Bridged Tetraquaternary Salts from N,N′-Polyfluoroalkyl-4,4′ -bipyridine

Abstract

4,4′-Bipyridine (1) with excess of polyfluoroalkyl bromide or iodides 2a-d at 100-110 °C without solvent gave the monoquaternary salts 3a-d in >90% yields. However, 1 with 2.5 equiv of 2a-c in DMF at 110 °C resulted in the diquaternary salts 5a-c in >85% yields. In DMF, 5a-c were obtained in comparable yields when a molar excess of 2a-c reacted with 3a-c. 1,4-Dibromobutane with 3a,b in DMF at 100 °C led to the tetraquaternary salts 7a,b in ∼85% yields. In water or acetone/water as a solvent, salts 3a-d and 5a-c were metathesized with LiN(SO2CF3) 2 and KSO3CF3 to produce monoquaternary ionic liquids 4a-h in >88% yields and diquaternary ionic liquids 6a-f in >86% yields, respectively. Tetraquaternary ionic liquids 8a,b were obtained when LiN(SO2CF3)2 was reacted with salts 7a,b. These compounds were stable to 340 °C as determined by DSC. They are the first N-mono-, N,N′-di-, and N,N,N′,N′-tetra-4,4′ -polyfluoroalkylbipyridinium quaternary salts and ionic liquids.