Trimethylsilyl allylation

Trimethylsilylated allylic alcohols such as 804 react readily with allyltrimethyl-silane 82 in the presence of ZnCl2 in CH2CI2 to give, after 1.5 h at 25 °C, an approximately ca. 22 78 mixture of 805 and 806 in 94% yield, and HMDSO 7 [17]. 

New catalytic allylation methodologies continue to emerge. For example, iridium-catalyzed transfer hydrogenation of a-(trimethylsilyl)allyl acetate in the presence of aldehydes mediated by isopropanol and employing the iridium catalyst... 

Finally, addition of the carbanions derived from 83 to non-enolizable aldehydes is a facile process. Aryl and tertiary alkyl aldehydes gave trimethylsilyl allyl ethers 85 by a [1,4]-Brook isomerization (equation 30). The stereochemistry of the intermediate alkoxides 84 dramatically influences the reaction conditions required . 

The trimethylsilyl substituent in 2-(trimethylsilyl)allyl cations is enforced into a perpendicular conformation and thus fi-C—Si hyperconjugative stabilization is essentially not possible. The carbocationic centre Cl (<513C = 295.0 ppm) and the terminal methylene carbon C3 of the allyl system (<513C = 166.6 ppm) in 348a are deshielded by 11.5 and 1.2 ppm, respectively, compared with the silicon-free analogue 348 (613C = Cl 283.5 C3... 

Sharpless kinetic resolution of y-trimethylsilyl allylic alcohols can be highly efficient in the case shown (equation 28), the epoxyalcohol and the remaining allylic alcohol were both formed in greater than 99% ee. Further synthetic applications of the product chiral... 

Organozinc reagent prepared from the 2-(trimethylsilyl)allyl bromide 156 and zinc react with alkynes or carbonyl compounds as well as nitriles to give the corresponding coupling products in moderate to good yields (equation 130)225. 

Consistent with the stability of the divalent oxidation states see Formal Oxidation State) of ytterbium and europium, the triflates of Yb(III) and Eu(III) are reduced by the bis(trimethylsilyl)allyl anion, leading to Ln(II) species (equation A) The same compounds can be made in higher yield by starting with Yb(II) and Eu(II) triflates directly. 

Protodesilylation, A new preparation of -unsaturated carboxylic acids involves the amide acetal Claisen rearrangement of a 3-(trimethylsilyl)allyl alcohol such as 1 to allylsilanes (2). Desilylation of 2 by usual methods results in formation of stereoisomers. However, use of liquid HF at low temperatures results only in (E)-3 in 88% yield. The HF-pyridine complex is not so stereoselective. Amides such as 3 can be converted into carboxylic acid esters by Meerwein s trialkyloxonium salts (—70% yield). 

Lithium (3-Chlor-3-trimethylsilyl-allyl- E19d, 882 (PbR3 - Li)... 

The rearrangement of l-(trimethylsilyl)allylic alcohols to 3-(trimethylsilyloxy)allyllithiums in the presence of base is a convenient source of lithium homoenolates. These can be alkylated to yield the corresponding silyl enol ethers. 

Trimethylsilyl)allylation. Photoinduced radical allylation as well as those via ionic pathways (e.g., reaction with acid chlorides ) are useful synthetically. 

Trimethylsilylacetonitrile, 427-428 7-Trimethylsilyl alcohols, 51 Trimethylsilylalkynes, 126 Trimethylsilylallene, 428-429 a-T i iniethylsilylallenes. 433-434 [(Trimethylsilyl)allyll lithium, 430 a-Trimethylsilylcrotyl-9-borabicyclo[3.3.1) nonane, 430-431... 

In the presence of Pd(PPh3)4, allyl ethers are reduced by LAH or LiEt BH in THE (Section 5.3). Methyl or trimethylsilyl allyl ethers are reduced to the corresponding unsaturated hydrocarbons by NaBH4-NiCl2 in EtOH [G02], Lactones and epoxides remain intact under these conditions, as do ethers of saturated alcohols (Figure 2.21). 

The 1,3-bis(trimethylsilyl)allyl anion, frequently in the form of its potassium salt, has been used extensively, and it reacts with CrCB, FeCB, CoCB, or NiBr2(dme) in THF to produce the corresponding [ 1,3- (SiMes) 2 C3H3] 2M compounds in good yields. 

Lanthanide (III) triflates (Ln(OTf)3) react with three equivalents of the l,3-bis(trimethylsilyl)allyl anion to produce neutral, solvated tris(allyl) species [l,3-(SiMe3)2C3H3]3Ln(thf) (Ln = Ce, Nd, Tb). The neodymium complex has three rf -coordinated allyl ligands, with an approximate threefold axis through the Nd-0 bond (11) Nd-C distances range from 2.64 to 2.78 A. 

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