posted on 2016-02-02, 00:00authored byJuliana de Oliveira
Silva, Ricardo A. Angnes, Vitor
H. Menezes da Silva, Bruno M. Servilha, Muhammad Adeel, Ataualpa A. C. Braga, Aaron Aponick, Carlos Roque D. Correia
New computationally driven protocols
for the Heck desymmetrization
of 3-cyclopenten-1-ol with aryldiazonium tetrafluoroborates were developed.
These new conditions furnished remarkable product selectivity originating
from a resident hydroxyl group and the critical choice of the reaction
solvent. Mechanistic insights gleaned from theoretical calculations
of the putative transition states predicted toluene as an adequate
solvent choice to attain high enantioselectivity by strengthening
the noncovalent interaction of the substrate hydroxyl group and the
chiral cationic palladium catalyst. Laboratory experiments validated
the theoretical predictions, and by employing 2% MeOH/toluene as solvent,
the Heck–Matsuda reaction provided exclusively the cis-4-arylcyclopentenols 3a–l in good to excellent yields in enantiomeric excesses up to 99%.
The performance of the new PyOx ligand (S)-4-tert-butyl-2-(3,5-dichloropyridin-2-yl)-4,5-dihydrooxazole
was also successfully evaluated in the Heck–Matsuda desymmetrization
of 3-cyclopenten-1-ol. The synthetic potential of these highly functionalized cis-4-arylcyclopentenols is illustrated by a gold-catalyzed
synthesis of cyclopenta[b]benzofuran skeletons.