a-And P-tosylated alkenylaromatic systems 5c,d and 9a-c are cyclized to 6c,d and 10a-c in FS0,H-containing SO, in synthetically useful processes. Dibal-H treatment of cr-substituted 6c,d brings about rapid, high-yield detosylation to 7c,d; the 0-tosylated isomers 1Oa-c give, with Dibal-H, after 18 h in refluxing toluene, mainly unreacted sulfones together with minor amounts of sulfides lla-c. Ring-disrupted congeners 1 5 a d and 18a-c behave likewise, with cr--tosylated 1 5 a d being rapidly detosylated by Dibal-H to 1 6 a d and their P-substituted isomers undergoing low-yield reductions to sulfides 19a-c. Dibal-H mediated detosylation appears to be limited to benzylic substrates.Recent reports from these laboratories have described novel entries into 4,5,6,7-tetrahydrobenzo[b]thiophenes such as 3l and aromatic resin acid derived frameworks I11,and VI'. The method proceeds via FSO,H/SO,-promoted cyclizations of tosylated mono-and diolefins 1, I and IV, and subsequent detosylation of the resulting 2, II and V, by Dibal-H (Schemes 1 and 2).
Results and discussionCompound 5c,d and 9a-c: synthesis and cyclization Preparation of 5c,d parallels previous procedures for 5a,b'. The appropriate ArCH,CI was treated with NaTos in Tosyl = p-toluenesulfonyl.' Dibal-H = Diisobutylaluminium hydride.