17922-43-9Relevant academic research and scientific papers
Evaluation of β- and γ-Effects of Group 14 Elements Using Intramolecular Competition
Sugawara, Masanobu,Yoshida, Jun-Ichi
, p. 3135 - 3142 (2000)
To evaluate β-effects and γ-effects of group 14 elements, we have devised a system in which the intramolecular competition between γ-elimination of tin and β-elimination of silicon, germanium, and tin can be examined. Thus, the reactions of α-acetoxy(arylmethyl)stannanes with allylmetals (metal = Si, Ge, Sn) in the presence of BF3·OEt2 were carried out. The reactions seem to proceed by the initial formation of an α-stannyl-substituted carbocation, which adds to an allylmetal to give the carbocation that is β to the metal and γ to tin. The β-elimination of the metal gives the corresponding allylated product, and the γ-elimination of tin gives the cyclopropane derivative. In the case of allylsilane, the cyclopropane derivative was formed as a major product, whereas in the case of allylgermane the allylated product was formed predominantly. In the case of the allystannane the allylated product was formed exclusively. These results indicate that the y-elimination of tin is faster than the β-elimination of silicon, but slower than the β-elimination of germanium and tin. The theoretical studies using ab initio molecular orbital calculations of the carbocation intermediates are consistent with the experimental results. The effect of substituents on silicon was also studied. The introduction of sterically demanding substituents on silicon disfavored the β-elimination of silicon probably because of the retardation of nucleophilic attack on silicon to cleave the carbon-silicon bond.
Silicon Grignard Reagents as Nucleophiles in Transition-Metal-Catalyzed Allylic Substitution
Xue, Weichao,Oestreich, Martin
, p. 233 - 239 (2019/01/04)
A broad range of transition-metal catalysts is shown to promote allylic substitution reactions of allylic electrophiles with silicon Grignard reagents. The procedure was further elaborated for CuI as catalyst. The regioselectively is independent of the leaving group for primary allylic precursors, favoring α over γ. The stereochemical course of this allylic transposition was probed with a cyclic system, and anti -dia-stereoselectivity was obtained.
Donor cyclopropanes in synthesis: Utilising silylmethylcyclopropanes to prepare 2,5-disubstituted tetrahydrofurans
Dunn, Jonathan,Motevalli, Majid,Dobbs, Adrian P.
scheme or table, p. 6974 - 6977 (2012/02/13)
The use of donor-only silylmethylcyclopropanes in the Lewis acid promoted reaction with aldehydes to generate 2,5-disubstituted tetrahydrofurans is described. The diastereoselectivity obtained in the product is very much dependent upon the temperature of
Controlled introduction of allylic group to chlorosilanes
Li, Zhifang,Cao, Xiaojun,Lai, Guoqiao,Liu, Jinhua,Ni, Yong,Wu, Jirong,Qiu, Huayu
, p. 4740 - 4746 (2007/10/03)
Allylation of chlorosilanes has been achieved with allylsamarium bromide, especially in a controlled manner. Thus allylation of trisubstituted chlorosilanes (R3SiCl) afforded a variety of aryl, aralkyl, and alkenyl substituted allylsilanes. Dichlorosilanes (R2SiCl2) can either afford monoallylated silanes or diallylated silanes depending on the amount of allylsamarium bromide used. Similarly, trichlorosilanes (RSiCl3) can selectively afford mono-, di-, and tri-allylation products. Finally, perchlorosilane (SiCl4) was allylated stepwise and the corresponding silanes containing one, two, three or four allylic groups, respectively, were obtained in satisfactory yields.
Highly stereoselective synthesis of bicyclo[n.3.0]alkanes by titanium tetrachloride promoted [3 + 2] cycloaddition of allylsilanes and 1-acetylcycloalkenes
Knoelker, Hans-Joachim,Foitzik, Norbert,Goesmann, Helmut,Graf, Regina,Jones, Peter G.,Wanzl, Guenter
, p. 538 - 551 (2007/10/03)
The titanium tetrachloride promoted reaction of allylsilanes 1 with 1-acetylcyclohexene is shown to afford the silylbicyclo[4.3.0]nonanes 9 ([3 + 2] cycloaddition products) along with the 1-acetyl-2-allylcyclohexane 4 (Hosomi-Sakurai product). Here we report that systematic variation of the substituents at the silicon atom of 1 allows suppression of the classical Hosomi Sakurai reaction in favor of the [3+2] cycloaddition. Cycloaddition of the allylsilanes 1d, 1i, and 1k with 1-acetylcycloalkenes 10, containing a 5-, 6-, 7-, 8-, or 12-membered ring, gives rise to the corresponding silylbicyclo[n.3.0]alkanes 11-13. The cycloaddition of allyltriisopropylsilane (1k) and 1-acetyl-2-methylcycloalkenes 15 provides silylbicyclo[n.3.0]alkanes 16 with two contiguous quaternary carbon centers. The stereochemistry of the silylbicyclo[n.3.0]alkanes 11a-c and 14 is unambiguously determined by X-ray analysis and 13C NMR spectroscopy.
