Synthesis of Karahanaenone

Article abstract of DOI:10.1021/jo00217a028

Karahanaenone (1) has been prepared from dehydrolinalyl acetate.Electrochemical epoxidation of dehydrolinalyl acetate provided the corresponding epoxide 6a (75percent) which was converted to keto acetate 7a (82percent) by an electrogenerated acid-catalyzed rearrangement.Hydrogenation followed by alkaline hydrolysis gave 6-hydroxy-2,6-dimethyl-7-octen-3-one (7c) (86percent), which was subjected to thermal dehydration at 200 deg C to give 1 (85percent) via Claisen type rearrangement of the intermediate 2-methyl-2-ethenyl-5-propylidenetetrahydrofuran (2).An alternative route to 1 via thermolysis of the xanthate of 1-(5-ethenyl-5-methyl-2-tetrahydrofuranyl)-1-methylethanol (10b) is also described.