This project is focused on the development of a novel radical process - spontaneous generation and coupling of cobalt-complexed propargyl radicals - allowing the stereoselective conversion of propargyl alcohols and cations to D,L-3,4-diaryl-1,5-alkadiynes with a high degree of stereocontrol. The major objectives are: 1) identification of the structural and electronic parameters responsible for spontaneous generation of dicobalt hexacarbonyl-complexed propargyl radicals; 2) expansion of the scope of the spontaneous cation-to-radical conversion by testing the alternative combinations of pi-bonded ligands and transition metals; 3) development of the intramolecular variant of the parent reaction yielding, in a highly stereoselective manner, topologically diverse, diacetylenic 4 - 10 membered carbocycles and heterocycles; and 4) studies of spontaneous cross-coupling reactions involving cobalt-complexed propargyl radicals of different topology, both persistent and transient in nature. The spontaneous radical generation forming the heart of these investigations effectively converts 18-electron, diamagnetic complexes into paramagnetic species, at variable and structure - dependent rates, offering unique opportunities for additional physical organic and materials-oriented studies.
With the support of this Research at Undergraduate Institutions award from the Organic and Macromolecular Chemistry Program, Professor Gagik G. Melikyan, of the Department of Chemistry and Biochemistry at California State University - Northridge, is studying novel reactions of organic radicals (molecules bearing a single unpaired electron) that are complexed to various transition metals. These reactions offer promise for the facile and selective synthesis of a large variety of otherwise inaccessible organic structures that are rich in functionality, offering promise in the selective syntheses of organic molecules of practical importance. More broadly, these studies are expected to advance knowledge at the interface of radical organic and organometallic chemistry.
