Allylphenolate ions

Unlike the acid-catalyzed ether cleavage reaction discussed in the previous section, which is general to all ethers, the Claisen rearrangement is specific to allyl aryl ethers, Ar—O—CH2CH = CH2. Treatment of a phenoxide ion with 3-bromopropene (allyl bromide) results in a Williamson ether synthesis and formation of an allyl aryl ether. Heating the allyl aryl ether to 200 to 250 °C then effects Claisen rearrangement, leading to an o-allylphenol. The net result is alkylation of the phenol in an ortho position. 

Aresta (54) has investigated the platinum complexes formed with o-allylphenol and o-allylthiophenol. The phenolic ligand reacts with the PtCl4 ion (in a suitable acetate buffer) to form the chelate complex shown in Fig. 40. The coordinated double bonds of this compound are successively replaced by two equivalents of pyridine. 

The amination of 2-alkenylphenols occurred efficiently compared to 2-allylphenols and -naph-thols69. The mechanism involves a proton exchange equilibrium between the phenolic and amino functions and the photoinduced proton transfer (PPT) from the ammonium ion to the alkenyl group, followed by attack of the amine on the intermediate benzylic carbocation. No photoamination of O-methylated and O-acetylated phenols occurred at all. As a single example of diastereoselective amination, the amine 6 was produced from 5 with good yield and diastereoselectivity, although the configuration was not determined. 

The fragmentation of protonated allyl phenyl ethers, and their phenolic isomers, such as ortho-allylphenol 113, is much simpler than that of their open-shell congeners generated by El mass spectrometry. Under CI(CH4) conditions, both the protonated phenol, [113 4- H] ", and the protonated parent ether, [115 4- H]+, behave very similarly (Scheme 31) . The by far major fragmentation path of these closed-sheU ions is the elimination of ethene, generating ions o-9 m/z 107, see below). Ionized or protonated phenol m/z 94 and 95) are formed in negligible amounts only. Nevertheless, Claisen rearrangement induced by... 

Allylphenol novolacs can be further modified by epoxidation of the allylic group using peroxides in the presence of buffer compounds, such as sodium acetate or sodium hydrogen phosphate, in a solvenf such as chloroform. The epoxidized allylphenol novolacs are free of chloride and alkali metal ions and are useful as materials in the production of integrated circuits [ 144]. As an alternative modification, free phenolic hydroxy groups can be reformed by rearranging the allylether so that the allyl group is substituted onto the aromatic... 

The epoxy novolacs synthesized by reaction of novolacs with chloromethyloxiiane may contain traces of hydrolyzable and nonhydrolyzable organically boimd chlorine as impurities, which reduce not only the functionality of the epoxidized novolac but negatively affects the properties of the crosslinked products. Furthermore, traces of chloride and alkali metal ions also need to be carefully removed. In contrast to this, epoxy novolacs obtained by epoxidation of allylphenol are fiee of chloride and alkali metal ions. 

The labeling experiment just described eliminates from consideration a mechanism in which the allyl phenyl ether dissociates to produce an allyl cation (Section 13.4) and a phenox-ide ion, which then subsequently undergo a Friedel-Crafts alkylation (Section 15.6) to produce the o-allylphenol. Explain how this alternative mechanism can be discounted by showing the product (or products) that would result from it. 

The alternating copolymers of p-hydroxystyrene and p-isopropenyl-phenol with MA (Table A.6) have recently received a fair amount of study. These copolymers, with two different types of functional acid groups, are being studied in polyion complexes for membranes, detergent additives, epoxy resin curatives, rubber additives, coatings, adhesives, laminates, ion-exchange resins, and other applications. The equimolar 2-allylphenol and 2-methallyl-phenol-MA copolymers (Sec. 10.2.1) are potentially useful in many of the same applications.Maruzen Oil has announced their intention to produce and test market the p-hydroxystyrene copolymer. 

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