To verify the first hypothesis A (i.e., eliminationeaddition sequence
instead of additioneelimination sequence), the corresponding
acetylenic ketone (4-phenylbut-3-yn-2-one) as
a potential intermediate of the whole transformations sequence
was treated with 4-bromophenol under optimized conditions: at
room temperature in dry acetone in presence of K2CO3 for 24 h. No
reaction was observed in this case. The conversion of the initial
ynone and formation of the target enone 2b achieved 30% only after
standing the reaction mixture at room temperature for two weeks
(Scheme 5). Therefore, this way of the formation of pushepull
aroxyenones 2 from a-haloenones 1 appears to be less favourable,
and so was removed from consideration in this case.
In