We report the first experimental evidence for the generation of highly strained cis,trans-cycloheptadienones by electrocyclic ring opening of 4,5-fused cyclobutenamides. In the presence of AlCl3, the cyclobutenamides rearrange to [2.2.1]-bicyclic ketones; DFT calculations provide evidence for a mechanism involving torquoselective 4π-electrocyclic ring opening to a cis,trans-cycloheptadienone followed by a Nazarov-like recyclization and a 1,2-alkyl shift. Similarly, 4,6-fused cyclobutenamides undergo AlCl3-catalyzed rearrangements to [3.2.1]-bicyclic ketones through cis,trans-cyclooctadienone intermediates. The products can be further elaborated via facile cascade reactions to give complex tri- and tetracyclic molecules.
CITATION STYLE
Wang, X. N., Krenske, E. H., Johnston, R. C., Houk, K. N., & Hsung, R. P. (2015). AlCl3-catalyzed ring expansion cascades of bicyclic cyclobutenamides involving highly strained cis,trans-cycloheptadienone intermediates. Journal of the American Chemical Society, 137(16), 5596–5601. https://doi.org/10.1021/jacs.5b02561
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