Highly enantioselective organocatalytic formation of a quaternary carbon center via chiral Brønsted acid catalyzed self-coupling of enamides

Abstract

The enantioselective BINOL-phosphate catalyzed formation of a quaternary carbon center, bearing a N-atom has been achieved through the self-coupling reaction of enamides; the corresponding products have been isolated in up to >99% ee and their application for the synthesis of versatile synthetic building blocks-beta-aminoketones-has been demonstrated.

Enantioselective Synthesis of Amines by Chiral Brønsted Acid Catalysts

“…Tsogoeva and coworkers reported the enantioselective formation of a quaternary stereogenic center bearing the nitrogen atom through the homocoupling reaction of enamides (Scheme 3.33) [73]. The enamides were isomerized in situ to ketimines under the influence of phosphoric acid catalyst 1e, as previously depicted in Figure 3.4.…”

One-pot synthesis of (R)-convolutamydine A involving in situ chiral organocatalyst formation

“…Following our previous work on organocatalytic aldol reactions [18,19] and applying our expertise in the research fields of the organocatalytic construction of quaternary carbon centers [20][21][22] we decided to study the direct aldol reaction of acetone with 4,6-dibromoisatin. Since amino alcohols 2a and 2b have already been reported by one of us as active external catalysts for the aldol addition of acetone to 4,6-dibromoisatin (entries 1 and 2, Table 1) [15], we were interested in exploring whether selected amino alcohols 2c-2f would perform as well as or even better than catalysts 2a and 2b in the same aldol addition.…”

Imine and iminium precursors as versatile intermediates in enantioselective organocatalysis

“…65 The products containing quaternary stereocenters were obtained in meager to good yields and good to excellent enantioselectivities (Scheme 40). The limiting factors for reactivity were observed to be 2-and 3-substitution of the aryl group, with 2-chlorophenyl enamide giving no product at all.…”