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Coordination-Accelerated Catalysis in the Heck Reaction Using N-H N-Heterocyclic Carbene Pd Complexes
Alexis P Harper1, Alexandra J S Larson1, Lindsey M Brown1
1Brigham Young University, Department of Chemistry and Biochemistry, Provo, Utah 84602, United States.
Abstract:
We report that monosubstituted N-H N-heterocyclic carbene (NHC) complexes can engage coordinating alcohol substrates, which leads to higher conversions and higher regioselectivity in the Heck reaction. We demonstrate that the monosubstituted NHC ligand, the coordinating group on the substrate, and the length of the tether between the alkene and the alcohol group are all essential for improved catalysis. We also demonstrate a broad substrate scope for Heck couplings with different aryl bromides and substituted olefins. The resulting Heck products can be converted to aldehyde or amide products via redox isomerization reactions. Tandem Heck couplings/hydroalkoxylation reactions are also reported that generate tetrahydrofuran products in good yield.
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