A mild chlorination method of unactivated aliphatic alcohols using a triphosene-amine base mixture has recently been explored. Using a triphosgene-triethylamine base mixture yielded primary alkyl chlorides or diethylcarbamate products, with selectivity being driven by sterics. A switch in amine base to pyridine alleviated the selectivity issue and led to the production of alkyl chlorides from unactivated secondary alcohols and a-branched primary alcohols. This mild method has also been used to simultaneously chlorinate unactivated aliphatic 1,3-diols to the corresponding 1,3-dichlorides. While 1,3-anti diols readily afford 1,3-anti dichlorides, 1,3-syn diols result in the cyclic carbonate byproduct as the major product.  Through mono protection of 1,3-syn diols with a silylether, the selectivity problem was improved to yield the 1,3-syn dichloride product. A screen of silyl ethers proved that dimethylphenylsilyl ether was effective in producing the dichloride product.

Triphosgene-pyridine mediated dichlorination reactions: 1,3-<i>?anti </i>vs 1,3-<i>syn</i> diols

248th National Meeting (2014)

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Triphosgene-pyridine mediated dichlorination reactions: 1,3-?anti vs 1,3-syn diols