Science of Synthesis

Braun, M., Science of Synthesis, (2007) 35, 343.

Trialkylsilyl ethers have developed into frequently applied synthetic intermediates and building blocks. Although mostly considered as “protected alcohols”, they have also been found to be useful starting materials for the preparation of alkyl halides. It turns out to be advantageous that they are not only readily accessible but moreover cleaved under conditions that are distinctly milder than those required for dialkyl ethers. Problems of regioselectivity that are inherent to the cleavage of dialkyl ethers vanish when using silyl ethers, as they give the alkyl bromide exclusively. Various protocols are suitable for the conversion of silyl ethers into bromoalkanes, usually under mild conditions. Some of the reagents that also permit the conversion of alcohols into alkyl bromides, such as triphenylphosphine–bromine and triphenylphosphine–carbon tetrabromide, are outlined in Section ‌35.2.1.5.2‌. In addition, triphenylphosphine–2,4,4,6-tetrabromocyclohexa-2,5-dienone, bromotrimethylsilane, and boron tribromide lead to cleavage of silyl ethers with concomitant formation of bromoalkanes.

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