An improved procedure for the asymmetric aldol reaction of the titanium enolate of an N3-propionyl-3,4,5,6-tetrahydro-2 H-1,3,4-oxadiazin-2-one

Abstract

The direct formation of the titanium enolate of N 3-propionyl-3,4,5,6-tetrahydro-2 H-1,3,4-oxadiazin-2-one has been achieved through complexation with titanium tetrachloride at 25°C, followed by deprotonation with triethylamine (−78 to 25°C). The preformed titanium enolate has been reacted with D 2O/DCl to afford deuterated derivative 6 and also reacted with a series of aromatic and aliphatic aldehydes affording aldol adducts 4a– f with crude diastereoselectivities ranging from 8:1 to 38:1.