To a suspension of 2-(7-amino-9H-thioxanthen-4-yl)-6-morpholin-4-yl-pyran-4-one (1)(0.50 g, 1.27 mmol) in ethanol (4 mL) at room temperature was added tetrafluorboric acid (supplied as 54 wt % in diethyl ether, 0.35 mL, 2.54 mmol). The solution was then cooled to 0° C., when t-butyl nitrite (750 μL, 6.33 mmol) was added. After 1 hr, the reaction was diluted with diethyl ether (10 mL), and after 20 mins the precipitate was filtered and washed with diethyl ether. The orange coloured salt was then dissolved in MeCN:Et2O (1:1) (15 mL), when triisopropylsilane (222 mg, 1.40 mmol) and Pd(OAc)2 (5.47 g, 24.37 mmol) were added successively. A CO pressure of 10 atm was then applied for 10 minutes, after which the reaction was filtered. The organic layer was washed with saturated NaHCO3 then brine, dried over MgSO4, filtered and concentrated in vacuo. The resulting yellow/orange solid was dried under vacuum at 50° C. to give the crude title compound (0.392 g, 75%, 2 steps) which was used without any further purification. m/z (LC-MS, ESP), RT=3.40 min, (M++1)=406.3
