Dudley reagent

The Dudley reagents are eonveniently prepared from readily available starting materials and are indefinitely stable to storage and handling under standard laboratory eonditions. Alternatively, both reagents are eommereially available. 

The Dudley reagents are employed for the protection of alcohols as benzyl or PMB ethers, respectively, under mild conditions. Carboxylic acids are readily protected as well. Activation of the appropriate Dudley reagent in the presence of an alcohol furnishes the desired aiylmethyl ether. The benzyl reagent is activated upon warming to approximately 80-85 °C, whereas activation of the PMB reagent occurs at room temperature upon treatment with methyl triflate (CHsOTf) or protic acid." Aromatic solvents, most commonly trifluorotoluene, often provide the best results. Magnesium oxide (MgO) is typically included in the reaction mixture as an acid scavenger. For benzylation of carboxylic acids, triethylamine (EtsN) is used in place of MgO. ... 

Dudley and co-workers have designed pyridinium triflate reagent 58 for the preparation of benzyl ethers <06JOC3923>. This reagent is easily prepared in two steps with good yield. Since it is also bench-stable and preactivated, the benzylation reaction occurs upon warming 58 in the presence of an alcohol with no need for acidic or basic promoters. 

Benzylation of a monoacetylated diol is shown in Example 1. The Dudley benzyl reagent was uniquely effeetive for protection of the free alcohol without loss and/or migration of the labile acetyl group. 

The Dudley PMB reagent can also be activated under mildly acidic conditions using catalytic camphorsulfonic acid (CSA) in lieu of CHsOTf (Example 3). ... 

Example 4, In j//M-formation of the Dudley benzyl reagent is achieved by treating a mixture of an alcohol and 2-benzyloxypyridine with CHsOTf ... 

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