Allyl cinnamyl ethers

Pd(Ph3P)4, RS02Na, CH2CI2 or THF/MeOH, 70-99% yield. These conditions were shown to be superior to the use of sodium 2-ethylhexanoate. Methallyl, allyl, crotyl, and cinnamyl ethers, the Alloc group, and allyl-amines are all efficiently cleaved by this method. ... 

A third approach to the preparation of allyl lluorovinyl ethers is the reaction of an allylic alcohol with trifluoroacetaldehyde, as illustrated by an alternative synthesis of 37a.17 Cinnamyl alcohol (47) forms with trifluoroacetaldehyde a hemiacetal, which is converted into bromide 48 via the mesy late. Reductive elimination affords 37a, which undergoes Claisen rearrangement within one hour in refluxing carbon tetrachloride to give 2,2-difluoro-3-phenylpent-4-enal (38a).17... 

The structure of XXVI was deduced from the fact that it was different from the 2-cinnamylphenol obtained by direct C-cinnamylation of phenol.16 Later investigators showed that XXVI is the sole product ozonization yielded formaldehyde but not benzaldehyde. 7-Methyl-allyl phenyl ether also rearranges with inversion, yielding 2-(a-methyl-allyl)-phenol 36 the structure of the rearrangement product has been definitely established87 38 by a combination of degradative and synthetic procedures. 

The extent of C-alkylation as a side reaction in etherification varies about 1% of allyl 2-allylphenyl ether is formed when phenol is used in the acetone and potassium carbonate method with allyl bromide with cinnamyl bromide or 7,7-dimethylallyl bromide the extent of C-alkylar tion is greater.16 A complicated mixture of C- and O-alkylation products results from the treatment of phenol with 4-bromo-2-hexene and 4-chloro-2-hexene. 9 4-Hexenylresordnol has been obtained in about 40% yield from the reaction of l-bromo-2-hexene, resorcinol, and potassium carbonate in boiling acetone.99 An appreciable amount of C-alkylation occurs when 2,6-dimethyIphenol is treated with allyl bromide and sodium ethoxide in ethanol.70 Since, in general, the ampunt of C-alkylation is greatly increased by carrying out the alkylation on the sodium salt of the phenol in benzene,16 this method is unsuitable for the preparar tion of allyl aryl ethers. 

Farina has shown that the reaction of 129 with cinnamyl chloride in THF with Pd2(dba)3 and tri-(2-furyl)phosphine as precatalytic system, results in incomplete formation of the C-allylated 130a, the isomeric cinnamyl ether of 129 being also isolated (91JA9585). 

Oxopentanals may be synthesized from allylic alcohols by 3,3 sigmatropic rearrangement of their vinyl ethers, and subs uent oxidation of the terminal double bond. Cinnamyl alcohol (31) was converted to the allyl vinyl ether (32), which was subjected to Qaisen reairangement to give 3-phenyl-4-pentenal (33) in 50% yield. Oxidation of the terminal double bond of (33) gave 3-phenyl-4-oxopentanal... 

The only kinetic study of acid-catalyzed isomerization of a simple allylic ether was published by Braude and Gore who found that methyl a-phenylallyl ether isomerizes to methyl cinnamyl ether in anhydrous dioxane containing either boron trifluoride or hydrogen chloride. At 25°C, the ether is a quarter to an eighth as reactive as the corresponding alcohol. 

Less reactive allylic alcohols are carbonylated under harsh conditions. However, carbonylation of allylic alcohols proceeds smoothly in the presence of phenol as a nucleophile. Phenyl 4-phenyl-3-butenoate (374) was obtained in 80 % yield from cinnamyl alcohol under 5 atm of CO at 100 °C. The carbonylation may proceed by the formation of allyl phenyl ether, which is a reactive compound [145]. Allyl alcohol was carbonylated under high pressure of CO2 (50 atm) and CO (50 atm) in dioxane to provide 2-butenoic acid as the main product and 3-butenoic acid as the minor product at 110°C. Presumably monoallyl carbonate 375 is generated from... 

Hartwig et al. demonstrated that the same combination of iridium precursor and phosphoramidite LI also catalyzes allylic etherifications (Scheme 9) [68]. Lithium and sodium aryloxides were shown to react with cinnamyl and hex-2-enyl carbonates to form the branched allylic ethers in high yield, with high branched-to-linear... 

Unstabilized enolates react with allylic carbonates in the presence of metalacyclic iridium-phosphoramidite catalysts. Although ketones and aldehydes have not yet been used directly as pronucleophiles with this catalyst system, silyl enol ethers [80] and enamines [81] react with linear allylic carbonates to form, after workup, p-branched, y-8 unsaturated ketones (Scheme 13). Both methods form products in high yield, branched selectivity, and enantioselectivity for a range of cinnamyl and alkyl-substituted allylic carbonates. However, the silyl enol ethers derived from aliphatic ketones reacted in lower yields than enamines derived from the same ketones. 

Disubstituted dihydrofurans and dihydropyrans were prepared via allylic etherification [68] in a similar manner to dihydropyrroles (cf Section 9.4.6). Thus, diaste-reoisomeric ethers were generated by the reaction of cinnamyl tert-butyl carbonate with the copper alkoxide prepared from (Rj-l-octen-3-ol, depending on which enantiomer of the phosphoramidite ligand was used (Scheme 9.39). Good yields and excellent selectivities were obtained. RCM in a standard manner gave cis- and trans-dihydrofuran derivatives in good yield, and the same method was used for the preparation of dihydropyrans. 

Doyle et al. have demonstrated the catalyst-dependent diastereoselectivity in Rh(ii) complex-catalyzed reaction of cinnamyl methyl ether 36 and ethyl diazoacetate 35 (Scheme 6). " The change of the diastereoselectivity of the products 38a and 38b with different Rh(ii) catalyst provides strong evidence that Rh(ii) catalyst is associated with the ylide in the rearrangement process. The moderately high level of asymmetric induction (4-69% ee) is also observed with allyl iodide (Equation (4)). In this case, the chiral metal complex must be in the product-forming step, because free iodo ylide is achiral. 

Allyl 2,2,2-lrifluoroethyl ethers 36 are obtained from the alkoxides and cinnamyl chloride (for 36a) or allyl bromide (for 36b).17 Claisen rearrangement of the vinyl ethers 37 is complete within one to several hours at 80 C to give a, -difluoro aldehyde 38a or ketone 38b. 

Cinnamyl phenyl selenide, 79 Tetrakis(triphenylphosphine)-palladium(O), 289 Vinyltrimethylsilane, 343 Allylic ethers... 

Grape Allyl salicylate Cinnamyl anthranilate Guaiol acetate Isobutyl anthranilate Isovalerophenonc Octyl isobutyrate Phenylpropyl acetate, ether. 

Honey Allyl phenoxyacetate, phenylaceiate Benzyl cinnamate Carvacryl acetate Cinnamyl butyrate p-Cresyl acetate p-Cresyl ethyl ether /rt-Cresyl phenylaceiate />-Cresyl phenylaceiate Cyclohexyl phenylacctate Ethyl phenoxyacetate. phenylaceiate Guaiol phenylaceiate Isobutyl phenylaceiate Linalyl butyrate Methyl phenylaceiate Phenethyl acetate, butyrate, phenylaceiate Phenylacetic acid Propyl phenylaceiate Santalyl phenylaceiate. 

Allyl ethers of orf/io-disubstituted phenols rearrange to the corresponding p-allylphenols. It is noteworthy that the para rearrangement is not usually accompanied by inversion of the allyl group.8-4-6-6-7 For example, cinnamyl 2-carbomethoxy-6-methylphenyl ether (III) rearranges without inversion8 to yield the p-cinnamyl derivative (IV). 

The-Claisen rearrangement to the ortho position is a first-order reaction,67 68 and the process does not require catalysis by acids and bases. The rearrangement is intramolecular, since rearrangement of mixtures of ethers such as allyl /3-naphthyl ether and cinnamyl phenyl ether,60 or cinnamyl 4-methylphenyl ether and allyl 4-aminophenyl ether,68 yields none of the cross products which would result from an intermolecular reaction. The process is best represented by the cyclic mechanism, in which the following processes take place, with the electronic shifts during reaction indicated by the arrows.23 39 69... 

Compounds of type LXXIII cannot be made by the rearrangement of the 7-substituted allyl ethers, because these compounds yield LXXIV by inversion. a,7-Dimethylallyl bromide,16 7,7-dimethylallyl bromide,29 cinnamyl chloride,84 and phytyl bromide 86 (a vitamin K synthesis) have been used in C-alkylation procedures. The silver salt of 2-hydroxy-l,4-naphthoquinone is converted to a mixture of C-alkylation product and two isomeric ethers by treatment with allylic halides and benzyl halides. ... 

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