Chemistry of Heterocyclic Compounds. Vol. 34. No. 7, 1998 HETEROCYCLES WITH A BRIDGING NITROGEN ATOM. 9.* RECYCLIZATION OF AN OXAZOLE FRAGMENT TO A PYRROLE FRAGMENT. SYNTHESIS AND CRYSTAL STRUCTURE OF 5-HEXAMETHYLENIMINO-2- p-NITROPHENYLINDOLYZINE E. V. Babaev, A. V. Ef'nnov, S. G. Zhukov, and V. B. Rybakov X-ray diffraction structural analysis was used to determine the structure of 5-hexamethylenimino-2-p-nitro- phenylindolyzine formed in the reaction of 5-methyl-2-p-nitrophenyloxazolo[3,2-a]pyridinium perchlorate with hexamethylenimine. We have theoretically predicted [2] and then experimentally discovered a previously unreported class of oxazole-pyrrole recyclizations in the case of the transformation of 5-methyloxazolo[3,2-a]pyridines into indolyzines [1, 3]. The structure of the indolyzine products was demonstrated by spectral methods. In the present communication, we finally confirmed the formation of the indolyzine skeleton during recyclization using x-ray diffraction structural analysis. The recyclization took place upon heating oxazolopyridinium salt I with hexamethylenimine in acetonitrile at reflux to give aminoindolyzine II in 65 % yield. H o- / QO 4- | I1 The x-ray diffraction structural data of the indicated indolyzine are given in Tables 1 and 2 and its structure is shown in Fig. 1. The twist of the phenyl ring relative to the plane of the bicyclic system is 18.5 + 2.8*, while the nitro group is twisted by - 16.3 -I- 3.1 * relative to the benzene ring. Marked alternation of single and double bonds typical for indolyzines as a whole is found in the six-membered ring of the indolyzine system in II [4]. Such alternation is not pronounced for the five-membered ring in the bicyclic system. Although the dialkylamino group is bound to the most electron-deficient atom of the indolyzine system, marked conjugation of the unshared pair of this group with the heterocycle is nevertheless not observed in this system. Firstly, the hexamethylenimine fragment is twisted by 23.7 + 2.6 ~ relative to the plane of the indolyzine system. Secondly, an interesting feature is found by comparing the lengths of the single and double bonds in the six-membered ring in II with the reported values for other indolyzines [5]. Greater alternation of the bond lengths (deviation from the ordinary C-C art- *For Communication 8, see [1]. M. V. Lomonosov Moscow State University, 119899 Moscow. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 983-985, July, 1998. Original article submitted March 23, 1998. 852 0009-3122/98/3407-0852520.00 9 Kluwer Academic/Plenum Publishers