Benzene → trans-1-Methyl-3-phenyl-4-phenylthiopiperidine hydrochloride

Participants

Reaction Steps

A suspension of 8.30 g of N-phenylthiophthalimide in 75 ml of dry benzene at room temperature under nitrogen is treated with 6.58 g of tri-n-butylphosphine. After 15 minutes a dark orange solution is obtained and 4.78 g of cis-1-methyl-3-phenyl-4-piperidinol of Example 22 are added all at once. After 5 minutes the solid dissolves. After stirring for 24 hours at room temperature, the resultant suspension is filtered and the solid is washed well with hexane. The filtrate is concentrated in vacuo to an oil which is triturated for 18 hours with 250 ml of hexane. The undissolved material is filtered off, triturated with another 100 ml of hexane, and discarded. The filtrate is washed with water and then saturated aqueous NaCl solution and concentrated in vacuo to an oil. This material is dissolved in ether and extracted with 2 N HCl solution. The phases are separated and the ether phase is extracted with 2 N HCl solution. The combined acid extracts are washed with ether and then extracted with dichloromethane, keeping the two extracts separated. The first extract affords an oil which crystallizes upon standing for 18 hours. This material is triturated with petroleum ether and the solid is filtered and washed with petroleum ether until nearly colorless needles are obtained, m.p. s 51°, 55°-57° C. The filtrate is concentrated in vacuo to give an oil, which is combined with the oil obtained from the second dichloromethane extract and chromatographed on silica gel, using acetone as solvent. Another portion of purified free base is obtained as an oil which crystallizes rapidly on standing. The hydrochloride salts prepared by dissolving the free base in 250 ml of ether, filtering and treating the filtrate with HCl-saturated ether solution until acidic to wet pH paper. The resulting colorless solid is filtered, washed with ether and dried to afford a colorless salt, mp s 180°, 182°-184° C. This material is recrystallized by dissolving in a boiling mixture of 200 ml of ethylacetate and 150 ml of acetone, filtering hot and boiling down the filtrate to obtain crystalline needles of trans-1-methyl-3-phenyl-4-phenylthiopiperidine hydrochloride, mp s 167°, 168°-171° C.

Provenance & Evidence