Abstract: | Under carefully controlled conditions, boron trichloride or alkoxydichloroborane/ethyldiisopropylamine in CH2Cl2 can be used to effect diastereoselective aldol additions of ethyl ketones to saturated, α, β-unsaturated, or aromatic aldehydes. The C? C bond formation takes place with relative topicity ul (‘syn,’ configuration of the aldols), in selectivities ranging from 90 to 99% ds (Tables 1–3). Mechanistic aspects of the reaction are discussed. |