Synthesis of 9,10-Bis-ketoenaminoanthryl and 9,10-Bis-isoxazolylanthryl Linked Biscalix[4]arenes: Atropisomers and Molecular Recognitions

An efficient synthetic pathway for the synthesis of biscalix[4]­arenes 5–10 using 1,3-dipolar cycloaddition reactions
is reported. Biscalix[4]­arene 10 is capable of forming
a complex with methyl viologen because of favorable cation−π
interactions and a proper cavity size to accommodate the guest. Moreover,
biscalix[4]­arenes 8a and 8b were found to
be atropisomers at room temperature. These two conformers were unable
to exchange at room temperature because of the restricted rotation
of the C9–C11 or C10–C12 bonds of the β-amino-α,β-unsaturated ketones
of anthracene.