STRUCTURAL STUDY OF INDOLIZINE DERIVATIVES. Oscar Au-Alvarez, Dept. of Chemistry, University of Oriente, Santiago de Cuba 90500, Cuba, Victor A. Tafeenko and Leonid A. Aslanov, Dept. of Chemistry, University of Moscow, 119899 Moscow, Russia

The effect of substituents in position 1 and 3 in the distribution of double and

single bonds in the indolizine ring is determined and explained using the theory of resonance. If nitro, nitroso or carbonyl groups are in position 3, shortening of bond lengths corresponding to double bonds occurs in C1-C2 but if nitro group is in position 1, shortening of bond lengths occurs in C2-C3. The 6-member ring of indolizine shows an alternation of double and single bonds from C5 to C9. The planarity of substituents with respect to the indolizine ring is clear if no steric hindrance is present. These results became evident after the determination of the structures of 7 indolizine derivatives: 2-methyl-3-nitroindolizine, 2,8-dimethyl-3-nitroindolizine, 2-methyl-3-benzoylindolizine, 2-methyl-3-trichloro-acetylindolizine, 2-phenyl-3-nitrosoindolizine, 2-methyl-1-nitroindolizine and 2,8-dimethyl-1-nitroindolizine. The determination of the crystal structures of these indolizine derivatives is a part of the study of their chemical reactivi- ties and its relation to the bond distribution of the indolizine ring.