Tetrakis(benzoxazine) calix[4]resorcinarenes as hosts for small molecules

Abstract

Tetrakis(l,3-dihydrobenzoxazine) calix[4]resorcinarenes 4–6 were synthesized via the Mannich reaction from the corresponding resorcin[4]arenes 1–3 with S-(−)-α-methylbenzylamine or R-(+)-α-methylbenzylamine and formaldehyde (aq.). The products were well characterized by FT-IR, ¹H NMR, ¹³C NMR spectroscopies and single crystal X-ray diffraction analysis. Molecular structures of compounds 4, 5 and 6 showed the same R/S configuration to the starting amines. Compounds 4–6 are stabilized by a collar of intramolecular hydrogen bonding networks between the hydroxy groups and the oxygens from the benzoxazine rings. Compounds 4 and 5 could encapsulate the guest molecules of acetone and dichloromethane, respectively. The UV and ¹H NMR titration experiments were performed to study the host-guest chemistry between compound 4 and small acetone molecules, indicating that compound 4 exhibited encapsulation behavior towards acetone molecules through hydrogen bonding interactions.