Oxidative dimerisation of some indolizines by Pd/C in p-xylene was undertaken in order to evaluate reaction conditions for cyclophane syntheses.Surprisingly, alkylation by the solvent occurred at the 3-position of the indolizines 2 and 5 as a side reaction.In toluene, yields of alkylation products 4b and 8 exceeded those of dimerisation products 3 and 6.The alkylation by the solvent was fully suppressed by using chlorobenzene and chlorotoluene.Alkylation products of indolizines with p-xylene or toluene and previously unknown dimeric indolizines are described. - Key Words: Indolizines / Oxidative dimerisation, palladium-promoted / Cyclophanes
Facile Dehydrogenative Dimerization of Indolizine Derivatives
Treatment of 3-unsubstituted indolizines with a dehydrogenating agent such as palladium on carbon in refluxing xylene gave the corresponding 3,3'-biindolizine derivatives in 19-74percent yields.