Regioselective Synthesis of Thieno[3,2-β]Indole by Tandem Cyclization of 1-Acetyl-3-(4'-Aryloxybut-2'-Ynylthio)Indole (Experimental Section)

A number of thieno[3,2-b]indoles have been regioselectively synthesized in 85-90% yield by the tandem cyclization of 1-acetyl-3-(4'-aryloxybut-2'-ynylthio)indoles on treatment with one equivalent of m- CPBA in CH2Cl2 at rt for 1 h. 1-Acetyl-3-(4'-aryloxybut-2'-ynylthio)indoles were in turn prepared from indole via (i) formation of thiuronium salt (ii) then reacting with 1-aryloxy-4-chlorobut-2-yne (iii) acetylation with acetyl chloride under PTC condition.