Ap alladium-catalyzed coupling between aryl halides and monocyclopropanated pyrroles or furans has been developed, leading to valuable six-membered N-and Oheterocycles.A st he key step,as elective cleavage of the nonactivated endocyclic CÀCb ond of the 2-heterobicyclo-[3.1.0]hexane framework is achieved. The developed method offers access to highly functionalized piperidines,p yridines, and pyrans that are challenging to access by traditional methods.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.
Herein, we report a versatile approach
for the endocyclic ring
opening of bicyclic vinylcyclopropanes triggered by Heck arylations.
The key step for this transformation is a β-C-elimination 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 toward a facile
β-C-elimination with a concomitant shift of Pd along the cyclopropane
moiety, which can successfully compete with the usual termination
step of a Heck reaction via a syn-β-hydride elimination.
Here we report Rh(II)-catalyzed monocyclopropanation reactions on pyrroles in the presence of aryldiazoacetates, providing the corresponding dearomatized products with high levels of enantioselectivity (up to >99% ee). Under the catalysis of Rh 2 (R-p-PhTPCP) 4 , a broad range of pyrrole substrates and aryldiazoacetates are shown to be compatible. Utilizing these valuable chiral building blocks, we further demonstrate the application of this transformation by synthesizing a homo-β-proline analog and a β-aminocarboxylic acid (β-ACC) derivative from the monocyclopropanated product.
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, 2<i>H</i>-pyrans,
2,3-dihydro-1<i>H</i>-azepines and
1,4-cyclohexadienes, respectively. Additionally, <i>gem</i>-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 <i>syn</i>-b-hydride elimination.<br>
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