Anomalous C-C bond cleavage in heteroatom-centered cation radicals containing vicinal hydroxy group: mechanism revisited and refined

ORGN 414

Andrei G. Kutateladze and Zaiguo Li. Department of Chemistry and Biochemistry, University of Denver, 2190 E. Iliff Ave., F.W. Olin Hall, rm.202, Denver, CO 80208-2436

1,3-Dithianyl cation radicals having a-hydroxy-neopentyl or similar groups in position 2, which are generated via photoinduced electron transfer, undergo anomalous fragmentation necessitating refinement of the accepted mechanism of cleavage in heteroatom-centered cation radicals containing vicinal hydroxy group. Experimental and computational data supports a rationale in which proton abstraction from the hydroxy group in the initial cation radical does not cause a Grob-like fragmentation, but rather produces a neutral radical species, the alkoxy radical, that undergoes fragmentation in either direction, i.e. cleaving the C-C bond to dithiane or to the tertiary alkyl group. These results will undoubtedly have implications for the general mechanism of fragmentation in heteroatom-centered cation radicals containing vicinal hydroxy groups. Additionally, utilizing these results we were able to develop the next generation bis-dithiane based photochemical "latch" and increase the quantum efficiency of the externally sensitized fragmentation to over 50%.

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