Journal
JOURNAL OF ORGANIC CHEMISTRY
Volume 86, Issue 14, Pages 9670-9681Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.joc.1c00941
Keywords
-
Categories
Funding
- JSPS KAKENHI [JP 18H02550]
Ask authors/readers for more resources
The article elucidates the selectivity difference between platinum and palladium in the Friedel-Crafts-type synthesis reaction, and reveals the mechanism of the behavioral differences of the two metals through density functional theory calculations and experimental studies.
Following the discovery of an unusual transition-metal-catalyzed reaction, the elucidation of the underlying mechanism is essential to understand the characteristic reactivity of the metal. We previously reported a synthetic method for tricyclic indoles using Pt-catalyzed Friedel-Crafts-type C-H coupling. In this reaction, the Pt catalyst selectively formed a seven-membered ring, but the Pd catalyst only afforded a six-membered ring. However, the reasons for the different selectivities caused by Pd and Pt were unclear. We performed density functional theory (DFT) calculations and experimental studies to reveal the origin of the different behaviors of the two metals. The calculations revealed that the formation of the six- and seven-membered rings proceeds via and eta(1)-allenyl eta(3)-propargyl/allenyl complexes, respectively. A molecular orbital analysis of the eta(3)-propargyl/allenyl complex revealed that, for the platinum complex, the energy required to convert the unoccupied molecular orbital on the reactive carbon into the lowest unoccupied molecular orbital (LUMO) was lower than that for the palladium complex. In addition, DFT calculations revealed that the combination of platinum and bis[2-(diphenylphosphino)phenyl] ether (DPEphos) reduced the activation energy of the seven-membered cyclization in comparison with palladium or PPh3. Additional experimental studies, including NMR studies and stoichiometric reactions, support the aforementioned examination.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available