Calixarenes. 17. Functionalized Calixarenes: The Claisen Rearrangement Route

Article abstract of DOI:10.1021/jo00350a072

Methods for the preparation of a variety of para-substituted calix<4>arenes via the Claisen rearrangement route are described.Starting with the readily available p-tert-butylcalix<4>arene 1, the tert-butyl groups are removed by an AlCl3-catalyzed retro-Friedel-Crafts reaction, and the calix<4>arene 2 that is formed is converted to the tetraallyl ether 3.This compound undergoes a heat-induced Claisen rearrangement to yield p-allylcalix<4>arene 4, which is a useful starting material for the introduction of functional groups.Along one route, the tosylate of 4 is ozonized to the aldehyde 7, the aldehyde is reduced to the alcohol 8, the alcohol is converted to the bromide 10 and then to the azide 11, and the azide is reduced with diborane to p-(2-aminoethyl)calix<4>arene 12, a compound of interest as a chelating species.Along a second route, the tosylate of 4 is rearranged to p-(1-propenyl)calix<4>arene 16 and ozonized to p-formylcalix<4>arene 17 from which the oxime 18 can be prepared.