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A practical method is developed for the cleavage of catechol monomethyl ethers and o-carbonylphenyl methyl ethers using aluminum chloride and sodium iodide in acetonitrile. Acid scavengers such as 1,3-diisopropylcarbodiimide and CaO are used to prevent acid-labile functional groups from sidereactions. This method is efficient for the deprotection of various o-hydroxyphenyl methyl ethers such as acetovanillone, eugenol, guaiacol, vanillin, isovanillin and ortho-vanillin. The AlCl 3 -NaI system is less efficient than AlI 3 for the cleavage of other typical aryl alkyl ethers without a neighboring hydroxyl or carbonyl group, or for the removal of bulkier alkyl groups from catechol monoalkyl ethers. This procedure represents a convenient approach for the preparation of catechols. 2 3 4 5 6 7 8

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Using eugenol and vanillin as model substrates, a practical method is developed for the cleavage o-hydroxyphenyl alkyl ethers. Aluminum oxide iodide (O=AlI), generated in situ from aluminum triiodide and dimethyl sulfoxide, is the reactive ether cleaving species. The method is applicable to catechol monoalkyl ethers as well as normal phenyl alkyl ethers for the removal of methyl, ethyl, isopropyl, and benzyl groups. A variety of functional groups such as alkenyl, allyl, amide, cyano, formyl, keto, nitro, and halogen are well tolerated under the optimum conditions. Partial hydrodebromination was observed during the demethylation of 4-bromoguaiacol, and was resolved using excess DMSO as an acid scavenger. This convenient and efficient procedure would be a practical tool for the preparation of catechols.

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