A proton nmr follow-up provided conclusive evidence for the involvement of two sequential Claisen rearrangements in the thermal rearrangement of 1,4-diaryloxy-2-butynes 1to 11a-methylpterocarpans 3. A detailed study of the rearrangement of 1,4-diaryloxy-2-butynes 1 in polyethyleneglycol-200 (PEG-200), indicated a definite possibility of selective synthesis of either benzofuron (3,2-b )benzofuran 4 or benzofuro(2,3-b)benzofuran 5 by varying the temperature of the reaction alone. © 1984.