Bifunctional asymmetric catalysis: amplification of Bronsted basicity can orthogonally increase the reactivity of a chiral Bronsted acid.

ABSTRACT: The reactivity of a series of symmetrical chiral Brønsted acids (polar ionic hydrogen-bond donors) follows the counterintuitive trend wherein the more Brønsted basic member is a more effective catalyst for the aza-Henry (nitro-Mannich) reaction. This new design element leads to a substantially more reactive catalyst for the aza-Henry reaction, one that can promote the addition of a secondary nitroalkane. Additionally, when an achiral Brønsted acid (TfOH) is used in slight excess of the neutral, chiral bisamidine ligand, diastereoselection can be optimized to levels generally greater than 15:1 while the enantioselection remains unchanged at generally >90% ee.

SUBMITTER: Davis TA 

PROVIDER: S-EPMC2838452 | biostudies-literature | 2010 Mar

REPOSITORIES: biostudies-literature