Small-molecule H-bond donors in asymmetric catalysis.

Stronger Brønsted acids

Hydrogen bonding is responsible for the structure of much of the world around us. The unusual and complex properties of bulk water, the ability of proteins to fold into stable three-dimensional structures, the fidelity of DNA base pairing, and the binding of ligands to receptors are among the manifestations of this ubiquitous noncovalent interaction. In addition to its primacy as a structural determinant, hydrogen bonding plays a crucial functional role in catalysis. Hydrogen bonding to an electrophile serves to decrease the electron density of this species, activating it toward nucleophilic attack. This principle is employed frequently by Nature's catalysts, enzymes, for the acceleration of a wide range of chemical processes. Recently, organic chemists have begun to appreciate the tremendous potential offered by hydrogen bonding as a mechanism for electrophile activation in small-molecule, synthetic catalyst systems. In particular, chiral hydrogen-bond donors have emerged as a broadly applicable class of catalysts for enantioselective synthesis. This review documents these advances, emphasizing the structural and mechanistic features that contribute to high enantioselectivity in hydrogen-bond-mediated catalytic processes.

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Asymmetric catalysis by chiral hydrogen-bond donors.

The current status of organic synthesis is hampered by costly protecting-group strategies and lengthy purification procedures after each synthetic step. To circumvent these problems, the synthetic potential of multicomponent domino reactions has been utilized for the efficient and stereoselective construction of complex molecules from simple precursors in a single process. In particular, domino reactions mediated by organocatalysts are in a way biomimetic, as this principle is used very efficiently in the biosynthesis of complex natural products starting from simple precursors. In this Minireview, we discuss the current development of this fast-growing field.

Asymmetric organocatalytic domino reactions.

Complete Field Guide to Asymmetric BINOL-Phosphate Derived Brønsted Acid and Metal Catalysis: History and Classification by Mode of Activation; Brønsted Acidity, Hydrogen Bonding, Ion Pairing, and Metal Phosphates

Enantioselective Brønsted Acid Catalyzed Transfer Hydrogenation: Organocatalytic Reduction of Imines

A Highly Enantioselective Brønsted Acid Catalyst for the Strecker Reaction

Cooperative Coexistence: Effective Interplay of Two Brønsted Acids in the Asymmetric Synthesis of Isoquinuclidines

A new Bronsted acid catalysed hydrogenation of imines with Hantzsch dihydropyridine as the hydrogen source has been developed. Diphenyl phosphate (DPP) and various other acids catalyse this first metal-free hydrogen transfer to give various amines under mild reaction conditions.

Cengiz Azap

Papers

Enantioselective Brønsted Acid Catalyzed Transfer Hydrogenation: Organocatalytic Reduction of Imines

A Highly Enantioselective Brønsted Acid Catalyst for the Strecker Reaction

Cooperative Coexistence: Effective Interplay of Two Brønsted Acids in the Asymmetric Synthesis of Isoquinuclidines

Brønsted Acid Catalysis: Organocatalytic Hydrogenation of Imines

Ein hoch enantioselektiver Brønsted‐Säure‐Katalysator für die Strecker‐Reaktion