Synthesis of stilbene crown ether p-tert-butylcalix[4]arenes

Photo-switch able calixarene crown ether derivatives were synthesized in or der to control the ring sizes and shapes of ionophores by isomerization bet ween two different geometrical isomers. Five stilbene crown ether calix[4]a renes were prepared via McMurry coupling of the corresponding bisbenzaldehy de-calix[4]arene derivatives. The coupling reactions yielded both cis- and trans-stilbenes from o- and m-bisbenzaldehydes while only the cis-isomer wa s obtained from the reaction of the p-isomer. Unlike diazobenzene analogues , the stilbene crown ether calix[4]arene derivatives did not undergo therma l isomerization. Nevertheless, the isomerization of all synthesized stilben e crown ether calix[4]arenes can be photochemically induced. (C) 2001 Elsev ier Science Ltd. All rights reserved.