Novel Redox-Active Cyclophanes Based on 3,3'-Biindolizines: Synthesis and Chirality.
The first compounds of a new series of redox-active cyclophanes were prepared by dehydrocyclization of bridged indolizines of type 1. The bridged dipyridino-compounds 2a and 2b obtained by reaction of 2 mol of lithiated alpha-picolines with dihalides were used as starting materials. Subsequent treatment of 2a,b with 2 mol of alpha-bromo ketones gave quaternary pyridinium halides. Ring closure in an alkaline medium (Chichibabin reaction) yielded the starting material for the synthesis of the macrocycles. Oxidative C-C coupling gave the diastereomeric cyclophanes of type 3. In all cases one pair of the enantiomers was obtained in excess. CV-investigations have shown that the main products are reversible redox systems. To clarify their conformations, compounds 3c, 3d/1, and3d/2 were subjected to X-ray analysis.
Sonnenschein
Helmut
H
Institut für Angewandte Chemie Berlin-Adlershof, Abteilung Organische Synthese and Abteilung Analytik, Rudower Chaussee 5, D-12484 Berlin, Germany.
Kreher
Thomas
T
Gründemann
Egon
E
Krüger
Ralph-Peter
RP
Kunath
Annamarie
A
Zabel
Volker
V