Esters a-allyloxy

It has been demonstrated that the oxygen anion of initially formed product (36) effectively catalysed the [2,3]-Wittig rearrangement as a Lewis base. Other Lewis-base catalysts such as lithio or sodio 2-pyrrolidone promote the same [2,3]-Wittig rearrangement of silyl enolates generated from a-allyloxy ketones, whereas rearrangements of enolates from a-allyloxy esters were efficiently catalysed by ammonium 4-methoxybenzoate.24... 

Silyl enolates generated from a-allyloxy esters undergo the [2,3]-Wittig rearrangement on treatment with Lewis base such as tetrabutylammonium acetate or tetrabuty-lammonium 4-methoxybenzoate (Scheme 10).14... 

It was previously noted that enolates of a-allyloxy ketones were capable of either 2,3- or 3,3-rear-rangement, depending upon counterion, reaction conditions and substituents. Ester enolates show a greater propensity for the 2,3-pathway, as illustrated by the geraniol-derived alkoxyacetate (198) which afforded hydroxy ester (200) as the sole product upon treatment with LDA in THF at -78 to 0 C. The 3,3-product (201) could be obtained by addition of TBDMS-Cl and HMPA to the enolate at -78 °C and thermal rearrangement of the TBS enol ether (199b Scheme 14). ... 

According to Eq. (11), Confalone has presented a new method of generation of azomethine ylides through the condensation of N-substituted a-amino esters with aldehydes (83JOC2994 84JA7175). Thus, 5-formylmethyldibenzo-[a,d]tropylidene or o-(allyloxy)benzaldehyde is heated with ethyl sarcosinate or methyl prolinate under reflux in toluene. The water formed is continuously driven off with the aid of a Dean-Stark trap. The ester-stabilized azomethine ylide 77 or 78 quantitatively generated is trapped in an intramolecular fashion. 

Polymerization of bis[ -(allyloxycarbonyl)phenyl] esters of aliphatic and aromatic dicarboxylic acids to produce highly cross-linked polymers witii good optico-mechanical properties [126]. This study should be compared with the more recent work of Ref. [80a] on the polymerization of ethyl a-[(allyloxy)methyl]acrylate. 

Thus, the reactive emulsifier is a compoimd that has a hydrophilic group, e.g., a sulfuric ester, a hydrophobic group, e.g., aliphatic alkyl or aromatic groups, and a radically reactive group, e.g., allyloxy and propenyl groups. 

The [2,3]-Wittig rearrangement of dienolates generated from a-allyloxy-substituted a, - and/or /S.y-unsaturated esters has been found to proceed with high diastereose-lectivity to give hexa-1,5-dienes in high yield. The greater reactivity of dienolate than enolate has been explained in quantum chemical terms. 

Stereochemical outcome of this rearrangement. Enolization of the regioisomeric esters (127) and (128) has been shown to afford a-allyloxy-substituted ester dienolates (129) which undergo a [2,3]-sigmatropic rearrangement to yield 3-alkoxycarbonyl-3-hydroxy-substituted hexa-1,5-dienes (130). These have been transformed to diastereomerically pure 2,3-dialkenyl-substituted (/-lactones (131). 

The chemistry of allyloxy(methoxy)carbene (55) depends on the temperature at which it is generated.55 At 110°C, the carbene homolytically dissociated yielding mainly allylic ester. At 50 °C, the carbene dimerized and underwent a Claisen rearrangement to (56). 

A 3-allyloxy-2-bromo ester 264 (Y=0, R2=C02Et) cyclized similarly using 20 mol% of (salen)Co complex 267 as a catalyst under reductive electrochemical conditions at a carbon fiber cathode and a sacrificial aluminum anode under constant current conditions. Tetrahydrofurancarboxylates 266 were isolated in 70% yield and a good 6 1 CK//r[Pg.266]

C,H6S 870-23-5) see Altizide allyl(l-methyl-2-pentynyl)malonic acid diethyl ester (C]6H2404 101448-52-6) see Methohexital 4-a lyloxy-3-chlorobenzaldehyde (Ci0H9C1O2 58236-91-2) see Alclofenac 4-allyloxy-3-chlorobcnzyl chloride (C I)Hi(1C120 20788-43-6) see Alclofenac 4-allyloxy-3-chlorohenzyl cyanide (CnHmCINO 20788-44-7) see Alclofenac... 

In another case, 1 was used to deprotect the 2-(allyloxy)phenylacetyl group, employed as a protecting functionality in carbohydrate chemistry242. Thus, heating compound 266 with a palladium catalyst/proton sponge system results in an almost quantitative yield of compound 268 (equation 29). In accordance with a postulated relay mechanism, the phenolic allyl ether is cleaved by the transition metal followed by intramolecular ester cleavage by nucleophilic attack of the released hydroxyl. The aforementioned conditions... 

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