Six new 4″-benzyloxyimino-4″-deoxyavermectin Bla derivatives were synthesized from avermectin Bla by the selective protection of C-5-hydroxy group,oxidation of C-4″-hydroxy group,and deprotection followed by reaction with O-substituted hydroxylamine hydrochlorides.Their structures were confirmed by IR,~1H NMR,~(13)C NMR and MS.Insecticidal activities of the derivatives against Phopalosiphum pseudobrassicae,Spodoptera exigua and Pluteua xylosteua were evaluated. 相似文献
The emulsifier-free emulsion polymerizations of styrene in the presence of about 1 wt% (related to styrene) of the water soluble comonomer, sodium methallyl sulfonate (NaMS), which has short hydrophobic group and strong hydrophilic ionic group, and of the initiator, potassium persulfate, are carried out. Under constant ionic strength, the number density of polymer particles (Np) is found to depend on 0.5-power of the initiator concentration and shows a minimum in the comonomer concentration plot. Under constant concentration of monomer, comonomer and initiator, Np is found to depend on ?1.1-power of the ionic strength. In the earlier period, the presence of styrene oligomer having MW about 1000 and water soluble poly(NaMS) or copolymer with high NaMS content suggests a micellar nucleation mechanism, by which the styrene oligomer behaves as emulsifier and the poly(NaMS) can either stabilize or destabilize the existing particles, depending on its concentration in the aqueous phase. The particle size is rather uniform having an uniformity very close to 1 (ca. 1.001) throughout the entire process. It is much larger than that of the conventional emulsion polymerization or emulsifier-free emulsion polymerization with the other comonomers by about 3 to 4 times in diameter or 27 to 64 times in volume, leading to that the average radical number in the particle could be much greater than 0.5. The (conversion)2/3 versus time plot is found to be linear from 6 to 50% conversion. During this period, for the conversion from 10 to 40% the polymerization rate increases twice but the particle volume increases four-fold. In addition, MWD shows bimodal (excluding the styrene oligomer peak in the earlier period) during the growth period. But the lower MW peak shifts to higher MW and become larger, while the higher MW peak decreases, and finally the MWD becomes single mode after 58.6% conversion. These results suggest a “gradient polymerization” or “transition stage to core-shell structure” in the earlier stage of particle growth and a “shell part polymerization” in the later stage. 相似文献
The reaction of phenyl lithium acetylide () with 2,6-diphenylpyrylium perchlorate () is solvent dependent. With diethyl ether as solvent, the isolated product differed from that previously reported and is reassingned as 2,6-diphenyl-4-phenylacetylenyl-4-pyran (). On the other hand, in THF the title compound () was obtained; its structure confirmed by single-crystal x-ray crystallography. 相似文献
The 2,5-dimethylthiophene (2,5-Me2T) ligand in the isomers Cp*Ir(η4-2,5-Me2T) (1) and Cp*Ir(C,S-2,5-Me2T) (2) is activated to react with the dimers Cp(CO)2M?M(CO)2Cp[M?Mo (3), W (4)] to give complexes (5,6) in which the thiophene is coordinated to three metals. Oxidation of 5 with Cp2Fe+ removes the Mo dimer to give Cp*Ir(η5-2,5-Me2T)2+. Reaction of 5 with CO displaces the Mo as [CpMo(CO)3]2 to give Cp*Ir(CO)(C,S-2,5-Me2T) (7). Ultraviolet photolysis of 1 provides a convenient route to the ring-opened isomer 2. Despite the remarkable nature of the thiophene coordination in 5 and 6, its reactivity does not suggest new pathways that would lead to the hydrodesulfurization of thiophenes. 相似文献
The first successful attempt to construct 3D supramolecular frameworks with high-nuclear 3d-4f heterometallic clusters as a node is reported. The self-assembly of Ln3+, Cu2+ and amino acid in solution leads to the formation of two polymers, 35-nuclear complex [Sm6Cu29] 1 with a primitive cubic net-like structure and 36-nuclear complex [Nd6Cu30] 2 with a face-centred cubic network type structure. Glycine and L-proline, respectively, were used as ligands. It should be noted that 2 has a chiral framework. X-ray structure analyses show that 1 crystallizes in the triclinic P1 space group (a=19.6451(8), b=20.4682(8), c=20.7046(8) A, alpha=89.453(1), beta=66.290(1), gamma=68.572(1) degrees, V=7003.0(5) A3 and Z=1) and 2 belongs to the cubic P2(1)3 space group (a=b=c=32.4341(3) A, V=34 119.7(5) A3 and Z=4). Both complexes utilize Ln6Cu24 octahedral clusters as nodes and trans-Cu(amino acid)2 groups as bridges. Electrical conductivity measurements reveal that both polymers behave as semiconductors. 相似文献