877204-00-7Relevant academic research and scientific papers
Lewis base activation of Lewis acids: Catalytic, enantioselective vinylogous aldol addition reactions
Denmark, Scott E.,Heemstra Jr., John R.
, p. 5668 - 5688 (2008/02/10)
(Chemical Equation Presented) The generality of Lewis base catalyzed, Lewis acid mediated, enantioselective vinylogous aldol addition reactions has been investigated. The combination of silicon tetrachloride and chiral phosphoramides is a competent catalyst for highly selective additions of a variety of α,β-unsaturated ketone-, 1,3-diketone-, and α,β- unsaturated amide-derived dienolates to aldehydes. These reactions provided high levels of γ-site selectivity for a variety of substitution patterns on the dienyl unit. Both ketone- and morpholine amide-derived dienol ethers afforded high enantio- and diastereoselectivity in the addition to conjugated aldehydes. Although α,β-unsaturated ketone-derived dienolate did not react with aliphatic aldehydes, α,β-unsaturated amide-derived dienolates underwent addition at reasonable rates affording high yields of vinylogous aldol product. The enantioselectivities achieved with the morpholine derived-dienolate in the addition to aliphatic aldehydes was the highest afforded to date with the silicon tetrachloride-chiral phosphoramide system. Furthermore, the ability to cleanly convert the morpholine amide to a methyl ketone was demonstrated.
Lewis base activation of Lewis acids. Vinylogous aldol addition reactions of conjugated N,O-silyl ketene acetals to aldehydes
Denmark, Scott E.,Heemstra Jr., John R.
, p. 1038 - 1039 (2007/10/03)
N,O-Silyl dienyl ketene acetals derived from unsaturated morpholine amides have been developed as highly useful reagents for vinylogous aldol addition reactions. In the presence of SiCl4 and the catalytic action of chiral phosphoramide (R,R)-3,
