Chiral Calcium Complexes as Brønsted Base Catalysts for Asymmetric Addition of α-Amino Acid Derivatives to α,β-Unsaturated Carbonyl Compounds
作者:Susumu Saito、Tetsu Tsubogo、Shū Kobayashi
DOI:10.1021/ja0709730
日期:2007.5.1
promote the catalyticasymmetric 1,4-addition reactions and [3+2] cycloaddition reactions of α-amino acidderivatives with α,β-unsaturated carbonyl compounds have been developed. The reactions proceeded smoothly in the presence of 5−10 mol % of the chiral calcium catalyst to afford the desired adducts in high yields with high diastereo- and enantioselectivities. A wide range of α,β-unsaturated esters and
4-addition and [3 + 2] cycloaddition reactions using chiral calcium species prepared from calcium isopropoxide and chiral bisoxazoline ligands have been developed. Glycine Schiff bases reacted with acrylic esters to afford 1,4-addition products, glutamic acid derivatives, in high yields with high enantioselectivities. During the investigation of the 1,4-addition reactions, we unexpectedly found that a [3
A new asymmetric two-center phase-transfercatalyst was designed and a catalyst library containing more than 40 new two-center catalysts was constructed. The catalysts were applied in phase-transferalkylations and Michael additions to afford the corresponding products in up to 93% ee and 82% ee, respectively.
was used in phase-transfer alkylations and Michael additions to afford various opticallyactive α-amino acid equivalents in up to 93% yield. Moreover, dramatic counter anion effects were observed in phase-transfer catalysis (PTC) for the first time, making it possible to further improve reactivity and selectivity. These findings validate the usefulness of three-dimensional fine-tuning of the catalyst
作者:Ting Ma、Xiao Fu、Choon Wee Kee、Lili Zong、Yuanhang Pan、Kuo-Wei Huang、Choon-Hong Tan
DOI:10.1021/ja1098353
日期:2011.3.9
A new chiral entity, pentanidium, has been shown to be an excellent chiralphase-transfercatalyst. The enantioselective Michaeladdition reactions of tert-butyl glycinate-benzophenone Schiff base with various α,β-unsaturated acceptors provide adducts with high enantioselectivities. A successful gram-scale experiment at a low catalyst loading of 0.05 mol % indicates the potential for practical applications