2-Chloro-6-(4-piperidinylthio)pyridine:
The reaction is carried out under an argon atmosphere. 0.27 g of 80% sodium
hydride (0.009 mol) are suspended in 10 ml of dimethylacetamide; the
mixture is cooled with ice and then 0.615 g (0.004 mol) of solid 4-
mercaptopiperidine hydrochloride are added and stirred for 10 minutes. A
solution of 0.588 g (0.004 mol) of 2,6-dichloropyridine in 5 ml of
dimethylacetamide are then added dropwise to this mixture and the reaction
mixture is stirred for 2.5 hours at room temperature.
Working up of the reaction mixture: 25 ml of water are added dropwise with
cooling, 20 ml of methylene chloride are then added, the organic phase is
separated off, the aqueous phase is then extracted twice with 15 ml of
methylene chloride each time, the combined organic phase is washed twice, in
each case with 10 ml of water, dried with sodium sulfate, the solution is
concentrated on a rotary evaporator, the residue is mixed with 10 ml of
absolute ethanol and then reconcentrated.
The product which is obtained on removal of the eluant is diluted with 10 ml
of ether, an equivalent quantity of HCl in isopropanol is added dropwise and
the mixture is placed for several hours in a deep freezer after addition of seed
crystals. The hydrochloride of the 2-chloro-6-(4-piperidinylthio)pyridine which
crystallizes out is filtered off with suction, washed with ether and dried under
oil pump vacuum at 50°C. Melting point of the hydrochloride 132°-133°C.
