Direct Carbon−Carbon Bond Formation via Soft Enolization: A Biomimetic Asymmetric Mannich Reaction of Phenylacetate Thioesters
作者:Mark C. Kohler、Julianne M. Yost、Michelle R. Garnsey、Don M. Coltart
DOI:10.1021/ol101152b
日期:2010.8.6
cinchona alkaloid-based amino (thio)urea catalysts is reported that employs proximity-assisted soft enolization. This approach to enolization is based on the cooperative action of a carbonyl-activating hydrogen bonding (thio)urea moiety and an amine base contained within a single catalytic entity to facilitate intracomplex deprotonation. Significantly, this allows thioesters over a range of acidity to react
Highly efficient and diastereoselective synthesis of 1,3-oxazolidines featuring a palladium-catalyzed cyclization reaction of 2-butene-1,4-diol derivatives and imines
A palladium-catalyzed protocol for effective synthesis of 1,3-oxazolidines has been reported. This method is featured by the high diastereoselectivity (dr up to >98/2) and using the readily available 2-butene-1,4-diol derivatives and imines as substrates.
Stereoselective Formation of α-Quaternary Stereocenters in the Mannich Reaction
作者:Erica A. Tiong、James L. Gleason
DOI:10.1021/ol802643k
日期:2009.4.16
Condensation of α,α-disubstituted lithium enolates derivedfrom bicyclic thioglycolate lactams with benzenesulfonyl imines affords Mannich addition products with excellent diastereoselectivity. Cleavage of the auxiliary under hydrolytic or reducing conditions affords β-amino acids and alcohols, respectively.
The synthesis of 4‐sulfonyl‐3‐pyrrolines, from a propargylic sulfone and activated imines, is described. The annulation is initiated by sodium benzenesulfinate as organocatalyst, which allows isomerization of the alkynyl precursor to the analogous allene. A proof of concept towards an asymmetric version involving an unprecedented enantiopure sulfinate–ammonium cooperative ion pair was then highlighted