Br[C:2]1[CH:7]=[CH:6][C:5]([CH3:8])=[CH:4][C:3]=1[Cl:9].C1(P(C2C=CC=CC=2)CCCP(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=CC=1.C(N(CC)CC)C.[CH3:46][OH:47].CN([CH:51]=[O:52])C>CC([O-])=O.CC([O-])=O.[Pd+2]>[Cl:9][C:3]1[CH:4]=[C:5]([CH3:8])[CH:6]=[CH:7][C:2]=1[C:46]([O:52][CH3:51])=[O:47]
To 4-bromo-3-chlorotoluene (4.97 g, 24.2 mmol) in DMF (25 mL) is added Pd(OAc)2 (0.54 g, 2.42 mmol), 1,3-bis(diphenylphosphino)propane (0.998 g, 2.42 mmol), triethylamine (12.5 mL) and methanol (12.5 mL). The reaction vessel is evacuated and purged three times with carbon monoxide gas. A balloon filled with carbon monoxide gas is used to maintain the carbon monoxide atmosphere. The reaction mixture is heated at 80° C. for 8 hr. After cooling H2O (50 mL) is added. The mixture is extracted with hexanes (2×50 mL). The combined organic layers are dried over Na2SO4, filtered, concentrated and chromatographed with 0–3% EtOAc in hexanes. 1.24 g (28%) of methyl 2-chloro-4-methylbenzoate is isolated as a colorless oil. EIMS m/e 184 (M+; 35Cl) and 186 (M+; 37Cl).
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