C([N:8]1[CH2:13][CH2:12][P:11](=[O:17])([CH:14]([CH3:16])[CH3:15])[CH2:10][CH2:9]1)C1C=CC=CC=1.C(O)C.O.O.[C:23]([OH:28])(=[O:27])[C:24]([OH:26])=[O:25]>O.[Pd]>[C:23]([OH:28])(=[O:27])[C:24]([OH:26])=[O:25].[CH3:15][CH:14]([P:11]1(=[O:17])[CH2:12][CH2:13][NH:8][CH2:9][CH2:10]1)[CH3:16]A 10 L auto clave was charged with the product of Step 2 (200.0 g, 796.8 mmol), ethanol (4000 mL) and oxalic acid dihydrate (100.4 g, 797.0 mmol) in water (1000 ml). To the reaction mixture was added palladium on carbon (10% w/w, 99.6 g) and stirred at room temperature under H2 pressure (50 psi) for 16 h. After completion, the reaction mixture filtered and concentrated. Obtained solid was triturated with hot ethanol (250 mL) and kept in a cold room for 90 minutes, filtered, washed with diethylether and hexane to give 4-(propan-2-yl)-1,4-azaphosphinane 4-oxide oxalate salt (105 g, 53%) as a colorless solid. Mp 223-224° C. LC ESI: [M]+ m/z 162. HPLC (ELSD method)=99.9%.
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