Event Information
Gold(I) and Platinum(II)-Catalyzed Hydrofunctionalization of Allenes and Alkenes with Carbon, Oxygen, and Nitrogen nucleophiles
- Abstract:
The wide-spread occurrence of oxygen and nitrogen heterocycles, combined with the limitations associated with traditional methods for the synthesis of these compounds, prompted us to develop new and efficient methods for their synthesis.
Platinum(II) complexes catalyzed the intermolecular hydroarylation of unactivated alkenes such as ethylene, 1-alkenes, and vinyl arenes with indoles in moderate to good yield. A mechanism involving outer-sphere, anti addition of indole on a Pt(II)-complexed alkene was established by studying a deuterium-labeling experiment.
A mixture of AuCl[P(t-Bu)2o-biphenyl] (5 mol %) and AgOTs (5 mol %) served as an effective catalyst system for the intramolecular exo-hydroalkoxylation of γ-hydroxy allenes and δ-hydroxy allenes to form the corresponding tetrahydrofurans and tetrahydropyrans. The first examples of catalytic intramolecular enantioselective hydroalkoxylation of allenes have been developed by employing a gold(I)-phosphine complex bearing a chiral bulky electron-rich bisphosphine ligand. A range of enantiomerically enriched tetrahydrofurans and tetrahydropyrans were synthesized in excellent yield with up to 99% ee.
A mixture of gold(I)-phosphine complex (S)-Au2Cl2(DTBM-MeOBIPHEP) and AgClO4 catalyzed the enantioselective hydroamination of N-allenyl carbamates to form the corresponding pyrrolidines in excellent yield with enantioselectivities up to 91% ee. This general and effective protocol protocol tolerated a diverse range of carbamate and carboxamide nucleophiles. The first examples of the dynamic kinetic enantioselective hydroamination (DKEH) of axially chiral 1,3,3-trisubstituted N-(γ-allenyl) carbamates have been demonstrated. Experimental evidence has been provided to support the dynamic nature and mechanism of these transformations.
A cationic gold(I)-NHC complex catalyzed the intermolecular hydroalkoxylation of allenes to form (E)-allylic ethers in high regio- and stereoselectivity. The protocol was effective for a number of primary and secondary alcohols, methanol, phenol, and propionic acid, and was effective for monosubstituted, 1,1- and 1,3-disubstituted, trisubsituted, and tetrasubstituted allenes. Gold(I)-catalyzed intermolecular hydroalkoxylation was extended to the hydration of allenes to form (E)-allylic alcohols via selective delivery of water to the terminal allenyl carbon.
A mixture of AuCl[P(t-Bu)2o-biphenyl] and AgSbF6 catalyzed intermolecular hydroamination of unactivated alkenes with cyclic ureas in good yield. This protocol was effective for a wide range of gaseous and liquid 1-alkenes, and tolerated a number of polar functional groups to selectively form the Markovnikov addition product.
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