Chemoselective aldol condensation in 5 mol dm 3 lithium perchlorate-nitromethane. A comparison with lithium perchloratediethyl ether medium

Aldol reactions of silyl enol ethers with aldehydes proceed in 5 mol dm 3 lithium perchlorate-nitromethane medium at ambient temperature. The reaction is highly chemoselective such that only aldehydes and cyclic ketones reacted while acyclic and aromatic ketones failed to react. The same reaction is not promoted in 5 mol dm"3 lithium perchlorate-diethyl ether medium. The difference between these two media is explained by the increased Lewis acidity of the lithium ion in nitromethane compared to that in ether.