Boron trifluoride etherate → (+)-4,5,6,7-Tetrahydro-6-[2-[4-(2-pyridinyl)-1-piperazinyl]ethyl]-2-benzothiazolamine

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Reaction Steps

To a solution of (+)-1-[(2-amino-4,5,6,7-tetrahydro-6-benzothiazolyl)acetyl]-4-(2-pyridyl)piperazine (2.70 g) (Example M) in 250 ml of tetrahydrofuran is added sodium borohydride (1.07 g) under nitrogen. This suspension is cooled in an ice bath and boron trifluoride etherate (4.6 ml) added dropwise. The mixture is stirred at room temperature for one hour and the solvent removed in vacuo. The residue is dissolved in 250 ml of a 10% solution of hydrochloric acid and stirred for two hours. The solution is made basic with ammonium hydroxide and extracted with chloroform (2×200 ml). The combined chloroform extracts are dried (magnesium sulfate), filtered, and concentrated. The residue is purified by MPLC (silica; 5% methanol, 95% chloroform) to give 1.74 g of (+)-4,5,6,7-tetrahydro-6-[2-[4-(2-pyridinyl)-1-piperazinyl]ethyl]-2-benzothiazolamine, containing one-fourth of a molecule of water, as a colorless solid; mp 176°-190° C.; [α]D =+52.2° (c=1.02; 0.1 N hydrochloric acid solution).

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