Partially fluorinated crown ether derivatives : synthesis, phase transfer catalysis and recycling studies

A series of N,N'-dialkyl-4,13-diaza-18-crown-6 derivatives containing C8H17 [2.6], (CH2) 3C8F17 (2.36), (CH2) 3C10F21 [2.37], and (CH2) 2C8F17 [2.19] sidearms were synthesized in good yields by N-alkylation of 4, 1-diaza-18-crown-6 [ 2.7]. Potassium picrate could be extracted form an aqueous solution into an organic phase by all of the perfluoroalkylated macrocycles demonstrating their potential to be used as phase transfer catalysts. They each gave higher catalytic activities under solid-liquid than under liquid-liquid phase-transfer conditions. The light fluorous macrocycles gave similar, if not better, catalytic activity compared to the present, non-fluorinated phase-transfer catalyst [2.6] under solid-liquid conditions in conventional organic solvents in both an aliphatic and an aromatic nucleophilic substitution. N,N' -Bis(1H,1H,2H,2 H,3H,3H-perfluoro-undecyl)-4,13-diaza-18-crown-6 [2.36] was recycled six times in the iodide displacement reaction of 1-bromooctane and four times in the fluoride displacement reaction of 2,4-dinitrochlorobenzene using fluorous solid-phase extraction without any loss in activity.;A series of functionalized dibenzo-18-crown-6 derivatives possessing C7H15 [4.17], (CH2)2C 6F13 [4.26], (CH2)2C 8F17 [4.27], NHC17F15 [4.31a-b], and NHCH2C6F13 [ 4.35a-b] sidearms were synthesized following different approaches. All of the non-fluorinated and partially-fluorinated dibenzo-18-crown-6 derivatives showed their potential to act as phase transfer catalysts by extracting potassium and sodium picrate from an aqueous solution into dichloromethane. By adding perfluoroalkyl sidearms to a dibenzo-18-crown-6 type structure, [4.26 ] and [4.27], the phase transfer catalytic activity was improved significantly. Bis(1H,1 H,2H,2H-perfluorooctyl)dibenzo-18-crown-6 [4.26] was recycled four times in the iodide displacement reaction of 1-bromooctane using supported fluorous phase catalysis and four times in the fluoride displacement reaction of 2,4-dinitrochlorobenzene using fluorous solid-phase extraction without any loss in activity.