Asymmetric Catalysis of Carbon-Carbon and Carbon-Nitrogen Bond-Forming Reacti

In this era of heightened environmental awareness and ever-increasing demand for higher efficiency from chemical processes, one of the major challenges facing organic synthesis is the utilization of abundantly available carbon sources for fine chemical synthesis. The dual problems of activation of thermodynamically stable precursors and their stereoselective incorporation pose new challenges, solutions of which may have broader implications in homogeneous catalysis, and, at a practical level, how we manufacture chemical intermediates. In this context, we have discovered new protocols for a nearly quantitative and highly selective codimerization of ethylene (and propylene), and various functionalized vinylarenes, 1,3-dienes and strained alkenes. This talk will deal with the development of various strategies for stereochemical control in an enantioselective version of this reaction. These include design and synthesis of new ligands and applications of the ‘hemi-labile ligand concept’. The products of thisreaction are potentially useful for the synthesis of several classes of compounds, especially with intricately placed methyl-bearing chiral centers. Examples include 2-arylpropionic acids, amphiletanes like pseudopterosins, cyclopenta[G]indoles, pyrrolidinoindolines with all-carbon quaternary centers, and steroid D-ring derivatives with unnatural side-chains. A bimetallic Y-catalyst, designed on the basis of a tentative mechanistic proposal, was found to effect highly enantioselective desymmetrization of meso aziridines. The same catalyst also brings about a regio-divergent parallel kinetic resolution of racemic aziridines with exceptional selectivity.

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