An investigation of [1,5] suprafacial halide shift and its competing [1,5] hydride shift in a boron activated diene system is presented. This functionalization of remote sp2 carbon (C5) proceeds via a low energy concerted path when the carbon at the migration terminus (C5) is electrophilic. Incorporation of electron acceptors such as boronyl group at C4, assist in creating such electrophilic centre. As a result, transition state of this migration is strongly influenced by the combined effect of boron-acidity, interaction of halogen lone pairs with the migration terminus and the strength of carbon-halogen bond (C-X). In general, [1,5] halide shifts were favored when migration origin (C1) was substituted with bromide or chloride, whereas [1,5] hydride shift was favored when fluorine was attached to C1. Interestingly, the competing barriers for [1,5] hydride shifts were not only lower than the corresponding [1,5] halide shift and the parent 1,3 pentadiene substrate, but were also affected by the electron donating ability of groups at migration source (C1) and the acidity of boronyl group at C4 carbon.

Functionalization of remote sp2 carbon: [1, 5] sigmatropic shift controlled by an in-built donor-acceptor switch

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.