Hydrochloric Acid → 2-(2-Thien-3-yl-5-pyridyl)propanenitrile

Beteiligte Stoffe

Reaktionsschritte

A solution of 960 mg (4.8 mmol) of 5-acetyl-2-bromopyridine, 676 mg (5.28 mmol) of thiophene 3-boronic acid, 222 mg (0.19 mmol) of tetrakis(triphenylphosphine) palladium and 995 mg (7.2 mmol) of potasium carbonate in 13 ml of dioxane and 3 ml of water, was heated at 90° C. overnight. Brine was added and extracted three times with ethyl acetate. The organic phase was dried over Na2SO4, filtered and concentrated in vacuo. To a solution of the crude and 475 mg (14.4 mmol) of lithium cyanide in 16 ml of THF, 2.2 ml (14.4 mmol) of diethylcyanophosphonate was added neat at ambient temperature. The mixture was stirred at ambient temperature for 30 min. Water was added and extracted with a 1:1 solution of ethyl acetate/hexane. The organic solution was dried over Na2SO4 filtered and concentrated in vacuo. The crude was disolved in 10 ml of THF and added dropwise to a solution of samarium iodide, prepared from 3.32 g (22.08 mmol) of samarium and 3.89 g (13.8 mmol) of 1,2-diiodoethane. The mixture was stirred for 1 h. A 2.5 N solution of hydrochloric acid was added and extracted three times with diethyl ether. The organic phase was washed with a 1 N solution of sodium thiosulfate. The organic solution was dried over Na2SO4 filtered and concentrated in vacuo. Chromatography (100 g of silica gel, 25% ethyl acetate/hexane) of the residue afforded 225 mg (22%) of the title compound. B. To an ambient temperature solution of 214 mg (1 mmol) of material prepared in step A in 5 ml of THF was added dropwise 0.11 ml of a 10 M solution borane-methyl sulfide complex (1.1 mmol) in THF. The mixture was stirred at ambient temperature for 2 h. Then, 0.1 ml of a 10 M solution borane-methyl sulfide complex (1.0 mmol) in THF were added and the mixture stirred overnight. A saturated solution of hydrochloric acid in methanol (5 ml) was added, and stirred for 10 min. The solution was concentrated in vacuo. The crude was disolved in dichloromethane (5 ml) and cooled to 0° C., triethylamine 0.44 ml (3.2 mmol) was added, followed by isopropylsulfonyl chloride (0.14 ml, 1.2 mmol). The ice-bath was removed and the solution was stirred at ambient temperature for 2 h. The organic solution was washed with 1N hydrochloric acid, sodium bicarbonate saturated solution, brine, dried over Na2SO4 filtered and concentrated in vacuo. Chromatography (50 g of silica gel, 33% ethyl acetate/hexane) of the residue afforded 25 mg (7%) of the title compound. Field Desorption Mass Spectrum: M=324.

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