How is 3-Isopropenyl-4a,5-dimethyl-1,2,3,4,4a,5,6,7-octahydronaphthalene (CAS: 4630-07-3) typically synthesized?

3-Isopropenyl-4a,5-dimethyl-1,2,3,4,4a,5,6,7-octahydronaphthalene is synthesized through a reaction of 3-isopropenyl-1,2,3,4-tetrahydronaphthalene with dimethyl sulfate using a phase transfer catalyst. The reaction involves the introduction of methyl groups at the 4a and 5 positions, resulting in high selectivity and yield. The process typically requires mild heating and is conducted under anhydrous conditions to prevent side reactions.