3,4-Dimethoxybenzyl Ethers

The acetal can also be cleaved with DDQ (CH2C12, H2O, 66% yield) to afford the monobenzoate. Treatment of a 3,4-dimethoxybenzyl ether containing a free hydroxyl with DDQ (benzene, 3 A molecular sieves, rt) affords the 3,4-dimethoxy-benzylidene acetal. ... 

With zeolite Beta and the 2,5-dimethoxybenzyl ether, the reaction stops at the aldehyde. However, with the slimmer 3,4-dimethoxybenzyl ether, the reaction proceeds via a dehydration and a cyclization, to give a dihydronaphthalene ... 

A synthesis of the protein phosphatase inhibitor Tautomycin by the Oikawa group155 employed the superior hydrolytic lability of the 3.4-dimethoxybenzyli-dene acetal group in a synthesis of the maleate side chain [Scheme 3.84]. Thus treatment of the 3,4-dimethoxybenzyl ether 84.1 with DDQ effected oxidative... 

There is sufficient latitude in the rates for selective removal of a 3,4-dimethoxy-benzyl ether in the presence of an adjacent p-methoxybenzyl ether as illustrated in Scheme 4T74, taken from Smith s synthesis of Zampanolide,247 324 For other examples of the beneficial lability of 3,4-dimethoxybenzyl ethers, see Smith s synthesis of Phorboxazole131 and Nicolaou s synthesis of Apoptoli-dine.325... 

Protection of hydroxyl groups (11, 166).- 3.4-Dimethoxybcnzyl ethers are oxidized by DDQ more readily thanp-methoxybenzyl ethers. Moreover, the dimethoxybenzyl ethers of secondary alcohols can be selectively oxidized in the presence of the corresponding ethers of primary alcohols. Benzyl, p-methoxybenzyl, and 3,4-dimethoxybenzyl ethers all undergo hydrogenolysis catalyzed by Pt/C or Pd/C, but selective hydrogenolysis of benzyl ethers is possible with W-2 Raney Ni. 

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