvents, provide solutions which become perfectly miscible with the organic reaction phase upon heating. After cooling the reaction mixture, phase separation is observed and the catalyst returns into the fluorous phase, making it easily and repeatedly recyclable. Another strategy to alleviate the aforementioned toxicity issue, involves grafting the organotin reagent onto an insoluble solid support. 26−28 In this way, other types of environmentally friendly organotin catalysts, which can easily be removed from the desired reaction products by simple filtration of the insoluble support to which they are grafted, are being designed. The forecasted deliverables of such systems include improved catalyst recycling ability and a better control

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Section: Catalyst Interactionsmentioning

confidence: 99%

Tin in Catalysis

et al. 2008

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“…Moreover the thickness of the film was so as to have a starting spectra with a -NCO absorption band!1.0 so as to be in the linear part of the Beer-Lambert relationship between -NCO concentration and the observed absorptions. This method was already successfully used by other authors to follow macrodiol-isocyanate reaction kinetics [10][11][12][13][14][15]. IR spectroscopies were carried out using a Perkin Elmer spectrum 2000 FTIR in transmission mode.…”

Section: Ftir Spectroscopy Measurementsmentioning

confidence: 99%

Hydrogenated hydroxy-functionalized polyisoprene (H-HTPI) and isocyanurate of isophorone diisocyanates (I-IPDI): reaction kinetics study using FTIR spectroscopy

Burel

Feldman

Bunel

2005

Polymer

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“…To better understand the behavior of FPEs of various molecular weight and structures, we have studied the kinetics of some model reactions. These include the tin‐catalyzed reactions of cyclohexyl isocyanate (CHI) at NCO:OH = 1 with (1) FPE diol (Z‐DOL H‐1000) of the structure and (2) monofunctional alcohols of different molecular weights, such as trifluoroethanol (TFE) and some 2‐substituted TFEs, GAL 7002X, GAL‐402, and CF 3 ‐Z‐DOL‐OH, which has a structure similar to that of Z‐DOL: Unlike in our previous works,1, 2 in which isophorone diisocyanate (IPDI), with two NCO groups of different reactivities,3–9 was studied, in this study CHI was used. Its simple structure and the selection of the aforementioned monoalcohols make possible the definition of model systems that give useful information about the kinetics and mechanism of the investigated reactions.…”

Section: Introductionmentioning

confidence: 91%

“…Hydroxy‐terminated fluoropolyethers (FPEs) react with aromatic and cycloaliphatic diisocyanates in polar ethyl acetate (EA), methyl isobutyl ketone (MIBK), and nonpolar hexafluoroxylene (HFX) solvents at NCO:OH = 2 in the presence of the catalysts dibutyltin dilaurate (DBTDL) and 1,4‐diazabiciclo[2,2,2]octane to form NCO end‐capped FPE oligourethanes 1, 2. Catalyzed reactions are sometimes well described by a second‐order rate equation up to high degrees of conversion (90–100% by OH), but often positive deviations from linearity for the second‐order plots {−(2/ a ) × ln[2 − ( a / c )]} versus time have been observed around 40–60% conversions.…”

Section: Introductionmentioning

confidence: 99%

“…Catalyzed reactions are sometimes well described by a second‐order rate equation up to high degrees of conversion (90–100% by OH), but often positive deviations from linearity for the second‐order plots {−(2/ a ) × ln[2 − ( a / c )]} versus time have been observed around 40–60% conversions. These deviations are sensitive toward the solvent nature, temperature, catalyst, and reagent concentration 1, 2. Moreover, the dependence of the second‐order rate coefficients ( k eff ) for these urethane reactions on the reactant concentration was described by curves with maxima2 { k eff = 10 −2 k cat /[DBTDL], where k cat is the catalytic rate coefficient and [DBTDL] is the concentration of the catalyst (mol %) based on diisocyanate}.…”

Section: Introductionmentioning

confidence: 99%

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Brachytherapy in total coronary occlusions: Quidquid agis, prudenter agas, et respice finem

Hehrlein¹

2003

Cathet Cardio Intervent

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In the study by Jain et al. presented in this issue, vascular brachytherapy was performed, applying a betaradiation source (BetaCath TM) to reduce restenosis rates after PTCA of chronic total occlusions (CTOs). The outcome of radiotherapy after percutaneous revascularization of 82 CTOs were analyzed from the RENO registry database, which contains 1,098 consecutive patients undergoing brachytherapy. The results were comparable with those known for brachytherapy of nonocclusive in-stent restenosis with respect to prevention of new restenosis. Why is this finding remarkable?It has become general knowledge that treating chronic coronary occlusions by conventional PTCA is a "different animal" compared with PTCA of plain coronary artery stenosis [1]. Many studies have shown that restenosis rates are extremely high in patients with CTO, even when stenting is performed [2]. Some institutions leave treatment of symptomatic CTOs primarily to the cardiac surgeon. Revascularization of CTO is favorable over medical treatment at least when treated surgically [3]. Therefore, it is important to realize from the report by Jain et al. that restenosis rates of PTCA in CTO have been reduced dramatically using vascular brachytherapy. However, there is the problem of thrombotic vessel occlusion increasing MACE rates, which needs to be understood and acted on. Brachytherapy was plagued from the beginning with the occurrence of late and "late late" thrombosis [4]. Yet only half of all patients of the RENO registry were kept on the combined antiplatelet therapy of aspirin and clopidogrel for a period of 6 months. In addition, new stents were implanted, which tended to reocclude the coronary arteries. What are the lessons we learn from this report? In the words of Gesta Romanorum: "Quidquid agis, prudenter agas, et respice finem." Whatever you do, do it thoughtfully, and kept in mind the goal.Brachytherapy of chronic coronary occlusions requires special attention to the increased risk of thrombotic vessel occlusion. Potential means for reducing the risks of MACE are as follows: apply aspirin and clopidogrel for a minimum period of 12 months (perhaps as lifelong addition of clopidogrel to aspirin medication); use a minimum of new stents to reduce foreign-body activation of platelets; study an increased loading and maintenance dose of clopidogrel in a randomized fashion in the setting of CTO; and, most importantly, remember that CTO patents only benefit from revascularization if viable myocardium is present [5].Mixed results were obtained by other investigators in two recent studies applying brachytherapy in CTO. One group reported similar efficacy and complication rates with intracoronary brachytherapy of occluded in-stent restenosis using a gamma-emitter (Ir-192) compared with irradiation for nonocclusive in-stent restenosis [6]. The other group, however, clearly pointed out that radiotherapy of total occlusions from in-stent restenosis causes increased MACE rates compared with brachytherapy of plain in-stent restenosis [7]. In summary, m...

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Fluoropolyethers end-capped by polar functional groups. II. Effect of catalyst and reagents concentration, solvent nature, and temperature on reaction kinetics of ?,?-bis(hydroxy)-terminated fluoropolyethers with cycloalyphatic and aromatic diisocyanates

Cited by 15 publications

References 15 publications

Tin in Catalysis

Tin in Catalysis

Hydrogenated hydroxy-functionalized polyisoprene (H-HTPI) and isocyanurate of isophorone diisocyanates (I-IPDI): reaction kinetics study using FTIR spectroscopy

Brachytherapy in total coronary occlusions: Quidquid agis, prudenter agas, et respice finem

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