Experimental and Computational Study of the (Z)-Selective Formation of Trisubstituted Olefins and Benzo-Fused Oxacycles from the Ruthenium-Catalyzed Dehydrative C–H Coupling of Phenols with Ketones

Document Type

Article

Language

eng

Publication Date

7-23-2018

Publisher

American Chemical Society

Source Publication

Journal of the American Chemical Society

Source ISSN

0002-7863

Original Item ID

doi:org/10.1021/jacs.8b05875

Abstract

The cationic Ru–H complex was found to be an effective catalyst for the dehydrative C–H coupling of phenols with ketones to form the trisubstituted olefin products. The coupling of phenol with linear ketones led to highly stereoselective formation of the (Z)-olefin products. The dehydrative coupling of phenol with enones and diones efficiently formed the benzopyrene and related oxacyclic derivatives. The reaction of 3,5-dimethoxyphenol with cyclohexanone-2,2,6,6-d4 showed a significant H/D exchange to both vinyl and α-CH2 positions on the olefin product (72–75% D). A significant carbon isotope effect was observed on the ortho-arene carbon of the olefin product. The free energies of intermediate species for the entire catalytic cycle were successfully computed by using the DFT method. The DFT study revealed that the E/Z stereoselectivity is a result of the energy difference in the insertion step of ortho-metalated phenol to an enol form of the ketone substrate (ΔΔE = 9.6 kcal/mol). The coupling method provides a direct catalytic C–H olefination method for ketones to form trisubstituted olefins without employing any reactive reagents or forming any wasteful byproducts.

Comments

Accepted version. Journal of the American Chemical Society, Vol. 140, No. 32 (July 23, 2018): 10289-10296. DOI. © 2018 American Chemical Society. Used with permission.

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