Polycyclic Compounds. Part I. Synthesis of Sesquiterpene Compounds

A synthesis of 1,6-dimethyl-4-isopropyhlaphalene (VII) from the ketone (II) is described. 3-Methyl-6-isopropyl-2-hydroxymethylenecyclohexanone (I: R=CHO) on alkylation with 4-diethylaminobutan-2-one methoiodide according to the known procedure, followed by treatment with dilute methanolic alkali, leads to 5-methyl-/8-isopropyl-2-oxo-10-formyl-2,3,4,5,6,7,8,10-octahydronaphthalens (II :R=CHO). The basic cleavages of the hydroxymethylene group under such mild condition is not effected.