1- and 2-Naphthols were successfully alkenylated in a regioselective manner by treating
the corresponding lithium 1- and 2-naphtholates with magnesium alkylidene carbenoids.
The magnesium alkylidene carbenoids were generated in situ by a sulfoxide–magnesium exchange reaction of 1-chlorovinyl 4-tolyl sulfoxides with
isopropylmagnesium chloride. The reaction of magnesium alkylidene carbenoids with
lithium 2-naphtholates took place at the 1-position of the naphthyl ring to give 1-(alk-1-enyl)-2-naphthols
in respectable yields. The alkenylation of 1-naphthols proceeded at the 2-position
of the naphthol ring to give 2-(alk-1-enyl)-1-naphthols in yields of 56–67%. In contrast
to the reaction of lithium naphtholates with magnesium alkylidene carbenoids, the
reaction of lithium phenolates gave low yields of the corresponding alk-1-enyl aryl
ethers.
Key words
alkenation - phenols - carbenoids - sulfoxides - alkenes - arenes - organometallic
reagents