2- Methoxyethoxymethyl ether cleaved

P2I4, CH2CI2, 0° - It, 30 min, 62-86% yield. These conditions also cleave methoxymethyl and methoxyethoxymethyl ethers. 

Cleavage of methoxyethoxymethyl ethers. The reagent selectively cleaves MEM ethers in the presence of benzyl, silyl, allyl, and methyl ethers as well as aeetals, acetates, and benzoates. However, methoxymethyl ethers and aeetonides are cleaved at about the same rate as MEM ethers. 

Isopropyhhiomethyl ethers, ROCH2SCH(CHj)2. Methoxyethoxymethyl (MEM) ethers on reaction with 1 and 4-dimethylaminopyridine in CH2CI2 are converted into isopropylthiomethyl ethers. In the absence of DMAP, the MEM ether is cleaved to the free alcohol. Isopropylthiomethyl ethers can be cleaved to the alcohol under nonacidic conditions by silver nitrate and 2,6-lutidine. 

Cleavage of MEM ethers. 2-Methoxyethoxymethyl (MEM) ethers are cleaved by NaI/ClSi(CH,)3 in CHjCN at —20 or 25° in moderate to high yield, lodotrimethylsilane (commercial) is less effective. Fairly selective cleavage of MEM ethers is possible in the presence of lactones, methyl or benzyl ethers, and methyl esters. 

Deprotection of MEM and MOM ethers. Methoxyethoxymethyl and methoxy-methyl ethers are cleaved to the alcohol by this reagent in high yields. Either 2-butanone or 2-methyl-2-propanol is recommended as solvent. The procedure is particularly useful for cleavage of ethers of allylic alcohols, for which ZnBr, and TiCh are not useful. 

Protection of Phenols. Methoxyethoxymethyl chloride can also be used to protect phenols. The conditions for its introduction are similar to those used for alcohols (NaH, THE, 0°C MeOCH2CH20CH2Cl, 0°C 25°C, 2 h, 75% yield). In contrast to the alcohol derivatives, phenolic MEM ethers can be cleaved with Trifluoroacetic Acid (CH2CI2, 23 °C, 1 h, 74% yield). 1 M HCl (THE, 5 h, 60 °C) and HBr/EtOH will also effect cleavage. In general, the cleavage conditions used for alcohols are also effective with the phenolic derivatives. During an examination of the asymmetric reduction of an acetophenone derivative with (+)-B-Chlorodiisopinocampheylborane, it was found that a phenolic MEM ether was slowly cleaved (eq 4). ... 

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