Synthesis of β-hydroxymalonates: the direct aldol addition of malonates to aldehydes in the presence of SiCl4 and i-Pr2EtN

The direct aldol addition of malonates to aromatic, hetero-aromatic and unsaturated aldehydes leading to β-hydroxymalonates is described. The stability of these products, the trimethyl silyl protection of the hydroxyl group as well as the role of both SiCl4 and i-Pr2EtN in attaining the final products are also discussed.