Dialkylaminium cation radical

Other thiohydroxamic acid derivatives have been used for the generation of radicals. Acyl derivatives of iV-hydroxythiazole-2-thione (75) have been explored by Barton as precursors for carbon radicals [86JCS(P1)39]. It has also been shown that similar precursors can be used for the generation of dialkylaminium cation radicals, N-hydroxy-4-methyl-thiazole-2-thione carbamates, TTOC carbamates 76 (91JOC1309). In contrast to... 

Cyclization of the aminyl radical 22 is slow and reversible [53], and the kinetics of related cyclizations and ff-fragmentations were measured directly by LFP [54]. Protonation of the dialkylaminyl radicals gives dialkylaminium cation radicals such as 24 that react much more rapidly [55], and Lewis acid complexes of aminyl radicals such as 23 are intermediate in reactivity [56]. Clocks such as 23 and 24 are in equilibrium with the neutral aminyl radicals, and the concentrations of the proto-nated or complexed forms are necessary if one is to use these clocks equilibrium constants for protonations and Lewis acid complexations in some solvents were determined in the initial kinetic calibration studies. 

Monoalkyl aminium radicals cannot be prepared from PTOC carbamates 29 due to an equilibrium in solution favoring 2-mercaptopyridine-Ar-oxide and an alkyl isocyanate [Eq.(ll)]. With Af-(monoalkyl)thiazole-2-thione carbamates, TTOC carbamates, the equilibrium lies far to the side of the carbamate 84, and these precursors can be prepared from an isocyanate and Ar-hydroxythiazole-2-thione [Eq. (12)]. Under UV photoinitiation in acidic media, TTOC carbamates are efficient precursors for monoalkyl aminium cation radicals (Scheme 26). Monoalkylaminium radical 85 ey-clizes as efficiently as its analogous dialkylaminium radical 66, and the resulting carbon radical 86 can be trapped by a variety of radicophiles (91JOC1309) to prepare substituted pyrrolidines. 

Cation radicals react as electrophiles with aromatics. The scope of this type of substitution is not too well explored, though. Amination of aromatics with dialkylaminium radicals has been known for some time ( 2). In recent years the arylation of organosulfur cation radicals was discovered in our own laboratories (eq. 27) (33, 34). The reaction is limited in that the... 

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