Synthesis and Photochemical Isomerization of 1,2-Di-9-anthrylethanol and 1,2-Di-9-anthrylethanone

Article abstract of DOI:10.1021/jo00365a019

1,2-Di-9-anthrylethanol has been synthesized by Grignard reaction of 9-anthrylmagnesium bromide with 9-anthrylacetaldyhyde which, in turn, was obtained by oxidation of 9-anthrylethanol with 1,1,1-triacetoxy-1,1-dihydro-1,2-benziodoxol-3(1H)-one ("Dess-Martin periodinane").This oxidant also was found to be the reagent of choice for the conversion of dianthrylethanol into 1,2-di-9-anthrylethanone.The photochemical isomerization of dianthrylethanol in benzene solution proceeds with a quantum yield of 0.34 by intramolecular <4+4> cycloaddition involving the excited singlet state.Remarkably, the course of photochemical isomerization of 1,2-di-9-anthrylethanone is dependent on the substrate concentration, affording mainly intramolecular <4+2> cyclomers in dilute (0.00001 M) solution but the intramolecular <4+4> cycloadduct in concentrated (0.01 M) solution.The proposed triplet state pathway for the formation of intramolecular Diels-Alder products from dianthrylethanone is supported by oxygen quenching results and sensitization experiments with biacetyl.The photochemical isomerization of di-9-anthryl ketone and 1,3-di-9-anthrylpropan-1-one gives rise to intramolecular <4+2> (ψ=0.0003) and <4+4> (ψ=0.65) cycloadducts, respectively.The differences in quantum yields and modes of cycloaddition are attributed to differences in molecular geometry.