Applications of Arene-Ruthenium Complexes in Synthesis

University Of Missouri-St. Louis, Saint Louis MO

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Abstract

DESCRIPTION: (provided by applicant) The research described herein seeks to uncover novel, concise, and stereocontrolled routes to structurally elaborate polycyclic ring systems via manipulation of readily available (eta6-arene)ruthenium(II)Cp complexes. The fundamental properties inherent to arene-Ru(II) complexes render these materials attractive synthetic intermediates; however, their use in preparative organic chemistry has received scant attention. The CpRu(II) fragment also offers distinct advantages as an arene activating group relative to other transition metal species. Foremost among these advantages is the ability to recover the CpRu(II) moiety in a reusable form after removal of the arene ligand. Research designed to maximize the unique properties of arene-ruthenium complexes has been proposed. The specific aims of this research are threefold: 1) To functionalize benzylic positions of coordinated indoline, tetrahydroquinoline, and tetrahydroisoquinoline ligands in a stereocontrolled manner by exploiting the increased acidity of these positions. Intramolecular reaction manifolds have been designed with the goal of achieving concise syntheses of complex polycyclic ring systems related to certain alkaloid natural products. 2) To fully investigate the synthesis of azaspirocyclic compounds constructed via a novel intramolecular addition of stabilized acetoacetamide nucleophiles to a coordinated arene nucleus. 3) To develop new approaches to heavily functionalized beta-tetralone derivatives utilizing a facile intramolecular SNAr reaction of stabilized nucleophiles attached to an arene-Ru(II) complex. Significantly, preliminary results demonstrating the feasibility of the three basic reaction manifolds enumerated above have been secured. Furthermore, compounds potentially accessible via this methodology will possess structural features also present in a number of biologically and therapeutically active natural products. Toward this end, several routes designed to deliver enantiomerically or diastereomerically pure (arene)Ru(II) complexes will be examined with the aim of ultimately accessing optically pure polycyclic materials.