ortho -Functionalization of Pillar[5]arene: An Approach to Mono- ortho -Alkyl/Aryl-Substituted A1/A2-Dihydroxypillar[5]arene.

Despite the fact that the rim and lateral functionalizations of pillar[ n ]arenes have been well explored, ortho -functionalization has rarely been realized. In this work, we report a facile method of introducing a single functionality ortho to the hydroxyl group in A1/A2-dihydroxypillar[5]arene via a Grignard addition to pillar[4]arene[1]quinone followed by a dienone-phenol rearrangement. The described ortho -alkylation/arylation method allowed formation of various mono ortho -alkyl/aryl-substituted A1/A2-dihydroxypillar[5]arenes previously difficult to obtain.