Heterocalixarenes. Part 4. Synthesis of oxocalix[1]heterocycle[2]arenes: aunique H-bonding network in calix[1]benzimidazol-2-one[2]arene center dot(1)/(2) H2O

The Friedel-Crafts aroylation of 2-methylanisole with 3-methylbenzoyl chlor ide followed by NBS bromination and cyclizations with 1,3-dihydrobenzimidaz ol-2-one, 1,3-dihydro-5,6-dinitrobenzimidazol-2-one, uracil, 6-methyluracil and quinazoline-2,4(1H,3H)-dione provide respective oxocalix[1]heterocycle [2]arenes 5-9. The X-ray crystal structure (solid) and H-1 NMR spectral (so lution) studies show them to have by and large inwardly flattened partial c one conformations which vary in torsion angles between the rings. The calix [1]benzimidazol-2-one[2]arene . 1/2 H2O complex shows a unique array of H-b onds in which three of the four CH and the imide oxygen of the benzimidazol -2-one unit, carbonyl oxygen and water molecule are involved in H-bonding w ith surrounding calixarene molecules. This heterocalixarene, in contrast to earlier reported benzimidazol-2-one-based calixarenes, does not show heter ocyclic pi-pi stacking.