Pyran Annelation: An Effective Route to a Tricyclic Dienone

Article abstract of DOI:10.1021/jo00353a014

A new pyran annelation reaction was investigated. 2,6-Dimethyl-4H-pyran-4-one (2) was converted to 2((p-tolylsulfonyl)methyl)-6-methyl-4H-pyran-4-one (7) which was alkylated at the C-2 methylene position regioselectively, and the p-tolylsulfonyl group can be easily eliminated with an aluminium amalgam reduction.On the other hand the pyran-4-one ring was easily transformed into an 1,5-diketone derivative.By joining and applying these selective alkylations and transformations, tricyclic dienone 22 was effectively synthesized from 2.