Alcohols, benzylic with ceric ammonium nitrate

Unlike benzylic groups, they cannot be made directly from the alcohol. Instead, the phenoxy group must be introduced by a nucleophilic substitution.30 Mitsunobu conditions are frequently used.31 The PMP group can be cleaved by oxidation with ceric ammonium nitrate (CAN). 

The p-methoxyphenyl group has recently been found suitable for alcohol protection, as the resulting ethers are stable both to acidic and basic conditions and can be cleaved by brief treatment with ceric ammonium nitrate. The same principle can be applied to carboxylic acid protection.Thus, the rather stable benzyl (64) and phenyl (65) esters can be cleaved as indicated by oxidation with DDQ or cerium(IV)(at pH 3) respectively. A recent total synthesis of (+)-Antimycin-A features the use of a... 

Ceric ammonium nitrate in water or in 50% acetic acid oxidizes ben-zylic alcohols at 90 °C in very good yields [420]. Only catalytic amounts of the reagent and sodium bromate as a reoxidant are needed to convert benzyl alcohol into benzaldehyde in 90% yield on heating in acetonitrile at 80 °C [421]. A similar result is obtained on treatment of benzyl alcohol with lead tetraacetate in pyridine at room temperature for a few hours (yield 85%) [442]. 

Primary TBDMS ethers can be cleaved selectively in the presence of THP ethers and ketals using ceric ammonium nitrate in methanol. Both phenolic and aliphatic TBDMS ethers undergo cleavage when exposed to catalytic amounts of PdCl2(MeCN)2 in the latter case, and with longer exposure, this also results in oxidation to the corresponding aldehyde or ketone, if the alcohol was primary or secondary, respectively. This cleavage and oxidation can be performed selectively in the presence of TIPS, TBDPS and benzyl ethers (equation 15). 

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