Kinetics of the 1, 5‐dipolar cyclization of ...
|Title||Kinetics of the 1, 5‐dipolar cyclization of 2‐Vinylpyridinium ylides to Indolizines. Determination of rate parameters by laser flash photolysis|
|Author(s)||M. Liu, Y. Romashin, R. Bonneau|
|Journal||International Journal of Chemical Kinetics|
|Abstract||Nanosecond laser flash photolysis (lambda = 355 nm) of an aqueous solution of 3-chloro-3-p-chlorophenyldiazirine in isooctane produces a transient absorption at 310 nm due to the formation of the carbene: In the presence of 2-vinylpyridine, a second transient with a broad absorption band peaking at 520 nm grows in. This absorption is attributed to 2-vinylpyridinium ylide. The ylide decays with a lifetime equal to 33 mu s at 25 degrees C independent of the concentration of 2-vinylpyridine. As the ylide decays, there isa concomitant growth of an absorption at 330 nm, attributed to the formation of indolizine. The activation parameters for the 1,5-dipolar cyclization of the ylide to indolizine were determined; E(alpha) = 12.1 kcal mol(-1) and log A = 13.4. (C) 1994 John Wiley & Sons, Inc.|
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