Electron-Deficient Olefins: New Ligands for Asymmetric Transition Metal Catalysis

Princeton University, Princeton NJ

Investigators

Abstract

? DESCRIPTION (provided by applicant): Transition metal catalysis has become one of the most powerful methods for chemical synthesis, due in large part to the ability to fine-tune the reactivity of the metal center with diverse sets of ligands. Subtle steric and electronic variation on the ligands can help tailor the metal center to selectively obtain the desired products. Olefins have been known to coordinate with transition metals for decades, and electron-deficient olefins (EDOs) display uniquely beneficial properties. In particular, EDO ligands have been shown to belong to a small subset of ligands that induce Csp3-Csp3 bond-forming reductive elimination. Despite this distinctive reactivity, EDO ligands have received far less attention than other ligand classes, and remain underappreciated and unexploited. Additionally, chiral variants of this ligand have never been described. In this research proposal, we will design and develop diverse and modular chiral EDO ligands for use in transition metal catalysis. These ligands are readily accessible from inexpensive chemical feedstocks. We first intend to apply these ligands to novel asymmetric cross-coupling reactions with aziridines. We hypothesize that these reactions proceed through a stereoablative mechanism via a prochiral organic radical, and have encouraging preliminary results showing a chiral EDO ligand can indeed generate an enantioenriched product. We also plan on applying this family of chiral EDO ligands to the rapidly growing field of C-H activation. Unlike traditiona ligands, these EDOs are compatible with the electrophilic metal catalysts necessary for C-H activation. The ability of chiral EDOs to facilitate asymmetric C-H activation reactions would be a powerful advancement in the field. This library of chiral EDO ligands has the potential to enable construction of previously inaccessible carbon-carbon bonds en route to complex molecular scaffolds of medicinal importance.