Catalytic Enantioselective Hydrostannation of Cyclopropenes
摘要:
The first examples of catalytic enantioselective hydrostannation of the C=C double bond of cyclopropenes has been demonstrated. This method allows for the efficient synthesis of 2,2-disubstituted cyclopropylstannanes with high degrees of diastereo- and enantioselectivity. The facial selectivity of this reaction is entirely controlled by steric factors. A variety of functional groups at C-3 of the cyclopropenes were tolerated.
Enantioselective, Facially Selective Carbomagnesation of Cyclopropenes
作者:Xiaozhong Liu、Joseph M. Fox
DOI:10.1021/ja058101q
日期:2006.5.1
Described is the facially selective and enantioselective addition of carbon nucleophiles to prochiral 3-hydroxymethylcyclopropenes. The process creates up to four stereocenters in a tandem addition/capture sequence that combines three simple materials to give complex and diverse products. The asymmetry is induced by the inexpensive and recoverable ligand (S)-N-methylprolinol. The enantioselectivity (90-98% ee with MeMgCl) is high for a range of cyclopropenes and electrophiles. Importantly, the diastereoselectivity is complementary to that obtained by enantioselective cyclopropanation with aryldiazoacetates. High enantioselectivities are obtained only when methoxide is included in the reaction. Evidence is provided that at least two chiral ligands are involved in the enantioselectivity-determining step.