A new protocol for the acetoxyallylation of aldehydes mediated by indium in THF.

A new precursor of a formal 1-hydroxy allyl anion is represented by 3-bromo-1-acetoxy-1-propene, which is synthesized by the ZnCl(2)-catalyzed addition of acetyl bromide to propenal. 3-Bromo-1-acetoxy-1-propene reacts with indium powder in THF to give the corresponding 3-acetoxylated ally indium complex, which regioselectively adds to aldehydes, affording monoprotected 1-en-3,4-diols. Diastereoselectivity mainly depends on the nature of the aldehyde; saturated aldehydes afford anti adducts, whereas the alpha,beta-unsaturated aldehydes preferentially lead to the syn isomers. Reaction: see text.