Purification of 1 (AS02) (attempt 2)¶
After allowing the solution to cool overnight, the product, as well as some impurities had crystallised out and were filtered off (fig:AS02vaccum). The crystalline precipitate was then washed with and hexane (fig:AS02product), resulting in an impure product (fig:AS02dry), that was confirmed with TLC.
|Vacuum filtration setup
|Crystals of crude product, washed with MeOH and hexane
|Visual yield of crude crystalline product
The impure product was redissolved in minimal DCM and purified by column chromatography with silica gel 60 as the solid phase and DCM:MeOH (200:1) for the liquid phase (fig:AS02column). Since the product is clear in solution, UV light was used to make it fluoresce (fig:AS02glow). TLC was used on each fraction to identify if it contained 1. Three fractions were collected that contained 1 and for each, the DCM was removed by rotary evaporation. The resulting powder fluoresced blue-green (fig:AS02productfinal), indicative of there being 1 present.The dried product was then dissolved in minimal DCM, placed in a weighed vial and the solvent was allowed to evaporate off in a fume cupboard.
|The column setup with (from the bottom up)cotton, sand, silica gel 60, the crude product, sand and the liquid phase
|Visualising the product under long wave UV light.
|The final rotary evaporated product glowing under long wave UV light
The dried product weighed in at 7.6 mg, with a calculated yield of 4.57%, indicating significant loss. Since column chromatography is my weakest wet skill, I suspect that it may have been the primary source of product loss. This was confirmed with NMR, indicating that while the product was there, the sample was very impure (fig:AS02NMR). The solution has been redissolved in minimal chloroform and is being allowed to recrystallise overnight.
In a 1 L round bottom flask was added, \(\sim\) 500 mL of THF, some sodium shavings and a small quantity of benzophenone. The round bottom flask was placed in a heating mantle and above it was set up a solvent still-head, double coil condenser and a gas bubbler. Argon gas was pumped through the setup and the THF/benzophenone/sodium mixture was brought to a boil.
The still-head was set up to allow the solvent to pass back down into the round bottom flask to continue being dried.
After a few hours, the sodium was completely consumed, so more was added, along with more benzophenone.
|The bottom of the THF still
|The top of the THF still
|Boiling THF - initial