Ring Contractions of 3-Azido-4H-quinolizin-4-ones and 3-Azido-4H-azino[1,2–x]pyrimidin-4-ones: a Novel Approach to 3-Aminoindolizines and their Aza Analogues
Simon Rečnik A , Anton Meden A , Branko Stanovnik A and Jurij Svete A BA Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, PO Box 537, 1000 Ljubljana, Slovenia.
B Corresponding author. Email: jurij.svete@fkkt.uni-lj.si
Australian Journal of Chemistry 61(2) 107-114 https://doi.org/10.1071/CH07318
Submitted: 10 September 2007 Accepted: 3 January 2008 Published: 11 February 2008
Abstract
Thermal transformations of 3-azido-4H-quinolizin-4-ones 4a,b and 3-azido-4H-azino[1,2–x]pyrimidin-4-ones 4c,d, available from the corresponding heteroarylamines 2a–d, were studied. The reaction products were mostly dependent on the solvent. Thus, heating of 3-azido-1-cyano-4H-quinolizin-4-one (4a) in toluene afforded 2-(pyridin-2-yl)fumaronitrile 5a, whereas 3-amino-1-cyano-4H-quinolizin-4-one (8) was obtained on treatment of 4a in a mixture of toluene and trifluoroacetic anhydride. However, heating of 4a in acetic anhydride and in acetic acid resulted in a ring contraction to produce 3-(diacetylamino)indolizine-1-carbonitrile 6a and 3-(acetylamino)indolizine-1-carbonitrile 7a, respectively. Similarly, ring contractions took place on heating ethyl 3-azido-4-oxo-4H-quinolizin-1-carboxylate 4b and 3-azido-4H-azino[1,2–x]pyrimidin-4-ones 4c,d in acetic anhydride or acetic acid to produce the N-acetylated 3-aminoindolizine derivatives 6b, 7b and 3-aminoimidazo[1,2–x]azine derivatives 6c,d in 30–89% yields. The structures of compounds 5–8 were determined by NMR spectroscopy and X-ray diffraction.
Acknowledgements
Financial support from the Slovenian Research Agency through grants P0–0502–0103, P1–0179, and J1–6689–0103–04 is gratefully acknowledged. We thank the pharmaceutical companies Krka d.d. (Novo mesto, Slovenia) and Lek d.d., a new Sandoz company (Ljubljana, Slovenia) for their financial support. Crystallographic data were collected on a Kappa CCD Nonius diffractometer in the Laboratory of Inorganic Chemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Slovenia. We acknowledge with thanks the financial contribution of the Ministry of Science and Technology, Republic of Slovenia, through grant Packet X-2000 and PS-511–102, which thus made the purchase of the apparatus possible.
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