Oliver Reiser University of Regensburg
Herein, we report a versatile approach for the endocyclic ring-opening of bicyclic vinylcyclopropanes triggered by Heck arylations. Key step for this transformation is a [1,3]-migratory shift of Pd allowing the ring expansion of cyclopropanated pyrroles, piperidines, furans as well as cyclopentadienes to grant access to the corresponding 1,2-dihydropyridines, 2H-pyrans, 2,3-dihydro-1H-azepines and 1,4-cyclohexadienes, respectively. Additionally, gem-disubstituted cyclopropanated furans showed unexpected behavior by giving diastereoselectively asymmetrically substituted dienes. Mechanistic studies and theoretical calculations point towards a facile [1,3]-migratory shift of Pd along the cyclopropane moiety, which can successfully compete with the usual termination step of a Heck reaction via a syn-b-hydride elimination.
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