Efficient and stereoselective synthesis of chiral organic molecules is critical to the availability of therapeutic agents. Development of catalysts that promote important bond forming reactions, and which are readily accessible, inexpensive, and air stable is a compelling goal of modern chemistry. In this context, chiral catalysts, required for enantioselective formation of small organic molecules, are of particularly high value. Among the most ubiquitous building blocks needed for preparation of a large assortment of biologically active and medicinally relevant molecules are enantiomerically pure amines and alcohols. Although enantioselective syntheses of these two important classes of molecules have benefited from recent advances, a significant number of shortcomings remain unresolved. We will address such issues through innovations in catalyst design and by advances in chemical reactivity. In the first segment of our program, we will design and develop amino acid-based catalysts for enantioselective silyl protection of alcohols. This unique class of catalysts delivers a range of otherwise difficult-to-access enantiomerically enriched alcohols;our goal is to discover catalysts that promote alcohol silylations with exceptional efficiency (i.e., <2 mol % catalyst). The availability of highly efficient catalysts would render this important class of transformations truly practical, as this class of reactions is performed under air, with reagent grade (or no) solvents. Moreover, we will use the same class of catalysts for enantioselective activation of alcohols through the corresponding alcohol tosylations. The resulting enantiomerically enriched tosylates can be readily converted to other useful organic molecules. In the second part of our program, we will develop new catalysts for another important and underdeveloped class of processes: enantioselective allylations of aldimines. The enantiomerically enriched allylic amines obtained through serve as precursors that various other useful nitrogen-containing molecules. The third objective of our program involves innovations in catalytic C-B bond formation. Carbon-boron bonds are among the most useful entities in organic chemistry, and a number of metal-catalyzed method for their enantioselective formation of have been developed. We have discovered the first set of metal-free set protocols for formation of C-B bonds;these reactions proceed by an entirely different mechanism versus the metal-catalyzed variants. We will develop methods for metal-free enantioselective C-B bond formation where readily available small organic molecule serve as catalysts. The entities used as catalysts will also be utilized as ligands in the corresponding Cu-catalyzed reactions.
Efficient, practical and stereoselective preparation of chiral organic molecules is critical to the availability of therapeutic agents;development of catalytic enantioselective methods is a compelling objective in modern chemistry and medicine. Among the most useful intermediates in organic synthesis are enantiomerically pure amines and alcohols. The investigations outlined in this proposal aim to design and introduce new catalysts and protocols for efficient, practical and enantioselective synthesis of a wide range of amines and alcohols, which are difficult to prepare by any other method.
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