Intramolecular cyclization of furfuryl 2-propynyl ether

Intramolecular cyclization of furfuryl 2-propynyl ether in the presence of a catalytic amount of potassium tert-butoxide in tert-butyl alcohol gives 3a,6-epoxy-1,3-dihydro-6H-isobenzofuran. The cyclization is presumed to be favored by preliminary isomerization of the 2-propynyl group into allenyl. Heating of the cyclization product with excess potassium tert-butoxide in tert-butyl alcohol results in cleavage of the epoxy bridge with formation of 6-hydroxy-1,3-dihydroisobenzofuran.