Allyl 2,4-dimethylphenyl ethers

In contrast to the thermal Claisen rearrangement, studies of isotopic labeling in the photochemical Claisen rearrangement support a dissociative mechanism. Figure 6.10 shows the results obtained from irradiation of 3- C-allyl 2,6-dimethylphenyl ether (37) to produce 2,6-dimethylphenol (38) and 4-allyl-2,6-dimethylphenol (39). In 39, the label was distributed nearly equally between the a and y positions, suggesting that it was formed by the recombination of 2,6-dimethylphenoxy and allyl intermediates and that rotation of the allyl fragment allows the label to become effectively scrambled between the two end carbon atoms of the allyl group by the time... 

The Claisen rearrangement of allyl 2,6-dimethylphenyl ether normally produces 4-allyl-2,6-dimethylphenol as the major product. When the reaction was carried out in molten maleic anhydride at 200°C, however, two products having the molecular formula C15H16O4 were isolated in addition to 4-allyl-2,6-dimethylphenol. What are the two compounds, and what does their isolation indicate about the mechanism of the reaction ... 

Problem 19.20 Predict the product of the Claisen rearrangement of (a) alIyl-3- C phenyl ether, (b) 2,6-dimethylphenyl allyl-3-" c ether. ... 

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