Chemoselectivity in Asymmetric Aminocatalysis

Chirality-driven self-assembly: application toward renewable/exchangeable resin-immobilized catalysts

Resin-immobilized catalysts were prepared through chirality-driven self-assembly. The method allows the resin-immobilized catalyst to be regenerated under mild conditions and in situ catalyst exchange to be carried out quantitatively. The uniqueness of the methodology was demonstrated by the preparation of a catalyst for TEMPO oxidation as well as a two-step sequential TEMPO oxidation/aldol condensation sequence enabled by facile catalyst exchange.

Selectivity-switchable construction of benzo-fused polycyclic compounds through a gold-catalyzed reaction of enyne-lactone

A gold-catalyzed selectivity-switchable reaction of enyne-lactone is reported. The choice of the gold complex is the key for the chemoselectivity.

Catalytic asymmetric chemodivergent arylative dearomatization of tryptophols

The first catalytic asymmetric arylative dearomatization of tryptophols has been established. By using quinone imine ketals as aryl group surrogates and modulating the reaction conditions, the cascade reaction of tryptophols with quinone imine ketals afforded two series of arylative dearomatization products in generally high yields, and excellent diastereo- and enantioselectivities.

Enantioselective Vinylogous Organocascade Reactions

Cascade reactions are powerful tools for rapidly assembling complex molecular architectures from readily available starting materials in a single synthetic operation. Their marriage with asymmetric organocatalysis has led to the development of novel techniques, which are now recognized as reliable strategies for the one-pot enantioselective synthesis of stereochemically dense molecules. In recent years, even more complex synthetic challenges have been addressed by applying the principle of vinylogy to the realm of organocascade catalysis. The key to the success of vinylogous organocascade reactions is the unique ability of the chiral organocatalyst to transfer reactivity to a distal position without losing control on the stereo-determining events. This approach has greatly expanded the synthetic horizons of the field by providing the possibility of forging multiple stereocenters in remote positions from the catalyst's point of action with high selectivity, while simultaneously constructing multiple new bonds. This article critically describes the developments achieved in the field of enantioselective vinylogous organocascade reactions, charting the ideas, the conceptual advances, and the milestone reactions that have been essential for reaching highly practical levels of synthetic efficiency.

Organocatalytic methods for C-C bond formation

Beyond doubt organocatalysis belongs to the most exciting and innovative chapters of organic chemistry today. Organocatalysis has emerged not only as a complement to metal-catalyzed reactions or to biocatalysis over the past decade, but also new asymmetric organocatalyzed reactions have been discovered that could not be accomplished by metal- or biocatalyzed reactions so far. This review gives a brief overview of organocatalyzed asymmetric C-C bond formation processes currently available.

Stereoselectivities of histidine-catalyzed asymmetric aldol additions and contrasts with proline catalysis: a quantum mechanical analysis

Quantum mechanical calculations reveal the origin of diastereo- and enantioselectivities of aldol reactions between aldehydes catalyzed by histidine, and differences between related reactions catalyzed by proline. A stereochemical model that explains both the sense and the high levels of the experimentally observed stereoselectivity is proposed. The computations suggest that both the imidazolium and the carboxylic acid functionalities of histidine are viable hydrogen-bond donors that can stabilize the cyclic aldolization transition state. The stereoselectivity is proposed to arise from minimization of gauche interactions around the forming C-C bond.