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

What is it about?

The angular spirodihydrofurans were produced by the Mn(III)-based oxidation of the aryl-substituted methylenebis(3-hydroxycyclopent-2-en-1-one)s. On the other hand, a similar reaction of alkyl-substituted methylenebis(3-hydroxycyclopent-2-en-1-one)s did not give the angular or linear spirodihydrofurans, but dispirocyclopropanes.

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Photo by John Cameron on Unsplash

Photo by John Cameron on Unsplash

Why is it important?

1. We demonstrated the facile synthesis of spiro compounds 2 and 5 using the Mn(III)-based oxidation of methylenebis(3-hydroxycyclopent-2-en-1-one)s 1 simply prepared by the condensation of cyclopentanedione with commercially-available aldehydes. 2. The reaction of the aryl-substituted 1a–g (R = aryl) produced the angular spirodihydrofurans 2a–g. On the other hand, the alkyl-substituted 1h–l (R = alkyl) yielded the dispirocyclopropanes 5h–l. 3. The production of the angular spirodihydrofurans 2 would proceed via the rearrangement of the dispirocyclopropanes 5. The aryl-substituent of the methylenebis(3-hydroxycyclopent-2-en-1-one)s 1 would be essential for the rearrangement stage.