Carbon Dioxide → (3aS,6aR)-hexahydro-1-[(R)-(1-phenylethyl)]-2-oxo-3-benzylthieno[3,4-d]imidazol-4-ylidene pentanoic acid

Participants

Reaction Conditions

Reaction Steps

0.802 g (33 mmol) of magnesium chips were put into 5 ml of tetrahydrofuran. Then 2.37 g (11 mmol) of dibromobutane in 30 ml tetrahydrofuran was added in 1 hour. The reaction mixture was refluxed for 2 hours, then 2.55 g (22 mmol) of tetramethylethylenediamine was added and refluxed for another hour. To the suspension, cooled to 0° C., was then added 3.52 g (10 mmol) of (3aS,6aR)-1-[(R)-(1-phenylethyl)]-3-benzyl-dihydro-1H-thieno-[3,4-d]-imidazol-2,4(3H,3aH)-dione in 50 ml of tetrahydrofuran. Then the reaction mixture was stirred for 2 hours at room temperature and then cooled to 0° C. Carbon dioxide gas was introduced in 1 hour at 0° C. and 1 hour at room temperature. The reaction mixture was poured onto a mixture of 85 g of ice and 11.5 ml of conc. hydrochloric acid and then extracted with ethyl acetate. The combined organic phases were washed with water and saturated sodium chloride solution, dried with magnesium sulfate and finally concentrated. 50 mg of p-toluenesulfonic acid was added to the residue, which was then taken up in 170 ml of toluene. The reaction water was refluxed and distilled off by means of a water separator. The remaining toluene solution was concentrated and the resulting oil was chromotographed over silica gel with acetic acid ethyl ester/toluene. 1.22 g (28 percent) of the title product was obtained as a light yellowish oil.

Provenance & Evidence