Chadron M. Friesen

Reactions of poly-hexafluoropropylene oxide acids and their corresponding salts

Abstract Investigation of the decomposition or fluorination of poly-hexafluoropropylene oxide (poly-HFPO) carboxylic acids and their salts reveals a new type of product from the decarboxylation of poly-HFPO and proposes an explanation for its formation.

A new oligo(hexafluoropropylene oxide)-b-oligo(ethylene oxide) diblock surfactant obtained by radical reactions

The synthesis and characterization of a new oligo(hexafluoropropylene oxide)-b-oligo(ethylene oxide), oligo(HFPO)-b-oligo(PEG), diblock co-oligomer are presented. First, the model reactions dealing with the radical addition of 1-iodoperfluorohexane (C6F13I) onto allyl alcohol and allyl-O-PEG-OCH3 were optimized in terms of the choice of the initiator (azobisisobutyronitrile [AIBN], tert-butylperoxypivalate [TBBPi], and benzoyl peroxide [BPO]) and of the solvent, temperature, and time. Allyl-O-PEG-OCH3 was obtained from the etherification of ω-hydroxy-PEG with allyl bromide. End-capping of oligo(HFPO) with PEG was successfully achieved by the radical addition of 1-iodoperfluoropropyl-2-oligo(hexafluoropropylene oxide) [oligo(HFPO)-CF(CF3)CF2I] onto allyl-O-PEG-OCH3 using the best conditions of the model reactions. Although TBPPi failed and led to oligo(HFPO)-isobutyl iodide, AIBN and BPO yielded oligo(HFPO)-CH2CHICH2-oligo(PEG). The selective reduction of the latter compound led to oligo(HFPO)-b-oligo(PEG) in 77% yield, the surface tension properties of which were compared to those of commercially available ammonium perfluorooctanoate (APFO) and perfluorooctanoic acid (PFOA). Its critical micelle concentration was 0.04 g mol−1. All models, intermediates, and diblock co-oligomers were characterized by 1H, 19F, and 13C NMR spectroscopy as well as matrix assisted laser desorption ionization (MALDI) and atmospheric pressure solids analysis probe (ASAP) time-of-flight mass spectrometry (TOF-MS).

A Convenient Route to Tetraalkylammonium Perfluoroalkoxides from Hydrofluoroethers

Hydrofluoroethers are shown to alkylate tertiary amines readily under solvent-free conditions, affording valuable tetraalkylammonium perfluoroalkoxides bearing α-fluorines. The reaction of R(F)CF2-OCH3 (R(F)=CF2CF3, CF2CF2CF3, and CF(CF3)2) with NR(1)R(2)R(3) produces twenty new α-perfluoroalkoxides, [(CH3)NR(1)R(2)R(3)][R(F)CF2O] under mild conditions. These α-perfluoroalkoxides are easy to handle, thermally stable, and can be used for the perfluoroalkoxylation of benzyl bromides.

Synthesis of α,β-unsaturated esters of perfluoropolyalkylethers (PFPAEs) based on hexafluoropropylene oxide units for photopolymerization

α,β-unsaturated esters are usually synthesized for polymer applications. However, the addition of maleate (cis-configuration) to a fluorinated moiety is challenging due to its potential isomerization during esterification. Various synthetic routes were attempted and led to very low conversion or side-products. The immiscibility of both reagents combined with an easy isomerization or attack on the double bond were potential explanations. In this paper, the synthesis of maleates oligo(hexafluoropropylene oxide) is reported by Steglich esterification and the reaction conditions are discussed depending on the molecular weight of the fluorinated moieties. After UV-curing, hydrophobic polymers were obtained by copolymerization with vinyl ethers by electron acceptor–donor systems.

Base-Catalyzed Transesterification of Thionoesters

Here we report a convenient synthesis of thionoesters by base-catalyzed transesterification. Benzyl and alkyl thionobenzoates and thionoheterobenzoates were efficiently prepared using various alcohols catalyzed by the corresponding sodium alkoxide. This methodology features a broad substrate scope, good to excellent yields, short reaction times, while simultaneously driving the reaction toward completion through the removal of the methanol byproduct. We also report the conversion of a small collection of thionobenzoates into the corresponding α,α-difluorobenzyl ethers to demonstrate the conversion of alcohols into difluorobenzyl or difluoroheterobenzyl ethers, a process that could prove useful for lead optimization in medicinal chemistry.