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Paper | Special issue | Vol 69, No. 1, 2006, pp.123-132
Published online, 27th January, 2006
DOI: 10.3987/COM-05-S(O)1
5-Acyl-2H-pyran-2-ones in the Schmidt Reaction: Migration of the Pyran-2-one Ring

Franc Pozgan, Maja Krejan, Slovenko Polanc, and Marijan Kočevar*

*Faculty of Chemistry and Chemical Technology, University of Ljubljana, Askerceva 5, SI-1000 Ljubljana, Slovenia

Abstract

The Schmidt reaction of the 5-acyl-2H-pyran-2-ones (1af) using NaN3/H2SO4 was investigated. The reaction proceeded with complete regioselectivity in the 5-acetyl series to give the corresponding 5-acetylamino derivatives (2ac) via pyran-2-one ring migration. In contrast, the reaction applied to the 5-benzoyl-2H-pyran-2-ones (1df) led to the formation of both regioisomers, (2df) and (3df). The latter resulted from the phenyl shift in this reaction and were obtained as minor products. The 3,5-diacylamino-2H-pyran-2-ones (2a) and (2d) were selectively debenzoylated at position 3.