Organocatalytic Enantioselective Decarboxilative Addition of Malonic Half Thioesters to Imines
Alfredo Ricci, Daniel Pettersen, Luca Bernardi, Francesco Fini, Mariafrancesca Fochi, Raquel P. Herrera, Valentina Sgarzani, V.. Organocatalytic Enantioselective Decarboxilative Addition of Malonic Half Thioesters to Imines. Adv. Synt. Catal. . 2007, Vol. 349 / 2007, p. 1037-2007.
<p>We describe a biomimetic organocatalytic enantioselective decarboxylative addition of malonic acid half thioesters to imines. This simple protocol makes use of readily available Cinchona-derived organocatalysts and nucleophiles at the carboxylate oxidation state. The resulting b-amino thioesters, being attractive precursors for the preparation of optically active b-amino acids, are formed in good yields and in up to 79% ee. As suggested by several mechanistic insights the desired products are formed via initial formation of a thioester acetate enolate via decarboxylation of the malonic acid half thioester, followed by addition to the imine.</p>
<p>We describe a biomimetic organocatalytic enantioselective decarboxylative addition of malonic acid half thioesters to imines. This simple protocol makes use of readily available Cinchona-derived organocatalysts and nucleophiles at the carboxylate oxidation state. The resulting b-amino thioesters, being attractive precursors for the preparation of optically active b-amino acids, are formed in good yields and in up to 79% ee. As suggested by several mechanistic insights the desired products are formed via initial formation of a thioester acetate enolate via decarboxylation of the malonic acid half thioester, followed by addition to the imine.</p>