An aromatic ion platform for enantioselective Brønsted acid catalysis
作者:Chirag D. Gheewala、Bridget E. Collins、Tristan H. Lambert
DOI:10.1126/science.aad0591
日期:2016.2.26
first applied as a ligand in metal catalysis, and more recently as a conjugate base in acid catalysis. Gheewala et al. report a class of chiral carbon acids based around a cyclopentadiene framework that are easily accessible from readily available precursors. The compounds are showcased as highly selective catalysts for asymmetric Mukaiyama Mannich and oxocarbenium aldol reactions. Science, this issue
Chiral Zirconium Catalysts Using Multidentate BINOL Derivatives for Catalytic Enantioselective Mannich-Type Reactions; Ligand Optimization and Approaches to Elucidation of the Catalyst Structure
Catalytic enantioselective Mannich-type reactions of silicon enolates with aldimines were investigated using chiral zirconium catalysts prepared from Zr(O(t)Bu)(4), N-methylimidazole, and newly designed multidentate BINOL derivatives. These new multidentate BINOL ligands were designed on the basis of an assumed transition state structure of a chiral zirconium catalyst derived from two molecules of
A Powerful Chiral Phosphoric Acid Catalyst for Enantioselective Mukaiyama-Mannich Reactions
作者:Fengtao Zhou、Hisashi Yamamoto
DOI:10.1002/anie.201603929
日期:2016.7.25
A new BINOL‐derived chiral phosphoric acid bearing 2,4,6‐trimethyl‐3,5‐dinitrophenyl substituents at the 3,3′‐positions was developed. The utility of this chiral phosphoric acid is demonstrated by a highly enantioselective (ee up to >99 %) and diastereoselective (syn/anti up to >99:1) asymmetric Mukaiyama–Mannich reaction of imines with a wide range of ketene silyl acetals. Moreover, this method was
dialkyl phosphate was synthesized starting from (+)-diethyl tartrate. Its catalytic activity as a chiral Brønsted acid has been examined in the Mannich-type reaction of a ketene silyl acetal with aldimines as a model reaction. The corresponding β-amino acid esters were obtained with high enantioselectivity.
Mannich-typereaction of ketene silyl acetals with aldimines proceeded catalytically by means of a phosphoric acid diester, derived from (R)-BINOL, as a chiral Brønsted acid to afford beta-amino esters with good diastereoselectivity in favor of the syn isomer and high enantioselectivity (up to 96% ee). The highest enantioselectivity was achieved by the phosphoric acid diester bearing 4-nitrophenyl