How to improve efficiency of the diamine synthesis from fluorescein? In this work, fluorescein was incorporated with an equal molar of 1-chloro-4-nitrobenzene and double potassium carbonate (molar ratio), the solvent of this reaction is dimethylacetamide (50 ml for 5 g of fluorescein).

The solution was stirred in at 110 °C for 24 h, after that cooled to the room temperature and precipitated in cold water, but a solid, similar to potassium carbonate, remains at the bottom of the reaction vessel, and the efficiency is very low (25%). I don't know the cause of this problem.

This is the structure that I expected for first stage:



In the next step the solid that was obtained from the previous stage, incorporated with 10% Pd/C and methanol. 30 eq hydrazine monohydrate was added dropwise and the solution refluxed at 50 °C for 12 h. After that the solution was filtered to separated catalyst and the crystals of diamine was obtained, but the efficiency of this stage is very low too.
What I think is happening is that you are not getting enough mixing between your reagents, the solid remaning is unreacted potassium carbonate. I think you can reduce the amount of potassium carbonate you are using - you only need 1 eq as it is dibasic, and use finely powdered if you have access to it. Run the reaction more dilute with a more powerful stirrer (have you an overhead stirrer?) so that material does not stick to the side and follow it by TLC. If this does not improve the outcome I would consider using a strong organic base such as DIPEA or DBU in place of the potassium carbonate so that everything is in solution.