Enamine acylation, diketene

Morpholinocyclohex-l-ene is smoothly acylated by diketene to give a fused pyranone (61CB486, B-68MI22400). The initially formed diketone ring-closes and the pyranone results from elimination of morpholine. Using the cyclopentanone-derived enamine, much resinous material is formed and the yield of pyranone is reduced. 

The acylation of the enamine of a cyclic ketone with diketene leads directly to bicycUc 4-pyrones, as indicated below. ° ... 

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