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

Scheme 2.25 Mechanistic pathway for synthesis of allylic chloride
2.2.3.2 Synthesis of 2-chlorobut-3-enyl benzoate and related Allylic Chlorides
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Chapter Two
Scheme 2.26 General reaction scheme for synthesis of allylic chlorides (108) – (113)
(For a definition of R see Table 2.17)
The same methodology was then extended to the chlorination of the derivatised benzoyl
alcohols and the desired products were obtained in moderate yields (32-74 %) (Table 2.17).
Both (100) and (101) proceeded in good conversion to product and were isolated by column
chromatography [DCM: cyclohexane (50:50)] in 65 % and 74 % yields respectively. The
main by-products were the rearranged chlorides 4-chlorobut-2-enyl benzoate and 4-
chlorobut-2-enyl 4-fluorobenzoate, however, as these were not desired products, no attempts
were made to isolate or characterise them.
The isolated yields of (110) – (113) were lower than expected. Here chromatography
revealed both unreacted starting material and 1-chloroallyl product. Although the addition
of aliquots of tetramethyl-�-enamine and longer reaction times were attempted, isolated
yields of the products could not be improved substantially. All products were fully
characterised by 1 H, 13 C and 19 F NMR spectroscopy and mass spectrometry.