Organocatalytic Asymmetric Addition of Naphthols and Electron-Rich Phenols to Isatin-Derived Ketimines: Highly Enantioselective Construction of Tetrasubstituted Stereocenters

Chiral Primary Amine Catalysis for Asymmetric Mannich Reactions of Aldehydes with Ketimines: Stereoselectivity and Reactivity

The application potential of primary amine catalysts in the context of Mannich reactions of aldehydes with ketimines is exemplified by isatin-derived ketimines and cyclic trifluoromethyl ketimines. Primary amine catalysts exhibit either unusual stereoselectivity or reactivity, which is not observable with secondary amine catalysts. Moreover, reversal of diastereofacial selectivity between primary and secondary amine catalysts is disclosed. These new reactions provide useful methods for the syntheses of chiral 3-substituted 3-amino-2-oxindoles and dihydroquinazolinones bearing a trifluoromethylated quaternary stereocenter. The synthetic utility of the reactions is demonstrated through the formal synthesis of AG-041R and DPC 083 and the total synthesis of (-)-psychotriasine.

Chiral Brønsted Acid-Catalyzed Enantioselective α-Amidoalkylation Reactions: A Joint Experimental and Predictive Study

Enamides with a free NH group have been evaluated as nucleophiles in chiral Brønsted acid-catalyzed enantioselective α-amidoalkylation reactions of bicyclic hydroxylactams for the generation of quaternary stereocenters. A quantitative structure-reactivity relationship (QSRR) method has been developed to find a useful tool to rationalize the enantioselectivity in this and related processes and to orient the catalyst choice. This correlative perturbation theory (PT)-QSRR approach has been used to predict the effect of the structure of the substrate, nucleophile, and catalyst, as well as the experimental conditions, on the enantioselectivity. In this way, trends to improve the experimental results could be found without engaging in a long-term empirical investigation.

Enantioselective Synthesis of Spirooxindole Enols: Regioselective and Asymmetric [3+2] Cyclization of 3-Isothiocyanato Oxindoles with Dibenzylidene Ketones

A novel cinchona-alkaloid-derived organocatalyst has been developed to catalyze the asymmetric regioselective [3+2] cycloaddition of 3-isothiocyanato oxindoles with dibenzylidene ketones. A series of spirooxindole enols could be obtained in high yields with good-to-excellent diastereo- and enantioselectivities.

Enantioselective Organocatalytic Construction of Spiroindane Derivatives by Intramolecular Friedel-Crafts-Type 1,4-Addition

The highly enantioselective organocatalytic construction of spiroindanes containing an all-carbon quaternary stereocenter by intramolecular Friedel-Crafts-type 1,4-addition is described. The reaction was catalyzed by a cinchonidine-based primary amine and accelerated by water and p-bromophenol. A variety of spiro compounds containing quaternary stereocenters were obtained with excellent enantioselectivity (up to 95 % ee). The reaction was applied to the asymmetric formal synthesis of the spirocyclic natural products (-)-cannabispirenones A and B.