Rhodium-catalyzed polycyclization reaction of enediynes: Formation of 5-7-5 and 5-7-6 ring systems via the CO-SiCaT and CO-CaT reaction

ORGN 450

Victor C. Vassar, Bibia Bennacer, and Iwao Ojima. Department of Chemistry, State University of New York at Stony Brook, Stony Brook, NY 11794-3400

The use of metal catalysts to form polycyclic molecules from simple acyclic precursors is an important tool in organic synthesis. Fused polycyclic molecules are of interest due to their prevalence in biologically active molecules. Previously we reported the efficient formation of 5-7-5 ring systems by rhodium catalysis via the CO-SiCaT and CO-CaT reactions. The formation of the 5-7-6 ring skeleton is of special interest to us due to its occurrence in pharmaceutically interesting compounds such as phorbol, karajinone B, and cyclomyrsinol. The formation of 5-7-6 ring systems is anticipated to be more difficult than 5-7-5 ring systems. In fact, the formation of 5-6-6 ring systems (3, n=1) was often observed as a side reaction. Also, reaction of enediyne 1 (n=1, R=H) under CO-SiCaT conditions yielded bicyclization product 4 as the major product. The scope and limitations for the formation of 5-7-6 ring systems as compared to 5-7-5 ring systems from homologous starting materials will be discussed.

Physical Organic, Materials, Heterocycles, Aromatics, Metal-Mediated Reactions 8:00 PM-10:00 PM, Tuesday, September 9, 2003 Hilton New York -- Americas Hall 1, Poster Division of Organic Chemistry The 226th ACS National Meeting, New York, NY, September 7-11, 2003