A stirred solution of 4-(5-chloro-3-nitropyridin-2-yl)morpholine (500 mg, 2.05 mmol), thiomorpholine 1,1-dioxide (333 mg, 2.46 mmol), Pd2dba3 (94 mg, 0.10 mmol), X-Phos (98 mg, 0.20 mmol), sodium tert-butoxide (394 mg, 4.1 mmol) in toluene (19.7 mL, 184.7 mmol) was heated at reflux for 14 h. After this time the reaction was cooled to rt and partitioned between EtOAc (100 mL) and NaHCO3 (satd aq. solution, 50 mL). The separated organic layer was washed with brine (50 mL), dried over magnesium sulfate, filtered and evaporated in vacuo. Column chromatography (hexanes:EtOAc, 1:0 to 1:1) gave 4-[5-(1,1-dioxidothiomorpholin-4-yl)-3-nitropyridin-2-yl]morpholine.
