The general procedure for the synthesis of 2-mercaptopiperidine from 1,1,3,3-tetramethoxypropane and N-methylthiourea is as follows:
Example 4 Synthesis of 2(1H)-pyrimidinethione, 1-methyl: A mixture of 1-methyl-2-thiourea (76.6 g, 0.85 mol) and malondialdehyde bis(dimethyl acetal) (126.8 g, 0.77 mol) in ethanol (1.5 L) was stirred, and 10 M hydrochloric acid (76.6 mL, 0.77 mol) was added in one go. The reaction mixture was stirred at 25 °C for 18 h and subsequently concentrated under vacuum by rotary evaporator. The residue was dissolved in water (1.25 L), the solution was alkalized by batchwise addition of potassium carbonate and extracted with dichloromethane (4 x 500 mL). The organic phases were combined, dried with magnesium sulfate and subsequently concentrated to a solid under vacuum by rotary evaporator. The crude product was recrystallized with ethanol (600 mL) and then dried under vacuum at room temperature to constant weight to give 22.9 g (23% yield) of the target product with a melting point of 186-188 °C (uncorrected). The reaction process was repeated to obtain a total of 40.7 g of product.
