2-Bromo-5-methylpyridine → ethyl 4-((2S,4R)-1-acetyl-2-methyl-4-((5-methylpyridin-2-yl)amino)-1,2,3,4-tetrahydroquinolin-6-yl)benzoate

Participants

Reaction Conditions

Reaction Steps

Sodium tert-butoxide (135 mg, 1.41 mmol)) was added to a suspension of ethyl 4-((2S,4R)-1-acetyl-4-amino-2-methyl-1,2,3,4-tetrahydroquinolin-6-yl)benzoate (for a preparation see Intermediate 16) (450 mg, 1.28 mmol), 2-bromo-5-methylpyridine (439 mg, 2.55 mmol), 2′-(dicyclohexylphosphino)-N,N-dimethyl-[1,1′-biphenyl]-2-amine (40 mg, 0.102 mmol) and tris(dibenzyldieneacetone)dipalladium(0) (47 mg, 0.051 mmol) in anhydrous toluene (4.5 mL). The mixture was heated under microwave irradiation to 120° C. for 1 h in a sealed vial. The mixture was partitioned between EtOAc and water, the aqueous layer was extracted twice with EtOAc, the combined organic phases were dried by passing through a hydrophobic frit and concentrated in vacuo to give a residue. The residue was purified by chromatography (10 g column, EtOAc/cyclohexane gradient followed by MeOH/EtOAc gradient) to give a residue. This residue was dissolved in a mixture of EtOAc (0.6 mL) and cyclohexane (0.4 mL). The solution was treated with cyclohexane (3 mL) to give an emulsion, which was allowed to stand at room temperature over a weekend. The solution was decanted from the precipitated dark brown oil and concentrated to dryness under a stream of nitrogen to give an oil. This oil was triturated with cyclohexane (2×3 mL), the residual gum isolated by decanting off the cyclohexane, dissolved in EtOAc and concentrated to dryness under a stream of nitrogen to give crude ethyl 4-((2S,4R)-1-acetyl-2-methyl-4-((5-methylpyridin-2-yl)amino)-1,2,3,4-tetrahydroquinolin-6-yl)benzoate as a pale brown foam (240 mg) which was used directly in the next step without further purification.

Provenance & Evidence