The present disclosure provides a process for the preparation of crystalline Form C of Compound II:comprising:(1) adding Compound II to from about 0.4% v/v wet methyl tert-butyl ether (MTBE) to about 1.5% v/v wet MTBE to provide a reaction mixture；(2) refluxing the reaction mixture；(3) cooling the reaction mixture to about room temperature； and(4) isolating the crystalline Form C of Compound II from the reaction mixture.
