SYNTHESIS AND PROPERTIES OF N-SUBSTITUTED AZACALIX[N]ARENES

Side arm modifications of hexahomotriazacalix[3]arene (1) were achieved by simple synthetic methods. Compound 5 has picolyl side arms and liquid-liquid extraction experiments showed that the alkali cation affinity of 5 is much stronger than that of 1. A chiral group was also introduced into the azacalixarene structure. Calix[4]arene was converted into dihomoazacalix[4] arene (2) in 8% yield. Clathrate formation of 2 with various solvents is described. MM3 calculations were carried out on p-substituted analogs of 2. The 'self-filled' structure, in which the benzyl side arm is placed in its cavity, is the most stable structure when the p-positions of the aromatic rings carry small substituents. Strong hydrogen bonds between nitrogen and phenolic hydroxyl groups in dihomoazacalix[4]arene (2) were observed at low temperatures. The H-1-NMR signals of phenolic hydroxyl groups appeared as six singlets in the range of 9.8 similar to 17.1 ppm at -70 degrees C.