Diisopropylamine → Ethyl 5-[1-(pyridin-3-yl)-1H-indol-3-yl]penta-2,4-dienoate

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Reaction Steps

A solution of 1.27 ml of diisopropylamine in 25 ml of tetrahydrofuran is cooled to -65° under nitrogen and 5.7 ml of 1.6M n-butyllithium in hexane is added. After 30 minutes at -65°, 2.0 ml of triethyl 4-phosphonocrotonate is added dropwise. The reaction mixture is stirred for 30 minutes before a solution of 2.0 g of N-(3-pyridyl)indole-3-carboxaldehyde in 20 ml of tetrahydrofuran is slowly added while maintaining the temperature less than -60°. When the addition is complete, cooling is suspended and the reaction mixture slowly warms to room temperature at which temperature it is stirred for 4 hours. The solvent is evaporated and the residue is partitioned between 30 ml of methylene chloride and 20 ml of half saturated ammonium chloride solution. The organic phase is washed with 20 ml of water, dried over sodium sulfate and evaporated to give an oil which crystallizes from hot ethyl acetate to yield 3-[4-(ethoxycarbonyl)butadienyl]-N-(3-pyridyl)-indole, m.p. 112°-113°.

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