Functionalized indolizines were prepared by Lewis acid‐catalyzed cyclizations of 3‐(pyridin‐2‐yl)‐propiolates with enones. This new type of reaction provides a convenient and regioselective approach to ester‐substituted indolizine derivatives which are not readily available by other methods. Based on density function theory (DFT) calculations, a mechanism of the reaction has been suggested.

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The reaction of perfluorinated 3,5‐dioxoesters with 1,2‐diaminobenzenes or 2,3‐diaminonaphthalenes afforded two types of 1H‐benzo‐1,5‐diazepine derivatives containing a perfluorinated side chain. 2,5‐Dihydro‐1H‐benzo‐1,5‐diazepin‐2‐ones were formed by cyclocondensation via the central keto and the ester group, whereas 1H‐benzo‐1,5‐diazepines resulted from cyclocondensation via the two keto groups. The tautomerism and isomerization of these compounds have been investigated by 1H‐, 13C‐, and 19F‐NMR spectroscopy. The 1,5‐diazepines appear in CDCl3 solution as mixtures of two tautomeric forms, the enaminoimine I and diaminodiene II. In DMSO solution, besides I and II, two further species, III and IV, are formed by (E/Z) isomerization on the exocyclic C=C bond.

Synthesis of Functionalized Indolizines by Lewis Acid-Mediated Cyclocondensation of 3-(Pyridin-2-yl)-propiolates withEnones. -(SPECOWIUS, V.; BENDRATH, F.; WINTERBERG, M.; AYUB, K.; LANGER*, P.; Adv. Synth. Catal. 354 (2012) 6, 1163-1169, http://dx.doi.org/10.1002/adsc.201100795 ; Inst. Chem., Univ. Rostock, D-18059 Rostock, Germany; Eng.) -Nuesgen 37-157