Tetra-O-alkylated Calixarenes in the 1,3-Alternate Conformation

Article abstract of DOI:10.1021/jo00046a021

A general method has been developed for the preparation of tetra-O-alkylated calix<4>arenes in the 1,3-alternate conformation (3a,c-e) starting from p-tert-butylcalix<4>arenes 1a,b using Cs2CO3 in DMF.The 1,3-alternate conformation was unequivocally proved by an X-ray structure determination of 3a.The scope of the reaction was investigated starting from a series of diametrically di-O-alkylated calix<4>arenes 4a-e having different substituents R₂ (t-Bu, CHO, NO2, Br, CN) at the para positions of the phenolic rings.The reaction of 4a-d (R₂ = t-Bu, CHO, NO2, Br)yielded the corresponding tetra-O-alkylated calix<4>arenes in the 1,3-alternate conformations 5a-d (51-73percent).However, the dicyanocalix<4>arene 4e gave the partial cone conformer 6 as the major reaction product.