Journal of the American Chemical Society p. 5470 - 5477 (1986)
Update date:2022-08-11
Topics:
Colborn, Robert E.
Vollhardt, K. Peter C.
The mechanism of the Reppe cyclization to cyclooctatetraene was investigated by employing ethyne-1-13C as a substrate in the nickel-catalyzed reaction.The specific catalytic systems studied were nickel acetylacetonate-calcium carbide and nickel acetylacetonate-diethylaluminum ethoxide.In both cases, the label pattern in the cyclooctatetraene produced was consistent with either a stepwise coupling or concerted "zipper-type" mechanism of formation.These results preclude the possibility of cyclobutadiene or benzene intermediates or any carbon-carbon bond cleavage processes which do not leave the original connectivity in the alkyne intact.These conclusions were based upon analysis of the isotopic label in C4 fragments, obtained by chemical degradation of the cyclooctatetraene produced.
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