The First Lateral Functionalization of Calix[4]arenes by a Homologous Anionic Ortho-Fries Rearrangement

Abstract

Treatment of calix[4]arene bis-O-carbamates 4a,b-6a,b with LDA in THF results in the regio- and stereoselective introduction of both axial and equatorial carboxamide groups at the methylene bridges via a homologous anionic ortho-Fries rearrangement to give 7-16. The stereochemical outcome of the rearrangement is dependent on the reaction conditions and the conformation of the starting material. Stereochemical and structural proof has been secured by the X-ray crystal structure of calix[4]arene 10 having only one equatorial carboxamide moiety. The use of this novel class of methylene bridge-functionalized calix[4]arenes is illustrated by the formation of bis--lactone 19, while the enhanced acidity of the remaining hydroxyl groups, owing to the presence of axial carboxamide groups at the methine bridges, followed from the easy propylation of bisrearranged calix[4]arene 7.