Synthesis and extraction abilities of mono-formylated calix[4]-1,3-aza-crown and its hydrazone derivatives

By formylation of calix4]-1,3-aza-crown in hexamethylenetetramine/trifluoroacetic acid system, the first formylated calix4]-aza-crown derivative 6 was synthesized in yield of 61%. Reacting compound 6 with salicyloyl hydrazine, 2,4-dinitrophenyl hydrazine, nicotinyl hydrazine or phenyl thiosemicarbazide afforded four novel calix4]crown hydrazone derivatives 7a–d in yields of 70–90%. By condensating compound 6 with series of bifunctional reagents, the novel mono-bridged biscalix4]-aza-crown hydrazone derivatives 8a–c were prepared in high yields. The extraction experiments showed that all new compounds were good receptors for metal cations, especially, for soft metal cations. The extraction results suggested that the hydrazone groups produced favorable influences for binding soft cations. The two calix4]arene units in compounds 8a–c could bind metal cations concurrently.