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

[GRAPHICS] A new precursor of a formal 1-hydroxy allyl anion is represented by 3-bromo -1-acetoxy-1-propene, which is synthesized by the ZnCl2-catalyzed addition of acetyl bromide to propenal. 3-Bromo-1-acetoxy-1-propene reacts with indi um powder in THF to give the corresponding 3-acetoxylated ally indium compl ex, which regioselectively adds to aldehydes, affording monoprotected 1-en- 3,4-diols. Diastereoselectivity mainly depends on the nature of the aldehyd e; saturated aldehydes afford anti adducts, whereas the alpha,beta -unsatur ated aldehydes preferentially lead to the syn isomers.