(2-Methylphenyl)methanethiol → 1-methyl-8-((2-methylbenzyl)thio)-3,4-dihydro-1H-pyrimido[1,6-a]pyrimidin-6(2H)-one

To a suspension of 8-chloro-1-methyl-3,4-dihydro-1H-pyrimido[1,6-a]pyrimidin-6(2H)-one (200 mg, 1.002 mmol) and o-tolylmethanethiol (166 mg, 1.202 mmol) in tetrahydrofuran (THF) (5 mL) stirred in air at room temperature was added potassium tert-butoxide (112 mg, 1.002 mmol) in one charge. The reaction mixture was stirred at rt for 3 hr. The resulting mixture was concentrated and purified by prep-HPLC to give 50 mg 1-methyl-8-((2-methylbenzyl)thio)-3,4-dihydro-1H-pyrimido[1,6-a]pyrimidin-6(2H)-one (50 mg, 0.158 mmol, 15.73% yield).