Dynamic control of selectivity for synthetically useful carbocation rearrangements

Representative trajectories for formation of the two products of Sarpong’s carbocation rearrangement. The frames illustrated are incremented by 20 fs, in addition to the start and end frames. In general, products arising from migration of the less massive group occur more quickly, consistent with the experimental observation that such products form preferentially.
Representative trajectories for formation of the two products of Sarpong’s carbocation rearrangement. The frames illustrated are incremented by 20 fs, in addition to the start and end frames. In general, products arising from migration of the less massive group occur more quickly, consistent with the experimental observation that such products form preferentially.

In a recent publication (Tantillo, Sarpong and coworkers, JACS, DOI: 10.1021/jacs.8b05804), results from calculations carried out by Stephanie Hare in the Tantillo lab shed light on the origins of selectivity for a synthetically useful carbocation rearrangement developed by the Sarpong lab at UCB. Stephanie’s results indicate that non-statistical dynamic effects control which of two polycyclic products are formed, showcasing the potential of harnessing such effects for controlling reaction selectivity.