Base-mediated cascade synthesis of indole diolefins: a route to spiro[cyclopentene-indole]thiones and thiepino[2,3- b ]indoles.

Base-mediated cascade reactions of 3-hydroxymethyl-3-propenylindole-2-thiones afforded diolefins and involved deformylation, thioenolate alkylation and the thio-Claisen rearrangement. Subsequent ring-closing metathesis reactions of the diolefins furnished 3-spiro[cyclopentene-indole]-2-thiones or thiepino[2,3- b ]indoles.