Beilstein J. Org. Chem.2016,12, 260–270, doi:10.3762/bjoc.12.28
rate-determining one and that the [1,9]-H shift is the one with the lowest energy barrier.
Keywords: acetal; benzindenes; DFT calculations; fulvene; hydrogen shift; Introduction
Fulvenes (also known as pentafulvenes), [1][2][3][4] a unique class of trienes, have intrigued chemists for decades due to
) shift as the first step of the previously discussed conversions since, in such a case, we should have found deuterium linked to C4/C9 of the benzindenes 18/19 resulting from the first labelling experiment.
Next we tried to understand why the regioisomeric benz[f]indenes were, in all our reactions
10a and 11a can lead respectively to the final benzindenes 5a and 6a. Thus, intermediate 11a undergoes a disrotatory 6π-electrocyclic ring closure [49] via the transition structure TS6 to give the tricyclic species 13a. By an analogous electrocyclic ring closure through TS7, compound 10a is converted
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Graphical Abstract
Scheme 1:
Lewis acid-catalyzed [1,4]-H transfer/1,5-electrocyclization tandem processes of benzylidenemalonat...