118921-08-7Relevant academic research and scientific papers
Valence Isomerizations, 17. - Persubstituted cis-9,10-Dihydronaphthalenes and their Valence Isomerizations
Maier, Guenther,Wiegand, Norbert Hermann,Baum, Stefan,Wuellner, Reinhold,Mayer, W.,Boese, Roland
, p. 767 - 780 (2007/10/02)
The tricyclic diester 10 is available from 2-butyne in a six-step synthesis with an overall yield of 10percent.Thermolysis of 10 gives the bicyclic diester 11 which upon UV irradiation yields 12 as the first persubstituted cis-9,10-dihydronaphthalene.X-ray analysis of 12 shows the molecule considerably twisted along the central bond.In addition, the planes of the ester groups are at an angle of approximately 60 deg to the "planes" of the six-membered rings so that conjugation of the diene systems with the carbonyl functions is virtually interrupted, an effect which is reflected by the unusual spectroscopic properties of 12.The same structural features can be found in decamethyl-cis-9,10-dihydronaphthalene (16).When heated slightly, 12 is converted to the tetracyclic valence isomer 34.On reduction of 12 with diisobutylaluminium hydride both, dihydronaphthalene dicarbinol 25 as well as its unexpected positional isomer 26, are formed depending on the reaction conditions.Etherification of the reduction products with CH2N2/Et2O-BF3 furnishes a mixture of the three isomeric bis(methoxymethyl) compounds 31, 32, and 33.They can be separated by chromatography in the cold, but revert to the mixture of the three isomers at room temperature.We consider diradical 38 to be the intermediate of this intriguing valence isomerization. - Keywords: Molecular twisting / cis-9,10-Dihydronaphthalenes, persubstituted / Valence isomerizations
