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31.
Megan A. Cole Christopher N. Bowman 《Journal of polymer science. Part A, Polymer chemistry》2013,51(8):1749-1757
Polysiloxanes are commonly used in a myriad of applications, and the “click” nature of the thiol‐ene reaction is well suited for introducing alternative functionalities or for crosslinking these ubiquitous polymers. As such, understanding of the thiol‐ene reaction in the presence of silicones is valuable and would lead to enhanced methodologies for modification and crosslinking. Here, the thiol‐ene reaction kinetics were investigated in functionalized oligosiloxanes having varying degrees of thiol functionalization (SH), π–π interactions (from diphenyls, DP), and ene types (C?C). In the ene‐functionalized oligomers, π–π interactions were controlled through the use of dioctyl repeats (DO). The polymerization rate and rate‐limiting steps were determined for all systems containing an allyl‐functionalized oligomer, and rates ranging from 0.10 to 0.54 mol L?1 min?1 were seen. The rate‐limiting step varied with the oligomer composition; examples of rate‐limited propagation (5:3:2 C?C:DP:DO/1:1 SH:DP) or chain transfer (5:3:2 C?C:DP:DO/3:1 SH:DP) were found in addition to cases with similar reaction rate constants (5:2:3 C?C:DP:DO/1:1 SH:DP). None of the siloxanes were found to exhibit autoacceleration despite their relatively high viscosities. Instead, the allyl‐, vinyl‐, and acrylate‐functionalized siloxanes were all found to undergo unimolecular termination based on their high α scaling values (0.98, 0.95, and 0.82, respectively) in the relation Rp ∝ Riα. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
32.
Hakan Durmaz Muge Butun Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2012,50(15):3116-3125
We demonstrated the successful postfunctionalization of poly(oxanorbornene imide) (PONB) with two types of double bonds using sequential orthogonal reactions, nucleophilic thiol‐ene coupling via Michael addition and radical thiol‐ene click reactions. First, the synthesis of PONB with side chain acrylate groups is carried out via ring‐opening metathesis polymerization and nitroxide radical coupling reaction, respectively. Subsequently, the resulting polymer having two different orthogonal functionalities, main chain vinyl and side chain acrylate, is selectively modified via two sequential thiol‐ene click reactions, nucleophilic thiol‐ene coupling via Michael addition and photoinduced radical thiol‐ene. The orthogonal reactivity of two diverse double bonds, vinyl and acrylate functionalities, for the abovementioned consecutive thiol‐ene click reactions was first demonstrated on the model compound. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
33.
Gokhan Temel Nurcan Karaca Nergis Arsu 《Journal of polymer science. Part A, Polymer chemistry》2010,48(23):5306-5312
Main chain polymeric benzophenone photoinitiator (PBP) was synthesized by using “Thiol‐ene Click Chemistry” and characterized with 1H NMR, FTIR, UV, and phosphorescence spectroscopies. PBP as a polymeric photoinitiator presented excellent absorption properties (ε294 = 28,300 mol?1L?1cm?1) compared to the molecular initiator BP (ε252 = 16,600 mol?1L?1cm?1). The triplet energy of PBP was obtained from the phosphorescence measurement in 2‐methyl tetrahydrofurane at 77 K as 298.3 kJ/mol and according to phosphorescence lifetime, the lowest triplet state of PBP has an n‐π* nature. Triplet–triplet absorption spectrum of PBP at 550 nm following laser excitation (355 nm) were recorded and triplet lifetime of PBP was found as 250 ns. The photoinitiation efficiency of PBP was determined for the polymerization of Hexanedioldiacrylate (HDDA) with PBP and BP in the presence of a coinitiator namely, N‐methyldiethanolamine (MDEA) by Photo‐DSC. The initiation efficiency of PBP for polymerization of HDDA is much higher than for the formulation consisting of BP. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
34.
Three New Diterpenoids from Euphorbia wallichii 总被引:2,自引:0,他引:2
Three new abietane diterpene lactones, 3α-hydroxyjolkinolide A (1), ent-8α, 14β-dihydroxy-13(15)-ene-16(12α)-abietanolide (2) and ent-8α,14α-dihydroxy-13(15)-ene-16(12α)-abietanolide (3) as well as a known abietane diterpene jolkinolide A (4) were isolated from the roots of Euphorbia wallichii. Their structures were elucidated on the basis of spectroscopic analysis. 相似文献
35.
A stereoselective total synthesis of xyolide, a naturally occurring bioactive nonenolide, has been accomplished. The acid fragment of the molecule has been prepared from D ‐mannitol and the alcohol fragment from (2Z)‐but‐2‐ene‐1,4‐diol. The synthesis involves the coupling of these two fragments using the Yamaguchi esterification protocol, followed by intramolecular ring‐closing methathesis. The diastereoisomeric alcohol fragment has also been utilized in this synthesis by employing the Mitsunobu esterification. 相似文献
36.
From Polymer to Monomer: Cleavage and Rearrangement of Si‐O‐Si Bonds after Oxidation Yielded an Ordered Cyclic Crystallized Structure 下载免费PDF全文
Yujing Zuo Zhiming Gou Jinfeng Cao Zhou Yang Haifeng Lu Prof. Shengyu Feng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(31):10972-10977
Polymerization reactions are very common in the chemical industry, however, the reaction in which monomers are obtained from polymers is rarely invesitgated. This work reveals for the first time that oxone can break the Si‐O‐Si bond and induce further rearrangement to yield an ordered cyclic structure. The oxidation of P1 , which is obtained by reaction of 2,2′‐1,2‐ethanediylbis(oxy)bis(ethanethiol) (DBOET) with 1,3‐divinyl‐1,1,3,3‐tetramethyldisiloxane (MMVi), with oxone yielded cyclic crystallized sulfone–siloxane dimer ( P1‐ox ) after unexpected cleavage and rearrangement of the Si‐O‐Si bond. 相似文献
37.
Lilong Gao Qiang Sun Ying Wang Weipu Zhu Xiaojun Li Qiaojie Luo Xiaodong Li Zhiquan Shen 《先进技术聚合物》2017,28(1):35-40
Water‐soluble poly(ethylene glycol) derivatives with multiple “clickable” mercapto groups or double bonds were facilely synthesized in a large scale by direct polycondensation of oligo(ethylene glycol) diol with mercaptosuccinic acid or maleic acid catalyzed by scandium trifluoromethanesulfonate under mild conditions. Injectable hydrogels containing doxorubicin hydrochloride (DOX · HCl) could be rapidly formed using these poly(ethylene glycol) derivatives as precursors via in situ thiol‐ene “click” reaction under physiological conditions without light, initiator, or metal catalyst. DOX · HCl could be sustained released from the hydrogels as a result of the hindrance of the three dimensional hydrogel network on the drug molecules, which makes this kind of DOX‐loaded hydrogels a promising candidate for localized tumor chemotherapy. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
38.
《Acta Crystallographica. Section C, Structural Chemistry》2017,73(9):749-753
The CdII three‐dimensional coordination poly[[[μ4‐1,4‐bis(1,2,4‐triazol‐1‐yl)but‐2‐ene]bis(μ3‐5‐carboxybenzene‐1,3‐dicarboxylato)dicadmium(II)] dihydrate], {[Cd2(C9H4O6)2(C8H10N6)]·2H2O}n , (I), has been synthesized by the hydrothermal reaction of Cd(NO3)2·4H2O, benzene‐1,3,5‐tricarboxylic acid (1,3,5‐H3BTC) and 1,4‐bis(1,2,4‐triazol‐1‐yl)but‐2‐ene (1,4‐btbe). The IR spectrum suggests the presence of protonated carboxylic acid, deprotonated carboxylate and triazolyl groups. The purity of the bulk sample was confirmed by elemental analysis and X‐ray powder diffraction. Single‐crystal X‐ray diffraction analysis reveals that the CdII ions adopt a five‐coordinated distorted trigonal–bipyramidal geometry, coordinated by three O atoms from three different 1,3,5‐HBTC2− ligands and two N atoms from two different 1,4‐btbe ligands; the latter are situated on centres of inversion. The CdII centres are bridged by 1,3,5‐HBTC2− and 1,4‐btbe ligands into an overall three‐dimensional framework. When the CdII centres and the tetradentate 1,4‐btbe ligands are regarded as nodes, the three‐dimensional topology can be simplified as a binodal 4,6‐connected network. Thermogravimetric analysis confirms the presence of lattice water in (I). Photoluminescence studies imply that the emission of (I) may be ascribed to intraligand fluorescence. 相似文献
39.
《Acta Crystallographica. Section C, Structural Chemistry》2017,73(7):531-535
3‐Aminocarbonyl‐1‐benzylpyridinium bromide (N‐benzylnicotinamide, BNA), C13H13N2O+·Br−, (I), and 1‐benzyl‐1,4‐dihydropyridine‐3‐carboxamide (N‐benzyl‐1,4‐dihydronicotinamide, rBNA), C13H14N2O, (II), are valuable model compounds used to study the enzymatic cofactors NAD(P)+ and NAD(P)H. BNA was crystallized successfully and its structure determined for the first time, while a low‐temperature high‐resolution structure of rBNA was obtained. Together, these structures provide the most detailed view of the reactive portions of NAD(P)+ and NAD(P)H. The amide group in BNA is rotated 8.4 (4)° out of the plane of the pyridine ring, while the two rings display a dihedral angle of 70.48 (17)°. In the rBNA structure, the dihydropyridine ring is essentially planar, indicating significant delocalization of the formal double bonds, and the amide group is coplanar with the ring [dihedral angle = 4.35 (9)°]. This rBNA conformation may lower the transition‐state energy of an ene reaction between a substrate double bond and the dihydropyridine ring. The transition state would involve one atom of the double bond binding to the carbon ortho to both the ring N atom and the amide substituent of the dihydropyridine ring, while the other end of the double bond accepts an H atom from the methylene group para to the N atom. 相似文献
40.
An efficient synthetic method has been developed for the synthesis of 2-arylacrylic esters from the corresponding aryl methyl ketones via Wittig reaction and singlet oxygen ene reaction. Wittig reaction to aryl methyl ketones with (methoxymethyl)triphenylphosphonium chloride in basic condition afforded the methyl enol ethers, and then 2-arylacrylic esters were obtained by singlet oxygen ene reaction, followed by tosylation and elimination in one-pot to the methyl enol ethers in good yields. 相似文献