Ru(II)‐Catalyzed Hydroarylation of in situ generated 3,3,3‐Trifluoro‐1‐propyne by C‐H Bond Activation: A Facile and Practical Access to β‐trifluoromethylstyrenes

International audienceIn this study, a practical and straightforward synthesis of β-( E )-trifluoromethylstyrenes by ruthenium-catalyzed C-H bond activation was developed. The readily available and inexpensive 2-bromo-3,3,3-trifluoropropene (BTP), a non-ozone depleting reagent, was used as a reservoir of 3,3,3-trifluoropropyne. With this approach, the monofunctionalization of a panel of heteroarenes was possible in a safe and scalable manner (23 examples, up to 87% yield). Mechanistic investigations and density functional theory (DFT) calculations were also conducted to get a better understanding of the mechanism of this transformation. These studies suggested that 1) a cyclometallated ruthenium complex enabled the transformation, 2) this latter exhibited high efficiency in this transformation compared to the commercially available [RuCl 2 ( p -cymene)] 2 and 3) the mechanism proceeded through a bis-cyclometallated ruthenium intermediate for the carboruthenation ste