High diastereoface selection in an ester enolate addition to α-alkoxy aldehydes: stereoselective synthesis of α-methylene-β-hydroxy-γ-alkoxy esters

The aldol-type condensation of β-(dimethylamino)propionates 3 and 4 with a series of α-alkoxy aldehydes proceeds with unprecedented high stereoselectivity (up to 24:1) to give anti α-methylene-β-hydroxy-γ-alkoxy esters. The best results were obtained when the reaction was carried out in diethyl ether and the ester enolate was allowed to equilibrate to the thermodynamically more stable geometric isomer. © 1984 American Chemical Society.