ORGN 491 |
Elucidation of the mechanism of an unprecendented rearrangement in the photocyclization of a stilbene analog
| Colleen K. Regan and Frank B. Mallory. Department of Chemistry, Bryn Mawr College, 101 North Merion Avenue, Bryn Mawr, PA 19010-2899 |
| Pentahelicene 3 was discovered as a significant photocyclization product of diarylethylene 1 in addition to the anticipated picene 4. Formation of 3 was surprising, as 1 is very similar to many other diarylethylenes which produce only phenacenes. We believe that 3 is formed by the unique closure to an angular carbon in a polycyclic aromatic ring from photocyclization of rotamer 1a followed by oxidative trapping of the transient dihydroaromatic intermediate 2 and subsequent CC bond homolysis and formation. Photocyclizations of related diarylethylenes have revealed that the formation of a helicene product depends greatly on the warping of the aromatic backbone of analogs of 1 resulting from tertiary butyl substitution. We report our experimental findings as well as ab initio calculations which have allowed insight into this new mechanism. 
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Total Synthesis, Process R&D, Combinatorial, Bioorganic, Physical Organic Chemistry
8:00 PM-10:00 PM, Tuesday, August 24, 2004 Pennsylvania Convention Center -- Hall D, Poster
Sci-Mix
8:00 PM-10:00 PM, Monday, August 23, 2004 Pennsylvania Convention Center -- Hall D, Sci-Mix
Division of Organic Chemistry
The 228th ACS National Meeting, in Philadelphia, PA, August 22-26, 2004
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