Regioselective upper-rim functionalizations of calix[4]arene by diphenylphosphino groups

The regioselective upper-rim functionalization of calix[4]arene have been performed to prepare all the multisubstituted diphenylphosphine derivatives. In addition, the X-ray structures of 5,17-dibromo-11,23-bis(diphenylphosphino)-25,26,27,28-tetra-n-propoxycalix[4]arene and 5,11,17,23-tetrakis(diphenylphosphino)-25,26,27,28-tetra-i-propoxy-calix[4]arene have been determined. Regioselective functionalizations have been achieved using methods that involve appropriate choices of bases, alkyllithium-solvent systems, stoichiometry, and reaction times. A new and convenient method for selectively preparing derivitized calix[4]arenes at proximal positions in relative large scale quantity has been developed and involves a transesterification of the distal diester derivative into the proximal isomer.