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31.5.1.2.3.1 Variation 1: Reaction with Brønsted Acids

DOI: 10.1055/sos-SD-031-00271

González-Bello, C.; Castedo, L.Science of Synthesis, (200731308.

Strong protic acids cleave aryl methyl ethers giving the parent phenols. Typically, the cleavage occurs under acidic conditions such as by reflux in 48% hydrobromic acid. These conditions are employed in the efficient synthesis of phenol 12 from (4-methoxybenzyl)amine (11) (Scheme 6).[‌8‌] Trifluoroacetic acid can be also employed.[‌9‌] Aryl benzyl ethers are also cleaved under acidic conditions and the cleavage usually occurs faster than with methyl ethers. This has been exploited in the selective debenzylation of dibenzyl methyl triether 13 to afford the diphenol 14 in 81% yield (Scheme 7).[‌10‌]

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