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The reaction of various organometallics with cyclic and acyclic dialkoxysilanes has been studied.In the case of the acyclic compounds, phenyl-α-naphthylmethoxyborneoxy- and phenyl-α-naphthylmethoxycyclohexyloxy-silane, our results confirm those previously observed with phenyl-α-naphthylmethoxymethoxysilane. The reactions are selective. In ether, aromatic and saturated organomagnesium compounds substitute only the methoxy group with retention, but allylic and benzylic organomagnesium substitute the bulky alkoxy group with inversion.In THF and DME, irrespective of the type of organomagnesium compound, the methoxy group alone is substituted with retention of configuration.With the cyclic compounds, 2-methoxy-2-silaindane, both methoxy and menthoxy groups are substituted and our results confirm the tendency of cyclic derivatives to be substituted with retention of configuration. 相似文献
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R. J. P. Corriu G. F. Lanneau D. Leclercq 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-3):197-200
Abstract Opposite to the SN2(P) reactions taking place with inversion, which are highly dependent upon the nature of the nucleophile, exocyclic substitutions of five-membered ring chlorophosphates with retention show a marked kinetic levelling effect, emphasing silicon-type argumentations. 相似文献
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Moineau J Granier M Lanneau GF 《Langmuir : the ACS journal of surfaces and colloids》2004,20(8):3202-3207
The morphology of surfaces modified by pi-conjugated arylsilanes depends on various parameters such as the nature and the number of the hydrolyzable functions or the length of the aromatic segment. The grafting of phenyltrichlorosilane and phenyltrimethoxysilane leads to multilayers even when the reactions are carried out at 0 degrees C, the films obtained from phenyltrichlorosilane being much thicker than the one obtained from phenyltrimethoxysilane. A submonolayer is obtained using phenyltriethoxysilane. Whereas the trifunctional phenyltrichlorosilane forms an inhomogeneous multilayer, the difunctional phenyldichlorosilane (PhSiHCl2) and the monofunctional phenylchlorosilane (PhSiH2Cl) (the SiH bond is not reactive under these experimental conditions) deposit as dense homogeneous monolayers. For these two phenylchlorosilanes, the surface analytical data are similar except for contact angle measurements, which can be explained by a different orientation of the phenyl group at the surface. Concerning the influence of the length of the aromatic segment on the quality of the film, styryltrimethoxysilane and methylstilbenyltrimethoxysilane lead to dense monolayers indicating that adding a short group such as the vinyl group is sufficient to induce an organization between aromatic groups and to achieve a dense monolayer. 相似文献
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Richard Frantz Jean-Olivier Durand Gerard F. Lanneau 《Journal of organometallic chemistry》2004,689(11):1867-1871
The synthesis of para-substituted ferrocene analogues of stilbene was performed by using the Heck reaction, starting from vinylferrocene. The variation of the electronic density of these compounds with the electronic withdrawing strength of the substituents was studied using 13C NMR spectroscopy, absorption spectra and cyclic voltammetry. The correlation of Hammett constants with the redox properties of the substituted compounds using Nagy's method allowed us to revisit the determination of the Hammett constants of diethyl phosphonate ester and phosphonic acid substituents. Our measurements were in agreement with the literature except for the diethyl phosphonate group. 相似文献
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We prove that the dilatation of any pseudo-Anosov homeomorphism on a translation surface that belongs to a hyperelliptic component
is bounded from below uniformly by ?2{\sqrt{2}} . This is in contrast to Penner’s asymptotic. Penner proved that the logarithm of the least dilatation of any pseudo-Anosov homeomorphism on a surface of genus g tends to zero at rate 1/g (as g goes to infinity). 相似文献
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