Compound 3a

4-bromobenzoic trifluoromethanesulfonic anhydride

From: A general approach to intermolecular carbonylation of arene C–H bonds to ketones through catalytic aroyl triflate formation

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Compound data: CIF

Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.

In Situ Formation of 3a: Silver triflate (97 mg, 0.38 mmol) was transferred to a Teflon sealed, thick walled 50 mL glass reaction vessel equipped with a magnetic stir bar. 4-bromoiodobenzene (71 mg, 0.25 mmol) and [Pd(allyl)Cl]2 (2 mg, 0.0063 mmol) were dissolved in dichloromethane (1 mL) and added. The vessel was closed, removed from the glovebox, evacuated and backfilled with carbon monoxide three times, and finally pressurized with 4 atm carbon monoxide. After heating at 100 °C for 2 h with stirring, the reaction was cooled to room temperature, the carbon monoxide was released on a Schlenk line under nitrogen, and the vessel was brought into the glovebox. Hexamethylbenzene (6 mg, 0.04 mmol) was added as a standard and the reaction mixture was filter through celite. The yield of aroyl triflate 3a (90%) was determined by 1H NMR analysis relative to the external standard. In situ 1H NMR spectra of 3a: 1H NMR (400 MHz, CDCl3) δ 7.94 (d, J = 8.7 Hz, 2H), 7.75 (d, J = 8.7 Hz, 2H).

Synthesis and Isolation of 3a: Silver triflate (386 mg, 1.5 mmol) was transferred to a Teflon sealed, thick walled 50 mL glass reaction vessel equipped with a magnetic stir bar. 4-Bromoiodobenzene (282 mg, 1.0 mmol) and [Pd(allyl)Cl]2 (9 mg, 0.03 mmol) were dissolved in dichloromethane (4 mL) and added. The vessel was closed, removed from the glovebox, evacuated and backfilled with carbon monoxide three times, and finally pressurized with 4 atm carbon monoxide. After heating at 100 °C for 48 h with stirring, the reaction was cooled to room temperature, the carbon monoxide was released on a Schlenk line under nitrogen, and the vessel was brought into the glovebox. All volatiles were removed in vacuo, pentane (15 mL) was added, and the solution placed in a glovebox -35 oC freezer overnight to precipitate the product. The supernatant was decanted and residual pentane was removed in vacuo to afford p-bromobenzoyl triflate as a pale yellow solid in 82% yield (273 mg). 1H NMR (500 MHz, CD3NO2) δ 8.04 (d, J = 8.7 Hz, 1H), 7.85 (d, J = 8.7 Hz, 1H). 13C NMR (126 MHz, CD3NO2) δ 156.3, 132.9, 132.9, 132.1, 118.4 (q, J = 319.9 Hz). 19F NMR (471 MHz, CD3NO2) δ -75.8. The solid was redissolved in pentane (5 mL) and placed in the glovebox -35 oC freezer to grow crystals for X-ray diffraction. After two days, dark yellow crystals were obtained. The X-ray crystal structure is available at the Cambridge Crystallographic Data Centre (CCDC) under the deposition number 1513679.