6-Ethyl-2-thioxo-2,3-dihydropyrimidin-4(1H)-one (2). To a 250 mL round bottom flask equipped with stirbar, thiourea (5.99g, 78.7 mmol, 1 eq.) and potassium hydroxide (5.10 g, 90.9 mmol, 1.2 eq.) were added. The powders are then suspended with 60 mL of 200 proof ethanol and the mixture is heated while stirring to 75 °C. To this stirring mixture, ethyl 3-oxopentanoate (12.5 mL, 87.6 mmol, 1.11 eq.) is added in one portion. The flask was then sealed with a glass stopper and the solution is heated at 85°C overnight. White solid began crashing out of solution quickly, with the solution appearing orange/pink. After 16 hours, the suspension is removed from heat and allowed to slowly return to room temperature. The suspension was concentrated on in vcauo to remove about half of the volume of ethanol (~30 mL ethanol remaining). To this suspension, deionized water was added slowly while stirring until the mixture turns completely clear. The solution was then slowly neutralized while stirring by adding concentrated HCl (12 N in water) and diluted NaOH (1.0 N in water) to pH 7.0. As the solution approaches neutral pH, white solid should begin crashing out of solution. Once the mixture was neutralized, the suspension was filtered and washed with water. The white powder was then allowed to dry on filter paper under suction before being transferred to a vial and placed on hi-vac. The resultant powder 2 was collected and taken forward without further purification (7.46 g, 47.8 mmol, 61% yield). H NMR (500 MHz, Methanol-d4) δ 5.70 (s, 1H), 2.43 (q, J = 7.5 Hz, 2H), 1.21 (t, J = 7.5 Hz, 3H).