A joint experimental-theoretical study of a bifunctional squaramide-amine-catalyzed Michael addition reaction between 1,3-dioxo nucleophiles and nitrostyrene has been undertaken to gain insight into the nature of bifunctional organocatalytic activation. For this highly stereoselective reaction, three previously proposed mechanistic scenarios for the critical CC bond-formation step were examined. Accordingly, the formation of the major stereoisomeric products is most plausible by one of the bifunctional pathways that involve electrophile activation by the protonated amine group of the catalyst. However, some of the minor product isomers are also accessible through alternative reaction routes. Structural analysis of transition states points to the structural invariance of certain fragments of the transition state, such as the protonated catalyst and the anionic fragment of approaching reactants. Our topological analysis provides deeper insight and a more general understanding of bifunctional noncovalent organocatalysis.

This paper describes the preparation of highly efficient, easily accessible, and robust immobilized bifunctional organocatalysts. There was no need to employ any tether to secure high enantio‐ and diastereoselectivities in various Michael addition reactions. The synthetically useful Michael adducts were obtained within reasonable reaction times with the advantage of easy product isolation and the possibility of automation by using a flow chemistry apparatus.

The mechanism of cinchona–squaramide organocatalytic Michael addition was studied using in situ IR and NMR experiments. As a result, not only kinetic parameters were determined but a stereoselective retro-Michael reaction was also observed.

We report an expedient approach to highly functionalized cis- and trans-decalines that could function as key structural subunits toward the synthesis of various classes of terpenoids. Key to the strategy is an organocatalyzed Robinson annulation reaction of the Nazarov reagent that affords chiral enone building blocks with high enantioselectivities. The quaternary carbon stereogenic center can direct the subsequent reactions and allow the rapid and diastereoconvergent assembly of complex decalines with contiguous stereocenters.

Abstract-Several cinchona based squaramide catalysts were applied in asymmetric Michael addition of α-nitroethylphosphonates to acrylic acid aryl esters, resulting in high yield and enantioselectivity. The absolute configuration of one of the quaternary α-nitrophosphonate adducts was deduced from its experimental and calculated CD spectra. The adducts were reduced to their cyclic aminophosphonates by catalytic hydrogenation.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.