Sakurai conditions

The metathesis concept on a solid support has been extended to so-called crossmetathesis, whereby one of the reacting alkenes is attached to the solid support and a terminal alkene is present in solution [138], During metathesis, this terminal alkene becomes immobilized on the resin. The reaction conditions were optimized in such a way that the possible formation of macrocycles could be prevented. The allyl-dimethylsilyl polystyrene 116 used in the reaction was synthesized according to Scheme 55. After metathesis, terminal alkenes 117 are released by scission of the Si-C bond mediated by appropriate nucleophiles (Sakurai conditions). 

The intramolecular Sakurai reaction allows for the synthesis of functionalized bicyclic systems. By proper choice of the reaction conditions, especially of the Lewis acid or fluoride reagent used, high stereoselectivity can be achieved, which is an important aspect for its applicability in natural products synthesis. 

This section describes Michael-analogous processes in which, mostly under electrophilic conditions, ally - or alkynylsilanes undergo addition to enones or dienones (Sakurai reactions). The intramolecular addition of allylsilanes is an extremely useful reaction especially for the construction of carbocyclic ring systems, which occurs in a diastereoselective manner, in many cases with complete asymmetric induction. 

A "Tribochemical Tree" shown in Fig. 1.1 summarizes our knowledge of some of the most important processes occurring in the bulk oil and the effects of those processes on the mechanically activated surfaces under the boundary lubrication conditions (Dowson, 1998 Kajdas, 2001 Martin, 1999 Pawlak, 2001 Sakurai, 1981 Spikes, 2001 Willermet, 1998 . Yinetal., 1997a and 1997b). 

Optimum chromatographic conditions are summarised in Table 4.12. The methods of Sakurai et al. [322] and Morgan and Danielson [323] are both applicable to the analysis of waste waters and sewage effluents. 

Sakurai, M., et al. (2000), Experimental Study on Side-reaction Occurrence Condition in the Iodine-sulfur Thermochemical Hydrogen Production Process , International Journal of Hydrogen Energy, 23, 613-619. 

T. Uematsu, L. Parkanyiova, T. Endo, C. Matsuyama, T. Yano, M. Miyahara, H. Sakurai, and J. Pokorny, Effect of the unsaturation degree on browning reactions of peanut oil and other edible oils with proteins under storage and frying conditions, in G, 2002,445 446. 

Oxiranes of terminal monosubstituted and internal disubstituted olefins do not undergo the isomerization under standard conditions, but give aldehydes at elevated temperature. For the special substrates described in Sch. 35, different modes of reaction originated from intermediary carbocationic species, involve neighboring functional group participation, oxidation, etc. An improvement employing other silicon Lewis acids, for example Mc3SiI and McsSiBr, was developed by Kraus, Detty, and Sakurai [17,19f,62]. 

Reaction of compound 4 with dimethylphenylsilyllithium leads to the first generation polysilane dendrimer 6, which has been synthesized already by Sakurai et al [lb]. Again, treatment with HBr under the described conditions gives hexabromide 7, also in a clean reaction as a crystalline compound. Reaction of 7 with lithium aluminum hydride finally gives hydrosilane 8. 

Morita, T., Okamoto, Y., and Sakurai, H., A mild and facile synthesis of alkyl- and arylphosphonyl dichlorides under neutral conditions. Reaction of Z)ri(trimethylsilyl) phosphonates with PClj, Chem. Lett., 435, 1980. 

BTF is known to react with strong Lewis-Acids such as AICI3. [42] However, milder Lewis-Acids do not readily react with BTF. Zinc chloride catalyzed Friedel-Crafts acylation (8.1) leads to better yields in refluxing BTF compared to sym-tetrachloroethane. [43] The deactivating trifluoromethyl group is presumably responsible for the inertness of BTF towards aromatic substitution under these conditions. Titanium tetrachloride has successfully been used for Sakurai [44]... 

Miyazawa, S., Sakurai, T., Shindo, Y., Imura, M., and Flashimoto, T., The effect of tryptophan administration on fatty acid synthesis in the livers of rats under various nutritional conditions, /. Biochem., 78, 139, 1975. 

Sakurai, Okabe and Matsumura [5] used a somewhat different approach to obtain an expression for the effect of contact pressure and rubbing speed on wear rate under conditions of mixohydrodynamic lubrication. Figure 14-3 shows the relation they observed between the volumetric distance-dependent wear rate and contact pressure with rubbing speed as... 

The Bromley equation (though still widely used) can give significant errors under a variety of conditions. An extensive exercise on the correlation of pool film-boiling heat transfer from cylinders is reported by Sakurai and Shiotsu [180], whose expression for the mean convective heat transfer coefficient is expressed in dimensionless form as follows ... 

In Fig. 10, reaction of 1 with chlorosilane 6 yielded the N-silyl derivative 7 that was not isolated but directly transformed into alkene 8 (the precursor of epoxide 3 of Fig. 9) under Sakurai s conditions. Both the yield (50%) and the stereoselectivity (80 20 for the indicated isomer) were not very high, but the road was paved toward a better process. 

Parkanyiova, L., Trojakova, L., Reblova, Z., Zainuddin, A., Nguyen, H.T. T., Sakurai, H., Miyahara, M., and Pokomy, J. 2000. Resistance of high-oleic acid peanut oil against autoxidation under storage and deep frying conditions, Czech J. Food Sci., 18 (Spec.) 125-126. 

Fluorous solid catalyst 8 is highly effective for the Mukaiyama aldol reaction [Eq. (9)] and Sakurai-Hosomi allylation reaction [Eq. (lO)j. These reactions have been performed at -78 °C and room temperature, respectively, under heterogeneous conditions. Post-reaction, 8 has been recovered in high yield by decanting the liquids at room temperature. 

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