Formation of Quaternary Stereogenic Centers by NHC-Cu-Catalyzed Asymmetric Conjugate Addition Reactions with Grignard Reagents on Polyconjugated Cyclic Enones
The copper‐catalyzedconjugateaddition of various Grignard reagents to polyconjugated enones (dienone and enynone derivatives) is reported. The catalyst system, composed of copper triflate and an NHC ligand, led to the unusual selective formation of the 1,4‐addition products. This reaction allows for the creation of all‐carbon chiral quaternary centers with enantiomeric excesses up to 99 %. The remaining
Riceblastfungus, Magnaporthegrisea, produces a series of salicylaldehyde-typephytotoxins such as pyriculol, pyricuol, and pyriculariol. Plausiblebiosyntheticintermediates of these phytotoxins were synthesized in deuterium labeled forms using the Stille coupling reaction as the key step, and subjected to biotransformation by the fungus. Heptatrienylsalicylaldehyde was converted into dihydropyriculol