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In a 2 L round-bottomed flask was charged n-butyllithium 2.5M hexanes (99 ml, 248 mmol) in Et2O (1680 ml) to give a colorless solution. The reaction was cooled to -78 C. n-Butyllithium 2.5M hexanes (99 ml, 248 mmol) was added dropwise keeping the temperature below -70 C. The reaction was stirred for 1 hour and N,N-dimethylformamide (36.6 ml, 473 mmol) was added keeping the temperature below -70 C. The reaction was stirred for 1 hour and quenched with saturated ammonium chloride solution (2 L). The organic layer was washed with brine, dried over sodium sulfate and solvent removed under reduced pressure. The crude residue was purified by column chromatography eluting with 0-30% ethyl acetate to give 6-bromonicotinaldehyde. Yield 19.7 g, 44.8%In a 2 L round-bottomed flask was added Methyltriphenylphosphonium bromide (42.9 g, 120 mmol) in THF (600 ml) and cooled to -20 C. n-Butyllithium 2.5M hexanes (48.0 ml, 120 mmol) was added dropwise keeping the temperature below 0 C. The reaction was warmed to room temperature for 20 minutes and cooled back to 0 C. A solution of 6-bromonicotinaldehyde (18.6 g, 100 mmol) in THF (40 mL) was added. The reaction was warmed to room temperature and stirred overnight. The reaction was partitioned between water and diethyl ether (1 L) and the organic layer was dried over sodium sulfate, filtered and solvent removed at room temperature under reduced pressure. The product, 2-bromo-5-vinylpyridine, was purified by bulb to bulb distillation (600 mTorr, 80-100 C.). Yield 17.2 g, 93%2-Bromo-5-vinylpyridine (17.2 g, 40.1 mmol) was dissolved in ethanol (150 mL) and Adam's Catalyst (PtO2, 75%, 1.4 g) was added. The mixture was hydrogenated at 3 psi of hydrogen, continually checking the progress of the reaction by LC and 1H NMR between each charge of hydrogen. After 10 psi was consumed, the data showed completion of the reaction with <5% of reduction of the bromine. The catalyst was filtered off and the solvent was removed under reduced pressure at 20 C. to give 2-bromo-5-ethylpyridine. Yield 17 g, 98%.In a 1 L round-bottomed flask was compound 6 (10 g, 53.8 mmol) and <strong>[882670-69-1]4-methyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline</strong> (13.83 g, 59.1 mmol) in Dioxane (300 ml) followed by saturated sodium bicarbonate (150 ml). The mixture was degassed by passing a stream of nitrogen through the mixture for 20 minutes. Tetrakis(triphenylphosphine) palladium(0) (3.36 g, 2.91 mmol) was added and the mixture was heated to reflux becoming very thick then finally going to solution. The reaction was heated for 2 hours, cooled to room temperature and the solvent removed under reduced pressure. The residue was partitioned between ethyl acetate and water. The organic layer was dried over sodium sulfate and solvent removed under reduced pressure. The residue was purified by column chromatography 0-100% ethyl acetate/heptane to give 3-(5-ethylpyridin-2-yl)-4-methylaniline. Yield 8.7 g, 77%The urea was formed from 3-(5-ethylpyridin-2-yl)-4-methylaniline and 4-(2-amino-5-tert-butylthiophene-3-carbonyl)-3,3-dimethylpiperazine-2-one. |
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