Märkl, Gottfried and Stiegler, J. and Kreitmeier, Peter and Burgemeister, Thomas and Kastner, F. and Dove, Stefan (1997) Configurational and conformational isomeric antiaromatic tetraoxaporphyrinoids(126.96.36.199) and aromatic tetraoxaporphyrin(188.8.131.52) dications. A new type of molecular dynamics in macrocyclic systems. Helvetica Chimica Acta 80 (1), pp. 14-42.
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The tetraoxaporphyrinoids(184.108.40.206) I are synthesized by cyclizing Wittig reaction. An alternative path is the McMurry condensation. Four different configurational isomers of I were isolated and characterized by 1H NMR. The inner and outer protons of the (E,E)-dienediyl bridges in (Z,EE,Z,EE)-I exchange by rotation around the adjacent single bonds. In (Z,EE,E,EE)-I, the (E)-ethenediyl bridge is rotationally active, while in (E,ZE,E,EZ)- and (E,EZ,E,EZ)-I, rotation of both (E)-ethenediyl bridges is obsd. When the rotation of the active (E)-double bonds at temps. T <-90° is frozen, all configurational isomers of I appear to be antiarom. and paratropic. The oxidn. of (E,ZE,E,EZ)- and (E,EZ,E,EZ)-I with DDQ yields 2 arom., diatropic tetraoxaporphyrin(220.127.116.11) dications both with (E,EZ,E,EZ)-configuration but different fixed conformations. (Z,EE,Z,EE)-I is oxidized to give the (Z,EE,Z,EE)-dication, while the oxidn. of (Z,EE,E,EE)-I yields a mixt. of isomer dications. The std. formation enthalpies of the obtained and expected tetraoxaporphyrinoids I and tetraoxaporphyrin dications were calcd. with the AM1 method, showing good accordance with exptl. results.
|Institutions:|| Chemistry and Pharmacy > Institut für Organische Chemie > Lehrstuhl Prof. Dr. Oliver Reiser|
Chemistry and Pharmacy > Institute of Pharmacy > Pharmaceutical/Medicinal Chemistry II (Prof. Buschauer)
|Subjects:||500 Science > 540 Chemistry & allied sciences|
|Refereed:||Yes, this version has been refereed|
|Created at the University of Regensburg:||Yes|
|Owner:||Prof. Dr. Stefan Dove|
|Deposited On:||20 Jan 2009 16:49|
|Last Modified:||05 Aug 2009 13:50|