Several of the twenty most important Pharmaceuticals that are currently in use and many natural products with interesting biological activities contain C-N bonds. The development of methods to construct these bonds in a stereocontrolled manner will allow chemists to continue to efficiently prepare molecules of medicinal interest. Group (IV) transition metal imido complexes have been demonstrated to react with unsaturated substrates to form new C-N bonds. The proposed study builds on this chemistry to access aziridines, vicinal amino alcohols, enamides, ynamides and pyrrolidines that are important compounds in their own right, but also serve as intermediates for many useful synthetic transformations. The goal is to eventually develop enantioselective, catalytic syntheses of these molecules. The proposed research will examine the addition of group (IV) imido complexes to alkenes and strained cyclopropanes to form azametallacyclobutanes and pentanes. The steric and electronic properties of the substrates and the metal imido complexes necessary for facile reaction will be determined. The resulting azametallacycles will be treated with a variety of reagents to generate new nitrogen-containing compounds. The appropriate labeling experiments will be performed to determine the stereochemical outcome of these reactions. Group (IV) metal imido complexes bearing chiral metal-bound ligands or chiral auxiliaries on the imido nitrogen will be studied to develop enantioselective C-N bond-forming reactions. Particularly useful would be the development of a method to install C-N bonds via meso desymmetrization of alkenes. Protonation of the metal-carbon bond of an azametallacyclobutene has been shown to release the amine product and regenerate the active imido complex. This same approach will be utilized with azametallacyclobutanes in attempts to render the reactions catalytic in the group (IV) imido complex. Ultimately, the development of the proposed methodology is expected to allow rapid and stereocontrolled access to a number of useful nitrogen-containing compounds. ? ? ?
| Boyd, W Christopher; Crimmin, Mark R; Rosebrugh, Lauren E et al. (2010) Cobalt-mediated, enantioselective synthesis of C(2) and C(1) dienes. J Am Chem Soc 132:16365-7 |
| Schomaker, Jennifer M; Toste, F Dean; Bergman, Robert G (2009) Cobalt-mediated [3 + 2]-annulation reaction of alkenes with alpha,beta-unsaturated ketones and imines. Org Lett 11:3698-700 |
