Catalytic Enantioselective Tautomerization of Isolated Enols

Catalytic Enantioselective Tautomerization of Metastable Enamines

The first example of catalytic enantioselective tautomerization of structurally labile but isolable enamines for accessing their chiral imine-tautomers is described. Kinetically stable enamine-based dibenzo[b,d]azepines were tautomerized by a simple chiral BINOL-phosphoric acid, providing a variety of seven-membered imine products bearing both central and axial stereogenic elements in good yields (up to 96%) with excellent enantio- and diastereoselectivities (up to 97% ee, >20:1 dr).

Enantioselective protonation

Enantioselective protonation is a common process in biosynthetic sequences. The decarboxylase and esterase enzymes that effect this valuable transformation are able to control both the steric environment around the proton acceptor (typically an enolate) and the proton donor (typically a thiol). Recently, several chemical methods to achieve enantioselective protonation have been developed by exploiting various means of enantiocontrol in different mechanisms. These laboratory transformations have proven useful for the preparation of a number of valuable organic compounds.

Homogeneous pd-catalyzed enantioselective decarboxylative protonation

General homogeneous conditions for the palladium-catalyzed synthesis of carbonyl compounds with tertiary carbon stereocenters at the alpha-position are reported. The highly reactive catalyst tolerates a variety of substrate substitution and functionality, and generates enantioenriched cyclic ketones from racemic allyl beta-ketoester starting materials.