Allyl trimethylsilane

The zinc-mediated allylation of racemic branched a-oxoalkanoic esters proceeds with moderate stereoselectivity46, better results are obtained with (2-propenyl)trimethylsilane/titanium(IV)... 

Hydroxy(tosyloxy)iodobenzene 2014 reacts with phenyltrimethylsilane 81 in boiling acetonitrile to give diphenyliodonium tosylate 2015 and trimethylsilanol 4 or HMDSO 7 [184, 185]. Likewise, treatment of 2,5-bis(trimethylsilyl)furan 2016 with 2014 in boiling acetonitrile/methanol affords 78% iodonium tosylate 2017 and trimethylsilanol 4 [185]. In the presence of Bp3-OEt2 iodosobenzene oxidizes allyl-trimethylsilanes such as 2018 to unsaturated aldehydes such as 2019 in 63% yield, with formation of iodobenzene and trimethylsilanol 4 [186]. Analogously, vinyltrimethylsilanes such as (Z)-l-trimethylsilyl-2-phenylethylene 2020 afford, via 2021, acetylenes such as phenylacetylene in 61% yield and iodobenzene and trimethylsilanol 4 [187] (Scheme 12.54). 

Entries 6 to 8 demonstrate addition of allyl trimethylsilane to protected carbohydrate acetals. This reaction can be a valuable method for incorporating the chirality of carbohydrates into longer carbon chains. In cases involving cyclic acetals, reactions occur through oxonium ions and the stereochemistry is governed by steric and stereo-electronic effects of the ring. Note that Entry 8 involves the use of trimethylsilyl... 

Regioselectivities that are usually high to excellent have been reported in novel palladium-catalyzed Heck arylation reactions with a variety of allylic substrates. The //-stabilizing effect of silicon enhanced regiocontrol in the internal arylation of allyl-trimethylsilane (Eq. 11.5) [18], and coordination between palladium and nitrogen... 

Allylation of aromatic aldehydes with allyl trimethylsilane catalyzed by chiral acyloxyborane gives good results. In contrast, the results are normally poor for aliphatic aldehydes.89 Costa et al.90 introduced another enantioselective allylation procedure aiming to overcome this problem. In the following example, the enantioselective allylation of aldehyde octanal was carried out using... 

Acetoxymethyl)allyl]trimethylsilane (5) in the presence of a Pd(0) reagent, for instance, acts as an equivalent of trimethylenemethane in cycloadditions to electron-deficient alkenes such as a,p-unsaturated ketones, esters, nitriles, sulphones and lactones [7] (Scheme 6.6). 

Methyl-2-propenyl)trimethylsilane reacts with cyclohexene at — 10°C for 25 min to give tra ,s-allylsilylated products, tranx-3-(2-methyl-2-propenyl)-6-tri-methylsilylcyclohexene (15%), and tranx-3-(2-methyl-2-propenyl)-4-tri-methylsilylcyclohexene (3%), but no [3 + 2] cycloaddition product. This result suggests that a methyl substituent on the middle carbon of the allyl group prevents the [3 + 2] cycloaddition reaction. 

In the reaction with ferrocene, allyldimethylchlorosilane reacts at 0 °C, allyl-(methyl)dichlorosilane reacts at the reflux temperature of methylene chloride, but allylsilanes containing two or more chlorine substituents at the silicon do not give alkylation products. In alkylations of ferrocene, allyldimethylchlorosilane shows the highest activity, allyl(methyl)dichlorosilane is less reactive, and allylsilanes containing two or more chlorine-substituents at the silicon have no activity. Allyl-trimethylsilane reacts with both benzene and ferrocene to give allylsilylation products but no alkylation product. 

The present method offers a more efficient and convenient two-step route to the parent a,B-unsaturated acylsilane derivative. The first step in the procedure involves the conversion of allyl alcohol to allyl trimethylsilyl ether, followed by metalation (in the same flask) with tert-butyllithiura at -75°C. Protonation of the resulting mixture of interconverting lithium derivatives (2 and 3) with aqueous ammonium chloride solution furnishes (1-hydroxy-2-propenyl)trimethylsilane (4), which is smoothly transformed to (1-oxo-2-propenyl)trimethylsilane by Swern oxidation. The acylsilane is obtained in 53-68% overall yield from allyl alcohol in this fashion. 

Another total synthesis of sufentanil has been described the cyclization of 2-(2-thienyl)ethylamine with allyl-trimethylsilane and formaldehyde gives 4-hydroxy-1-[2-(2-thienyl)ethyl]piperidine, which is oxidized with oxalyl chloride in DMSO/dichloromethane to 1-[2-(2-thienyl) ethyl]piperidin-4-one. The epoxidation of this compound by means of trimethylsulfonium iodide and the sodium salt of DMSO yields the spiro-epoxide, which is opened with... 

A computational study has been carried out593 on the rearrangement reactions of methylsilacyclopropane, and the pathway shown in Scheme 118 has been put forward594 to account for the formation of product (459) from the reaction of Me2AlCl with the (2 + 2)-cycloadduct (458) between naphthoquinone and allyl trimethylsilane. 

Allylsilanes 12 react with a-ketoesters 174 to give [3 + 2] cycloadducts 175 in 50-85% yields through 1,2-silyl migration (equation 73)59,228. Use of an allylic trimethylsilane produces an allyl alcohol by-product through a competing silyl elimination process. It can be circumvented by use of a bulkier silicon-containing reagent, such as the... 

The diene is prepared by oxidative dimerization of the cuprate of (2-bromo-allyl)trimethylsilane (equation I). 

At the end of his review [7] dealing with the acetalization of carbonyl compounds, Sakurai reported a previously unpublished observation. In the presence of catalytic amounts of iodotrimethylsilane and one equivalent of tetramethoxysilane 38, allyl-trimethylsilane 1 underwent smooth condensation with benzaldehyde 39, leading to adduct 41 in good yield. The silyl-modified Sakurai reaction was born (Scheme 13.15). 

Allyl trimethylsilane can be used to displace the reactive chlorine atom in ozonide 70 and further treatment with ozone gives a diozonide. Similarly, a triozonide can be obtained from the corresponding 2,4-bis-allyl ozonide <2004EJO3657>. 

Disilanes and trisilanes with olefinic substituents (such as vinyl- and allyl-disilanes) react in the presence of H2PtCl6 6 H20 undergoing a Si-Si cleavage692. A second reaction sometimes occurs so that simple cleavage products are not obtained. For example, vinylpentamethyldisilane reacts with the cleavage product trimethylsilane, giving an ethane derivative ... 

Adduct 180 can be transformed to various furan derivatives (Scheme 9)61). Dehydration is accompanied by cis/trans isomerization giving tra/w-dihydrofuran 186, and oxidation to ketone 187 followed by condensation provides the trisubstituted furan 188. Cyano and allyl trimethylsilane, respectively, lead to tetrahydrofuran derivatives 189 and 190 with high stereoselection, which carry new substituents suitable for further manipulation. These reactions work equally well for the ketone adduct 176 and a bicyclic y-lactol affording 191-193 93). 

Stereoselective, conjngate allylation of more remote positions nsing aUyl trimethylsilane and TiCU is possible. Further transformation by nucleophilic addition and ringclosing metathesis affords fused polycychc ring systems (Scheme 88). Stabilized anions and organocopper see Copper OrganometaUic Chemistry) reagents also participate in Michael-type additions to complexed Q, /3-unsaturated aromatic enones. 

The high selectivity of olefin metathesis with (2a) was key in the formation of diverse nonracemic vinyl cyclopropanes from chiral homoaUyhc alcohols and allyl chlorodimethylsilane in three steps, or allyl trimethylsilane in two steps, giving diastereomerically pnre cis or trans... 

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