Allyl trimethylsilyl ethers

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. 

OL, -Unsaturated acylsilanes (3). Allyl trimethylsilyl ethers (1) on metalla-tion with /-butyllithium (- 78 to - 30°) rearrange to organolithiums that on protonation form (a-hydroxyallyl)silanes (2). These silanes are thermally unstable, but can be oxidized by DMSO-oxalyl chloride or by NCS-S(CH3)2 to a,p-unsaturated acylsilanes (3).1... 

Allylsilanes.1 Allyl trimethylsilyl ethers are converted into allylsilanes by reaction with chlorotrimethylsilane (5 equiv.) and lithium sand in THF. 

Dienes Consecutive reactions of alkynes with CpjZr (from CpjZrClj and BuLi) and allyl trimethylsilyl ether generate (l,4-dien-l-yl)zirconocene derivatives which can be used to couple with iodoarenes under Pd(0)-Cu(I) catalysis. 

P-Aryl-ai,fi-unsaturated carbonyl compounds,2 In the presence of Pd(OAc)2-LiCl (1 5) aryl iodides react with allyl trimethylsilyl ethers in DMF to form (E)-/ -aryl-a,/ -unsaturated aldehydes and ketones. A similar reaction has been reported for allyl alcohols (7, 274). 

Allyl trimethylsilyl ethers have been shown to isomerize in good yields to silyl enol ethers in the presence of various hydridoruthenium complexes such as [H2Ru(PPh3)4] [equation (6)], thus making allyl alcohols potential synthetic... 

Among the applications of allyl silanes reported this year their reaction with phenylselenyl chloride and subsequent oxidation of the resulting allyl selenides to allylic alcoholshas been used in the sequence outlined in Scheme IS. 3-Bromoallyltrimethylsilane therefore behaves as a hydroxypropenyl synthon. Nitroalkenes react with allylsilanes to give, after hydrolysis, y,S-unsaturated ketones, and a synthesis of substituted cyclopentenones based on this procedure has been described.Allyl trimethylsilyl ethers undergo a palladium-promoted coupling with aryl iodides to give /3-aryl-a,/3-unsaturated ketones, and palladium also catalyses the reaction of various aryl bromides with trimethylsilyl acetylene to produce ethynylated aromatics. 

Preparative Methods allyl trimethylsilyl ether is lithiated with s-butyllithiumin TFIF-FIMPA to give a rapidly equilibrating mixture of a carbanion and a silylallyloxy anion (eq 1). Silylation of the mixture with chlorotrimethylsilane affords 3-trimethylsilyl-3-trimethylsilyloxy-l-propene (1) exclusively. Several other derivatives with bulky substituent(s) on the silyloxy group were also prepared. ... 

Allenyl Silyl enol ethers, 86 Allyl alcohol trimethylsilyl ether, 84 Allyl carbonates, 114-15 9 Allyl-ay 2 octalone, 34-5 2-Allyl-2 methylcyclohexanone, 106 (Allyldimethylsilyl)methyl chloride, 58, 59 (AUyldimethylsilyl)methylmagnesium chloride, 59... 

Transsilylation. Several reagents have been recommended for preparation of /-butyldimethylsilyl ethers by transsilylation. These include allyl-r-butyldimethyl-silane and /-butyldimethylsilyl enol ethers of pentane-2,4-dione and methyl aceto-ucelate,2 both prepared with r-butyldimethylchlorosilane and imidazole. Unlike the reaction of r-butyldimethylchlorosilane with alcohols, which requires a base catalyst, these new reagents convert alcohols to silyl ethers under slightly acidic conditions (TsOH) in good yield. The trimethylsilyl ethers of pentane-2,4-dione and methyl acetoacetate convert alcohols to trimethylsilyl ethers at room temperature even with no catalyst. The former reagent is also useful for silylation of nucleotides.3... 

Reduction of derivatives of ally lie alcohols. Nickel boride can effect reduction of allylic alcohols to alkenes, but yields are generally improved by reduction of the acetates, benzoates, or trifluoroacetates.1 Reduction of allylic benzyl ethers to alkenes is effected in higher yield with Raney nickel. Methyl ethers are not reduced by either reagent. The trimethylsilyl ethers of allylic alcohols are reduced to alkenes by nickel boride in diglyme.2... 

Zirconium imido complexes have been used to carry out S 2 reactions of allylic chloride, bromide, iodide, and alkyl, aryl, and trimethylsilyl ethers in high yields at room temperature.12 The syn stereochemistry, an inverse secondary (k /k Oy = 0.88 obtained using the ( )-l-(r-butyldimethylsilyloxy)-3-deuterioprop-2-ene and the rate expression led the authors to suggest the reactions occurred via the mechanism in Scheme 4 with transition state (9). 

Ring opening of the oxaspiropentane 343 upon treatment with sodium phenylselenide (vide supra, Sect. 4.5, Eq. (34)) 59) and O-silylation produce the vinylcyclopropanol trimethylsilyl ether 344 which, on flash thermolysis at 670 °C, gave the siloxycyclo-pentene 345 as a 2 1 mixture of epimers at C(8). Then, allylation of the more substituted enolate arising from 345, opens a convenient way to the antitumor agent, aphidicolin 346 181>. 

Several methods promoted by a stoichiometric amount of chiral Lewis acid 38 [51] or chiral Lewis bases 39 [52, 53] and 40 [53] have been developed for enantioselective indium-mediated allylation of aldehydes and ketones by the Loh group. A combination of a chiral trimethylsilyl ether derived from norpseu-doephedrine and allyltrimethylsilane is also convenient for synthesis of enan-tiopure homoallylic alcohols from ketones [54,55]. Asymmetric carbonyl addition by chirally modified allylic metal reagents, to which chiral auxiliaries are covalently bonded, is also an efficient method to obtain enantiomerically enriched homoallylic alcohols and various excellent chiral allylating agents have been developed for example, (lS,2S)-pseudoephedrine- and (lF,2F)-cyclohex-ane-1,2-diamine-derived allylsilanes [56], polymer-supported chiral allylboron reagents [57], and a bisoxazoline-modified chiral allylzinc reagent [58]. An al-lyl transfer reaction from a chiral crotyl donor opened a way to highly enantioselective and a-selective crotylation of aldehydes [59-62]. Enzymatic routes to enantioselective allylation of carbonyl compounds have still not appeared. 

B(C6Fs)3 works as an effective catalyst for the allylation of propargylic esters.217 Allyl and propargyl trimethylsilyl ethers bearing a 7r-electron-donating group at the a-position are smoothly allylated at the a- or 7-position under catalysis by McjSiOTf.218 Chiral titanium catalyst 29 enables highly enantioselective allylation of racemic benzyl trimethylsilyl ethers by a dynamic kinetic resolution (Equation (57)).219... 

Limitations of the reaction due to the substitution pattern of the allylic alcohols were overcome by the use of tetrapropylammonium perruthenate (TRAP) as a catalyst and monosubstituted, disubstituted and trisubstituted allyl alcohols were converted into the corresponding saturated aldehydes and ketones [5]. Intermediacy of the ruthenium alkoxide in this reaction was evidenced from the complete lack of reactivity of the trimethylsilyl ether derived from the allylic alcohol. 

Although the second type using other traditional Lewis acids, for example BF3 OEt2 and TiCU, has been described by several groups [42], there are few examples employing la and other silicon Lewis acids. Marko and coworker extended their SMS reaction to the diastereoselective version [37]. According to one scheme illustrated in that paper, trimethylsilyl ethers of chiral 1-arylethanol were examined to afford diastereoselectivity in an allylation of allyltrimethylsilane and cyclohexanecar-boaldehyde (Sch. 11). A diastereomeric ratio of up to 10 1 was achieved at lower temperatures. 

Tietze et al. emphasized the usefulness of chiral trimethylsilyl ethers of readily accessible amino alcohol derivatives in allylation of aldehydes and ketones [43]. As a consequence, careful design of the norpseudoephedrine derivatives and proper choice of silicon Lewis acids have led to the convergent preparation of enantiomerically enriched secondary and tertiary homoallylic alcohols in high yields (Sch. 12) [43a], It should be noted that the configuration of the newly formed stereogenic center of the secondary homoallylic alcohols is the opposite of that in the allylation of ketones [43c], They also described in detail mechanistic studies of the above allylation reaction by use of and NMR. 

Oxidations by pyridinium chlorochromate resemble those by dipyridine chromium(VI) oxide, both in scope and the mild conditions required. At room temperature, primary alcohols give aldehydes [604, 605], secondary alcohols afford ketones [605], allylic and benzylic methylene groups are oxidized to carbonyl groups [606, 6d7], enol ethers are converted into esters [608] or lactones [609], trimethylsilyl ethers of diphenols are transformed into quinones [610], and alkylboranes are converted into aldehydes (yll]. 

The asymmetric allylation of unfunctionalized aliphatic ketones has also been described (Scheme 10-23) [43]. Simple aliphatic ketones are treated with a mixture of the trimethylsilyl ether of norpseudoephedrine (58), two equivalents of allyltrimethylsilane, and a catalytic amount of triflic acid. The homoallylic ethers... 

Photolysis of tris(trimethylsilyl)mesitylene (98) in the presence of allyl ethyl ether at 10°C afforded a thermally stable silacyclopropane (99) which could not be isolated in pure form. Treatment of the photolysis mixture with methanol gave 1-allyl-1-mesityl-1-methoxytrimethyldisilane in 40% yield (Scheme 30). Similar reactions of less highly substituted silylenes gave much poorer yields of the methanolysis products <83JOM(248)25l>. 

Cone conformations are established when 48 is converted to its tetra-allyl ether 51c, benzyl ether 5Id, or trimethylsilyl ether 51 e, when 47 is converted to its... 

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