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71.
Several transition metal salts were found to catalyze aza-Michael reactions of enones with carbamates efficiently. The catalytic activity was strongly dependent on the nature of the metal salts. While conventional Lewis acids such as BF(3).OEt(2), AlCl(3), or TiCl(4) showed lower activity, group 7-11 transition metal salts in higher oxidation states such as ReCl(5), Fe(ClO(4))(3).9H(2)O, RuCl(3).nH(2)O, OsCl(3).3H(2)O, RhCl(3).nH(2)O, PtCl(4).5H(2)O, or AuCl(3).H(2)O exhibited higher catalytic activity. [reaction: see text] 相似文献
72.
Highly Efficient Access to Both Geometric Isomers of Silyl Enol Ethers: Sequential 1,2‐Brook/Wittig Reactions 下载免费PDF全文
Prof. Dr. Yuji Matsuya Kentaro Wada Dr. Daishiro Minato Dr. Kenji Sugimoto 《Angewandte Chemie (International ed. in English)》2016,55(34):10079-10082
Novel sequential 1,2‐Brook/Wittig reactions were developed for the preparation of silyl enol ethers. This method enables highly selective preparation of both geometric isomers of glyoxylate silyl enol ethers, using aldehydes (E‐selective) and tosylimines (Z‐selective) as a Wittig electrophile. The salt‐free conditions of this reaction system are likely to be advantageous for switching the selectivity. The optimal reaction conditions and generality of the reaction were investigated, and plausible explanations for the observed selectivity were also discussed. 相似文献
73.
Shitao Wang Dr. Tomohisa Sawada Dr. Kazuaki Ohara Prof. Dr. Kentaro Yamaguchi Prof. Dr. Makoto Fujita 《Angewandte Chemie (International ed. in English)》2016,55(6):2063-2066
Guest‐induced M18L6–M24L8 capsule–capsule conversion is reported. Both capsules are composed of PdII ethylenediamine units (M) and 1,3,5‐tris(3,5‐pyrimidyl)pyrimidine (L), and form trigonal bipyramidal (M18L6) and octahedral (M24L8) closed‐shell structures with huge hydrophobic inner spaces. The M18L6 trigonal bipyramid is converted to the M24L8 octahedron through encapsulation of large aromatic guests, with the latter capsule possessing a cavity volume three times larger than the former. Despite the dynamic properties of the capsule host, the encapsulated guests are difficult to extract and are thus isolated from the external environment. 相似文献
74.
Optically pure P-chiral (dialkyl)arylphosphine-boranes having high structural diversity were prepared by two- or three-component coupling of fluorobenzenechromium complexes, P-chiral secondary phosphine-boranes, and other nucleophiles. The stereochemical integrity at the P-stereogenic center was completely retained during the SNAr process when the reaction was carried out in THF at low temperature. 相似文献
75.
A new non-C2-symmetrical antimony-phosphorous ligand, (±)-2-diphenyl-phosphano-2′-di(p-tolyl)stibano-1,1′-binaphthyl (BINAPSb) 3, has been prepared from 2-bromo-2′-diphenylphosphano-1,1′-naphthyl 4 via its borane complex 6, and could be resolved by the separation of a mixture of the diastereomeric palladium complexes 8A and 8B derived from the reaction of (±)-3 with optically active palladium reagent (S)-7. The enantiomerically pure BINAPSb 3 has proved to be highly effective in the palladium-catalyzed asymmetric hydrosilylation of styrene as a chiral auxiliary. 相似文献
76.
Sasaki M Kawanishi E Nakai Y Matsumoto T Yamaguchi K Takeda K 《The Journal of organic chemistry》2003,68(24):9330-9339
Metalated O-silyl cyanohydrins of beta-silyl-alpha,beta-epoxyaldehyde have been found to serve as functionalized homoenolate equivalents by a tandem sequence involving base-promoted ring opening of the epoxide, Brook rearrangement, and alkylation of the resulting allylic anion. On the basis of mechanistic studies involving competitive experiments using the diastereomeric cyanohydrins, we propose a reaction pathway involving a silicate intermediate 36 formed by a concerted process via an anti-opening of the epoxide followed by the formation of an O-Si bond. 相似文献
77.
Asakura H Teramura K Shishido T Tanaka T Yan N Xiao C Yao S Kou Y 《Physical chemistry chemical physics : PCCP》2012,14(9):2983-2990
A combination of in situ time-resolved DXAFS and ICP-MS techniques reveals that the formation process of Rh nanoparticles (NPs) from rhodium trichloride trihydrate (RhCl(3)·3H(2)O) in ethylene glycol with polyvinylpyrrolidone (PVP) at elevated temperature is a first-order reaction, which indicates that uniform size Rh NPs appear consecutively and these Rh NPs do not aggregate with each other. 相似文献
78.
Kurinomaru T Tomita S Kudo S Ganguli S Nagasaki Y Shiraki K 《Langmuir : the ACS journal of surfaces and colloids》2012,28(9):4334-4338
The development of technology for on/off switching of enzyme activity is expected to expand the applications of enzyme in a wide range of research fields. We have previously developed a complementary polymer pair system (CPPS) that enables the activity of several enzymes to be controlled by a pair of oppositely charged polymers. However, it failed to control the activity of large and unstable α-amylase because the aggregation of the complex between anionic α-amylase and cationic poly(allylamine) (PAA) induced irreversible denaturation of the enzyme. To address this issue, we herein designed and synthesized a cationic copolymer with a poly(ethylene glycol) backbone, poly(N,N-diethylaminoethyl methacrylate)-block-poly(ethylene glycol) (PEAMA-b-PEG). In contrast to PAA, α-amylase and β-galactosidase were inactivated by PEAMA-b-PEG with the formation of soluble complexes. The enzyme/PEAMA-b-PEG complexes were then successfully recovered from the complex by the addition of anionic poly(acrylic acid) (PAAc). Thus, dispersion of the complex by PEG segment in PEAMA-b-PEG clearly plays a crucial role for regulating the activities of these enzymes, suggesting that PEGylated charged polymer is a new candidate for CPPS for large and unstable enzymes. 相似文献
79.
Sato H Tashiro K Shinmori H Osuka A Aida T 《Chemical communications (Cambridge, England)》2005,(18):2324-2326
Upon complexation with 4,4[prime or minute]-bipyridine, a cyclic dimer of a fused porphyrin zinc complex, having two pi-electronically coupled binding sites, shows a strong negative cooperativity in the second guest binding, to allow stepwise formation of 1 : 1 and 1 : 2 inclusion complexes. 相似文献
80.
Kentaro Suzuki Taro Toyota Katsuhiko Sato Masakazu Iwasaka Shoogo Ueno Tadashi Sugawara 《Chemical physics letters》2007,440(4-6):286-290
Collagen-containing tubular giant vesicles (Col–tGVs) under a high static magnetic field were found to constitute characteristic curved structures (e.g. circular, 8-figure, and hairpin-loop), which were sustained by polymerization of collagen units inside the tGV. We ascribed the formation of these structures to the elasticity of the tGV and to the competing diamagnetic anisotropies between collagen and the tGV. These curved structures can be well expressed by the equation of elastica. 相似文献