Crystalline Forms 2-[3-[4-Amino-3-(2-Fluoro-4-Phenoxy-Phenyl)-1H-Pyrazolo[3,4-D]Pyrimidin-1- YL]Piperidine-1-Carbonyl]-4-Methyl-4-[4-(Oxetan-3-YL)Piperazin-1-YL]Pent-2- Enenitrile

A process of preparing crystalline Form C of Compound (I):

• wherein C* is a stereochemical center and
• wherein crystalline Form C is characterized by an X-ray powder diffractogram having a signal at at least three two-theta values chosen from 9.8±0.2, 10.2±0.2, 15.6±0.2, 16.6±0.2, 18.6±0.2, 18.9±0.2, 19.6±0.2, and 21.6±0.2,
• the process comprising:
• adding acetonitrile to amorphous (R)-2-[3-[4-amino-3-(2-fluoro-4-phenoxy-phenyl)pyrazolo[3,4-d]pyrimidin-1-yl]piperidine-1-carbonyl]-4-methyl-4-[4-(oxetan-3-yl)piperazin-1-yl]pent-2-enenitrile to form a solution;
• seeding the solution with crystalline Form B of Compound (I) to form a mixture and stirring the mixture to obtain a slurry, wherein the crystalline Form B is characterized by an X-ray powder diffractogram having a signal at at least three two-theta values chosen from 10.8±0.2, 15.3±0.2, 16.3±0.2, 17.9±0.2, 18.4±0.2, 18.7±0.2, 22.0±0.2, and 22.9±0.2;
• and
• isolating crystalline Form C by filtering the slurry.