Pummerer rearrangement methylthio methyl ethers

CcHiimon by-products in these reactions are (methylthio)methyl ethers (3) formed by a Pummerer rearrangement which occurs via an alternative breakdown of (2), as shown in Scheme 3. The proportion of the Pummerer rearrangement derived product varies with the electrophilic activator used. 

In comparison to some of the other activation methods however, the dimethyl sulfoxide-acetic anhydride procedure has certain disadvantages. The method often requires the use of long reaction times (1 24 h), which can result in many side reactions, especially with sensitive substrates. Notable in this respect is that it is not uncommon for this procedure to result in the formation of substantial yields of the thiomethyl ethers obtained from the Pummerer rearrangement product as described above. In fact upon attempted oxidation of cholesterol with this system, the major product obtained was the corresponding (methylthio)methyl ether. Acetates may also be formed if the alcohol is unhindered. For example the sugar derivative (9) reacts under these conditions to form an enol acetate (derived from the requir carbonyl compound) in 40% yield contaminated with 30% of the acetate (10 equation S). ... 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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