Synthesis, reactions, and mass spectra of some indolizines

Abstract

The methods of synthesis and known properties of indolizines are reviewed.
A number of indolizine compounds substituted in both the
5 membered and 6 membered rings have been prepared by known synthetic routes. The use of an ion exchange resin to bring about ring closure of an intermediate quaternary compound is described.
Reduction with lithium aluminium hydride will usually convert indolizine esters to hydroxymethyl derivatives except in the case of the 1 position where reduction proceeds to the alkyl derivative.
Reduction of 2-methyl-7-cyanoindolizine with lithium aluminium hydride gives the expected aminomethyl compound while 2-methyl-6-cyano­indolizine does not. Reduction of the ring system may be occurring.
Reduction of indolizine with sodium and ethanol gives a mixture of a dihydro and tetrahydro product; further treatment yields only the tetrahydro product, 5,6,7,8-tetrahyclroindolizine.
The mass spectra of indolizine and some of its derivatives
are presented and the cracking patterns discussed. A marked similarity between the spectra of monomethylindolizines and monomethylindoles is noted and a possible explanation is put forward.