73593-83-6Relevant academic research and scientific papers
Electron Donor-Acceptor Compounds, XX: Intramolecular Quinhydrones of the Metacyclophane Series: Synthesis, Stability, and Charge Transfer Absorptions of Stereoisomeric Metacyclophane Quinhydrones
Staab, Heinz A.,Herz, Claus P.,Doehling, Annelie,Krieger, Claus
, p. 241 - 254 (2007/10/02)
On the attempt to synthesize the syn- and anti-metacyclophane quinhydrones 1 and 2 by demethylation of 3 and 4, resp., and subsequent oxidation the same (2,6)-p-benzoquinonophane (5) was obtained which on catalytic hydrogenation yielded syn-metacyclophane quinhydrone 1.Partial demethylation, however, and following oxidation led from 3 to the dimethyl ether 7 of the syn-quinhydrone 1, and analogously from 4 to the dimethyl ether 8 of anti-metacyclophane quinhydrone 2.The structural assignment of the stereoisomers was confirmed by an X-ray structure analysis of 7.In addition to 7 and 8, the corresponding monomethyl ethers 10 and 12 were obtained. - The anti-metacyclophanes 8 and 12 undergo a complete thermal rearrangement to the syn-isomers 7 and 11, resp., from which a stronger ground state stabilisation by charge transfer interaction is concluded for the donor-acceptor systems of the syn-series. - The quinhydrones 7, 8, 10, 11, and 12 show broad, intensive charge transfer absorptions in the range from 300 to 550 nm which for the pairs of stereoisomers 7/8 and 11/12, in spite of the very different donor-acceptor orientation, are surprisingly similar; the absorption intensity of the CT band, however, is considerably stronger for the anti-quinhydrones than for their syn-isomers.
