Iodoethane → 10H-Phenothiazine, 1-ethyl-

This compound was prepared according to a procedure by A. R. Katritzky et al., Synthesis, 1988, 215-217. To a solution of phenothiazine (10.0 g, 50.18 mmol) in anhydrous THF (200 mL) and cooled to −78° C. was added a solution of n-BuLi (24.1 mL, 60.2 mmol, 2.5 M in hexanes) dropwise. The mixture is stirred until a yellow precipitate forms and then allowed to warm to room temperature, until a clear yellow solution results. the solution is again cooled to −78° C. and CO2 gas is bubbled through the mixture for 5 min. The resulting solution is allowed to warm to RT and the solvent was evaporated to give a residue. The residue was again dissolved in anhydrous THF (200 mL) and cooled to −78° C., before t-BuLi (50 mL, 85 mmol, 1.7 M in pentane) was added dropwise. The resulting mixture was allowed to warm to −20° C. and was stirred at this temperature for 2 h. The reaction mixture was again cooled to −78° C. and a solution of ethyl iodide (100.0 mmol) in THF (50 mL) was added dropwise. The mixture was stirred at this temperature for 1 hour then allowed to warm to −20° C. and stirred for 2 h. The reaction mixture was quenched with ice cold 1N HCl and extracted with EtOAc. The combined organic layers were washed with brine, dried over MgSO4, filtered and evaporated to give a residue. The residue was purified by flash silica gel chromatography to give the desired product.