Efficient process to induce enantioselectivity in procarbonyl compounds
The present invention provides an efficient method to induce the enantioselectivity in procarbonyl compounds using chiral organometallic complexes. The present invention also provides a method for producing chiral organometallic complexes using a chiral additive, achiral additive, a base and a metal salt.
1. A process for the preparation of an amino alcohol of formula
comprising the steps of
a) treating (1R,2S)—N-pyrrolidinyl norephedrine of formula
and trifluoroethanol (F 3 CCH 2 OH) with sodium hydride to obtain a sodium salt of (1R,2S)—N-pyrrolidinyl norephedrine and trifluoroethanol,
b) adding a zinc salt to the resultant sodium salts of (1R,2S)—N-pyrrolidinyl norephedrine and trifluoroethanol to obtain chiral (1R,2S)—N-pyrrolidinyl norephedrine and trifluoroethanol zincate complex of formula,
c) reacting a terminal alkyne compound of formula
with sodium hydride and MgCl 2 to give a cyclopropylacetylide complex of formula
d) mixing the chiral (1R,2S)—N-pyrrolidinyl norephedrine and trifluoroethanol zincate complex with the cyclopropylacetylide complex of formula
to obtain chiral organozinc complex of formula
e) mixing the chiral organozinc complex with a ketone of formula
to obtain the amino alcohol.
2. The process of claim 1 , wherein the zinc salt is zinc chloride, zinc bromide, zinc acetate, or zinc sulfate.