The Regioselective 1,4-Addition Reaction of Alkenylboronic Acids to α,β,α′,β′-Unsaturated Ketones

The effect of substituents on the double bond of α,β-unsaturated ketones for the 1,4-addition reaction rate of alkenylboronic acids induced by cyanuric fluoride was studied in detail. When the steric hindrance around the β-carbon of the unsaturated ketones increased, the 1,4-addition reaction rate significantly decreased. An alkyl substituent on the α-carbon was also found to significantly affect the 1,4-addition reaction. From these results, unsymmetric α,β,α′,β′-unsaturated ketones (10a—f) were designed for the regioselective 1,4-addition reaction with alkenylboronic acids (4a—j). Since they have substituents to disturb the 1,4-addition reaction on only one double bond, the alkenylboronic acids reacted with them from only one side to selectively provide γ,δ,α′,β′-unsaturated ketones (11a—q). Further transformations of the resulting γ,δ,α′,β′-unsaturated ketones were also performed.