ASYMMETRIC MICHAEL ADDITION REACTIONS OF CHIRAL PROP-9-ENYL- AND BUT-2-ENYLPHOSPHONATE ANIONS WITH CYCLIC ENONES

摘要

Reactions of anions derived from chiral allyl- and crotylphosphonates with alpha,beta-unsaturated cyclic ketones took place at the gamma-position of the reagents and led to diastereomerically enriched products of conjugate addition, suggesting efficient enantiotopic face discrimination caused by remote asymmetric induction. Using mixtures of crotylphosphonates with different E/Z ratios, we found that the E/Z stereochemistry of the reagent was highly translated into the products. A tandem vicinal dialkylation based on Michael addition-enolate methylation was carried out to give the trans alpha,beta-dialkylated product with high selectivity. Oxidative cleavage of the Michael adducts resulted in the formation of the optically active delta-keto aldehyde corresponding to the formal conjugate addition of an acetaldehyde or a propionaldehyde anion equivalent to alpha,beta-unsaturated carbonyl compounds.