Tris aminium salts

This type of reaction can be induced also by radiolysis [133,134] or by chemical oxidation, particularly with tris-(p-bromophenyl)aminium salts (cation radical catalyzed Diels-Alder reaction) [10]. The scope of this reaction and its synthetic utility have been delineated in detail. The results unambiguously support a free radical cation chain mechanism [10]. 

In the past decade, there has appeared only one report, which can be classified under this heading, on the monodeoxygenation of spiro-adamantane-l,2-dioxetanes induced by catalytic amounts of tris-(2,4-dibromophenyl)-aminium hexachloroantimonate <1998T6939>. An electron-transfer mechanism from the aminium salt has been proposed for the observed formation of various ketones. Reports citing the electrophilic ring opening of dioxetanes by boron trifluoride, trifluoroacetic acid, and various other Lewis acids have been summarized in CHEC-II(1996) <1996CHEC-II(1B)1041>. 

Reaction of various thiiranes 208, catalyzed by aminium salts (tris-(4-bromophenyl)aminium hexachloroantimonate 209 or tris-(2,4-dibromophenyl)aminium hexachloroantimonate 210) in freshly distilled dichloromethane, led to desulfurization of starting thiiranes to alkenes 211 in good yield (typically 80%) (Scheme 53) <1995T8935>. The mechanism of desulfurization of thiiranes catalyzed by aminium salts is presented in Scheme 54. 

Various other miscellaneous salts have been used from time to time to initiate cationic polymerisation. These include tris-p-bromophenyl aminium hexa-chloroantimonate (97), anilinium hexafluoroantimonate (98), nitronium tetra-fluoroborate (95), thianthrenium perchlorate (99), and hexachloroantimonate (100), and N-methyl acridinium and N-methylphenazonium salts (75). In general... 

The stable radical cation salts tris(4-bromophenyl)aminium hexachloroantimonate (1) and tris(2,4-dibromophenyl)aminium hexachloroantimonate (2) catalyze the cyclopropanation of certain alkenes, 1,3-dienes and arylalkenes by ethyl diazoacetate (solvent dichloromethane, 0°C for 1 or — 78°C for 2, 2-10 min 10-50 mol% of catalyst e.g. formation of 3). " ... 

Electron-transfer/organocatalytic reactions were postulated in oxamination reactions [9] later it was demonstrated [10] that the reaction follows preferentially a polar enamine activation manifold when FeCls was used in DME as oxidizing agent the metal coordinates rapidly to the nitroxyl radical of TEMPO (2,2,6,6-tetramethylpiperidine-l-oxyl) (Scheme 39.2) [llj. SOMO conditions were find by replacing the metal salt by a non-coordinating oxidizer such as tris(p-bromophenyl) aminium hexachloroantimonate [12]. Under these conditions the ET reaction arguably afforded the enamine radical cation, which was trapped by TEMPO, or by styrene as a purported SOMOphile partner. 

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