Process for controlled crystal size in 1,2-substituted 3,4-dioxo-1-cyclobutene compounds

A process for providing a crystalline mass of the monohydrate Form 4 of the compound of Formula I affording filter cake specific resistance of less than 7.9×1011 m/Kg, as measured in accordance with Specific Cake Resistance Measurement Procedure “V(i)” described herein,

• the process comprising:
• (a) providing a solution of the compound of Formula I in a mixture of solvent and anti-solvent at the temperature of dissolution of the compound of Formula I afforded by the solvent/anti-solvent system selected;
• (b) cooling the solution from step “a” to a temperature just above a temperature at which nucleation of the compound of Formula I commences in the solvent/antisolvent mixture selected for step “a” and seeding the batch with a solid crystalline form of the compound of Formula I monohydrate Form 4, thereby forming a mixture;
• (c) cooling the mixture from step “b” to a temperature at which substantially all of the compound of Formula I dissolved in step “a” is crystallized into a slurry using a cooling rate of from about 0.01° C./min. to about 5° C./min;
• and
• (d) cycling the temperature of the slurry from step “c” by heating it to a temperature below the temperature of seeding employed in step “b” at a rate of from about 0.01° C./min. to about 5° C./min and cooling the heated slurry at a rate of from about 0.01° C./min. to about 5° C./min to a temperature of about the crystallization temperature achieved in step “c” and repeating until crystals of the desired cross-section are obtained, thereby providing a filter cake specific resistance of less than 7.9×1011 m/Kg when the precipitated crystals are isolated by filtration.