CONFORMATIONAL PROPERTIES OF METHYLENE-BRIDGED RESORCARENES

Conformations and conformational interconversions of resorcarene 1c ha ve been studied by molecular mechanics calculations. As with calix[4]a renes the general stability of the four basic conformations is cone > partial cone > 1,2-alternate > 1,3-alternate. The lowest energy is cal culated for a pinched cone conformer with C-2v symmetry stabilised by intramolecular hydrogen bonds of the two ''parallel'' resorcinol units as donors. The topomerisation of the cone conformation proceeds via t he partial cone and 1,2-alternate intermediates with a calculated barr ier of 9.9 kcal mol(-1) which is in excellent agreement with the exper imental value. (C) 1998 Elsevier Science Ltd. All rights reserved.