Allyl dimethylsilane

Preparative Methods treatment of trichlorosilane with 3-methylbut-2-en-l-ylmagnesium chloride followed by methylmagnesium bromide (2 equiv) provides (aja-dimethyl-allyl)dimethylsilane (bp 108 °C) in 76% yield with 99% isomeric purity. The hydrosilane is converted to the ethoxysi-lane quantitatively by the reaction with ethanol catalyzed by hydrogen hexachloroplatinate(IV), and then fluorinated in situ with tetrafluoroboric acid to give the fluorosilane in 87% yield. The latter is methylated with a small excess of methyllithium to give (Q, Q -dimethylallyl)trimethylsilane in 96% yield. Alternatively, (a,Q -dimethylallyl)trimethylsilane can be prepared from 3-methylbut-l-yn-3-ol in six steps. ... 

Me3SiCH2CH=CH2, TsOH, CH3CN, 70-80°, 1-2 h, 90-95% yield. " This silylating reagent is stable to moisture. Allylsilanes can be used to protect alcohols, phenols, and carboxylic acids there is no reaction with thio-phenol, except when Cp3S03H is used as a catalyst. The method is also applicable to the formation of r-butyldimethylsilyl derivatives the silyl ether of cyclohexanol was prepared in 95% yield from allyl-r-butyl-dimethylsilane. Iodine, bromine, trimethylsilyl bromide, and trimethylsilyl iodide have also been used as catalysts. Nafion-H has been shown to be an effective catalyst. ... 

It has also been shown that dimethylsilyl enolates can be activated by diisopropylamine and water and exhibit a high reactivity toward iV-tosyl imines to give Mannich-type reaction products in the absence of a Fewis acid or a Bronsted acid.51 For example, the reaction of [(1-cyclohexen-l-yl)oxy]dimethylsilane with 4-methyl-A -(phenylmethylene)benzene sulfonamide gave re/-4-methyl-N- (f )-[(15)-(2-oxocyclohexyl)phenyl-methyl] benzenesulfonamide (anti-isomer) in 91% yield stereoselectively (99 1 anti syn) (Eq. 11.30). On the other hand, Fi and co-workers reported a ruthenium-catalyzed tandem olefin migration/aldol and Mannich-type reactions by reacting allyl alcohol and imine in protic solvents.52... 

It is well known that thermal decomposition of allyl-substituted silanes proceeds by retro-ene reaction with formation of transient species having a Si=C bond, such as silaben-zene, silatoluene and dimethylsilaethylene4b e. The kinetic data on the gas-phase pyrolysis of a similar allyloxysilane derivative, (l,l-dimethylallyloxy)dimethylsilane (16), and the results on thermolysis of allyloxydimethylsilane (17) in a flow system both indicate the participation of an intermediate silanone, (CH3)2Si=0 (10), as shown in Scheme 523. 

Allyl(allyloxy)dimethylsilane (18) was also proposed by Barton and coworkers as being the source of 10 in gas-phase pyrolysis24. It has been suggested that the generation of 10 by pyrolysis of 18 results from consecutive loss of two allyl radicals. 1,5-Hexadiene and cyclosiloxanes 19 (D3) and 20 (D4) were the final pyrolysis products of 18 (Scheme 6). 

Pyrolytic fragmentations of other suitable precursors also lead to dimethylsilanone (97). For example, 6-oxa-3-silabicyclo[3.1.0]hexane 96 is reported to be split into 97 and 1,3-butadiene upon pyrolysis104. Other possible routes to 97 consist in the pyrolysis of (allyloxy)dimethylsilane (99)105 or Diels-Alder adduct 98104. Matrix-isolated 97 gives its trimer hexamethylcyclotrisiloxane when the matrix is warmed up to 35-40 K. The SiO stretching vibration of 97 was found at 1210 cm-1. This frequency fits the calculated force constant and bond order and has to be considered as evidence for significant double bonding in 97104. Octamethylcyclotetrasiloxane, allyl(allyloxy)dimethylsilane and 2,2,6-trimethyl-2-silapyrane failed as precursors for 97 and only the SiO molecule (cf Section V.B) and CH3 radicals were found on the matrix holder105. 

Li and Navasero49 reported a two-step method that involves the synthesis of vinylsilane from allyl(isopropoxy)dimethylsilane, 32, and the subsequent Pd-catalyzed cross-coupling of the resulting vinylsilane. The strategy was applied to the synthesis of disubstituted homoallylic alcohols, 33a-f. 32 was treated with s-BuLi, followed by reaction with the corresponding aldehyde or ketone, subsequent neutralization with AcOH and treatment with Arl/I2/Pd2(dba)3. When iodobenzene was used with Pd2(dba)3 as catalyst, disubstituted homoallylic alcohols 33a-c were obtained in 62 to 87% yields. In the case of 2-iodoanisole, with (allylPdCl)2 as catalyst, the alcohols 33d-f were obtained in 41 to 71% yields (Scheme 15). 

Rearrangement of 1-alkenylsilanesf Alkenyl(chloromethyl)dimethylsilanes, readily available from hydrosilylation of alkynes with (chloromethyl)dimethylsilane, rearrange in the presence of aluminum chloride to allyl- and/or cyclopropylsilanes. (Z)-l-Alken-ylsilanes rearrange exclusively to (Z)-allylsilanes (equation I). (E)-l-Alkenylsilanes rearrange to (E)-allylsilanes as the major product (equation II). Cyclopropylsilanes are formed... 

C12H17N03 4-butoxy-N-hydroxybenzeneacetamide 2438-72-4 434.65 37.642 2 24462 C12H180SI allyl(4-methoxyphenyl)dimethylsilane 68469-60-3 526.15 46.402 1,2... 

The action of mercury(ll) acetate on 165 in a THF solution followed by demercuration with an alkaline solution of sodium borohydride, gave a substituted 3-silapyrrolidine 166 in 58% yield. Analogously, under the same conditions of aminomercuration-demercuration, allyl(phenylaminomethyl)dimethylsilane 167 easily formed C-methyl-substituted five-membered heterocycle 43 (Equation 29). 

Butyldimethylsilyl ethers can be prepared in the same way from allyl-f-butyl-dimethylsilane (b.p. 65-66°/47 mm). 

Silylmethyl radical cyclizations are a related class of reactions in which the heterocycle serves a temporary purpose to direct the introduction of a methyl or hydroxymethyl group adjacent to the hydroxy group. Starting from the optically active allylic decalin alcohol, reaction with bromomethyl(chloro)dimethylsilane gives the a-bromosilyl ether. Treatment with tributyltin hydride affords the stereoselective cyclization to a five-membered siloxane62. The siloxane ring is converted either to the a.r-dihydroxy compound, or to the ot-methylated derivative63. 

Synthesis of Precursors for Photochemical and Cationic Cyclizations. Allyl(2-chloroethyl)dimethylsilane (4) was converted to thiol 15 by nucleophilic displacement with thiolacetic acid and treatment of the resultant thioacetate with ammonia. UV irradiation of 15 gave exclusively the 7-endo cyclization product 16 (eq 8). ... 

Olefins andAlkynes. The increased scope of the silicon tether in radical chemistry, which is still the most important reactivity allowed by the (bromomethyl)dimethylsilane moiety, has been reviewed. Some authors have again illustrated the synthetic interest of Nishiyama-Stork radical cyclizations of allylic (bromomethyl)dimethylsilyl ethers. Jenkins achieved stereoselective cyclizations on a fused cyclopentanol, while Herdewijn prepared pyranosyl nucleosides. Starting from /-substituted... 

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