Asymmetric direct aldol reactions catalyzed by amino acid derivatives and their coordination complexes

OLGA C. SÁNCHEZ MONTILVA; FLORENCIA DI SALVO; FEDERICO MOVILLA

Iguazú

Simposio; Simposio Latinoamericano de Química de Coordinación y Organometállica; 2017

UBA, CONICET, Fundación Humboldt

The use of amino acids as catalysts for organic reactions have received increasing attention over the last decade, due to they provide an efficient and reliable strategy for stereoselective preparation of valuable chiral compounds. The amino acid L-Proline is one of the most commonly studied organocatalyst and also a great variety of its derivatives and metallic complexes have recently been reported as catalysts for C?C bond-forming reactions. It was suggested that other amino acids could be able to carry out these reactions, however only a few published papers report the catalytic activity of amino acids or their derivatives different than L-proline. Herein we report the synthesis and characterization of new amino acid derivatives and their metal complexes, and the study of their catalytic activity for asymmetric aldol reactions. These molecules were obtained as reduced Schiff bases from L-amino acids and aromatic aldehydes, and based on their similarities with L-proline we studied their application as organocatalyst in the formation of chiral β-hydroxyketones from aliphatic ketones and aldehydes. As a result, their efficiency are apparently better than the related organocatalysts reported in literature, presenting higher yields (>95%), shorter reaction times (2?5 h) and a smaller amount of catalyst required (2% vs. 10%). It is important to highlight that although they act as homogeneous catalysts NMR studies confirmed that they can be recovered unaltered after the reactions.