In a 100 mL round bottom flask, 13 (0.11 g, 0.24 mmol) was dissolved in C6H6 (50 mL). An ethereal solution of 1.0 M HCl in Et2O (0.24 mL, 0.24 mmol) was added to the solution, and the mixture was allowed to react at RT for 1 h. The C6H6 was then removed under reduced pressure to afford a yellow-brown oil of 15. Yield: 0.10 g, 99%.