Cyclisation Studies of 5–Substituted Arylalkyl – 1,2,3,4,5,6,7 – octahydroisoquinolines

Treatment of 2-methyl-5-(3-phenylpropyl)-1,2,3,4,5,6,7,8-octahydroisoquinoline with 48% HBr results in isomerisation of the double bond and cyclisation at position-5 of the octahydroisoquinoline ring system to give a novel spiro structure. This is in contrast to the corresponding reaction with 5-[1-(2-phenethyl)]-1,2,3,4,5,6,7,8-octahydroisoquinoline where cyclisation takes place at position-6 of the octahydroisoquinoline ring system. Similar treatment of 5-benzyl-2-methyl-1,2,3,4,5,6,7,8-octahydroisoquinoline results in cyclisation at position-7 of the octahydroisoquinoline ring system to give a novel tetracyclic structure.