The utility of triphosgene and DMAP
as mild reagents for chemoselective
dehydration of tertiary alcohols is reported. Performed in dichloromethane
at room temperature, this reaction is readily tolerated by a broad
scope of substrates, yielding alkenes preferentially with the (E)-geometry. While formation of the Hofmann products is
generally favored, a dramatic change in alkene selectivity toward
the Zaitzev products is observed when the reaction is carried out
in dichloroethane at reflux.
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