P-tolylboronic acid

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

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...

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

The boronic acid in 1200 ml of water in a 2 L beaker is heated and stirred for 15-20 min to azeotropically remove a trace of bitolyl and other organic materials. The hot solution is filtered with suction to remove any insoluble matter, and then the beaker and filter cake is rinsed with two 30 mL portions of hot water. The filtrate is slowly cooled to room temperature and then to 0 °C for a few hours. The precipitated white crystals are collected in a Buchner funnel with suction, and are then allowed to stand overnight in air or in a desiccator to obtain p-tolylboronic acid. 50 g, 80-90% yield, mp 240 °C. ... 

The cross-coupling reaction of p-tolylboronic acid with p-iodo- or p-bromoanisole is accompanied by the formation of undesired biaryls... 

Table 3. Effects of substituents on the Selectivity of Biaryl Coupling between p-Tolylboronic Acid [Ar BCOHlj] and Haloarenes (ArX) ...

Table 4. Effects of Catalysts, Bases, and Solvents on the Selectivity of Biaryl Coupling of p-Tolylboronic Acid and 4-lodo- or 4-Bromoanisole...

Synthesis of 1 -p-Tolyl-1 H-benzimidazole Using Cupric Acetate and p-Tolylboronic Acid p-Tolylboronic acid (0.09 g, 0.667 mmol, 2 equiv), benzimidazole (0.039 g, 0.333 mmol), anhydrous cupric acetate (0.091 g,... 

Lam discovered that imidazoles and pyrazoles underwent N-arylation with 2.0 equiv. of p-tolylboronic acid under typical conditions (Scheme 5.15) [9]. Electron-poor azoles such as triazoles and tetrazole gave poor yields. Recently, dark and co-workers [30] reported N-arylation at the N-2 position of 4,5-diaryl-l,2,3-triazole (no specified yield) (Scheme 5.15). This is in contrast to the results on the parent 1,2,3-triazole where N-arylation occurs on N-1 [9j. The r ochemical preference of Clark s system can be explained by the high sensitivity to steric hindrance of these cross<oupling reactions (vide infra). 

Scheme 10.3 Suzuki coupling of iodobenzene and p-tolylboronic acid.

Selecttiuor (1.3 equiv) catalyst (10%) Na2HP04 (4 equiv) p-tolylboronic acid (1 equiv) MgS04 (3.3 equiv) p-xylene/ethylcyclohexane (1 1)... 

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