Highly Sterically Encumbered Gold Acyclic Diaminocarbene Complexes: Overriding Electronic Control in Regiodivergent Gold Catalysis
| Autor: | Matthew C. Ellison, LeGrande M. Slaughter, Aaron A. Ruch, John K. Nguyen, Sachin Handa, Fanji Kong, Vladimir N. Nesterov |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
chemistry.chemical_classification
Steric effects 010405 organic chemistry Alkene Isocyanide Organic Chemistry 010402 general chemistry 01 natural sciences Combinatorial chemistry Medicinal chemistry 0104 chemical sciences Catalysis Cyclopropane Inorganic Chemistry chemistry.chemical_compound chemistry Terphenyl Moiety Physical and Theoretical Chemistry Selectivity Alkyl |
| DOI: | 10.26434/chemrxiv.13338116.v1 |
| Popis: | Two series of sterically encumbered gold(I)-acyclic diaminocarbene (ADC) complexes were prepared by reaction of mono- and dialkylamines with gold-bound 2-mesitylphenyl isocyanide (monomesityl series) and 2,6-dimesitylphenyl isocyanide (dimesityl series). X-ray crystal structures and solution 1H NMR data showed that the ADC-gold complexes adopt major rotameric conformations with the bulky biaryl/terphenyl group and one alkyl group located syn to gold. This engenders substantial steric hindrance at the metal, as evidenced by percent buried volume (%Vbur) parameters of 35.7 – 37.2 for the monomesityl series and 46.4 – 52.4 for the dimesityl series. Modest out-of-plane distortions of the ADC N-substituents in the dimesityl series were attributed to attractive CH···π interactions between alkyl groups and mesityl rings on the basis of dispersion-corrected density functional theory calculations. Gold-catalyzed regiodivergent domino cyclization/hydroarylation reactions of a 1,6-enyne with indole revealed that the bulky biaryl/terphenyl substituents of the ligands exert a strong influence on product selectivity, with the bulkier dimesityl ADC-Au catalysts inducing a shift away from the cyclopropane-fused product toward the normally disfavored alkene product. Incorporation of a yet bulkier bis(2,6-diisopropylphenyl)-substituted terphenyl moiety into the ADC led to a gold catalyst that provided exclusive selectivity for the alkene product. Computational modeling suggested that bulky terphenyl groups hinder attack at the a carbon in the initially formed organogold intermediate, allowing steric effects to override the intrinsic electronic preference for the cyclopropane product. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|