Metal-hydroxide-catalyzed addition reactions of hydrazonoester
with allenylboronate in aqueous media are described. The propargyl
adduct was obtained selectively by using copper(II) hydroxide, whereas
the allenyl adduct was produced preferentially using bismuth(III)
hydroxide in water-DMF (1:3). The reactions proceeded smoothly
in pure water without the use of any organic solvents by addition
of a small amount (1.7 mol%) of sucrose.
allenylation - propargylation - hydrazones - green chemistry - chemoselectivity