Synthesis of dihydroactiniolide [5,6,7,7a-tetrahydro-4,4,7a-trimethylbenzofuran-2(4H)-one] and 6,7,8,8a-tetrahydro-5,5,8a-trimethylnaphthalene-1,3(5H)-dione from 6,7,8,8a-tetrahydro-2,5,5,8a-tetramethyl-5H-chromen

Abstract

Autoxidation of 6,7,8,8a-tetrahydro-2,5,5,8a-tetramethyl-5H-chromen (2), obtained by photolysis of β-ionone, afforded a mixture of dihydroactiniolide (4), a cyclohexylideneacetaldehyde (5), and 3,5,6,7,8,8a-hexahydro-2,5,5,8a-tetramethyl-2H-chromen-2,3-diol (6). By refluxing in benzene, compound (6) was converted into a hexahydroindenone (15), which, in several steps, afforded 6,7,8,8a-tetrahydro-5,5,8a-trimethylnaphthalene-1,3(5H)-dione (20).