Polyfluorinated sulfonamides

Perfluoroalkyl acids (PFAs) are synthetic, perfluorinated, straight- or bran-ched-chain organic acids characterized by a carboxylate or sulfonate moiety [1]. PFAs are manufactured directly but can also be formed through transformation of many precursor molecules containing a perfluoroalkyl moiety [2], These include fluorotelomer alcohols (FTOHs) and perfluoroalkyl-sulfonamides (Table 1, Fig. 1), however, others likely exist. Collectively, this family of chemicals including PFAs and their polyfluorinated precursors will be referred to in this document as perfluoroalkyl substances (PFSs). 

Polyfluorinated compounds comprise hundreds of chemicals characterized by hydrophobic linear alkyl chains partially or fully fluorinated (as the perfluorinated compounds [PFCs]) and containing different functional groups. Polyfluorinated compounds include perfluoroalkyl sulfonamides (PFASAs), fluorotelomer alcohols (FTOHs), polyfluorinated alkyl phosphates (PFAPs), fluorotelomer unsaturated carboxylic acids (FTUCAs), perfluoroalkyl acids (PFAAs), and their salts. The most common PFAAs are perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFASs). In particular, PFASs contain one or more fluorinated alkyl chains bonded to a polar head, which at neutral pH can be charged (anionic, cationic, and amphiphilic surfactants) or noncharged (nonionic surfactants). 

ESI operating in the negative ion (NI) mode has been the interface most widely used for the analysis of anionic polyfluorinated surfactants. In addition, ESI has also been optimized for the determination of neutral compounds such as the sulfonamides PEGS A, Et-PEOSA, and t-Bu-PEOS. The use of atmospheric pressure photoionization (APPI) has been explored in few works [72-74]. Takino et al. [72] fotmd the absence of matrix effects as the main advantage of this technology, but the limits of detection were considerably higher than those obtained by LC-ESI-MS/MS. 

Although Beringer s arylations of aniline and piperidine resulted in poor yields, reactions with sulfonamides dehvered the N-arylated products in 50% yield under basic conditions [87]. McEwen found that arylation of sodium azide was facile at 80 °C in dioxane/water, delivering arylazides in excellent yields [88]. The chemoselective arylation of azides has been demonstrated with an luisymmetric polyfluorinated salt [90], and a computational study supports the ligand coupling pathway [32, 33]. 

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