Palladium-catalyzed carbonyl allylation by allylic alcohols with SnCl 2. A solvation-controlled diastereoselection

Abstract

Diastereocontrol in the allylation of benzaldehyde by (E)-but-2-en-1-ol using catalyst PdCl 2(PhCN) 2 and SnCl 2 was achieved by the choice of polar solvents; use of DMSO at 25 °C led to syn selection, while anti selection was found at -10 °C in THF. The addition of 3–10 equivalents of H 2O in any solvent enhanced the selectivities, and the control of the amount of H 2O in DMSO permitted both syn selection (a small amount of H 2O) and anti selection (a large amount of H 2O).