Santanu Mukherjee

The catalysis by primary and secondary amines of electrophilic substitution reactions in the α-position of carbonyl compounds and related reactions via enamine intermediates is called enamine catalysis. To a large degree this chemistry can be considered the catalytic variant of the classical preformed enamine chemistry (Scheme 1) pioneered by Stork. In such transformations an enamine (III) is generated by reacting a carbonyl compound (I) with an amine (II) under dehydration conditions. Reaction of the enamine (III) can proceed via an addition (route A) or substitution (route B) route depending on the nature of the reaction partner (electrophile). In either case, iminium ions (IV) are usually formed, which are then hydrolyzed to afford the products (V). A vast array of transformations has been achieved via preformed enamine chemistry. Therefore, a catalytic version of this chemistry was highly desirable.

We have developed a highly enantioselective Pd/chiral acid-catalyzed α-allylation of α-branched aldehydes with an allyl amine as the allylating species that creates all-carbon quaternary stereogenic centers in high yields and enantioselectivities. To our knowledge, this is the first time that a chiral anionic ligand is applied for achieving asymmetric induction in a palladium-catalyzed allylic alkylation reaction.

Novel tasks for a venerable molecule: Bifunctional organocatalysts of the type shown, with a quasi Lewis acidic urea or thiourea unit and a Brønsted basic amine functionality, effect the dynamic kinetic resolution of azlactones with high enantioselectivity. N-Benzoyl amino acid esters were obtained with up to 91 % ee in high yields from racemic azlactones.

Organocatalysis: The first catalytic enantioselective iodoetherification of oximes is developed using commercially available N-iodosuccinimide. In the presence of a dihydrocinchonidine-derived thiourea (10 mol %), β,γ-unsaturated oximes undergo facile iodoetherification to produce Δ2-isoxazolines containing a quaternary stereogenic center generally in high yield with good to excellent enantioselectivity. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.