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Takanashi K Lee VY Matsuno T Ichinohe M Sekiguchi A 《Journal of the American Chemical Society》2005,127(16):5768-5769
The anionic complex of [tetrakis(di-tert-butylmethylsilyl) tetrasilacyclobutadiene]dicarbonylcobalt, [(R4Si4)Co(CO)2]-.K+ (R = SiMetBu2) 2-.K+, was synthesized by the reaction of tetrasilacyclobutadiene dianion dipotassium salt [R4Si4]2-.2K+ 1 with an excess of CpCo(CO)2 in THF. X-ray analysis of 2-.[K+(diglyme)2(THF)] showed an almost planar Si4 ring of rectangular shape with an in-plane arrangement of the silyl substituents. 2- was also prepared as a free anion with the [K+[2.2.2]cryptand] counterion by complexation with [2.2.2]cryptand and as a dimer {2-.[K+(THF)3]}2 without complexing reagents in THF. Such a tetrasilacyclobutadiene fragment represents a new type of ligand for Co complexes, being the first example of a cyclobutadiene containing only heavier group 14 elements. 相似文献
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Revisiting thiol-yne chemistry: Selective and efficient monoaddition for block and graft copolymer formation
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Johannes K. Sprafke Jason M. Spruell Kaila M. Mattson Damien Montarnal Alaina J. McGrath Robert Pötzsch Daigo Miyajima Jerry Hu Allegra A. Latimer Brigitte I. Voit Takuzo Aida Craig J. Hawker 《Journal of polymer science. Part A, Polymer chemistry》2015,53(2):319-326
The untapped potential of radical thiol-yne mono-addition chemistry is exploited to overcome the known limitations of thiol-ene chemistry in polymer coupling and block copolymer formation. By careful choice of alkyne, the reaction can selectively lead to the mono-addition product with efficiencies surpassing those achieved by traditional thiol-ene chemistry. This improvement is illustrated by the nearly quantitative synthesis of a variety of diblock and graft copolymers. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 319–326 相似文献
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Kanki A Tamada T Higaki A Noda Y Tanimoto D Sato T Higashi H Ito K 《Magnetic resonance imaging》2012,30(3):356-360
The aim was to clarify whether enhancement effects of the liver parenchyma in the hepatobiliary phase (HP) of gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced MR imaging were correlated with the morphological grading of the severity in cirrhosis. A total of 62 patients with chronic hepatitis or cirrhosis underwent Gd-EOB-DTPA-enhanced MR imaging. Relative enhancement (RE) of liver parenchyma was calculated from signal intensity (SI) measurements obtained at precontrast images (SIpre) and 20-min postcontrast HP images (SIpost) as: (SIpost-SIpre)/SIpre. Morphological MR grades of severity in cirrhosis were divided into four groups. Then, RE of liver parenchyma and morphologic MR grading were correlated. Regarding the morphologic severity of cirrhosis, the numbers of patients with MR grade 1, 2, 3 and 4 were 14 (23%), 7 (11%), 28 (45%) and 13 (21%), respectively. The mean REs of liver parenchyma in each group of MR morphologic grade 1, 2, 3 and 4 were 0.71±0.21, 0.62±0.16, 0.70±0.22 and 0.77±0.18, respectively. There was no significant correlation between the MR grading of morphologic severity and the RE of liver parenchyma at 20-min HP. Hepatic parenchymal enhancement in the HP of Gd-EOB-DTPA-enhanced MR imaging did not necessarily decrease according to the severity of morphologic changes in cirrhosis. This fact may suggest that the hepatic uptake of Gd-EOB-DTPA depends on the preserved hepatocytes function rather than the severity of morphologic changes in cirrhosis. 相似文献
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Kawasaki T Shinada M Kamimura D Ohzono M Ogawa A 《Chemical communications (Cambridge, England)》2006,(4):420-422
The concise total synthesis of marine alkaloids, (-)-flustramines A and B, and (-)-flustramides A and B has been achieved through the domino olefination/isomerization/Claisen rearrangement (OIC) for highly enantioselective construction of the asymmetric quaternary carbon center and the chemoselective reduction-cyclization (RC) for pyrrolidine formation as key steps. 相似文献
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2-Benzyl-1,4,5,6-tetrahydropyrimidines 1 (as ene-1,1-diamine N,C-tautomers) in diglyme reacted with ethyl benzoylacetate at 160 °C in an oil bath to give 1,2,3,4-tetrahydropyrido[1,2-a]pyrimidin-6-ones 3 and with dimethyl acetylenedicarboxylate in methanol at room temperature, leading to methyl 1,2,3,4-tetrahydropyrrolo[1,2-a]pyrimidin-7-ylideneacetates 5, respectively. 相似文献