Ethyl 4-bromobenzoate

The Suzuki coupling reaction was examined between four different aryl halide substrates and phenylboronic acid on fresh catalyst. Initially, 4-bromo-benzotrifluoride was successfully coupled at 25 °C with 98 % conversion in 12 h. However, at 50 C the reaction was much faster with 99 % conversion in 1.8 h (curve 1 in Figure 2). Ethyl 4-bromobenzoate was also successfully coupled at 25... 

We were interested if catalyst deactivation was substrate dependent. After an initial reaction with ethyl 4-bromobenzoate the catalyst was washed with water. However, retesting with ethyl 4-bromobenzoate lead to 33 % conversion over 22 h (25 °C) down from a conversion of 98 % after 12 h (25 °C) with the fresh catalyst. In the third cycle, the catalyst was washed with warm water, aqueous NaOH (5 %) and ethanoFwater but the conversion of the ethyl 4-bromobenzoate was only 25 % after 66 h. With 4-bromoanisole, retesting at 80 °C gave only 32 % conversion down from 85 % for the fresh catalyst. Using the same catalyst but switching to the more reactive 4-bromobenzotrifluoride (50 °C) resulted in improved conversion of 60 % after 40 h. This indicates that the catalyst is still active toward electron deficient aryl bromides but after three cycles its activity is considerably reduced. These studies show that catalyst deactivation beyond the first cycle is independent of the aryl bromide substrate. 

C2sH25Br05, (lR,S)-2-(5,6,7,7a-Tetrahydro-(7aS,R)-methyl-1,5-dioxo-4-indanyl)-1-(3-methoxyphenyl)ethyl 4-bromobenzoate, 39B, 116 C29H2BN2O4, Indan-1,2,3-trione 2-(N-p-t-butylbenzoyl-N-phenylhydraz-one) acetone solvate, 44B, 152... 

A 100-mL, oven-dried, round-bottom flask containing palladium chloride (44 mg, 0.25 mmol), 2-(di-/-butylphosphino)biphenyl (149 mg, 0.50 mmol), and ethyl 4-bromobenzoate... 

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