Skip to content

Thursday 31/1/2018

Oxidation of 1 to form 2 (AS06)

The reaction mixture was taken off the heat and filtered through celite, before being dried with the rotary evaporator, re-dissolved in minimal DCM and left to crystallise overnight, in a dark fume hood.

Reduction of 2 to form 3 (AS05)

{label="fig:AS05banda"}
Before and after the reduction[]{label="fig:AS05banda"}

Before and after the reduction
After returning to the lab, the reduction had turned a pale yellow colour (fig:AS05banda) and was ready for processing. The reaction mixture was reduced under rotary evaporation and diluted with DCM. 2 M \(\ce{HCl}\) was added dropwise to react any remaining \(\ce{NaBH4}\). The mixture was then washed with water (4\(\times\)150 mL), washed with 1 M brine (2\(\times\)150 mL) and finally washed with saturated brine solution (2\(\times\)150 mL), before being dried under rotary evaporation. An NMR spectra was taken of the dried compound at this point before further processing.

{label="fig:AS05NMR1"}

NMR of the crude, washed solution
During the washing step, a fair amount of yellow precipitate formed (as can be seen in subfig:AS05washing) that wasn’t soluble in DCM, water, or brine. It was assumed that since 1 mentioned that the product is soluble in DCM and forms a white solid, that the yellow is some side product.

{label="subfig:AS05washing"}
{label="subfig:AS05ppt"}
Washing the reaction mixture in water Precipitate falling out of hexanes:ethyl acetate (5:1)

After the NMR showed no discernible product, I decided to continue on with the process, to see if something might pop out if we kept on purifying as per the method, so: The NMR sample was combined with the remaining dry crude from the previous step and was dissolved in minimal DCM. \(\sim\) 50 mL of hexanes:ethyl acetate (5:1) was added to the DCM and a fine white precipitate formed (subfig:AS05ppt). This was left overnight to reduce the solvent and hopefully allow the precipitate to grow into slightly larger crystals for filtering.

  1. Maniam, S.; Sandanayake, S.; Izgorodina, E. I.; Langford, S. J. Unusual Products from Oxidation of Naphthalene Diimides. Asian J. Org. Chem. 2016, 5 (4), 490–493. https://doi.org/10.1002/ajoc.201600048. ↩