Synthesis of linear triquinanes by round-trip radical cyclizations

ORGN 16

Jonathan C. Tripp and Dennis P. Curran. Department of Chemistry, University of Pittsburgh, Chevron Science Center Rm #1114, 219 Parkman Ave, Pittsburgh, PA 15260
Diastereoselective synthesis of linear triquinanes by cascade radical reactions from acyclic precursors is complicated by the formation of multiple diastereomers. It was recently reported that when precursor 1 was subjected to radical cyclization conditions at different temperatures, the diastereoselectivity was greatly improved.

We have shown that the diastereoselectivity of this cyclization is not sensitive to temperature and our observations suggest that prematurely reduced radical products may have mistakenly been assigned as the additional tricyclic diastereomers. The diastereodiversity in this reaction arises in the second of the three 5-exo cyclizations where the relevant hexenyl radical is shown in structure 2. We have determined the cyclization selectivity of such hexenyl radicals in a number of related systems with and without the ester of the α,β - unsaturated ester moiety, and we present a consistent picture of the stereoselectivity of these types of reactions.

 

New Reactions and Methodology
8:00 AM-12:00 PM, Sunday, March 28, 2004 Anaheim Convention Center -- 303A, Oral

Division of Organic Chemistry

The 227th ACS National Meeting, Anaheim, CA, March 28-April 1, 2004