Allyl alcohol trimethylsilyl ether

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... 

Notes, (a) Rate of metallation with t-BuLi varies from case to case. Lithiation of allyl alcohol trimethylsilyl ether proceeds to completion in 2 h at —78°C, whereas the corresponding methallyl derivative requires 3.5h at -33°C. 

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. 

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... 

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. 

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. 

Unfortunately, attempts to perform this substitution reaction on cyclohexenol and geraniol led to the exclusive formation of the corresponding silyl ethers. It thus would seem that one requirement for effective carbon-carbon bond formation is that allylic alcohols be secondary and have possess y,y-disubstitution. Pearson, however, discovered a method with less restriction on the natiue of the substrate he used allylic acetates with y-mono-substitution or primary alcohols [96]. Not only ketene silyl acetals but also a diverse set of nucleophiles including aUyl silane, indoles, MOM vinyl ether, trimethylsilyl azide, trimethylsilyl cyanide, and propargyl silane participate in the substitution of y-aryl allylic alcohol 90 to give allylated 91 (Sch. 45). Further experimental evidence suggests that these reactions proceed via ionization to allylic carboca-tions—alcohols 90 and 92 both afforded the identical product 93. 

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. 

Epoxidation of acyclic allyl alcohols with peracid and Mo/TBHP displays an opposite stereospecificity to that for the V/TBHP system. Trimethylsilyl-substituted allylic alcohols give t/zreo-epoxyalcohols with MCPBA and erythro-alcohols with VO(acac)a-TBHP, with high stereoselectivity. In the stereospecific epoxidation of cis- and trans-allyl alcohols, formation of a transition state is assumed with the development of two H bonds between the hydrogen atom of the hydroxy group of the allyl alcohol and the oxygen of the peracid, and between the hydrogen of the peracid OH and the oxygen of the ether 10. An analysis of the diastereometric transition-state interactions for stereoselective epoxidation of acyclic allylic alcohols has been published. A conformational effect may be responsible for the unexpected cis major product in Eq. 2. 

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 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. 

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). 

A mixture of 10 mmol of allylic alcohol, 637 mg (2 mmol) of Hg(OAc)2 and 1.5 g (10 mmol) of ethyl l-(trimethylsilyl)vinyl ether is stirred at r.t. for 8- 12 h. The mixture is then poured into 5% aq KOH and extracted with hexane. After drying over Na2S04, the hexane extracts are concentrated. The crude residual is purified by column chromatography (hexane or Et20, hexane 1 50). 

Modified Sakurai reaction.3 The original reaction involved the TiCI4-catalyzed addition of allyllrimclhylsilanc to aldehydes and ketones or the acetals and kctals to form homoallylic alcohols or ethers (7,370-371). Marko et al. have extended this reaction to a synthesis of homoallylic ethers by a Lewis acid catalyzed reaction of allyl-trimcthylsilanc with a carbonyl compound and a trimethylsilyl ether. 

Since the C13-C14 olefin does not alter the reactivity of the C1-C9 portion of the myriaporone intermediates, subsequent efforts were explored on the C13-PMB ether (Scheme 12). Substrate 26 was successfully reduced with Raney nickel, and the trimethylsilyl ether was selectively cleaved with TBAF at -35 C. The C5 alcohol was selectively protected as the corresponding TBS ether, and C7 allylic alcohol was then oxidized under Dess-Martin conditions to provide bis-silyl ether 31. 

Acid-catalysed addition of primary, secondary, and tertiary alcohols to 3,4-dihy-dro-2//-pyran in dichloromethane at room temperature is the only general method currently in use for preparing THP ethers and the variations cited below concern the choice of acid. The reaction proceeds by protonation of the enol ether carbon to generate a highly electrophilic oxonium ion which is then attacked by the alcohol. Yields are generally good. Favoured acid catalysts include p-toluenesulfonic acid or camphorsulfonic acid. To protect tertiary allylic alcohols and sensitive functional groups such as epoxides, the milder acid pyridinium p-toluenesulfonate has been employed (Scheme 4.316]. A variety of other acid catalysts have been used such as phosphorus oxychloride, iodotrimethylsilane- and bis(trimethylsilyl)sulfate. but one cannot help but suspect that in all of these cases, the real catalyst is a proton derived from reaction of the putative catalysts with adventitious water. Scheme 4.317 illustrates the use of bis(trimethylsilyl)sulfate in circumstances where other traditional methods failed. - For the protection of tertiary benzylic alcohols, a transition metal catalyst, [Ru(MeCN)2(triphos)](OTf)2 (0.05 mol%) in dichloromethane at room temperature is effective. ... 

New fatty compounds have been synthesized in high yields using radical addition reactions. Alkyl 2-haloalkanoates have been added to the double bond of unsaturated fatty compounds to give y-lactones. 2-Haloalkanenitriles have been added as well to give 4- haloalkanenitriles. 2-Halo fatty compounds, e.g., methyl 2-bromopalmitate, have been added to alkenes, allyl alcohol, vinyl esters, and trimethylsilyl enol ethers to give interesting branched and functionalized compounds. Key features of the re-... 

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