Z. Naturforsch. 2014,
69b, 554 – 566
doi:10.5560/ZNB.2014-4021
A Simple Metal-free Synthesis of 2,4,5-Trisubstituted Pyridines and Pyridine N-Oxides by [2+2] Cycloaddition of Enaminones to Propyne Iminium Salts
Jure
Bezenšek1,
Benjamin
Prek1,2,
Uroš
Grošelj1,
Amalija
Golobič1,
Katarina
Stare1,
Jurij
Svete1,2,
Willi
Kantlehner3,
Gerhard
Maas4, and
Branko
Stanovnik1,2
1 Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, P. O. Box 537, 1000 Ljubljana, Slovenia
2 EN-FIST Centre of Excellence, Trg Osvobodilne fronte 3, 1000 Ljubljana, Slovenia
3 Fakultät Chemie/Organische Chemie, Hochschule Aalen, Beethovenstr. 1, 73430 Aalen, Germany
4 Institute of Organic Chemistry I, University of Ulm, Albert-Einstein Allee 11, 89081 Ulm, Germany
Received February 13, 2014 / published online May 7, 2014
Herein a simple one-pot metal-free synthesis of 2,4,5-trisubstituted pyridines and pyridine N-oxides by [2+2] cycloaddition of enaminones, which are prepared in situ from alkyl, aryl and heteroaryl methyl ketones using N,N-dimethylformamide dimethyl acetal (DMFDMA), and propyne iminium salts as electron-poor acetylenes, is described.
Key words: Enaminones, Propyne Iminium Salts, [2+2] Cycloadditions, 2,4,5-Trisubstituted Pyridines, 2,4,5-Trisubstituted Pyridine N-Oxides