Pd(OAc)2 253mg (1.127mmol) was dissolved in anh. benzene 17mL (10 min stirring with gentle heating) and pyridine 0.180mL (2.226mmol) was added dropwise over 5 min. The mixture color turned light and a precipitate formed. The closed flask was wrapped in aluminum foil and the mixture was stirred overnight (12 hours). The obtained slurry was evaporated to dryness, the flask with the solid residue was flushed with oxygen and neat trifluoroacetic acid 2.1mL (protein-sequencing grade) was added. The obtained yellow solution was diluted with methanol 20mL and the mixture was stirred under cotton-filled drying tube while wrapped in Al foil for 2 hours. The resulting slurry was filtered through a small medium-porosity frit, the precipitate on the frit was dissolved by gradual washing with 1:1 mixture methanol-dichloromethane (10mL). The combined filtrates were slowly evaporated and the residue was dried on highvac. Y=554mg (100%) of a yellow-white heavy powder.
1H(CDCl3, 400MHz): 8.512(m, 4H), 7.855(app tt, 7.7Hz, 1.5Hz, 2H), 7.405(m, 4H); 13C(CDCl3, 100MHz): 163.09(q, 37.2Hz, 2C), 151.11(4C), 139.83(2C), 125.70(4C), 114.09(q, 289Hz, 2C)
This is a slightly improved, higher-yielding preparation of a catalyst for the oxidative Pd(II)-catalyzed cyclization of phenols, carboxylic acids and alcohols: Stoltz et al, JACS 127 (2005), 17778-88