New β-amino thiols as efficient catalysts for highly enantioselective alkenylzinc addition to aldehydes
摘要:
A series of new optically active beta-amino thiols and thiolacetates prepared from the simple natural amino acid, (S)-(-)-valine, were found to be effective catalysts for the enantioselective addition of alkenylzinc to alclehydes and thereby providing an efficient route for chiral (E)-allylic alcohols with ees of up to >99% in the presence of 7a (1 mol %). (C) 2005 Published by Elsevier Ltd.
New β-amino thiols as efficient catalysts for highly enantioselective alkenylzinc addition to aldehydes
摘要:
A series of new optically active beta-amino thiols and thiolacetates prepared from the simple natural amino acid, (S)-(-)-valine, were found to be effective catalysts for the enantioselective addition of alkenylzinc to alclehydes and thereby providing an efficient route for chiral (E)-allylic alcohols with ees of up to >99% in the presence of 7a (1 mol %). (C) 2005 Published by Elsevier Ltd.
Highly Enantioselective Aryl Transfer to Aldehydes: A Remarkable Effect of Sulfur Substitution in Amino Thioacetate Ligands
摘要:
Chiral amino thioacetate ligands were prepared from the corresponding amino alcohols and used as catalysts for enantioselective aryl transfer reaction. The amino thioacetates were remarkably superior to the corresponding amino alcohols, Low catalyst loadings of only 1-2.5 mol % were sufficient to achieve excellent enantioselectivity as well as high conversion in short reaction time. The results reveal that the thioacetoxy moiety of the amino thioacetates has a surprisingly beneficial effect in enhancing the asymmetric induction.