Synthesis of Trisubstituted-4H-Pyrans via Unexpected Cycloaddition of Aldehydes with Acetylenic Ketones Mediated by DMAP and 2,4- Pentanedione

A cycloaddition of aldehydes and acetylenic ketones mediated by 4-dimethylaminopyridine and 2,4- pentanedione is reported. The method supplies a facile way to synthesize 3,4,5-trisubstituted-4H-pyrans in moderate to good yields under mild conditions.