Chiral framework: Chiral amines with pyrrolidine frameworks catalyze the enantioselective conjugate addition of a wide range of aldehydes to various vinyl sulfones and vinyl phosphonates in high yields and with enantioselectivities up to >99 % ee (see scheme). The high versatility of the Michael adducts is exemplified by various functionalizations with conservation of the optical purity.
1,2-Sulfone rearrangement in organocatalytic reactions
作者:Adrien Quintard、Alexandre Alexakis
DOI:10.1039/c0ob00818d
日期:——
The 1,2-sulfone rearrangement resulting from nucleophilic addition to bis activated vinyl-sulfones has been studied in more detail. Various nucleophiles activated by different types of catalysts (enamine, Brönsted base, thiourea) are able to promote such rearrangement in excellent yields and moderate to excellent enantioselectivities (up to 94% ee). Mechanistic studies have led to a better understanding of the mechanism and allowed its application to other electrophiles such as vinyl-sulfone acrylates.
F rigid cats: The power of conformationallystabilizedcatalysts is demonstrated. By taking appropriate advantage of fluorineinsertion (see scheme), purely conformationalcatalyst design led to a notable improvement in enantioselectivities from around 70 % to 91–98.5 % ee. The other advantage of this approach is the better understanding of the origin of the stereoselectivity in the given catalytic
Joined together, organocatalysts aldehydes and sulfones: A diaryl prolinol silyl ether was found to catalyse efficiently and enantioselectively the conjugate addition of aldehydes to vinyl sulfones (see scheme). The ample synthetic utility of the resulting adducts is illustrated.
A New Class of Structurally Rigid Tricyclic Chiral Secondary Amine Organocatalyst: Highly Enantioselective Organocatalytic Michael Addition of Aldehydes to Vinyl Sulfones
A new class of chiral secondary amine organocatalyst was rationally designed as an efficient catalyst to catalyze the elusive Michaeladdition of aldehydes to vinyl sulfones. High yield and excellent enantioselectivities could be obtained at room temperature without having to resort to high catalyst loading, anhydrous solvents, and low temperatures. Efficient control of enamine conformation and face