Catalysis of 3-Pyrrolidinecarboxylic Acid and Related Pyrrolidine Derivatives in Enantioselective <i>anti</i>-Mannich-Type Reactions: Importance of the 3-Acid Group on Pyrrolidine for Stereocontrol
作者:Haile Zhang、Susumu Mitsumori、Naoto Utsumi、Masanori Imai、Noemi Garcia-Delgado、Maria Mifsud、Klaus Albertshofer、Paul Ha-Yeon Cheong、K. N. Houk、Fujie Tanaka、Carlos F. Barbas
DOI:10.1021/ja074907+
日期:2008.1.1
The development of enantioselective anti-selective Mannich-type reactions of aldehydes and ketones with imines catalyzed by 3-pyrrolidinecarboxylic acid and related pyrrolidine derivatives is reported in detail. Both (3R,5R)-5-methyl-3-pyrrolidinecarboxylic acid and (R)-3-pyrrolidinecarboxylic acid efficiently catalyzed the reactions of aldehydes with alpha-imino esters under mild conditions and afforded anti-Mannich products with high diastereo- and enantioselectivities (anti/syn up to 99:1, up to >99% ee). For the reactions of ketones with a-imino esters, (R)-3-pyrrolidinecarboxylic acid was an efficient catalyst (anti/syn up to >99:1, up to 99% ee). Evaluation of a series of pyrrolidine-based catalysts indicated that the acid group at the beta-position of the pyrrolidine ring of the catalyst played an important role in forwarding the carbon-carbon bond formation and in directing anti-selectivity and enantioselectivity.