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Stereodefined synthesis of an unprecedented family of vinylgermanes bearing an allyl group, (E)-2-aryl-1-germylalka-1,4-dienes, or an allenyl group, (E)-4-aryl-5-germylpenta-1,2,4-trienes, via a cross-coupling reaction of (Z)-germyl(stannyl)ethenes with the respective allyl halide (Br, Cl) and propargyl bromide is described. In the reaction with allyl halides, either a Pd(dba) 2 -CuI combination (dba: dibenzylideneacetone) or CuI alone readily catalyzes or mediates the coupling reaction of (Z)-germyl(stannyl)ethenes, producing the novel vinylgermanes bearing an allyl group. The thienyl group or hydroxy group of the (Z)-germyl(stannyl)ethene survives the reaction. Copper(I) iodide alone readily mediates the reaction with allyl chloride or methallyl chloride upon addition of sodium bromide to produce the respective cross-coupled product in good yield. In contrast, crotyl halides (Br, Cl) or prenyl chloride couple with/without allylic transposition in the bromide or the chloride. In the reaction with propargyl bromide, a Pd(dba) 2 and CuI combination efficiently drives the coupling reaction of (Z)-germyl(stannyl)ethenes in NMP (N-methylpyrrolidone), providing the stereochemically defined allenyl vinylgermanes, (E)-4-aryl-5-germylpenta-1,2,4-trienes, in good yields.
Protodemetallation of (Z)-1-aryl-2-germyl-1-stannylethenes using hydrochloric acid in the presence of tetraethylammonium chloride (TEACl) proceeds at 0 • C with retention of configuration to afford trans-1-aryl-2-germylethenes with high yields. In contrast, the reaction using hydroiodic acid in the presence of tetrabutylammonium iodide (TBAI) brings about a novel 1,2-germyl migration accompanying the destannylation to form 1-aryl-1-germylethenes. These 1,2-germyl migration products result with especially high selectivity from adducts bearing a substituent at the ortho-or para-position on the aromatic ring in the adduct. However, the germyl(stannyl)ethenes bearing a substituent at the meta position on the ring produce a regioisomeric mixture of a trans-germylethene and a 1-aryl-1-germylethene.
o-Hydroxybenzophenone (Hbp) chromophores were immobilized on 3-aminopropyl silica gel (SiO2–NH2) by a reaction of succinimidyl 4-(4-benzoyl-3-hydroxyphenoxy)butanoate (2a) and -undecanoate (2b) with SiO2–NH2 to produce microbeads 1a and 1b in 25 and 21% yield, respectively. The bond formation was confirmed by appearance of an absorption at 1550 cm−1 due to the N–H bending of the amide bond in the IR spectra of 1a and 1b. In order to enhance the thermal and photochemical stabilities, the 1a and 1b residual amino group was acetylated by Ac2O in CHCl3 to produce 7a and 7b. Acetylation occurred on the aminopropyl group. However, it did not occur on the phenolic OH group of Hbp from the IR spectra where the absorptions of the bending of the methyl group and the bending of the phenolic OH group appeared at 1375 and 1348 cm−1, respectively. By degradation experiments, it was found that thermal and photochemical stabilities were high in 7a and 7b compared with that of 1a and 1b.
To develop fillers that adhere closely to a matrix polymer and reduce the glass transition temperature (T g ) of filler/polymer composites, N-acyl-3-aminopropyl silica gel fillers (1) were prepared by the reaction of 3-aminopropyl silica gel (SiO 2 -NH 2 ) and succinimidyl alkanoate (2) by controlling the amount and length of alkyl chains. The surface tension (c) of 1 was measured by the wicking method. The interfacial adhesion energy (W) of composites (1/PS) between 1 and polystyrene (PS) was calculated using the dispersive component (c D ) and the polar component (c P ) of c, according to the Equation) where subscripts m and f indicate matrix and filler, respectively. The W values of 1/PS composites were considerably smaller than those of the SiO 2 -NH 2 /PS composite. A good correlation between W and T g showed that the introduction of acyl groups on SiO 2 was effective for the enhancement of adhesion between 1 and the matrix polymer. Moreover, it was confirmed that the addition of less than 30 wt% of 1 to PS did not affect the tensile strength of composites. Keywords: adhesion energy; aminopropyl silica gel; glass transition temperature; interface energy; surface tension; tensile strength INTRODUCTION Modification of polymers with fillers is widely used to enhance the performance of polymers. 1,2 Inorganic materials such as talc, 3 calcium carbonate, 4,5 glass, 6,7 silica, 8,9 alumina, 10 zeolite 11-13 and wollastonite 14 have been widely used as fillers to improve mechanical performance such as the tensile strength and elongation strength of polymers. To enhance adhesion between inorganic fillers and the polymer matrix, organic additives such as maleic anhydride, carboxylic acids and silane-coupling reagents are mixed with the polymer. 4 However, problems such as the dispersibility of organic additives in the polymer, the increase in glass transition temperatures (T g ) and the elution of organic additives remain in the manufacturing process.Recently, alkyl group-bonded zeolite 12 and wollastonite 14 fillers have been prepared to prevent the elution of organic additives from the polymer and to improve the handling of organic additives in the manufacturing process. 15 Silica gel filler is a stable and safe material that has a wide surface area and the ability to adsorb various materials. 3-Aminopropyl silica gel (SiO 2 -NH 2 ) 16,17 can immobilize functional groups through a covalent bond. To develop a high-performance filler that achieves higher adhesion and a lower T g of filler/polymer composites, the surface tension of the acyl-bonded SiO 2 -NH 2 filler (1) can be modified by controlling the amount and length of alkyl chains (Scheme 1).
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