Synthesis and Comparison of the Reactivity of Allyl Fluorides and ...

Scheme 2.14 Reaction of cis-3-methyl-2-penten-1,5-diol with (59)
45
Chapter Two
Magid and co-workers demonstrated in 1977, that allylic alcohols could be converted into
the corresponding chlorides by using hexachloroacetone/triphenylphosphine. [42] The allylic
alcohol was reacted with hexachloroacetone and a slight excess of triphenylphosphine, with
a very rapid reaction (< 20 minutes), affording the corresponding chloride in excellent high
yields. Three allylic alcohols were tested; (E)-but-2-en-1-ol, (Z)-but-2-en-1-ol and but-3-
en-2-ol, affording the desired allylic chlorides in 99 %, 98 % and 94 % yields respectively.
In 1984 Ho and Davies also reported a convenient method utilising triphenylphosphine,
however, this time in conjunction with diethyl azodicarboxylate in THF in the presence of
anhydrous zinc chloride. [43] It was found that the covalent bond character between zinc
metal and oxygen led to the formation of a reactive alkoxyphosphonium halide (Scheme
2.15). Here the reaction proceeded via an SN2 type displacement of the resulting
alkoxyphosphonium species by the chloride anion. The reaction procedure converted
primary, secondary and allylic alcohols in good yields (66-92 %) to the corresponding
chlorides.
Scheme 2.15 Reaction of allylic alcohols with PPh3, diethyl azodicarboxylate and ZnCl2
Munyemana and co-workers [12] reported the synthesis of allylic and alkyl chlorides from the
corresponding alcohols by employing an equimolar amount of the reagent tetramethyl-�-