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61.
62.
Stepwise application of the Pd-catalyzed S(N)2' reaction and the desilylative S(E)2' reaction to the ambivalent 2-bromo-1-silyl-1,3-dienes provides a novel route to the highly enantioselective construction of tertiary and quaternary propargylic stereogenic centers via axially chiral allenylsilanes. 相似文献
63.
Tunneling spectra of size-selected single-layered platinum clusters (size range of 5-40) deposited on a silicon(111)-7x7 surface were measured individually at a temperature of 77 K by means of a scanning tunneling microscope (STM), and the local electronic densities of states of individual clusters were derived from their tunneling spectra measured by placing an STM tip on the clusters. In a bias-voltage (V(s)) range from -3 to 3 V, each tunneling spectrum exhibits several peaks assignable to electronic states associated with 5d states of a constituent platinum atom and an energy gap of 0.1-0.6 eV in the vicinity of V(s)=0. Even when platinum cluster ions having the same size were deposited on the silicon(111)-7x7 surface, the tunneling spectra and the energy gaps of the deposited clusters are not all the same but can be classified in shape into several different groups; this finding is consistent with the observation of the geometrical structures of platinum clusters on the silicon(111)-7x7 surface. The mean energy gap of approximately 0.4 eV drops to approximately 0.25 eV at the size of 20 and then decreases gradually as the size increases, consistent with our previous finding that the cluster diameter remains unchanged, but the number density of Pt atoms increases below the size of 20 while the diameter increases, but the density does not change above it. It is concluded that the mean energy gap tends to decrease gradually with the mean cluster diameter. The dependence of the mean energy gap on the mean Pt-Pt distance shows that the mean energy gap decreases sharply when the mean Pt-Pt distance exceeds that of a platinum metal (0.28 nm). 相似文献
64.
A new phenolic glycoside, dryopteroside (1), was isolated from the rhizomes of Dryopteris crassirhizoma (Dryopteridaceae), together with five known compounds, 4beta-carboxymethyl-(-)-epicatechin (2), isobiflorin (3), biflorin (4), 1-beta-D-glucopyranosyloxy-3-methoxy-5-hydroxybenzene (5) and (+)-catechin-6-C-beta-D-glucopyranoside (6). The new compound was elucidated to be 1-butanoyl-3-C-beta-D-glucopyranosyl-5-methyl-phloroglucinyl-6-O-beta-D-glucopyranoside (1) by chemical and various spectroscopic analyses. The known compounds 2-6 were first reported from the genus Dryopteris. 相似文献
65.
The C4h isomer of the 1,2-Nc (1,2-naphthalocyaninato) ligand has been efficiently isolated as a hydrated magnesium complex by the fractional crystallization from the benzene/acetone solution after treating the crude mixture of the four isomers (C4h, C(s), C2v, D2h) with benzene. The C4h symmetry has been confirmed by X-ray structure analysis. The central metal ion has been demetalated and subsequently converted to the Li2 complex followed by conversion to the cobalt(II) complex. Electrochemical oxidation of the Co(III)(1,2-Nc)(CN)2 anion prepared from the cobalt(II) complex with TPP (tetraphenylphosphonium) has yielded a partially oxidized salt, TPP[Co(III)(1,2-Nc-C4h(CN)2]2. The crystal comprises slipped stacked Co(III)(1,2-Nc-C4h)(CN)2 one-dimensional chains and one-dimensional arrays of TPPs. The conductivity at room temperature is 0.1 S cm(-1), and the temperature dependence is semiconducting with a small activation energy of about 0.05 eV. The positive temperature-independent value of about 60 microV deg(-1) observed in the thermoelectric power measurements suggests that the salt is in the correlated hopping regime. 相似文献
66.
Aldehydes reacted with zirconacyclopentane derivatives via insertion into the Zr‐sp3C bond to afford the corresponding 7‐membered zirconacycles. 相似文献
67.
Zeitschrift für Physik A Hadrons and nuclei - Die Änderung des remanenten Magnetismus des Eiseneinkristalls mit der Temperatur wird für seine drei Hauptachsen gemessen. Da dies... 相似文献
68.
Tamotsu Takahashi Masanori Ishikawa Shoquan Huo 《Journal of the American Chemical Society》2002,124(3):388-389
Reactions of zirconacyclopentadienes with dichlorocarbene afforded cyclopropanation products in good yields. In a similar manner, reactions of zirconacyclopentadienes with a Simmons-Smith type cyclopropanation reagent also gave vinylcyclopropanes in good yields after hydrolysis. Before hydrolysis, the formation of 1-zirconabicyclo[3.1.0]hexene was observed by 13C NMR spectroscopy. The 1-zirconabicyclo[3.1.0]hexene deriatives reacted with CO to produce 1,2,3,5-tetrasubstituted benzene derivatives in good yields via the C-C bond cleavage of the cyclopropane rings. This is in sharp contrast to the formation of usual 1,2,3,4-tetrasubstituted benzene derivatives from zirconacyclopentadienes. 相似文献
69.
1-Chloro-2-methyl-N,N-tetramethylenepropenylamine was found to be an efficient condensation reagent for the regioselective coupling reaction of propargyl alcohols with Grignard reagents to give allenes in good yields with high chemo- and enantioselectivities. The utility of the reaction was demonstrated in the stereocontrolled synthesis of methyl (E)-2,4,5-tetradecatrienoate, the pheromone of the male dried bean beetle. 相似文献
70.
Xi Z Zhang WX Song Z Zheng W Kong F Takahashi T 《The Journal of organic chemistry》2005,70(22):8785-8789
[reaction: see text] Vinyl allenes were prepared in high yields by the Wittig-Horner reaction of 1-lithio-1,3-dienyl phosphine oxides with aldehydes. 1-Lithio-1,3-dienyl phosphine oxides were generated in situ from lithiation of 1-iodo-1,3-dienyl phosphine oxides, which were obtained by iodination of alpha-phosphinozirconacyclopentadienes. As a whole, a vinyl allene is synthesized from two different alkynes and one aldehyde. 相似文献