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81.
Jinzhi Liu Jun Ling Xin Li Zhiquan Shen 《Journal of molecular catalysis. A, Chemical》2009,300(1-2):59-64
The mechanism of -caprolactone (CL) insertion into a Y–OCH3 bond was investigated using density functional theory (DFT) calculations. The optimized geometries and corresponding Gibbs-free energies of the intermediates were obtained, which confirmed a four-step coordination-insertion mechanism. The coordination of CL onto yttrium center led to a nucleophilic addition of the carbonyl group of CL, followed by an intramolecular alkoxide ligand exchange. A monomer insertion was completed by the CL ring opening via acyl–oxygen bond cleavage. The formation of the five-coordinated yttrium intermediate, 3, was found to be the rate-determining step. This study could be applicable to ring-opening polymerisation (ROP) of CL initiated by lanthanide metal complexes. 相似文献
82.
Yong-Hua Yang 《Tetrahedron》2006,62(10):2420-2427
Benzoxazoles 2 can be smoothly synthesized by treatment of starting materials of N-(2-hydroxyaryl) cyclopropyl amides 1 with PPh3/CCl4 in acetonitrile in good yields. When PPh3/CBr4/MS 4 Å was used in the reaction system, the corresponding ring-expanding products 3 were obtained in moderate to good yields in acetonitrile at 80 °C. Using DCE as a solvent in this reaction, the corresponding 2-(3-chloropropyl)benzoxazoles 5 were obtained as major products. 相似文献
83.
A series of magnesium, zinc, and calcium monoalkyl or monoamide complexes containing tridentate nitrogen ligands, CH3C(2,6-(iPr)2C6H3N)CHC(CH3) (NCH2CH2-D) (D = NMe2, N((CH2CH2)2CH2)), have been synthesized, and six of which were characterized by single-crystal X-ray diffraction. The X-ray diffraction results show that the metal complexes are all solvent-free monomers and the pendant arm D bonds to the metal ion. These metal complexes are highly active for the ring-opening polymerization of rac-lactide and give preference for heterotactic polylactide. 相似文献
84.
<正>A novel biodegradable copolymer,poly(5,5-dibromomethyltrimethylene carbonate-co-ε-caprolactone)(poly(DBTC-co-CL)) with pendant bromine groups,was synthesized via ring-opening polymerization(ROP) ofε-caprolactone(CL) and 5,5- dibromomethyltrimethylene carbonate(DBTC) using stannous octoate(Sn(Oct)_2) as catalyst.Then the pendant bromine groups were completely converted into azide form,which permitted"click"reaction with alkyne-terminated polyethylene(A-PEG) by Huisgen 1,3-dipolar cycloadditions preparing biodegradable amphiphilic poly(DTC-co-CL)-g-PEG graft copolymer.The graft copolymer was characterized by nuclear magnetic resonance(NMR) and size-exclusion chromatography(SEC). 相似文献
85.
WU Chun-zan HUANG Jia-xing ZHANG Qi-han XU Jia-xi 《高等学校化学研究》2006,22(1):36-39
IntroductionDuring the last decade,our group has investigateda series of cycloaddition reactions of2,3-dihydro-1,5-benzothiazepines withα-carbonyl-ketenes[1,2],nitrileoxides[3,4],nitrile imines[3,4],ketenes[5—8],andcarbenes[9—11].Normal cycloadducts ca… 相似文献
86.
G. Göndös L. Gera G. Dombi G. Bernáth 《Monatshefte für Chemie / Chemical Monthly》1996,127(11):1167-1171
Summary In contrast to their aromatic analogues, the corresponding saturated diamides5–9 are formed exclusively when hexahydro-3,1,4-benzoxazinones (3,4) are reacted with amines. The cyclodehydration reaction of the diamides5–9 cannot be carried out at arbitrarily high temperatures.Saturated Heterocycles, Part 217. Part 216: L. Simon, S. G. Talpas, F. Fülöp, G. Bernáth, G. Argay, A. Kálmán, P. Sohár (1995) J Heterocyclic Chem32: 161 相似文献
87.
An efficient method for preparation of substituted 1,2-phenylenedimethanols and aliphatic 1,4-diols that are valuable intermediates in organic synthesis, has been developed by the base-promoted reduction of isobenzofuran-1(3H)-ones and γ-lactones with silane under mild conditions. Compared with traditional procedures using stoichiometric amounts of metal hydrides and alkyl reductants, the present method avoids the use of sensitive reagents and is operationally simple, and a broad variety of functional groups are tolerated. 相似文献
88.
89.
Yi Lu Xu-feng Ni Zhi-quan Shen 《高分子科学》2007,(5):541-544
Ring-opening polymerization ofε-caprolactone has been carried out by using rare earth Schiff base complexes: lanthanide tris(N-pheny1-3,5-di-t-butylsalicylaldiminato)s[Ln(OPBS)_3]as single component catalyst for the first time.The influences of different rare earth elements,monomer and catalyst concentration as well as reaction time on the polymerization were investigated.Mechanism studies showed that monomer inserts into the active site with the acyl-oxygen bond scission rather than the break of alkyl-oxygen bond. 相似文献
90.
Tao Peng Jing Su Guang Lin Si-Xue Cheng Ren-Xi Zhuo 《Colloid and polymer science》2006,284(8):834-842
A series of biodegradable amphiphilic graft polymers were successfully synthesized by grafting poly(glycolide) (PGA) sequences onto a water-soluble poly-α,β-[N-(2-hydroxyethyl)-L-aspartamide] (PHEA) backbone. These novel graft polymers were synthesized by the ring-opening polymerization initiated by the macroinitiator PHEA bearing hydroxyl groups without adding any catalyst. The graft polymers were characterized by Fourier transform infrared spectroscopy (FTIR), 1H nuclear magnetic resonance spectroscopy (1H NMR), combined size-exclusion chromatography (SEC) and multiangle laser light scattering (MALLS) analysis, and differential scanning calorimetry (DSC). By controlling the feed ratio of the macroinitiator to the monomer, graft polymers with different branch lengths can be obtained. The degradation behaviors of the copolymers were studied. Based on the amphiphilicity of the graft copolymers, nanoparticle drug delivery systems were prepared by the direct dissolution method and the dialysis method, and the in vitro drug release behavior was investigated. Transmission electron microscopy (TEM) images demonstrated that these nanoparticles were regularly spherical in shape. The particle size and distribution of the nanoparticles were measured. 相似文献