ORGN 495 |
| Intermolecular energy transfer is the way of promoting triplet reactions in molecules that do not undergo efficient intersystem crossing. Although these reactions have been studied for many years, the possibility that the outcome of the triplet reactivity of organic molecules would depend on the energy of the sensitizer was never considered. Literature precedents show that most acyclic 1,4-dienes do not react, or only undergo cis-trans isomerization, when irradiated using sensitizers with a triplet energy c.a. 10 kcal/mol above the triplet energy of the alkene, or higher. However, studies in our group demonstrate that these compounds afford the corresponding di-π-methane photoproducts, in high yield, when sensitizers with triplet energies slightly above the energy of the alkene are used. Similarly, acyclic β,γ-unsaturated ketones previously reported as unreactive in the oxa-di-π-methane mode, undergo this reaction using sensitizers with energy values 1 to 5 kcal/mol above the triplet energy of the acceptor alkene. |
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Physical Organic Chemistry, Metal-Mediated Reactions, Asymmetric Reactions and Syntheses
8:00 PM-10:00 PM, Tuesday, August 21, 2007 BCEC -- Exhibit Hall - B2, Poster
Division of Organic Chemistry |