O-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... 

Open to the atmosphere, 4-bromoanisole (1.87 g, 10 mmol), o-tolylboronic acid (1.50 g, 11 mmol), KF (spray dried, dried in an oven overnight prior to use, 1.92 g, 33 mmol), and THF (10 mL) were added to a 100-ml round-bottomed Schlenk flask equipped with a stir bar. The reaction system was flushed with argon for about 5 min. P(t-Bu)3 (1.9 X 10 M stock solution in THF 2.31 mL, 5.0 x 10 mmol) and Pd2(dba)3 (2.16 x lO" M stock solution in THF 2.31 mL, 5.0 x 10 mmol) in THF were added sequentially. After 48 h at room temperature, the reaction mixture was diluted with ether or EtOAc, filtered through a pad of silica gel with copious washings, and then concentrated. The crude product was then purified via column chromatography eluting with 5% ether in hexane to yield 1.94 g (98%) of 4-methoxy-2 -methyl-biphenyl as a colorless liquid. 

Tolueneboronic acid See o-Tolylboronic acid, 75, 61 Toluene dioxygenase, 76, 80... 

Upon warming, alkylpalladium complex 4 underwent P-hydride elimination to generate allylbenzene and Pd(P(t-Bu)2Me)2HBr. This process was inhibited by the presence of excess P(t-Bu)2Me, consistent with a pathway that involves initial dissociation of a phosphine [45]. Oxidative-addition adduct 4 reacted with one equivalent of o-tolylboronic acid to generate the coupling product in 94% yield in addition, it served as a competent catalyst for cross-couplings of alkyl bromides and arylboronic acids. 

Coupling with o-tolylboronic acid diastereoselectively produces a kineti-cally controlled product in which the 2-methyl group is in syn-orientation... 

A drawback of the aqueous protocol in the Suzuki reaction is the possibility of protonolysis, which sometimes happens with sterically hindered boronic acids, in which case the rate of cross-coupling reaction may become lower than the rate of side reactions. Thus, in the reaction of methyl 5-bromonicotinate with sterically hindered o-tolylboronic acid, the use of a biphasic technique with Na2C03 as a base gave poor results in comparison with the reaction in anhydrous DMF in the presence of EtsN (Scheme 37). " ... 

Similarly, in the reaction of methyl 5-bromonicotinate with sterically hindered o-tolylboronic acid, the use of the biphasic technique with Na2C03 as a base gave poor results in comparison with the reaction in anhydrous DMF in the presence of Et3N [38] ... 

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