Thermal rearrangement of 1-aryloxy-4-carbazolyloxybut-2-ynes, regio- and stereoselectively led to the formation of benzofuropyranocarbazoles in a single step in good yields. An investigation into the mechanism of the formation of these heteroannulated pterocarpan derivatives led to the serendipitous formation of isomeric benzofurofurocarbazole ring system.