The aldol addition reaction between γ-oxygenated carboxylic esters derived from 2,6-dimethylphenol and piperonal
摘要:
The stereoselectivity of the aldol addition reaction between gamma-oxygenated DMP-esters 1a-b and piperonal depends on the nature of the gamma-oxygenated substituent. A syn-diastereoselectivity was observed from 1a. This reverse selectivity is due to the chelation properties of the ketal moiety leading preferentially to the Z-enolate 7a by altering the transition state of the deprotonation step.