Synthesis and applications of 3,4-dihydroxy-2,5-bis-(2'-(4'-substituted-oxazolinyl)) furan

Abstract

Three 3,4-dihydroxy-2,5-bis-(2'-(4'- substituted-oxazolinyl)) furans were synthesized at 90%-94% yields from reaction of 3,4-dihydroxyfuran-2,5-dicar-boxylic acid or its dimethyl ester with chiral ?-amino alcohol via a one-step process. Their chemical structures were determined by ¹H NMR, IR, MS, and elemental analysis. With these chiral bisoxazoline ligands, the asymmetric reductive reaction of ?-acetonaphthalene with KBH₄ or NaBH4 was preliminarily studied. The enantiomeric excess of the reduction product was up to 83.2% with cyclohexane as the solvent, the molar ratio of ligand: reductive agent: β- acetonaphthalene is 0.04:1.6:1, and 72-hours reaction time at 0!. Furan-containing bisoxazoline with 4-benzyl on oxazoline rings exhibited higher enatioselectivity than congeneric bisoxazolines with 4-ethyl on oxazoline rings.