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Published on: November 9, 2019
Temperature-dependent, competitive 1,3-acyl shift versus decarbonylation of a cyclopropanone intermediate
Ihsan Erden1, Jingxiang Ma, Christian Gärtner
1Department of Chemistry and Biochemistry, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132.
Abstract:
Photooxygenation of 1,1,3-trimethyl-1,2-dihydropentalene gives an unstable endoperoxide which upon decomposition delivers a bicyclic cyclopropanone intermediate; this species either extrudes CO to give a cycloheptadienone or undergoes a 1,3-acyl shift, both processes occurring most likely in a stepwise manner via diradical intermediates. Alternatively, C3a-C4 cleavage in the dioxygen diradical derived from the endoperoxide yields a 2-cyclopropyl substituted cyclopentadienone epoxide.
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Stability of Substituted Cyclohexanes
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...
Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation

