Trifluoromethanesulfonic acid, addition alkenes

Mechanistic studies of the diacetoxylation of alkenes using (diacetoxyiodo)benzene have demonstrated a protio-catalytic nature of this reaction [255]. Systematic studies into the catalytic activity in the presence of proton-trapping and metal-complexing additives indicate that strong acids act as catalysts in the reaction. When trifluoromethanesulfonic acid is used as catalyst, the selectivity and reaction rate of the conversion is similar or superior to most efficient metal-based catalysts, such as Pd(II) and Cu(II) metal cations. Based on a kinetic study as well as in situ mass spectrometry, a mechanistic cycle for the proton-catalyzed reaction was proposed in this work [255]. 

The addition of HN3 to nonactivated alkenes with formation of the saturated azides requires drastic conditions and a catalyst. Olefinic double bonds activated by conjugated, electron-withdrawing groups like -CN, -NO2, or -C(0)R react easily [8, 9]. The photolysis [10] and the pyrolysis [7] of HN3 with alkenes yields nitriles, N2, and decomposition products. The reaction of HN3 with alkines usually leads to 1,2,3-triazoles. Single or double addition with formation of vinyl azides or saturated diazides are rare [8, 9]. Arenes and HN3 form aniline derivatives directly and efficiently in the presence of trifluoroacetic acid and the strongly acidic trifluoromethanesulfonic acid [11]. The yield is frequently low in the presence ofH2S04[1]. 

The reaction of alkenes with acetyl hypofluorite436 439 or with fluorine,451-473-4 74 2,3,4,5,6-pentachloro-l-fluoropyridinium trifluoromethanesulfonate (A -FPCPy-OTf),441 711 cesium fluoroxysulfate,435 (V-fluorobis(triflyl)amine432 or l-(chloromethyl)-4-fluoro-l,4-diaza-bicyclo[2.2.2]octane tetrafluoroborate431 in acetic acid leads to the simultaneous addition of fluorine and the acetoxy group across the double bond. Examples of these additions are summarized in Table 34. Further examples are the formation of l439 and 2.439... 

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