Regioselective copper-mediated synthesis of thieno[2,3-c]pyrane-7-one, indolo[2,3-c]pyrane-1-one, and indolo[3,2-c]pyrane-1-one.

In the presence of copper(I) iodide, heteroaromatic ß-iodo-α,ß-unsaturated carboxylic acid systems opposed to terminal alkyne afford selectively 6-endo-dig cyclization products via a tandem coupling oxacyclization reaction.