N-Methylethylenediamine → 4,6-dimethylpyrimidine-2-thiol

Participants

Reaction Steps

To a stirred solution of N-methyl-ethylenediamine (0.10 mol. 8.8 cm3) in dioxane (50 cm3), at room temperature and under a nitrogen atmosphere, was added a solution of S-tert-butyloxycarbonyl-4,6-dimethyl-2-mercaptopyrimidine (0.05 mol, 12 g) in dioxane (50 cm3), dropwise, over 3 h. After the addition was complete, the solution was stirred at room temperature for a further 15 h. The precipitate which formed (4,6dimethyl-2-mercaptopyrimidine) was removed from the solution, and the filtrate conc. in vacuo to half its original volume (50 cm3). To this residue, was added water (80 cm3) and the solution then left to stand at room temperature for 15 min. The bis-(t-BOC)-diamine precipitate was then removed, and the filtrate conc. in vacuo. To the residue was added water (80 cm3), and the solution subsequently saturated with sodium chloride. This saturated solution was extracted with ethyl acetate (4×40 cm3), and the organic extracts combined, dried (MgSO4), filtered, and conc. in vacuo to give an oil. This oil was dissolved in water (50 cm3) and acidified to pH 3 with 1M hydrochloric acid. The solution was then extracted with ethyl acetate (3×100 cm3). The aqueous layer was then collected, decolourized with activated charcoal and filtered over Celite. The filtrate was then conc. in vacuo. If necessary, fractional recystallization from room temperature methanol was used to separate the required product from any diamine dihydrochloride by-product. The filtrate was then conc. in vacuo. The product was isolated by trituration from hexane, to give a fine off-white solid which consisted of a mixture of N-t-BOC, N-methylethylenediamine monohydrochloride and N-t-BOC, N′-methyl ethylenediamine monohydrochloride in a 4:1 ratio (4.8 g, 45%), m.p. 104-105° C. δH (400 MHZ; methanol-d4) 3.52-3.37 (2H, t, J 4.8 Hz), CH2NH; 3.31 (2H, t, J 4.8 Hz), CH2NH(CH3); 2.81 (3H, s), NCH3; 1.43 (9H, s) C(CH3)3. δC (75.4 MHz: methanol-d4) 157.88, C═O; 81.60 C(CH3)3; 47.47, CH2NH(CH3); 39.09, CH2NH; 28.65, C(CH3)3. Found: M+. 210.72.

Provenance & Evidence