Abstract
Two facile accesses to mono-cinchona alkaloid-derived ligands, by conventional heating conditions and solvent-free microwave irradiation, are described. 1,4-Dichlorophthalazine (PHAL) or 3,6-dichloropyridazine (PYDZ) reacted with quinine (QN), cinchonine (CN), or cinchonidine (CND) by using CaH2 as acid-bonding reagent in DMF at 90–100°C to provide mono-cinchona alkaloid-derived ligands 2a–f (87–95%) in 1.5 h. However, the coupling reactions were performed under solvent-free microwave conditions to yield 2a–f (64–89%) within 15 min.
ACKNOWLEDGMENT
We thank the National Science Foundation of China (NSFC 20672141) for financial support of this work.
Notes
a Isolated yield based on PHAL or PYDZ.
a QN (1.0 mmol), PHAL (0.5 mmol), K2CO3 (2.0 mmol), and TBAB (10 mol%) were used unless otherwise noted.
b Isolated yield based on 1,4-dichlorophthalazine (PHAL).
c Bis-QN ligand [(QN)2 PHAL] was obtained in 13% yield.
d The ratio of QN and PHAL is 1:1.
e The ratio of QN and PHAL is 3:1; bis-QN ligand [(QN)2 PHAL] was obtained in 67% yield.
a The ratio of cinchona alkaloids and PHAL or PRDZ is 1:1.
b Isolated yield based on PHAL or PYDZ.