A-Phenylallyl acetate

Winstein showed that the solvolysis of crotylmercury(II) acetate under kineticalfy contrtdled conditions gives >99.5% of a-methylallyl acetate (equation 13)." Subsequent work indicated that both the solvolysis of cinnamylmercury(n) acetate and the mercuiy(II) acetate oxidation of allylbenzene give ca. 60% ciimamyl acetate (35) and 40% a-phenylallyl acetate (36 equation 14)." An equilibrium exists between (35) and (36) favoring the primary ester which constitutes >99.5% of the equilibrium mixture at 75 C. Oxidation of a range of bodi 1- and 2-alkenes under kinetically controlled conditions exclusively gave the secondary allylic esters. 

The major product is cinnamyl acetate (2) a-phenylallyl acetate (3), 1,2-diacetoxy-.3-phenylpropane (4), and fran -propenylbenzene (5) are formed in trace amounts. A similar distribution of allylic acetates is obtained from the solvolysis of cinnamyl-mercuric acetate. C(,H5CH=CHCH2HgOAc, which presumably is the intermediate in the oxidation of allylbenzene. 

Qualitative studies of the effects of allylic substituents, acyl substituents, and reaction conditions on rates of isomerization of allylic esters played a prominent role in the development of mechanistic theories of anionotropic rearrangements . Burton and Ingold observed that a-phenylallyl p-nitrobenzoate isomerizes more rapidly than a-phenylallyl acetate, that electron-releasing a-substituents facilitate isomerization of a-substituted allyl acetates, and that the rate of isomerization of a-phenylallyl p-nitrobenzoate increases as the dielectric constant of the solvent increases. All of these observations support the mechanism, which involves dissociation of the allylic ester into an allylic carbonium carboxylate ion pair, which reassociates to the starting material and its allylic isomer, viz. 

Under electrochemical reduction conditions allyl acetates undergo Pd-catalyzed reduction to give alkenes in good yield (Scheme 1). The reaction may proceed via two-electron (2 e) reduction of the rr-allylpalladium intermediate. The allyl anion thus formed is protonated selectively at the terminal position to provide an internal alkene predominantly. In the presence of an excess of chlorotrimethylsilane (ca. 13 equiv), trimethylsilylation takes place at the less substituted allylic termini to provide allylsi-lanes in moderate to good yield (Scheme 1). The same products are obtained in similar yield by the protonation and silylation of a-phenylallyl acetate. The reaction may be... 

The aoss-coupling reaction of bis(pinacolato)diboron with allyl acetates provides the pinacol esters of allylboronic acids in high yield (Scheme The reaction is effectively catalyzed by Pd(dba)2 in DMSO at 50 °C. The reaction more or less accompanies the formation of biallyl, the amount of which markedly depends on the kind of leaving group of the al-lyhc substrates. E)- and (Z)-Cinnamyl acetate and a-phenylallyl acetate aU provide trans-cinnamylboronic acid ester selectively and in almost the same yield, which suggests that the reaction proceeds via ir-allylpalladium as a common intermediate. 

Bidentate palladium complexes of 5 were formed upon the addition of PdCl2, as shown by P-NMR spectroscopy, and even for the largest dendrimers steric interactions between the dendritic branches did not prevent the facile formation of the bidentate complex. Crotylpalladium chloride complexes were prepared in situ from these dendrimers and used as catalysts for allylic alkylation reactions. The regio-selectivity for the branched product for the alkylation of 3-phenylallyl acetate with diethyl sodio-2-methylmalonate increased when the higher-generation dendrimers were used, albeit at the cost of a lower activity. 

Another example of a dendritic effect observed for a core-funtionalized dendritic catalyst was described by Oosterom et al. (19) for allylic alkylation reactions (Section II). The palladium complexes of 5 catalyzed the alkylation of 3-phenylallyl acetate with sodium diethyl methylmalonate. It was observed that the reaction rate decreased and the fraction of branched product increased with increasing generation number. 

Cumene 5 2-Phenylacrolein, 25 a-bromo-methylstyrene, 10 2-phenylallyl acetate, 5... 

In the presence of bromide, the oxidation of alkenes by Mn(OAc)3 in acetic acid readily occurs it 70-80 °C and produces allylic acetates in good yields. Thus cyclohexene is oxidized to cyclo-lexenyl acetate in 83% yield,508 and a-methylstyrene to j3-phenylallyl acetate in 70% yield,509 vith a mechanism involving allylic hydrogen abstraction by bromine atoms coming from the ixidation of bromide by MniU (equation 206). 

Allylmetal compounds can be prepared by the Pd-catalysed allylation of dimetal compounds. The phenylallylboronate 195 is prepared by the reaction of 2-phenylallyl acetate with bis(pinacolate)diboron (194) catalysed by ligandless Pd in DMSO [95], A good synthetic route to the allylsilane 197 is the reaction of Me3SiSiMe3 with geranyl trifluoroacetate (196) catalysed by ligandless Pd via transmetallation of the n-allylpalladium intermediate at room temperature in DMF [96],... 

Various studies have been carried out to determine the effects of changes in a-substituents on the chemistry of cyclopropyl derivatives " An a-phenyl substituent was observed to accelerate the rate of acetolysis of cyclopropyl tosylate by a factor of 10. Even though the product was 2-phenylallyl acetate, it was suggested that the high sensitivity of a-arylcyclopropyl tosylates to the introduction of substituents onto the aromatic ring is due to the fact that the activated complex is an aryl-stabilized cyclopropyl cation, not a ring-opened allyl cation species. 

The oxidation of a- and -methylstyrenes by manganese(m) acetate is slow at 80 °C, but in the presence of KBr a rapid reaction leading to jff-phenylallyl acetate is observed ... 

The effect of hydrogen bonding on allylic alkylation was studied in the base-free reaction of phenylallyl carbonate with dimethyl malonate.1 31,1321 While the reaction proceeds rapidly in THF in the presence of four equivalents of PPh3, it is very sluggish in [C4Ciim][BF4], The reaction in THF was significantly inhibited when small quantities of the ionic liquid were added. Only with excess external base did the reaction proceed in a comparable rate in the ionic liquid. It was shown that the oxidative addition of allylic acetate to Pd(0) is reversible and in THF the resulting acetate anion... 

As mentioned already in the polymerization of meth of-phenylacrylate a steri-cally random pdymer was obtained. However, the fraction of heterotactic triad in the polymer did not exceed 50 % under any polymerization conditions with BuLi Initiator (Table 10). On the other hand, methyl a-(p-bromophenyl)acrylate and methyl ce-(p-chlorophenyl)acrylate gave the polymers whose heterotactic contents were 59 and 61 %, respectively, in THF by BuLi at -78 (Table 10). The tacticity was determined by the C-NMR spectra of poly(2-phenylallyI acetate)s derived from the original polymers via pdy(2-phenylallyl alcohol)s. The bulkiness of the o-substituent seems to be important for the heterotactic propagation in these cases, as pointed out by Nozakuia et al. in the formation of heterotactic poty(vinyl alcohol) derived from poly(vinyl trimethylsilyl ether). However, method o-phenylacrylate formed a heterotactic pdymer whose heterotactic content was 66 %, by octylpotassium in THF (Table 10),... 

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