To a mixture of 6-bromo-4-[(1,1-dioxidothiomorpholin-4-yl)methyl]-2-methylthieno[2,3-d]pyrimidine (200 mg), 4,4,5,5-tetramethyl-2-(spiro[2.5]octa-5-en-6-yl)-1,3,2-dioxaborolane (185 mg), and dioxane (4 mL) were added Pd2dba3 (25 mg), dicyclohexyl (2′,4′,6′-triisopropylbiphenyl-2-yl)phosphine (50 mg), K3PO4 (340 mg), and water (200 μL), followed by heating and stirring at 100° C. overnight. The reaction mixture was cooled to room temperature, and water was added thereto, followed by extraction with EtOAc. The organic layer was dried over MgSO4, and then concentrated under reduced pressure. The residue was purified by a basic silica gel column (hexane/EtOAc) to obtain 4-[(1,1-dioxidothiomorpholin-4-yl)methyl]-2-methyl-6-(spiro[2.5]octa-5-en-6-yl)thieno[2,3-d]pyrimidine (167 mg).
