4-Tolylboronic acid

Methoxy-2 -methylbiphenyl 1,1 -Biphenyl, 4 -methoxy-2-methyl- (11) (92495-54-0) o-Tolylboronic acid o-Tolueneboronic acid (8,9) (16419-60-6)... 

Methoxy-2 -methylbiphenyl. o-Tolylboronic acid, 10.0 g (73.6 mmol) (Note 1), 16.8 g (71.8 mmol) of 4-iodoanisole (Note 2), and 200 mL of acetone (Note 3) are combined in a 1-L, three-necked flask equipped with an efficient stirbar, two stoppers, and a reflux condenser attached to a gas-flow adapter with a stopcock. Potassium carbonate, 25.0 g (0.180 mol), is dissolved in 200 mL of water (Note 4) in a separate 250-mL Schlenk flask. In a third flask (25-mL Schlenk flask) 3.30 mg (0.02 mmol, 0.2%) of palladium acetate (Note 5) is dissolved in 10 mL of acetone. All three flasks are then thoroughly degassed by four freeze-pump-thaw cycles. Under an argon back flow, one of the stoppers on the three-necked flask is replaced with a rubber septum, and the carbonate and catalyst solutions are added via cannula to form a biphasic mixture. The top layer turns brown upon addition of the catalyst. The septum is... 

Chlorobenzonitrile was coupled with p-tolylboronic acid affording the important pharmaceutical intermediate 2-(p-tolyl)benzonitrile in good yield... 

Scheme 7.17 Microwave assisted copper(II) mediated coupling of jp-tolylboronic acid to various polymer bound heterocycles. 

It is not possible to obtain an analytically pure sample of arylboronic acids since, on drying, partial conversion to the trimeric anhydride occurs. A quantitative conversion to the anhydride is achieved in the case of m-tolylboronic acid by heating with forty times its weight of benzene in a flask fitted with a Dean and Stark water separator (Fig. 2.31(a)). When no further water droplets separate the benzene solution... 

Pd(PtBu3)2 does not appear to be the active catalyst in the Suzuki coupling process under Fu s conditions, since the reaction of 3-chloropyridine with 2-tolylboronic acid proceeds sluggishly at room temperature. However, the addition of phosphine-free Pd2(dba)3 to the Pd(PtBu3)2 leads to a marked increase in the rate of cross-coupling (Eq. (80)). 

To test these ideas the reaction of p-tolylboronic acid and iodobenzene (eq. 1) was studied.17 19 As seen in Table 1, the reaction does not occur with Pd(0) and basic alumina, but does to varying degrees using the transition metal and bases adsorbed on alumina. Because KF/A1203 was the most effective base in inducing the Suzuki reaction, it was used in all subsequent reactions. It is worth noting that the Pd(0) - KF/A1203 system could be reused for further Suzuki reactions by addition of more KF to the alumina. 

Table 1 Coupling of p-Tolylboronic Acid with Iodobenzene using Pd(0) and...

Table 3. Coupling of Organic Halides with p-Tolylboronic Acid on Pd-KF/Al203...

Table 6.5 Reaction of bromobenzene and tolylboronic acid with catalyst formed in situ from [C4C1im]2[PdCl4] and 4 equivalents of 1-methylimidazole...

Scheme 6.12 Rhodium-mediated coupling of cinnamyl alcohol andp-tolylboronic acid...

Fig. 19. Cationic intermediates in the oxidative Heck arylation of l-vinyl-2-pyrrolidinone by p-tolylboronic acid observed by ESI(+)-MS 18. ...

Lam and coworkers281 also showed that para-tolylboronic acid couples with a-aminoesters at room temperature with little or no racemization of the amino acid ester. The yields for the reactions of a series of para-tolylboronic acids ranged from 17-67% (equation 69). The general reaction conditions included boronic acid (2 equivalents), triethylamine (2 equivalents), ce-aminoester (1 equivalent), Cu(OAc)2 (1.1 equivalents) and 4 A molecular sieves. 

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