Mn(III)-based oxidative cyclization of 2,2′-(methylene)bis(3-hydroxycyclopent-2-en-1-one)s. Formation of angular spirodihydrofurans through dispirocyclopropanes

Abstract

The angular spirodihydrofurans, i.e., the 2′H,4′H-spiro[cyclopentane-1,3′-cyclopenta[b]furan]-2,4′,5-triones, were produced by the Mn(III)-based oxidation of the aryl-substituted (methylene)bis(3-hydroxycyclopent-2-en-1-one)s. On the other hand, a similar reaction of alkyl-substituted (methylene)bis(3-hydroxycyclopent-2-en-1-one)s did not give the angular or linear spirodihydrofurans, but dispirocyclopropanes, i.e., the 11-alkyldispiro[4.0.46.15]undecane-1,4,7,10-tetraones. The structure determination of the products and the reaction pathway for the formation of the angular spirodihydrofurans via the dispirocyclopropanes are discussed.