Tandem rearrangement involving a β-hydroxysulfoxide and cyclization processes toward the 1-benzenesulfonyl-5-benzenethio-1,2,2a,3,4,5-hexahydrobenz[c,d]indole oxygenated at the 4-position

Treatment of compound 4 with trifluoroacetic anhydride under reflux in chlorobenzene underwent a tandem rearrangement to produce compound 5 . When the acetylated derivative of 4 , was treated with trifluoroacetic anhydride in the presence of Lewis acids produced two cis cyclized conformers 7a and 7b , presumably through the intermediate B .