C-SHAPED AND Z-SHAPED DITOPIC CAVITANDS, THEIR BINDING CHARACTERISTICS, AND MONOTOPIC RELATIVES

Readily available octol 1, when treated with 3 mol of CH2ClBr, gave hexol 2 (3%), tetrol 3 (7%), diol 4 (17%), and tetra-bridged 5 (10%). The tetrol and diol served as starting materials for preparing mixed-bridged systems. Diol 4 reacted with 2,3-dichloroquinoxaline (7) to give 7% of cavitand 8, whereas tetrol 3 reacted with only one of the 2 mol of quinoxaline 7 to give the chiral diol 9 (18%). When 2 mol of diol 4 were treated with 1 mol of fluoranil (6), the mixture of 42% of Z-shaped 10 (Z-10) and 12% of C-shaped 10 (C-10) produced was easily separated. The crystal structures of 4.CHCl3.H2O, C-10.3CH3CN.CH2Cl2, Z-10.4CH3CO2CH2CH3, Z-10.4CH3COCH2CH3, and Z-10.6C6H5NO2 were determined and found to resemble what was predicted from molecular model examination. When 1 mol of diol 4 was mixed with tetrachlorotetraazaanthracene 12, a 16% yield of what is probably Z-11 was obtained. One-to-one association constants of C-10 in CD2Cl2 at 21-degrees-C were determined by H-1 NMR titrations with guests as follows: C6D5NO2 (K(a) = 0.6 M-1), C6D5CD3 (K(a) = 1.8 M-1), p-CD3C6D4CD3 (K(a) = 1.6), and CH3COCH2CH3 (K(a) = 1.2 M-1). Attempts to detect binding failed with 2-butyne, 2-pentyne, and methylcyclohexane, although molecular model examination suggested that all seven of the above guests are complementary to the highly preorganized ditopic cavity of C-10.