Novel Redox-Active Cyclophanes Based on 3,3‘-Biindolizines:  Synthesis and Chirality

Abstract

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.

Selected synthetic strategies to cyclophanes

“…Zabel and co-workers [ 253 ] have reported the synthesis of 3,3-biindolizine-based cyclophane 483 via Chichibabin reaction as a key step. Compound 480 was reacted with ω-bromoacetophenone ( 481 ) by adopting standard Chichibabin reaction conditions to deliver the crown ether derivative 482 (28%).…”

Metal‐ and Solvent‐Free, One‐Pot Synthesis of 3‐Unsubstituted Benzoindolizines

“…For example, they are employed as organic semiconductors, [ 6 ] novel fluorescence dyes [ 7 ] or electroluminescent probes. [ 8 ] Furthermore, indolizines are key synthetic intermediates for larger ring systems such as cyclophanes [ 9 ] or cyclazines. [ 10 ]…”

Synthesis, Electrochemical and Mass Spectrometric Properties of the Macrocycles with One, Two and Four 3,3´-Biindolizine Redox-Active Fragments on the 3-(Indolizin-2-yl)quinoxalin-2-one Platform

“…Среди индолизиновых макроциклов, кроме син-тезированных в наших работах, [13][14][15][16] известны ма-кроциклы с одним индолизиновым [17,18] и двумя [19][20][21][22] индолизиновыми (бииндолизиновым) фрагментами. Последние, благодаря редокс-активному фрагменту, относятся к макроциклическим соединениям, способ-ным обратимо реагировать на внешние воздействия.…”